Visionaries and Unsung Heroes: Engineers – Design – Tomorrow 9783955534615, 9783955534608

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Visionaries and Unsung Heroes Engineers   –   Design   –   Tomorrow

Visionaries and Engineers Unsung Heroes Design Tomorrow Edited by Werner Lang and Cornelia Hellstern

6 Engineers in the Building Sector Werner Lang, Cornelia Hellstern 9 Designing Life Wilhelm Vossenkuhl

On Inventors, Entrepreneurs, ­Problem-Solvers and Designers 14 Civil and Building Engineers – the Emergence of the ­Professions Bill Addis 20 Networks of Engineering Expertise Dirk Bühler 26 Women Pioneers of the Big Modern Building Sites – How They Became Who They Are Margot Fuchs 30 On the Education of Engineers Gerhard Müller 36 Engineering Aesthetics Nina Rappaport

Tensile Structures 65 Wide and Light 66 Lightweight Textile Construction – Development of Simulation Methods from the 1970s to the Present Kai-Uwe Bletzinger 71 The Spoked Wheel for Ring Cable Roofs in Lightweight ­Construction Knut Göppert 75 Lightweight Construction in Motion

Building Construction – Focus on Timber 77 Exploring New Dimensions with Timber 82 Material and Design – Is Hybrid the Future? Stefan Winter

Towers and High-Rises 87 Aiming High 89 Pushing the Limits Annette Bögle, Christian Hartz, Bill Baker 94 The Buttressed Core

WATER + ENERGY

ENCLOSURE + SPACE Arch and Shell Structures 43 Creating Spaces: Linking Aesthetics and Structure 44 On the Development of the Zeiss-Dywidag Shell Construction System Cengiz Dicleli 47 Form Finding – Graphical Tools, Experiments and Models, ­Numerical Methods 51  Computer-Based Processes for Biomimetic Structures Jan Knippers, Achim Menges 58  Structural Design and Form Finding Processes Christoph Gengnagel

Water Supply and Wastewater Disposal 99 Water in Cities 100 Water Transitions in Cities of the Future Jörg E. Drewes 105 Sewage Becomes Heat Energy 106 Emscher Conversion: Ecological Restructuring of a Wastewater System

Functional and Protective Structures 109 Protection and Safety, Water and Energy Supply 110 Protection from the Forces of Nature 114 Reinforcing Reservoir Dams: the Sylvenstein Dam Pilot Project Peter Rutschmann 116 Challenges in the Discourse Between Technology and Society Peter Rutschmann

Table of Contents

119 Engineers as Entrepreneurs – Influences on the Development of Civil Engineering and Society Roland Pawlitschko 124 The TUM Hydro Shaft Power Plant Innovation Peter Rutschmann

Offshore Wind Turbines 127 Wind Becomes Energy 128 Electricity from the Sea 130 The Energy Transition as an Assignment for Civil Engineers Christian Dehlinger 133 Floating Wind Farm – Hywind Scotland 134 Floating and Self-Erecting: TELWIND 135 Flexible Membrane Wings for Wind Turbines 136 The Role of Environmental Engineers in Limiting the Side Effects of Modern Technology Joachim Scheuren, Carl-Christian Hantschk

MOBILITY + TRANSPORTATION

162 The Development of Tunnel Construction and Tunnelling Machines Roberto Cudmani 166 Traversing Mountain Ranges 168 Geodesy – a Breakthrough Success Thomas Wunderlich 171 Using Tunnels for the Extraction of Geothermal Energy Roberto Cudmani

Cable and Suspension Bridges 175 Overcoming Distances 176 Linking Continents 178 Spanning Farther 180 Shortening Journeys

Traffic Technology 183 New Mobility 184 Mobility and Traffic as Dynamic Fields for Engineers Fritz Busch 188 Diagonal Crossings: Oxford Circus 189 Cooperative Systems

Construction of Roads and Railways 141 Gaining Access 145 Record Heights: the Zugspitze Cable Car 147 Slab Tracks for Rail Traffic Stephan Freudenstein

Outlook 192 Future Challenges for Civil Engineers Werner Lang

Beam Bridges 151 Bridges into the Future 152 Integral and Semi-Integral Bridges 154 Ulrich Finsterwalder and the Development of Cantilever Construction Cengiz Dicleli 157 Improving Quality and Efficiency through Procurement ­Procedures Involving Supplemental Offers and Alternative ­Proposals Roland Pawlitschko

Appendix

Tunnel Construction

Introductory texts and project descriptions are written by the curators of the exhibition.

161 Below the Water and Through the Mountain

198 Biographical Listing of Engineers 209 Index of Names 209 Project Index 210 Subject Index 211 Picture Credits 212 References 213 Authors, Panel of Experts and Specialist Advisors 216 Imprint

Engineers in the Building Sector

“The innovative power of engineers ensures the viability of our highly developed national economy and an appropriate standard of living. It is therefore imperative for both our self-preservation and for the successful advancement of society to value and esteem engineers and their achievements. Engineers in the building sector must position themselves in the public sphere in a manner that is commensurate with their importance and their responsibility.”1 With its mission statement, the Bayerische Ingenieurekammer – Bau (Bavarian Chamber of Civil Engineers) expresses the relevance and the duty of this branch of the engineering profession. Innovative power, entrepreneurship as well as design and practical abilities are essential characteristics of engineers in the building sector.2 Their services, such as the provision of needs for safety and security, water supply and wastewater removal, energy transformation and distribution as well as mobility, prove that life as we know it today would not be as fulfilling – or indeed possible – without them. But despite the key role they play in satisfying the fundamental requirements of our civil society, and specifically of a good communal coexistence, our knowledge of the tasks and accomplishments of engineers in the building sector is relatively limited. Even the great economic importance of the building industry, which in Germany has a total annual revenue of about €340 billion and employs more than 2.7 million people (2015) 3, does little to improve this state of affairs. According to the authors of “Zwischenruf”4 (“Interjection”), published in 2006, the serious consequences of undervaluing the importance of engineers in building include not only a shortage of skilled workers and a lack of consideration in the allocation of research

Preface

funds, but also the resulting loss in the quality of our infrastructure and thus in the material and cultural foundations of our lives. The duties of engineers in the building sector encompass a wide spectrum of activities that are relevant to our everyday existence. Aside from the design and construction of civil engineering structures and other individual built works, these also include facilities for gas and water supply, for hydraulic structures and for the removal of gasses, substances (including liquids that can endanger the water supply) and waste. Without structural engineers, surveyors and geotechnical engineers, the design and implementation of these types of buildings and installations would be impossible.5 Many of these spheres of activity occupy intersections with other disciplines and require different modes of thinking. An example of such a field is traffic planning, in which the goal is an integrated development of settlements and transportation systems with an eye to the interactions between space and traffic at an urban and regional level. In addition to the interdisciplinary angle, a visionary thought process is also important. To develop concepts for the immediate future, one must be able to consider a change in mobility behaviour just as one must be capable of imagining the coming effects of digitisation and technological advances on our society. Beyond the spheres of activity mentioned, engineers in the building sector also cover a wide range of consulting work that is important for our society. Work in this category is drawn, for example, from fields in building physics such as thermal insulation, energy balancing, building acoustics and noise abatement as well as spatial acoustics.

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1 Mission statement of the Bayerische Ingenieurekammer – Bau, http://www. bayika.de/de/kammer/index.php?navanchor=2110000 (7 August 2017). 2 Similarly to the mission statement quoted in the opening lines, the 2006 ­article “Zwischenruf: Verantwortung und Ansehen der Bauingenieure – ein Aufruf” draws attention to the central role of the profession in the design, construction and preservation of the infrastructure that shapes our lives. In: Bautechnik 10 / 2006, p. 737ff. 3 https://www.bundesstiftung-baukultur. de/sites/default/files/medien/78/downloads/bbk_bkb-2016_17_low_1.pdf (7 August 2017). 4 see note 2. 5 see HOAI Paragraph 41, http://www. hoai.de. 6 see note 2.

Opposite  Drawing of the triangulation net for the “Determination of the St. Gotthard Tunnel Axis” taken from the report of the same name by the civil engineer Otto Gelpke in Der Civilingenieur 16/1870

In order to act sustainably in the fulfilment of a social mandate – against the backdrop of global challenges such as climate change, environmental destruction, competition for ­resources and demographic change – it is more important now than ever to redefine the building-related responsibilities and tasks that arise from these challenges. One aspect of this approach is to consider the interactions of buildings and other infrastructure systems with the environment from the initial planning stages, with particular atten-

tion to resource consumption, emissions and their associated economic and sociocultural concerns. Analogue and, increasingly, digital methods and tools used in analysis, modelling and synthesis support design and construction processes and enable engineers in the building industry to confront and successfully address continually changing and more complex challenges in the service of society. To ensure that this ability remains secure in future, engineers in the building sector must “fight for improvements in their professional standing in order to be able to continue living up to their civilisational and cultural responsibilities. In pursuit of these aims, they must consistently adapt the quality of their work in research, education and practice to the people’s needs, and they must campaign for social recognition by making it clear that in engineering, too, quality has its price.”6 The promotion of these goals was the primary motivation for the exhibition Visionäre und All­tagshelden. Ingenieure – Bauen – Zukunft ­(Visionaries and Unsung Heroes. Engineers – Design – Tomorrow) as well as this accompanying publication. The exhibition was conceived by the Oskar von Miller Forum in collaboration with the Museum für Architektur und Ingenieurkunst Nord­rheinWestfalen e.V. (M:AI). Its goal is to represent the work of all engineers in the building sector as it really is: of central, civilisational importance, as well as being multi-faceted, exciting, fascinating and innovative from both a cultural and technological perspective. This recognition is important for society and its comprehension of and regard for the profession, but also for the education of engineers in the building field. The exhibition is therefore designed specifi­

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Enginieers in the Building Sector

cally to address students and the new generation of engineers. The significance, range and depth of the creations and work of selected outstanding engineers are illustrated. Taken from historical to contemporary times, projects are used to show the conditions under which the engineers were or are active and how their work must be evaluated in its societal, political and economic context. The focus lies not on projects that are impressive by virtue of their superlative qualities, but rather on those that have provided or are providing a significant stimulus and have paved the way for future building trends. Following an introduction by philosopher ­Wilhelm Vossenkuhl, this publication is separated into four basic sections. The first section deals with the development of the engineering professions, starting in the mid-17th century when the first textbooks on the subjects of hydraulic and bridge construction were published. Soon after, the first networks and alliances were formed, which played an important role in the exchange and communication of knowledge and experience and thus contributed to the spread of civil engineering. Female pioneers in the civil engineering branch – representative of the developing role of women in engineering in general – are portrayed. An overview of the education of engineers in the building sector, presenting the changes this training has undergone over the centuries, and a contribution outlining the importance of aesthetics in engineering culture round out the section. Proceeding just as in the exhibition, the three following sections address the fundamental needs of society and the challenges for building engineers that arise from these needs. The basic human need for shelter and security is explored in the section “Enclosure + Space”. This section includes contributions on contemporary developments in materials, in computation, simulation and construction methods as well as in building technologies. “Water + Energy” deals with the need for a sustainable and reliable supply and with the scope of tasks associated with this need. Urban water supply, defences against the forces of nature and the provision of energy are presented in this section, along with the interrelationships between technology, society and entrepreneurship. These are contextualised by the energy transition, which represents an important opportunity for building engineering. The necessity of the transportation of goods and the human need for connecting and net-

Preface

working are covered in the section “Mobility + Transportation”, which highlights the many options that exist for making spaces accessible, be they on land, underground, on water or in the air. The section also explores themes such as improvements in quality and efficiency and ground-breaking developments in geodesy and construction methods. A discussion of new, sustainable mobility concepts concludes the chapter. The section “Outlook” appended to the main body of the book describes trends that are already evident, and the challenges for building engineers that arise from these trends. Engineers’ relevance in future advances in technology and research, considered within the context of rapidly changing societal expectations, shows that they will continue to be in urgent demand as their critically important services to society secure a pathway for future sustain­ able development. This publication would not have been possible without the contributions from specialists who adopted the idea for the book with great enthusiasm and supported it with their substantial efforts. The same can be said of the advisory board for the exhibition and the other experts who acted as consultants. We would like to extend our special thanks to all of them. We would also like to thank the institutions that were closely involved with the content and the creation of the exhibition, such as the Oskar von Miller Forum – an educational initiative of the Bavarian construction industry – and the Museum für Architektur und Ingenieurkunst NRW e.V. (M:AI), as well as their employees. We hope that this publication contributes to a general understanding of how engineers in the building sector have always managed, even under difficult circumstances, to respond to the needs and challenges of society in a solution-oriented, economical, responsible and innovative way. They possess the critical ability to recognise and proactively address the questions and tasks of the future. This ‘inventive response’7 is one of the essential characteristics of constructive engineers and will continue to distinguish them as the inventors, designers, entrepreneurs and service providers of our society for many years to come. Werner Lang, Cornelia Hellstern Editors

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Peter Rice states the following as a ­­ relevant guiding principle for engineers: “I would distinguish the difference between the engineer and the architect by saying the architect’s response is ­primarily creative, whereas the engineer’s is essentially inventive.” See ­Martin Trautz: “Baugeschichte oder Bautechnikgeschichte?” Views on the topic “Was ist Bautechnikgeschichte?” in the context of the 1st International Congress on Construction History, ­Madrid 2003. https://gesellschaft.bautechnik­ geschichte.org/was-ist-bautechnik­ geschichte (7 August 2017).

Wilhelm Vossenkuhl

Designing Life

There is probably no greater praise than being singled out as someone who sets new standards. Achievements that merit this distinction are usually conspicuous, instantly recognisable, often spectacular. But there are standards we have become so accustomed to that we do not notice them anymore. They are part of our everyday existence, shaping our lives in ways that we no longer consciously perceive. Though they are unspectacular, they are inextricably integrated into our existence as a part of what the French sociologist Pierre Bourdieu called “symbolic order”. Engineers in the building sector have set many standards that people eventually came to see as commonplace. But they have also set standards that remain spectacular. In many of these works, entire buildings or even just roofs appear to float weightlessly above the ground, seeming to defy gravity. We are impressed by these sights and marvel at them, yet over time, like all magnificent things, they take on a museum-like quality, becoming objects of memory and threatening to fade into obscurity entirely. The everyday, on the other hand, is a lasting part of life precisely because we don’t have to think about it – or because we only notice it when it is no longer available. The standards that are part of our existence shape our perception, even if they themselves fade from notice. Like our native language or our dialect, they are part of who we are. We often pay attention to the bridges we cross – to name but one example – only when buffeted by wind gusts. We do not see their structures, the safety and elegance of their design, the refinement in the connections among elements, the interplay of building materials with mathematics and physics. It is a matter of course, below our level of aware-

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ness, that the extraordinary achievements of engineers characterise our everyday lives. We do not doubt their quality or reliability. It is, after all, exactly what we expect and take for granted. But that which guarantees our normality is intricate – extremely exacting and complex, and replete with conditions and constraints that are all unique. And this is not only the case for tunnels being excavated for underground rail lines, as is happening right now in the centre of Stuttgart. The Swiss art historian Jacob Burckhardt postulated that art creates a “total picture of mankind”. In doing this, art hews to a comprehensive, all-encompassing standard. This is keenly observed, since art concerns the whole of life. When we look for a label to describe all the many standards to which building engineers must conform, we should likewise speak of a comprehensive, all-­encompassing standard. Included within it are material sciences, structural and building physics, ecology, design and – more recently – ethics. What important standards for the shaping of our existence could there be beyond these? The expression ‘total picture of mankind’ is a bit pompous and can stay in the art world. For the art of building engineers, it is enough to speak of the ‘full picture of life’, which they design or at least have a main role in designing. We want to drink clean water, drive on safe bridges, live in good, earthquake-proof and attractive houses and enjoy the appearance of the cities in which we reside. Engineers in the building sector play no small part in our health and well-being, in our joie de vivre, maybe even in our happiness; and most certainly in environmental conservation and in energy production, both the clean and the not-so-clean kinds. Similar claims can also be made generally for many other scientists.

Designing Life

But there is a difference. In every little step of their work, in every single project, engineers in building think about the entirety of the living condition and not only of the solution to a single isolated problem – and they must think of the big picture. Building materials and struct­ ural engineering are as inseparable from health concerns as they are from questions of cost-­ effectiveness or urban development planning or environmental protection. This overall responsibility is hard to top. Whether and how well it is attended to is, of course, a different question. Since Antiquity, the areas of expertise of building engineers have grown in tandem with scientific developments. In the construction of pyramids, temples, churches or palaces, of water conduits or sewers, the level of civil engineering technology has always served as a gauge of cultural development. The notion that human beings are the creators of their own identity is broadly applicable to every individual. It could possibly apply to entire societies as well, provided that the societies have a sufficient number of skilled designers whom they support and whom they furnish with all the freedoms that they require. This depends on the prosperity of a society, but not exclusively. It also depends on the schools and universities in which designers are educated, on their talents and, last but not least, on cultural traditions.

Preface

Sometimes present and future design tasks rely on the invention of a new tradition.1 World War I was followed by the design traditions of the Bauhaus; after World War II came the Ulm School of Design. Certainly we cannot complain of a lack of traditions over the past 100 years. But one’s own identity should not be cobbled together thoughtlessly from mere copies of existing traditions. If Friedrich Nietzsche is right, even traditions serve life, but only if we maintain a critical relationship with them. We can gain strength for the future through a critical examination of the past. Criticism here means the ‘ability to discern’ between what should be preserved and what ought to be forgotten. If we maintain a critical relationship to tradition, we can invent our own traditions even by drawing on the past. What other way is there? The new cannot exist without the old just as there is no future without the past. Otl Aicher assigned engineers in the building sector a special role in the designing of our lives. He believed that engineers such as ­JOSEPH PAXTON, ISAMBARD KINGDOM BRUNEL and ­August von Voit ushered in the First Modernity with their glass palaces. Technology stood at the forefront. Then architects like Le Corbusier, Ludwig Mies van der Rohe and Peter Behrens, inspired by painters such as Piet Mondrian and Wassily Kandinsky, gave rise to

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1 Winfried Nerdinger described this in “Die ‘Erfindung der Tradition’ in der deutschen Architektur 1870–1914”. In: Werner Oechslin (ed.): Geschichte Macht Architektur. Munich 2012, pp. 69 – 79. 2 Otl Aicher: “the third modernism”. In: The World as Design. 2nd edition, Berlin 2015, pp. 40 – 61.

Opposite  View of the south side of the Crystal Palace in London (GB) 1851. Sir Joseph Paxton asked Isambard Kingdom Brunel to consult on this project. Below  Facade of the Centre Pompidou along the Rue du Renard, Paris (F) 1977, Peter Rice and Ted Happold (Arup), ­architects: Renzo Piano and Richard Rogers. Fascinated by the material cast iron and the associated manual workmanship, Rice developed the so-called gerberettes (in the style of Heinrich Gerber) of cast iron for the Centre Pompidou. These were manufactured by the same company that had been responsible for the cast steel elements of the Munich Olympic roof a few years earlier.

the Second Modernity. This stage was characterised by the formal as well as the structural. Finally, the Third Modernity began as a fusion of elements from the first and second, evident in the buildings by Norman Foster, for instance. The Third Modernity was not only formal but structural. For Aicher, the Centre Pompidou by Renzo Piano and Richard Rogers exemplifies this well.2 The Third Modernity currently stands poised on the threshold of the past. Will there be a Fourth Modernity? It would have to be one that not only provides the whole of life with an external form, but enables us to live safely and well. Every courageous transition thus far has had to fight opposition. The first heyday of engineering was met with great scepticism. It took the totalitarian Nazi state to stop the Second, architectural Modernity, but it had already been reviled by many beforehand. Even the Third Modernity encountered condemnation and plenty of rejection. It would be naïve to think that creating an existence on

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our endangered planet could happen without courage. If a Fourth Modern period succeeds, it will only do so against the opposition of those whose material interests outweigh the protection of life. Since time immemorial, human beings have longed for the ability to predict the future – through magic and wizardry in earlier eras and scientific prognosis and planning later on. No matter how intense this yearning was, it invari­ ably met with disappointment. However, we can learn to take that dreamy but also dull and ultimately strained feeling of longing and transform it into action, freeing us from false hopes. We can draw strength from our new-found freedom to develop a new form of living. If such a thing is possible now or at all, building engineers will be the first to know. And they will possess the curiosity to figure out how to do it. We should encourage their curiosity and challenge their creativity. They should set new standards again, no more and no less.

Designing Life

On Inventors, Entrepreneurs, Problem-Solvers and Designers

Civil and Building Engineers – the Emergence of the ­Professions

The engineering specialisations known by the modern terms civil and building engineering can trace their roots back to the very beginnings of civilisation and were already very ­sophisticated during Roman times. Hy­draulic engineers focused on managing water for the benefit of humankind: they redirected natural water sources for use in irrigation, provided potable water and removed and treated wastewater, drained land and managed floods, and created waterways to facilitate navigation. Such projects demanded moving large amounts of earth and building masonry structures for channels and dams. Bridge engineers built structures for crossing ­rivers, and ­ ater. All aqueducts for the transport of fresh w this construction required accurate surveying and land measurement methods. Military and civilian construction projects both required the same engineering skills and, in fact, usually employed the same people. Only once these fundamental requirements of civilisation had been provided, and relative peace reigned, ­ ngineers able to devote their efforts were e to non-military projects such as the religious, commercial and civic buildings of ancient Greece and Rome, Renaissance Italy and the European Enlightenment of the 18th century. In modern times, researchers studying the careers of the great historical figures involved in construction have succumbed to the somewhat romantic tendency of labelling them as ‘architects’ to distance them from the bloody world of war. However, Vitruvius was trained as a military engineer to build defensive earthworks and fortifications as well as bridges and large weapons of war. After his military service he was commissioned to manage the ­water supply (presumably of Rome) in addition to various civil construction projects. Filippo Brunelleschi worked for many years on the

­ anmicheli, fortifications of Florence; Michele S ­ rancesco di ­Giorgio the large Sangallo family, F ­M artini – who among other things was responsible for Siena’s water supply – and even ­Leonardo da Vinci were also all military engineers. During the Renaissance it was still common for the same civil and building engineers to work on military and non-military projects alike.1

Civil engineering in the Age of Enlightenment and in the Industrial Revolution Civil engineering in the 17th and 18th century focused on water management – land drainage, water supply and navigation – and on building roads and bridges. In France, especially, civil engineering works were considered to be of national importance for economic and commercial as well as for military purposes. Between 1662 and 1671, the Minister of ­Finance Jean-Baptiste Colbert increased the state expenditures on roads and ­bridges from 22,000 to 623,000 pounds (livres). In 1666 he also commissioned the civil engineer PierrePaul Riquet to build the 240-­k ilometre-long Canal du Midi linking the Mediterranean with the Atlantic Ocean. In 1669, Colbert ­created a Corps des commissaires des ponts et chaussées (Corps of Commissaries of ­Bridges and Roads) which, in 1716, became the Corps des ingénieurs des ponts et chaussées (Corps of Engineers). The first technical institute in France dedicated to military and civil engineering and building construction was the Académie royale d’architecture (Royal Academy of Architecture), founded in 1671 under the directorship of François Blondel, who was himself a military engineer and architect for Louis XIV as well as architect of the City of Paris. To attract more recruits and to raise

On Inventors, Entrepreneurs, Problem-Solvers and Designers

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Bill Addis

1

For further discussion on the growth of civil engineering during the Renaissance, see William Barclay Parsons: Engineers and Engineering in the Renaissance. ­Baltimore 1939, reprinted Cambridge, MA 1968. 2 The role of the École nationale des ponts et chaussées in the development of modern civil engineering is described in: Antoine Picon: L’invention de l’ingénieur modern: L’École des Ponts et Chaussées 1747–1851. Paris 1992. Below  Locks at Fonceranne on the Canal du Midi (FR) 1670s, engineer: Pierre-Paul Riquet

the quality of entrants into the Corps des ingénieurs des ponts et chaussées, the École des ponts et chaussées (School of Bridges and Roads) was founded in 1747. By the end of the century, the Corps was responsible for virtually all French public works in all branches of civil engineering. The importance of these two institutions cannot be overstated. They defined the modern civil engineer and developed the model for training engineers which is now used throughout the world. The first important textbooks on civil engineering (which included military applications) were published around this time – among them La science des ingénieurs dans la conduite des travaux de ­fortification et d’architecture civile (1729) and L’Architecture hydraulique (1737–1753) by Bernard Forest de Bélidor.2 In the late Middle Ages, German engineers were world leaders ­ ngineering as well as in metallurgy in military e and mining-related civil engineering, as demonstrated in the great books Bellifortis (c.1405) by Konrad Kyeser (1366–1405) and De re ­metallica (1556) by Georgius Agricola. However, from that time to the end of the 19th century, civil engineering in German-speaking countries did not achieve the same international impact as that of Britain and France. Nevertheless, there were many great German civil engineers in the 18th century who worked mainly on hydraulic engineering and bridge building and on developing a national infrastructure, chiefly for commercial purposes. Caspar Walter was a ­hydraulic engineer and bridge builder from Augsburg and is well-known today for his books Architectura hydraulica (1754), Brücken-­ Bau (1766) and ­Zimmerkunst (1769).

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During this era of emerging globalisation, civil engineering made possible the development and construction of the infrastructure needed to support maritime trade – docks and harbours, canals, wharves and warehouses – for the importation, storage and distribution of high-value commodities and raw materials not available in Europe, such as spices, cotton and silk. Alone among European countries, Britain developed the industries that converted these imported raw materials (mainly cotton and silk) into products (textiles) that could themselves be exported, generating vast profits. From the 1750s, this enormous trade led to an even greater demand for civil engineering works in harbours, as well as to a boom in the construction of multistorey textile factories and the manufacture of textile machinery. While early factories had been powered by water wheels, the second half of the 18th century saw water power replaced by steam engines. Since the textile factories were all located inland, a huge network of canals was constructed to connect them to the major ports. Demand for bridges and a larger system of roads grew as well. Starting in the mid-1830s, a new railway network for goods – and later for passengers – revolutionised transportation throughout the world. By the 1870s, British railway contractors had constructed not only the British rail network, but also thousands of kilometres of railway lines throughout Europe and in North and South America. The most remarkable difference between developments in Britain and in continental ­Europe was that all the commercial and construction activity in Britain – specifically, the

Civil and Building Engineers – the Emergence of the Professions

creation of the infrastructure for the Industrial Revolution – was financed through private capital, with no significant government contribution. The British government believed that its primary role was to establish and protect the international trade routes with its naval power, thus laying the foundations for the success of private enterprise. The British government needed engineers mainly for the construction of fortifications, both at home and in overseas trading centres. Only in the mid-19th century did government-employed engineers begin work on non-military projects in the British colonies, such as the development of water supply and railway networks in India, the Caribbean and parts of Africa. In the 1750s, JOHN SMEATON became the first engineer to describe himself as a ‘civil engineer’. The term identified him as an independent, non-government engineer and distinguished him from military engineers. This independence enabled him to amass a considerable fortune working on the construction of wind and water mills, canals and bridges. The private-sector British civil engineering entrepreneurs who built the infrastructure for the Industrial Revolution both at home and abroad between about 1750 and 1900 became some of the wealthiest people in the world.3

The new sciences of civil and building engineering During the 18th century, the approach to designing civil and building projects changed dramatically in three ways, heralding the beginning of the modern era of civil engineering. Already in the 17th century, engineers had developed the geometric technique of stereo­tomy for representing in two-dimensional drawings the complex three-dimensional shapes of large stones for use in arches and vaults. However, it was still difficult to use the information in the drawings to cut the stones accurately. The technique was also cumbersome when applied to other common design problems, such as choosing the best location for a fortress that would put it out of range of enemy cannons, or selecting the route for a road or canal through hilly terrain in order to ensure that the quantity of soil excavated corresponded to the amount needed to build up embankments and to fill in hollows. Gaspard Monge was a 20-year-old student at the French military college at Mézières when he developed a new technique called descriptive geometry, which allowed such design calculations to be completed in a few days rather than many weeks. So dramatic was this improvement that the French government

classified it as a military secret, which prevented it from being used outside France until the mid-19th century. The new technique was further developed into projective geometry, which today still forms the basis of all engineering drawings. In addition to using this to determine dimensions in complex three-­ dimensional space, French engineers also developed drawings that succinctly conveyed both the method and sequence of construction. Together, these new techniques gave French engineers considerable advantages over engineers in other countries. The second major development, also in mid18th century France, was the use of complex mathematical techniques (including differential calculus) to solve engineering problems such as the flow of water and the stability of abutments and embankments. Not only did these techniques lead to more reliable designs, but they also defined a new approach to engineering design which was not based solely on past experience and precedent. This new approach to engineering design was essential for the third major development: the introduction of iron as a new construction material into bridge and building engineering: both cast iron, which was very strong in compression though weak in tension and brittle; and wrought iron, which was equally strong in compression and tension, and ductile. Initially, from about 1780 –1830, cast iron was used in Britain as a substitute for stone in the construction of arch bridges because of its great strength in compression and because the overall weight of a cast-iron bridge was less than that of a similarly designed stone bridge. During the same period, cast iron replaced timber in columns

On Inventors, Entrepreneurs, Problem-Solvers and Designers

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3 The emergence of civil engineering contractors during the age of canals and their even greater success during the railway age is described in: Hugh ­Ferguson, Mike Chrimes: The ­Contractors. London 2013. 4 For a discussion on the introduction of iron into building construction, see Bill Addis: Building: 3000 Years of ­Design Engineering and Construction. New York / London 2007.

Above  St Katharine Docks, London (GB) 1826 –1828, engineer: Thomas Telford Opposite  Pont de la Concorde, Paris 1787–1791. The drawing shows the design, construction sequence and method.

and beams of multistorey factory buildings because of its superior resistance to fire. Wrought iron was first used in France in the 1780s as a fire-resistant replacement for timber in roof structures. However, it found its most dramatic and unprecedented use in suspension bridges in the 1820s and in railway bridges in the late 1830s – applications for which no traditional construction material was suited.4 The main reason why the introduction of iron heralded a fundamental transformation of the engineering profession between around 1780 and 1850 was that, unlike for the use of ­traditional materials – timber, stone and brick – there was no body of construction experience to draw upon, and little reliable data on the structural properties of iron. Much early iron construction was essentially experimental, which required careful consideration of three factors – the loads a structure had to bear, the properties of the structural material, and the behaviour of the structure itself. This approach was not usually necessary in buildings made with traditional materials, since past experience was embedded in the design rules governing such construction. Once this new methodology had been developed for iron between around 1790 and 1870, the engineering community was well prepared for a similar period of experimentation and progress with yet another new construction material – reinforced concrete – in the 20th century. This methodology still forms the basis of engineering design today.

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The education of civil engineers During the first flush of civil engineering from around 1750 to 1830, British engineers learned their trade during an apprenticeship and by training ‘on the job’ on actual projects. There was no formal education, and the few available books were very expensive. In the 1820s, a number of so-called Mechanics’ Institutes were founded, first in Scotland and then in the major industrial cities of England. They provided publicly accessible technical libraries as well as courses on mechanical (but not civil) engineering, with workers undertaking their studies on their own time after a ten- or twelve-hour working day. Many well-known mechanical engineers such as James Nasmyth, Joseph Whitworth and ROBERT  STEPHENSON supported these institutes because they recognised the benefit of a technically-educated workforce. The skills taught in the institutes, especially technical drawing and basic mechanics, were also useful for engineers working on civil engineering projects. Mechanics’ Institutes quickly spread to other English-speaking countries, and in Britain, many went on to become the first poly­ technics and later, universities. Nevertheless, the first professional association of engineers, the Institution of Civil Engineers, founded in 1818, did not immediately require its members to have an engineering education. The idea was first proposed by JOHN FOWLER (1817– 1898) in 1866 and finally adopted only in 1896, by which time Germany had about 30,000

Civil and Building Engineers – the Emergence of the Professions

engineers with an academic education from polytechnic institutes and more than 120,000 trained at less academic, vocational Berufs­ schulen (technical schools).5 Formal engineering education and the publication of engineering text books in support of the profession of civil engineering had begun in France in the second half of the 18th century (see “On the Education of Engineers”, p. 30). The first German Polytechnische ­Hochschulen (institutes) were founded in the ­ ecades of the 19th century (in Berlin first d in 1799 and 1821, Prague in 1806, Vienna in 1815, Nuremberg in 1823, Karlsruhe in 1825, Munich in 1827, Dresden in 1828, Stuttgart in 1829, Hanover in 1831 and Zurich in 1854). They all followed the basic model created in France. The early ­G erman-language books by Caspar Walter, written between 1750 and 1770, were followed by works by David Gilly on ­hydraulic engineering (1795) and agricultural architecture (1798); by Johann Albert Eytelwein on hydraulic engineering (with Gilly, 1802–1808), hydrostatics (1826), rigid body statics (1808) and perspective (1810) and by Gotthilf Hagen on hydraulic structures (1826). Each of these founding fathers of German civil ­engineering was involved in the early days ­ auaka­d emie (Building Academy) in of the B Berlin, and their many publications became standard texts at the new Technische Hochschule (Technical University) in Berlin and in the ­German-speaking world. As in other European countries, civil engineering in Germany was dominated from the 1830s by all the disciplines involved in the construction of the railways – ground engineering, bridge and tunnel engineering, and the construction of railway buildings. Some of the most eminent figures during this time

were Johann Borsig, FRIEDRICH AUGUST VON PAULI, KARL CULMANN, Johann Schwedler ­ EINRICH GOTTFRIED GERBER. Apart from and H ­Borsig, who manufactured locomotives and iron structures for railways, the others were known especially for their development of new economical bridge structures.6

The professions of civil and building engineer The modern idea of a ‘profession’ arose in ­Europe during the 18th and early 19th centuries, when many learned societies and professional associations emerged from the new approach to knowledge and learning that developed during the Enlightenment. These organisations sought to formalise the scopes of responsibility of their disciplines (for example law, medicine and architecture) and to award exclusive membership to those qualified to practise these disciplines. Both of these aims required agreed bodies of academic knowledge and associated methods of education that differentiated members from tradesmen. Nevertheless, in Great Britain, civil engineering did not fully achieve the hallmarks of such a professional organisation until early in the 20th century. Although JOHN SMEATON had founded the ­ ociety of Civil Engineers in 1771 with the S aim of sharing experience and developing ­engineering knowledge, by the end of the century the society had become more of a dining club than a professional society. In 1818, a breakaway group of young engineers formed the Institution of Civil Engineers (ICE) to promote the profession more effectively. It had little impact until the eminent civil engineer THOMAS TELFORD was elected as its first president in

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5 The emergence of engineering education in several European countries and the USA is discussed in Ulrich Pfam­ matter: The Making of the Modern ­Architect and Engineer. Basel 2000. 6 A thorough study of scientific developments in structural engineering and strength of materials is given in Karl-­ Eugen Kurrer: The History of the Theory of Structures: Searching for Equilibrium, 2nd edition, Berlin 2018. 7 For details of the founding and subsequent development of the ICE, see Hugh Ferguson, Mike Chrimes: The Civil Engineers: The Story of the Institution of Civil Engineers and the People Who Made It. London 2011. 8 A brief history of the VDI is given by Stefan Poser in the chapter “Der Berliner VDI – Das erste Jahrhundert (1856 –1945)” in: Siegfried Brandt, Stefan Poser: ­Zukunft des Ingenieurs – Ingenieure der Zukunft: 150 Jahre VDI Berlin-Brandenburg. Berlin 2006, pp. 89–229.

Top  The railway bridge Mainz-Süd-­ Gustavsburg near Mainz (DE) with Pauli trusses, built 1861-62, engineer: Heinrich Gottfried Gerber Opposite  With a span of 64.3 m, the largest railway station roof of the world at this time: New Street Station, Birmingham (GB) 1854, engineer: E ­ dward Alfred Cowper

1820. The new institution succeeded in raising the profession’s profile, ­especially among influential politicians and civil servants, by locating its headquarters just 200 metres from the ­British parliament building and government ministries (see “Networks of Engineering Expertise”, p. 20). To this day, the institution serves as a means for members to share their engineering experience through regular meetings and publications. It also produces numerous reports to inform the industrial, political and public sectors about major civil engineering issues. Since the beginning of the 20th century, the ICE has also exerted a strong influence on the content of university courses in civil engineering, not only in order to define minimum levels of knowledge for those entering the profession, but also to disseminate changes in scientific and technical knowledge and practice. In this respect, the ICE differs from organisations of professional engineers in other European countries.7 The clearly defined profession of ‘structural engineer’ emerged in Britain in the 1840s, when wrought iron began to be used for long-span roofs in workshops and railway stations, and for railway bridges. The economics and safety of these iron-frame structures depended critically

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on precise calculations of the relevant forces and deflections. Nevertheless, a professional ­association for structural engineers was not founded until 1908, when reinforced concrete came into widespread use; indeed, until 1922 it was known as ‘The Concrete Institute’. Today there are more than a dozen professional institutions in Britain encompassing the various specialist disciplines within civil and building engineering. In conclusion, it should be noted that, largely due to their early efforts in establishing the independence of civil engineers from the government, the nature of British professional institutions differs from those in other European countries. In Germany, for example, there are no directly equivalent organisations. The Verein Deutscher Ingenieure (Association of German Engineers), founded in Berlin in 1856, has always embraced all branches of engineering, and membership of the VDI is not a requirement for engineers practising in Germany. 8 By contrast, all civil engineers in the United Kingdom are required to be members of the Institution of Civil Engineers.

Civil and Building Engineers – the Emergence of the Professions

Networks of Engineering Expertise

For centuries, the knowledge and training of master builders and craftsmen lay in the hands of guilds, masons’ lodges and monastery libraries. Though this knowledge was jealously guarded during the Middle Ages, itinerant monks, master builders and journeymen passed their experience on within relevant circles. This form of knowledge transfer, limited to a small number of experts, changed with the societal and technical developments of the ­R enaissance. In part, this change could be traced back to the attitude of the master builder – the architect – himself, who was now ­recognised as an independent and active party in the building process and was eager to showcase his work for clients and colleagues. In addition, the advent of the printing press and the incremental opening of society facilitated the dissemination of specialist expertise. In tandem with the gradual decline in the importance of guilds that began in the era of industrialisation, the training of master builders and technicians shifted to royal and later to state-run technical colleges and academies. It became a scientific discipline, and therefore became accessible to a larger pool of applicants. New and increasingly effective methods of communication by land and over water promoted the development of global networks, created and extensively used by architects, engineers, technicians and craftsmen.

Associations as networks In the vanguard of industrialisation at the turn of the 19th century, Great Britain constituted the linchpin of this development. In 1771, JOHN SMEATON formed the first Society of Civil Engineers; however, the Institution of ­C ivil Engineers (ICE), founded in London in 1818, was the first professional association

of civil ­e ngineers in the world. Initially this association was meant to bring together as many e ­ ngineers with different educational backgrounds as possible, as building (or “civil”) engineering was not yet recognised in Great Britain as an independent profession. Up to this time, most engineers had been employed by the military to build fortifications, weapons and infrastructure. In 1820, after the founding engineers had tried to attract members to their association for two years with limited success, they offered the first presidency of the Institution to the famous engineer (and later, builder of the ­Menai ­Suspension Bridge) THOMAS TELFORD. His appointment had the desired effect of substantially boosting the membership enrolment, as he used his excellent social and political connections to recruit new members from Great Britain and the United States. At the height of his presidential term, in 1828, the British Crown officially recognised the Institution of Civil Engineers. The recognition, renewed by Queen Elizabeth II in 1975, conferred upon the association great respect and status as the leading organisation for civil engineers, a position which is emphasised by the location of the institution’s headquarters within striking distance of the Houses of Parliament in Westminster. The Telford Medal presented by the ICE remains one of the most sought-after awards for civil engineers. The foundation of this association marked the creation of a first, albeit primarily national network, which was to serve as both model and stimulus for similar organisations in nations throughout Europe. The following years saw, to name but a few examples, the foundation of the Swiss Ingenieur- und Architektenverein (SIA) in Aarau in 1837, the Société centrale des ingénieurs civils in Paris as well as the Öster-

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Dirk Bühler

Below  John Smeaton’s Eddystone Lighthouse was built between 1756 and 1759 from dove-tailed granite blocks joined with watertight cement mortar. Smeaton had previously improved cement as a building material in a series of systematic ­experiments and is thus himself considered a guiding light in cement and concrete research.

reichischer Ingenieur-Verein in Vienna in 1848, and the Verein Deutscher Ingenieure (VDI) in Berlin in 1856. Since the job description of engineers and especially civil engineers is continually changing, these organisations became increasingly complex, giving rise over the past two centuries to specialised branches – usually subordinate, but sometimes parallel subgroups such as building with iron, concrete, or new technologies. At the outset, many of the engineers that came together to form these associations had trained in the military, or had studied subjects such as mining, geodesy, chemistry or mathematics; but there were also mechanics, metalworkers and carpenters who referred to themselves as engineers on the basis of their professional accomplishments and became members as well. A consolidated description of the civil engineering profession and a formalisation of the educational requirements would soon put an end to this. At the beginning of the 18th century, particularly in France and Germany, the engineering corps had given rise to civilian training centres for civil engineers. One of the first was the École royale des ponts et chaussées founded in 1747 under King Louis XV, which became the most famous and important of these academies. JEAN-RODOLPHE PERRONET assumed the ­d irectorship of the school in 1775, at which time it was renamed the École nationale des ponts et chaussées. Because of the steadily growing technical and societal demands on the profession and consequently on the ­education of building engineers, the

ensuing years – especially from the 1830s until World War I – saw a proliferation of vocational schools for craftsmen and building technicians. At the polytechnics, the field of civil engineering was created, which became increasingly uncoupled from the study of architecture beginning around the middle of the century (see “Civil and Building Engineers – the Emergence of the Professions”, p. 14 and “On the Education of Engineers”, p. 30).

Travel forms – and informs – networks Networks and the dissemination of knowledge were not limited to professional societies and schools, but also flourished as a result of travel to the popular sites of technological progress. Just as artists, architects and natural philosophers of the Renaissance flocked to Italy alone or in the retinue of their royal employers, and inquisitive 18th-century travellers sought out pre-revolutionary France as a beloved additional destination, travellers at the start of the Industrial Revolution added Great Britain to the must-see list. First on the programme were the modern steam engines installed in the mines, but the innovative iron ore smelting techniques and the buildings in the new industrial centres were likewise destinations for visitors. Of course the technologies involved in the use of the new building material iron aroused great professional interest. The first cast-iron bridge over the Severn at Coalbrookdale, the cradle of industrialisation, became a tourist magnet when it was built in 1781. From 1819, the focus of attention shifted to the construction site of THOMAS TELFORD’S Menai Suspension Bridge, which was opened to traffic in 1826. Mainly, however, it was the enormously successful nascent railway system that drew engineers, entrepreneurs and businessmen to England. One of the most unusual of the German travellers was Georg Friedrich von Reichenbach, the son of a metalworker. Upon completion of his apprenticeship he was awarded a grant by his Prince Elector to travel throughout England from 1791 till 1793, where he became an “industrial spy” and, upon his return, an “inventive genius”, as his biography lovingly puts it. Von Reichenbach’s “spy journal”, which includes an exact drawing of a steam engine by James Watt, is stored in the archives of the Deutsches Museum. After his return, von Reichenbach gained rapid renown for his scientific and geodetic instruments, which he developed together with entrepreneur Josef von Utzschneider and professor of precision mechanics Joseph Liebherr. In 1808, he became an honorary member of the Bavarian Academy

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Networks of Engineering Expertise

of Sciences. But what really distinguished him as a civil engineer were his hydraulic engineering achievements, such as the brine pipeline from Bad Reichenhall to Traunstein and the innovative pumps that he developed. Also famous for their travels to England a few years later were the architect Karl Friedrich Schinkel and the entrepreneur Christian Peter Wilhelm Friedrich Beuth, who toured the British Isles together from April until August of 1826. They had been commissioned by King Frederick William III to familiarise themselves with new museum buildings, but both were even more interested in all manner of technological innovations and viewed monuments, factories and technical facilities. They used and promulgated their impressions and experiences through their publications, their lectures and, of course, their own works. This tradition of travelling civil engineers, which has now become a matter of course, was con­ xample, tinued in the 19th century by, for e KARL CULMANN (see p. 24) and the engineer Max Eyth, whose literary works pay homage to engineers and their profession and who was thus able to engender enthusiasm for the field in many young people. As a freshly-minted civil engineer, FRITZ ­LEONHARDT travelled to the United States in 1932–1933 as the first (and for a long time also last) German Academic Exchange Service student. On this trip he was able to study, at times from the Klepper folding kayak that he brought with him, the most modern bridges in New York and San Francisco. He also met famous engineers such as OTHMAR AMMANN, Leon Solomon Moisseiff and David Bernard Steinman. He remained in active contact especially with AMMANN. Thanks to his extraordinary knowledge and experiences, after his return LEONHARDT quickly became one of the

most important bridge builders in Germany. Together with Karl Wilhelm Schaechterle and Paul Bonatz he worked on the construction of the Cologne Rodenkirchen Bridge over the Rhine, which was completed in 1941. After the war he became an internationally active ­p ontifex maximus and founded Leonhardt, ­Andrä und Partner, still considered to be one of the world’s leading engineering firms.

Networks through collaboration In the early years of industrialisation, professional networks tended to be centred around family associations; for example, the family of the Swiss joiner and master builder HANS ­ULRICH GRUBENMANN, whose timber-­e ngineered ­structures were famous throughout Europe. In later networks, the family groups increasingly faded into the background as they were replaced by connections formed in professional life. Apprentices, trainees and students who were educated in a firm, studio or business and later became practicing engineers quickly formed networks of expertise. As a consequence the history of civil engineering could just as readily be described on the basis of personal networks, as the following examples illustrate. THOMAS BRASSEY – an arbitrarily chosen gateway into this history – had studied surveying before he accepted his first job at THOMAS TELFORD’S firm. During this time he had come to know GEORGE STEPHENSON and JOSEPH LOCKE. Owing to his successful execution of a building contract for a viaduct that he had won with the help of STEPHENSON in 1835, ­BRASSEY became an entrepreneur and worked profitably in the building of railways, first in Great Britain and later also in France, Spain and other European countries. From his head-

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Above  On 21 July 1826, Karl Friedrich Schinkel made an entry in his journal ­after viewing the Menai Suspension Bridge, which had been completed just a few months before. He wrote of an “admirable, audacious work” on which “no shaking during the carriage crossing” could be felt. He bought “the description of the structure” and made this drawing, in which he impressively highlights the special features of the bridge. Opposite (top)  For the design of the ­Crystal Palace for the first World’s Fair, held in London in 1851, Isambard ­Kingdom Brunel provided advice to its inventive and innovative builder, the ­botanist and architect Joseph Paxton. Opposite (bottom)  Paddington Station was the London terminal of the Great Western Railway, for which Isambard Kingdom Brunel built a glass railway building, drawing upon his experiences during the construction of the Crystal Palace. The station hall was opened in 1854, three years after the Crystal ­Palace.

quarters in Birkenhead he also exported locomotives and steel structures directly overseas. His plan to build a tunnel under the English Channel, however, was incompatible with the political mind of his day. Throughout this time BRASSEY supported other engineers and their innovative ideas. One of these men was I­SAMBARD KINGDOM BRUNEL. His father, already famous as an engineer, architect and inventor, was MARC ISAMBARD BRUNEL, a French Royal Navy officer who had fled to the United States before the Revolution and rose to the position of chief architect of New York City. In 1799, he moved to Great Britain, where he was granted patents for technical instruments and machines. His main achievement there, however, was the construction of the first tunnel under the Thames in London. The unusual feature in this project was his novel tunnelling shield, which spanned the entire bore cross-section and was advanced, depending on the progress of the excavation, with a screw. The invention laid the groundwork for the modern shield drive. Even Alexander von Humboldt visited the tunnel construction site in 1827, at

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which time it was under the management of ISAMBARD KINGDOM BRUNEL, and together with BRUNEL allowed himself to be lowered twelve metres in a caisson to view the work. Having been taught all manner of mathematical and technical arts by his famous father from a very tender age, ISAMBARD KINGDOM ­BRUNEL went on to study precision mechanics in Paris with horologist Abraham Louis Breguet. Armed with these skills, he became a pioneer of technology during the Industrial Revolution, a time during which the belief in societal progress through technology was boundless and everything seemed possible. His original notes and drawings are stored in the Brunel Collection of the University of Bristol. ISAMBARD KINGDOM BRUNEL made a name for himself chiefly through his buildings for an English railway company, the Great Western Railway (GWR), as well as through the construction of steamships and bridges. From 1833, he worked exclusively for the GWR, creating a network of about 1,500 kilometres of railway lines along with the corresponding viaducts, railway stations and tunnels. As Paddington was the terminus of the GWR in London at the time, it became the site of BRUNEL’S new glass station building, opened in 1854. Sometime prior, BRUNEL had advised JOSEPH ­P AXTON, the botanist and architect who designed the Crystal Palace for the first World’s Fair, the 1851 Great Exhibition in London. Drawing inspiration from PAXTON’S expertise, BRUNEL designed Paddington Station – a mutually productive relationship! BRUNEL was able to convince the shareholders of the railway company to build the Great Western, in 1837 the largest transatlantic steamship to date. With THOMAS BRASSEY’S help he was eventually also able to build the Leviathan, later renamed the Great Eastern, which in 1858 was another record holder with a length of 211 metres. ISAMBARD KINGDOM BRUNEL was also involved in the construction of large bridges, for example the Clifton Suspension Bridge near Bristol. The bridge pylons he (and THOMAS TELFORD previously) designed for this bridge were similar to those patented by SARAH GUPPY (see “Women Pioneers of the Big Modern Building Sites”, p. 26), with whom he corresponded extensively. The Royal Albert Bridge in Saltash, finished in 1859, was also designed by him. At 139 metres in length, the spans represented the longest Pauli (or lenticular) trusses that had ever been built. With the top chord comprising a tubular arch in compression and a chain supplying the lower chord tension, the design reflects a highly rigorous concept.

Networks of Engineering Expertise

Networks know no boundaries The Pauli truss employed by BRUNEL achieved technical maturity within another network, this one located in Bavaria. Together with the Glass Palace in Munich, built 1853–1854, the Großhesseloher Bridge (which was finished in 1857 and replaced with a new construction in 1985) was the kingdom’s most prominent civil engineering structure of the 19th century, and its effects spread far beyond its borders. The 259-metre long bridge was part of the Bavarian Maximilian Railway linking Munich and Trieste, and it crossed the valley of the Isar River at a height of 31 metres. The length of each of its two central Pauli trusses spanned 56 metres, while those at the ends were 30 metres long. FRIEDRICH AUGUST VON PAULI, from whom the truss takes its name, came to the Supreme Building Authority of Bavaria as a senior engineer, and was appointed a professor at the University of Munich and director of the ­Polytechnic. He travelled to Great Britain in 1843 and 1844. From 1841 on he had already been working on the Ludwig South-North Railway and is therefore considered one of the progenitors of the Bavarian State Railways. His first constructions were timber bridges with Howe trusses and, less frequently, Town trusses. One of the first innovations of his professional life was an iron bridge spanning the Günz River near Günzburg; the bridge’s truss, for which he improved the calculation methodology, is considered the forerunner of

the Pauli truss. PAULI worked closely with the Nuremberg-­based iron construction company Klett & Co., which had gained recognition with the construction of the Glass Palace in Munich and in the following years built many bridges with Pauli trusses. By 1870, five large bridges, including the Großhesseloher, and innumerable smaller bridges had been created. But when PAULI retired at the age of 68, the use of the Pauli system in Bavarian bridge construction essentially came to a halt. At PAULI’S special instigation, his colleague KARL CULMANN visited Great Britain and the United States in 1849 –1850 in order to study the many types of truss systems in use there. His publications describing the freer and more innovatively designed timber and iron trusses he saw overseas caused a sensation at home. In 1855, he became a professor at the Techni­sche Hochschule in Zurich. His book, Die ­graphische Statik (Graphic Statics) paved the way for a new theory of frameworks. His students included famous engineers such as MAURICE KOECHLIN. The framework system of the lenticular truss was thereafter improved by PAULI’S student HEINRICH GOTTFRIED GERBER and Karl von ­Bauernfeind. PAULI himself, whose achievements lay more in the realm of organisation, had never written anything about the lenticular truss; it was GERBER who first published an essay in 1865 about what he called the “Pauli” truss. Since the continuous beams that had been used thus far made calculations difficult,

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Above  The Royal Albert Bridge over the River Tamar was built under the direction of Isambard Kingdom Brunel from 1854 to 1859. It boasts two 139-metre Pauli trusses, the longest ever built. The force distribution in both of these trusses is readily observed: the upper chord is formed by a tube under compression, the lower by a chain under t­ ension. Opposite, left  The Walchensee Power Plant in Kochel am See is a high-­ pressure storage power station that was commissioned in 1924. It had been designed and built by entrepreneur and civil engineer Oskar von Miller starting in 1918. Its power output of 124 megawatts makes it one of the largest plants of its kind in Germany to this day. The Pelton turbines are coupled with single-phase generators (installed on 30 October 1924), which are designed to generate electricity for the ­railway. Opposite, bottom  The foundation and construction of the Deutsches Museum became a milestone in the history of ­civil engineering, a development for which we once again have Oskar von Miller to thank. The illustration depicts the state of construction in 1914: at the beginning of World War I, the finished copper roofing had to be taken off again and donated to the state. The museum building, located on an island in the Isar River, was not inaugurated until 1925.

a cantilevered hinged girder represented a practicable alternative. GERBER, who eventually worked at Klett in Nuremberg as a contractor and engineer and later at the Gustavsburg Works of the Augsburg-Nuremberg Machine Factory Corporation (MAN) (see “Engineers as Entrepreneurs”, p. 119) was granted a patent in 1866 for a hinged girder that bears his name. This system was used by BENJAMIN BAKER and JOHN FOWLER in their design for the Firth of Forth Bridge at Queensferry in Scotland, which was built from 1882 –1890 and spans 521 metres. The civil engineer OSKAR VON MILLER and his network, which extended to the United States and Japan, exemplify the state of affairs in the early 20th century. VON MILLER was determined to electrify the Bavarian railways and built storage and hydraulic power stations to supply the necessary electricity. In his first sensational attempt he transformed the hydraulic power of the Neckar River into electrical current and demonstrated that alternating current could be successfully relayed over long distances. In 1891, as the director of the International Electrotechnical Exhibition in Frankfurt am Main, he organised a 20,000-Volt power transfer between Lauffen and ­Frankfurt, marking an important breakthrough in the transmission of alternating currents. The American electrical engineer Nikola Tesla and the engineer and entrepreneur George Westinghouse made use of the German engineer and researcher’s findings when they installed alternating current generators in the Niagara Falls Power Plant, which was completed in 1895 and whose 78.3 megawatts made it the most powerful station of its day. From 1918 until 1924, VON MILLER was the project manag-

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er of the Walchensee Power Plant, which at the time was the largest hydroelectric power plant in the world and boasted an output of 124 megawatts (see “Engineers as Entrepreneurs”, p. 119). VON MILLER’S enthusiasm for technology caused him to draw on his network of contacts in order to found the Deutsches Museum in Munich as a beacon of technology. During the construction of a concrete dome for the Zeiss Planetarium in Jena, he became the nexus of a subsequent network of civil engineers including WALTHER BAUERSFELD, ULRICH ­FINSTERWALDER and FRANZ DISCHINGER (see “On the Development of the Zeiss-Dywidag Shell Construction System”, p. 44). There can be no doubt that the networks of shared information among civil engineers are essential for optimal design and building solutions. By facilitating the exchange of knowledge and expertise, networks contribute to a continual improvement in technological opportunities and increase their potential uses. With their individual abilities and their particular life aspirations, building protagonists do their part by creating masterworks that project their effects far beyond their own times. Especially since the years after World War II, increasingly denser and more effective networks have sprung up, and not just of engineering knowledge. The development of new and ever faster methods of communication, digitisation and specialised publications, ­disseminated also via new media, as well as the merging of different fields of expertise in project-specific collaborations, have all smoothed the way for the largely globalised network of the present day that we all use on a daily basis and as a matter of course.

Networks of Engineering Expertise

Women Pioneers of the Big Modern Building Sites – How They Became Who They Are

Female civil engineers are rare – and brave. Though today they are in demand by industry and universities alike, there are still many fewer women than men involved in building. Female role models can be found only through painstaking research, but they exist: the women pioneers of the great building sites of the Modern Age. Researchers into the history of civil engineering who are looking for its female contributors quickly learn that it was no small matter for them to gain a foothold in the civil engineering profession. In the United States, women were generally granted access to a secondary education at women-only colleges and at some state universities beginning in the 1840s. In Britain, Oxford accepted women in 1919, ­Cambridge not until 1948. Princeton and ­Harvard, as well as the French Grandes Écoles, on the other hand, refused to admit women into a technical course of study until the 1970s. In Western Europe, women were occasion-

ally accepted starting in 1871, while the first woman to graduate from the Swiss Federal Institute of Technology in Zurich did so in 1877. Here, women had been admitted as students since 1855, but it was not until 1918 that the first female civil engineer, Elsa Diamant from ­Hungary, earned her degree. In the German Empire, technical universities opened their doors to women between 1905 (Bavaria)1 and 1908 (Prussia), but in Austria it took until 1919, and only on the condition that their fellow (male) students were not to be disturbed. Only a few spirited women enrolled. Depending on their bearing, they either tolerated or self-­ confidently ignored the overt and covert discrimination to which they were subjected. What they all had in common was their indisputable courage: the women civil engineers of the Industrial Age, who found access to and used technology, and the women of the early Modern Age, who went even further to build their careers on it.

Margot Fuchs

1   Starting in 1899, women were accepted as auditors to what is now the Technical University of Munich, but they could not matriculate until 1905. 2   Madge Dresser: “Sarah Guppy”. In: ­Oxford Dictionary of National Biography, Oxford 2016. Online: www.oxforddnb. com/index/109/101109112. 3   Unknown writer in the Bristol Mercury, 14 December 1939. See also: www.cliftonbridge.org.uk/did-s ­ arah-guppy-designclifton-suspension-bridge (30 June 2017). 4   Richard G. Weingardt: “Emily Warren Roebling”. In: Engineering Legends. Great American Civil Engineers. 32 Profiles of Inspiration and Achievement. Reston, VA 2005, p. 55 ff. 5   ibid., p. 58.

Left  Patents by Sarah and Samuel ­ uppy in Bennet Woodcroft’s AlphabetiG cal index of patentees of inventions Above  Emily Warren Roebling, in a photograph taken between 1860 and 1880 Opposite  Brooklyn Bridge, documentary photograph of opening day on 24 May 1883

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cured the family business a lucrative contract. The Guppys kept company with I­SAMBARD ­KINGDOM BRUNEL and THOMAS TELFORD, the most respected engineers of the time; their son Thomas Guppy was BRUNEL’S assistant. The press, meanwhile, whispered that TELFORD and BRUNEL were using Sarah’s ideas, passing her over as the actual inventor.3 But it was not only as an innovator that SARAH GUPPY made a name for herself. As a businesswoman she invested in suspension bridge projects, was the part-owner of a railway company and contributed to the funding of the Bristol Institute for the Advancement of Science. As an author and reformer she not only participated in discourses on construction engineering, but also drew public attention to societal problems in her surroundings and campaigned for change.

Hands-on and on-site – self-taught doers In the early 19th century, there were families of affluent entrepreneurs in England and the United States in which women had significant standing without being relegated to the roles of housewife and mother, as the societal norms of later years dictated. These were the circles in which SARAH GUPPY moved. She came from a family of metalworkers and sugar traders. In 1795, SARAH married Samuel Guppy, a smelter, manufacturer of agricultural machines and merchant from Bristol. 2 She gained her technical training ‘on the job’ in the informal educational environment of the family business. She developed drawing skills, built a model of a suspension bridge and kept written records of all her technical knowledge. Ten patents were issued to her, ranging from the protection of railway embankments from erosion and landslides by the planting of poplars and willows (1811) to a method for caulking the hulls of ships (1844). While negotiating with the Admiralty one day, she cannily mentioned a patent for an antifouling paint, which se-

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In the second half of the 19th century, in the United States, EMILY WARREN ROEBLING occupied a similar place in society.4 She married the engineer WASHINGTON ROEBLING, the eldest son of the German immigrant JOHN ROEBLING, who was a cable manufacturer, architect and bridge-builder. Together, father and son planned the construction of a suspension bridge over the East River in New York. After the death of JOHN in 1869, WASHINGTON took over as chief engineer of what later became known as the Brooklyn Bridge. When he himself fell ill and was unable to work for extended periods, EMILY kept the construction work on track, since the family business depended heavily on the success of this project. Through self-study she acquired specialist knowledge in mathematics, the strength of materials, catenaries of chains, and in cable and bridge construction. In her daily inspections of the building site she learned the engineers’ language, handled the technical correspondence, and negotiated with subcontractors, materials suppliers, the authorities and public building clients – in constant consultation with her husband and in line with his ideas. From 1872 until the bridge was opened in 1883, EMILY ROEBLING was the public face of the Roebling engineering firm.5 After the bridge was completed, she went on to study mathematics and law in New York, graduating with a law degree in 1899.

Women civil engineers of the Modern Age: elite education and practical experience The engineering elites that came into being in industrialised societies up through the early 20th century believed that a formal scientific education at a university and hands-on experience obtained by working at a public or private

Women Pioneers of the Big Modern Building Sites – How They Became Who They Are

firm were essential for the proper practice of their profession. The young American feminist and graduate civil engineer Nora Stanton Blatch Barney came from an affluent business family. Her father was a brewer; her mother, Harriot Eaton Stanton Blatch, was a teacher, author, women’s rights activist and reformer. Nora regarded the profession of civil engineering as “one of the manliest” of them all, but fearlessly studied the subject at Cornell University anyway, graduating with honours in 1905.6 A few years later she married the inventor and electrical engineer Lee de Forest. Fascinated by radio technology and early electronics, the two of them ran experiments in Lee’s laboratory, travelled to promotional and sales events in Europe and entertained an enthusiastic public with wireless music and voice transmissions. Nora had probably long held out the hope of combining professional fulfilment with a family life. But de Forest disliked the fact that his educated and clever wife was not content to become just a homemaker and mother but instead wished to keep working, and soon after the birth of their daughter the couple separated. In 1919, Nora married the ship­builder ­Morgan Barney, with whom she had two children. Through a study of the water supply of New York City, as a chief draughtswoman in steel- and bridge-building enterprises and at the New York Water Authority, she amassed practical professional experience as a civil engineer and managed employees. From 1935 on she worked as an independent architect and civil engineer, while as an entrepreneur she also financed and developed building projects. She was denied full membership in the American Society of Civil Engineers (ASCE) in 1916. Though Barney sued for discrimination against women, she lost.7 In 2015 – better late than never – the ASCE posthumously made Barney a Fellow and celebrated her as a trailblazer of present and future ‘diversity leadership’8 in the civil engineering profession.

Knowledge transfer and academic careers The women civil engineers of the Modern Age were often ‘Daddy’s girls’, as the life stories of MARTHA SCHNEIDER-BÜRGER and Elfriede Tungl suggest. Father and daughter enjoyed a close relationship, and through him the women developed a love for technology and science. They often married a colleague, with whom they shared topics of interest, and who perhaps made the alienation the women experienced on the job more bearable. Qualitative interviews and biographical studies support such broad claims, though they clearly do not apply to all female civil engineers of that era.

MARTHA SCHNEIDER-BÜRGER, the eldest of four daughters of graduate engineer Hugo Bürger, graduated from a girls’ school in 1923. As a child she greatly admired her father, who was the construction manager of a steel bridge over the Rhine near Dusseldorf, among other projects. Thanks to him she developed a fascination for the topic and experienced her first eureka moments in statics and strength of materials through his work. In 1923, she enrolled at the Karlsruhe Institute of Technology to study building engineering, transferred to the Technical University of Munich after earning her intermediate diploma, and became the first German woman to earn a degree in civil engineering in 1927.9 She was employed briefly in an engineering firm until it closed. In 1929, she started working at the Beratungsstelle für Stahlverwendung (Counselling Centre for the Uses of Steel) at the Steel Industry Federation, where she remained until her marriage to the civil engineer Max Schneider. Though she subsequently gave up her position – as was, according to Schneider-Bürger, expected of women at the time10 – she kept working for the Beratungsstelle for many years on a freelance basis, with two breaks for the birth of her children. She spoke at conferences on behalf of economic, industrial and professional associations, manned booths at fairs and provided for good communication and networking. She was also active at the Deutsches Institut für Normung (German Institute of Standardisation) and in 1930 self-confidently joined the Verein Deutscher Ingenieure (Association of German Engineers), where she sat on various committees – always with an eye to advancing the role of women in the engineering profession. From the early 1930s until the end of her life, she worked continually on her book of tables Stahlbau-Profile – insiders refer to it as ‘The Martha’ – in which all profile standards, connections and regulations

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6 Cynthia Farr Brown: “Nora Stanton Blatch Barney”. In: American National ­Biography Online, www.anb.org. 7 Ruth Oldenziel: “Multiple-Entry Visas. Gender and Engineering in the US, 1870 –1945”. In: Annie Canel; Ruth ­Oldenziel; Karin Zachmann: Crossing Boundaries, Building Bridges. Comparing the History of Women Engineers 1870 –1990s. Amsterdam 2000, p. 12f. and footnote 31, p. 46. 8 Ben Walpole: “ASCE Recognizes ­Stanton Blatch Barney; Pioneering Civil Engineer, Suffragist”. http://news.asce. org/asce-recognizes-stanton-blatchbarney-­pioneering-civil-engineersuffragist/ from 28 August 2015 (20 July 2017). 9 See also Maritta Petersen: “Martha Schneider-Bürger”. In: Klaus Stiglat (ed.): Bauingenieure und ihr Werk. Berlin 2004, p. 379f. 10 ibid. 11 Walter Mudrak: “Elfriede Tungl” (obituary). In: TU aktuell 06 –1981/ 82, p. 39ff. I wish to thank Dr Juliane Mikoletzky at the university archives of the TU Vienna for important suggestions regarding this biography. 12 Karriereführer.de: “Women in Civil ­Engineering. Perseverance required”. www.karrierefuehrer.de/archiv/berufsbild-bauingenieurin-durchsetzungsfahigkeit-gefragt.html (30 June 2017). 13 Irène Troxler: “Wenn man Gott sein muss, bewerben sich keine Frauen” (“When the job is to be God, women don’t apply”). In: Neue Zürcher Zeitung, 29 December 2014. www.nzz.ch/zuerich/ region/wenn-man-gott-sein-muss-bewerben-sich-keine-frauen-1.18452007 (10 July 2017).

are presented. The newest (23rd) edition was published in 2001 and has since made life easier for thousands of civil engineers. A purveyor of knowledge in the academic arena was Elfriede Tungl, daughter of a business school graduate and commercial school teacher. One cannot help wondering if her father had to encourage her to study…. In 1940 she enrolled at the University of Vienna to study mathematics and physics. Excellent mathematical abilities were considered critical for a curriculum in civil engineering, and Elfriede must have had those, as she made a purposeful switch in 1941 to the Technical University Vienna to pursue a civil engineering degree. As a research assistant at the Institute for the Strength of Materials she gained experience in scientific research, and as deputy site manager of bridge building for the state she gained practical knowledge. Nevertheless, theory and the academic sphere maintained their hold on her. Of the fifteen women engineers who earned doctorates from the Technical University ­Vienna in 1950, Tungl was the only one to earn a Doctor of Technology in civil engineering, and presumably also the first European woman to earn a doctorate in that field anywhere. She went on to complete the postdoctoral qualification as a lecturer in Elasticity and Strength of Materials at university level in 1962 and, in the crowning achievement of her scientific career, was finally granted an associate professorship of Elasticity and Strength of Materials at the Technical University Vienna in 1973.11

“You can do this!” Technical knowledge and the ability to use technology rapidly gained importance during the Industrial Revolution. Access to the techni-

Opposite  Nora Stanton Blatch Barney, shown in a 1921 photograph (left) ­became the first female member of the ASCE, albeit a ‘junior member’. ­Pittsburgh Daily Post, 29 March 1906 (right) Top  Cover of the 2nd edition of Stahlbau-Profile from 1932 Above  Elfriede Tungl (around 1965) Right  Trends in the percentage of ­women in civil engineering (comparison between TU Munich und TU Vienna, as of August 2017)

cal professions was determined in large part by talent and education as well as social standing and connections. Out of this dynamic the engineering profession was born, though women were initially largely excluded from its ranks. But the biographical portraits demonstrate that a few women nevertheless managed to carve out a space for themselves in civil engineering. Why female civil engineering students of the present chose this profession is a question that the online survey Karriereführer 2017 sought to answer.12 The main impetus for the decision is most often given as “personal environment”: parents or siblings in engineering jobs play a role, as does practical experience, for example in building a house, and the school environment, in which teachers recognise and foster a mathematical talent. The formal limitations that once stopped ­w omen pursuing a technical education and gaining specialist knowledge have gone. The field of civil engineering is currently as popular with women as it is with men, with interest rising since 2010. In no other engineering specialty is the proportion of women as high. With the booming building industry and the increasing number of available jobs, the demand for qualified professionals is also likely to continue rising. Some years the number of females applying for interesting positions exceeds the number of women graduates. Clearly, women are highly motivated. In her teaching, Sarah Springman, the rector of the Swiss Federal Institute of Technology and a professor of geotechnical engineering, takes into account the differing behaviour of young women and men. She sees herself as a coach helping her charges to recognise their strengths. While men have a tendency to overestimate them sometimes women need to be told, “You can do this!”13

Percentage of women [%] 31 30 29 28 27 26

TU Munich

25 24

TU Vienna

23 22 21 20 2011/2012

29

2012/2013

2013/2014

2014/2015

2015/2016

Women Pioneers of the Big Modern Building Sites – How They Became Who They Are

On the Education of Engineers

Engineers – what makes them tick, how do they see themselves, what images can be used to describe them? Are they masters of the elements and the first line of defence against the dangers they pose? Are they mathematically and scientifically skilled ‘freaks’, possessed of special talents that should develop unfettered and without a fixed objective? Are they individuals fascinated by the manifestations of their own thoughts and by the possibilities of human ingenuity? Are they inquisitive and laterally-thinking creative individuals who make novel connections and extend them into new territories? Clearly they are the implementers and servants of society, whose manmade creations are structurally different from naturally-occurring objects but complement them in some meaningful way. Through them, scientific knowledge is converted into technological solutions to benefit mankind. A look at the motivations of today’s engineering students shows that each of these individual characterisations falls short. The group as a whole is a colourful collection of people with varying personalities, perspectives and aspirations. Are they masterful, intrigued, enthusiastic, ‘freakish’, curious? Now they stand at the threshold of engineering, where the passion arising from a love of technology and of human ingenuity is invested. The art of an ­engineering education lies in developing the required skills, abstraction and analysis abilities while building on the inner motivation and singular identity of every individual. The process is not ‘one size fits all’, but rather ‘designed to fit’. The final goal is a heterogeneous group of engineers with mutually complementary talents, in which each individual makes ­optimal use of his or her own strengths. And society will profit from its experts, servants and implementers. What society requires

is clearly outlined in Maslow’s Hierarchy of Needs: the foundation of the pyramid, consisting of existential physiological needs and the need for safety, are prerequisites for the needs on higher levels such as, for example, the desire for self-actualisation. Without the artefacts created by engineers – among them heated, dry buildings and infrastructures for mobility, energy and supply – and without a clever balance in the management of safety and unavoidable risk, the base of the needs pyramid will fail. The near-perfect functioning of our enormous systems for supply and shelter seem to be accepted in highly developed countries as a matter of course. A consequence of this is that the causes for this solid foundation – the good, creative work of engineers, for example – remain in the shadows of public perception, and see the light of day only during the (rare) occasions on which things cease to function as they should.

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Gerhard Müller

Structured thinking, not merely fascination

Self-­ actuali­ sation Personal needs Social needs

Security needs

Physical needs

1 Des Vitruvius zehn Bücher über Archi­ tektur. (The Ten Books on Architecture.) Translated by Franz Reber. Stuttgart 1865. 2 Heron von Alexandria: Mechanik und Katoptrik. (Mechanica and Catoptrica.) Translated and published by Ludwig Nix and Wilhelm Schmidt. Leipzig 1900.

Above  Hierarchy of Needs by Abraham Maslow (1908 –1970) Opposite  Example of a sham building: northern structure of the stepped mastaba complex of King Djoser, northern Saqqara (EG), about 2600 BCE

The path of the individual engineer from an ­e nthusiastic student to the accomplished, competent, technically versed expert is challenging and difficult. Likewise challenging and difficult was the development of the entire field of engineering, which reaches back over millennia. A fascination with the physical manifestation of human ideas has always been an important motivation for great accomplishments, even if these – like the enormous ­pyramids of Memphis in Ancient Egypt, 2600 BCE – were ‘merely’ ‘sham’ buildings that, in the absence of reasonable span lengths, offered no appreciable sheltered spaces. Clearly, fascination alone is not enough. What is needed is an intellectual examination of the structure of thought processes and of the ­systematics of learning, as took place in Antiquity. In Ancient Greece, great thinkers came to understand that verifiable knowledge was closely linked to mathematical methods ­(Pythagoras) and that the wisdom of designers lay not in the experience-based skills of the craftsman, but in the possession of concepts and the recognition of root causes (Aristotle). The curiosity of engineers must start with causes, and not just manual skills and pure observation. The separation between a hands-on approach and theoretical knowledge is often great, and bridging the gap takes patience. It is an age-old source of tension between academics and ‘impatient practitioners’. If the goal of an engineering education were primarily to generate on-the-job skills relevant to the practice of the profession, then engineers would certainly have a quicker road to a sense of achievement – at the cost, however, of the more hard-earned theoretical underpinnings. The complicated distinction between theory and practice is a common thread running through educational systems to this day.

Practitioners For many centuries, practical, empirically acquired experiences formed the basis of the knowledge that was passed along from person to person. The comprehensive structural drawings of the work De architectura libri ­decem 1 (from 33 BCE) by the Roman architect, engineer and architecture theorist Vitruvius were widely distributed: in the Middle Ages there were copies in at least 30 monastery libraries. But even now, a wide distribution does not guarantee the best possible, carefully deliberated substance. In the preface to his translation, Franz Reber speaks of imprecision in the depictions, noting that Vitruvius essentially de-

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scribes experiences without relying on scientific evidence. The much more scientific work Mechanica 2 by the Greek mathematician, engineer and inventor of windwheel-driven water pipes, coin-operated machines and theatrical machinery, Heron of Alexandria, survived as a single Arabic translation from the 9th century and was inaccessible until the 16th century. Compared to the writings of Vitruvius, this work would have provided a great deal more food for thought had it been available in the first millennium CE. In late Antiquity and in the Middle Ages there were practically no written works on structural engineering. Building was solid workmanship, lacking a scientific foundation but rich in practical experience that was passed along in cooperative associations (masons’ lodges). Many of the great buildings of the time are therefore documented badly or not at all. The first teaching works for building were written at the beginning of the modern era, among them Leon Battista Alberti’s De re aedificatoria (1452), Andrea Palladio’s I quattro libri dell’architettura (1570) and, later, Jacob Leupold’s volumes Theatrum Machinarum (beginning in 1724), in which empirical findings and experiences are linked with some outlandish assertions and mechanical (mis)interpretations. The practicus Leupold draws distinctions among three types of engineer: the theoreticus, who deals with the theoretical formulation of mechanics; the practicus, who is responsible for the construction work proper; and the empiricus, who operates the machines. To this day, a practicus uses modern theatrum machinariums for his daily work, including ­construction spreadsheets, standards, guidelines and software, in which state-of-the-art ­information and experience are reflected. A theoreticus deals with the overarching concept and the limitations of the available information. The importance of this role is evident when there is no experience to fall back on, and extrapolations and departures from the realm of known parameters become necessary. The goal of an engineering education is to train professionals that manage a continuous synchronisation between the state-of-the-art knowledge of the practicus and the scientific insights of the theoreticus to recognise the limitations of current knowledge and experience.

Liberation of thinking Where was the theoretical conceptual framework? Why did it lag behind over the centuries? In the rationalisations used in support of Christian belief, the traditions of Antiquity played a

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0

ings, but recorded them instead in boldly ­illustrated building manuscripts. This was true for greats ranging from Albrecht Dürer to ­Leonardo da Vinci, the latter of whom touched on many structural engineering topics (for example arch thrust, plate vibrations and stability failure). In references to his papers, which for all their genius contain many erroneous reductions to purely linear relationships, he himself said, “Let it be a collection without order; made up of many pages that I have put together here, in the hopes that they someday find their proper place according to the topics that they address.”3 Both the printing press invented by Johannes Gutenberg and the increasing use of the vernacular in writing made a wide dissemination of thoughts and information possible. A completely novel form of intellectual exchange, a prerequisite to the organisation of ideas, was opened up, among others, by Galileo Galilei. Based on empirical findings, creative thinkers began to map out patterns and formulate theories to describe reality.

1500

On Inventors, Entrepreneurs, Problem-Solvers and Designers

1550

1600

Below  The development of the field of engineering: selected protagonists until the early 20th century, from different ­scientific disciplines and from the practice of engineering

1650

1700

1750

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1800

1850

Ritz 1878 –1909

Galerkin 1871–1945 Kirchhoff 1824 –1887

Hamilton 1805 –1865

Cauchy 1789 –1857 St. Venant 1797 –1886

Navier 1785 –1836

Fourier 1768 –1830

Lagrange 1736 –1813

Euler 1707 –1783

Leupold 1674 –1727 Bernoulli 1654 –1705

Leibniz 1646 –1716

Newton 1643 –1727 Descartes 1596 –1650

Hooke 1635 –1702

Galilei 1564 –1641

Bacon 1561–1626

da Vinci 1452 –1519 Buridan 1300 –1358 750

3 Karl-Heinz Ludwig, Volker ­Schmidtchen: Propyläen Technik­ geschichte. V ­ olume 2: Metalle und Macht. 1000 bis 1600. Berlin 1997. 4 August Föppl: Vorlesungen über Technische Mechanik. Einführung in die Mechanik. 4th edition, Leipzig 1911.

Part of the learning process must include exposure to the manner in which creative ideas are structured, weighed and embedded into models, so that they can then be put into practice, modified or discarded. This requires ideas, reality checks, patience and hard work.

1475 –1564

Michelangelo

1377 –1446

Brunelleschi

Vitruvius 84 – 26 BCE Heron 10 – 70 BCE Philoponus 490 – 570

Plato  428 – 348 BCE

Aristotle  384 – 322 BCE

Euclid  365 – 300 BCE 600

Philo of Byzantium  280 – 220 BCE

569 – 475 BCE

Metagenes Pythagoras  570 – 510 BCE

Philosophy

Natural Sciences

Mathematics

Practice

significant role. Influenced by the philosophies of Plato and Aristotle, scholastics created an integrated system governing the philosophical interpretation of their world. Elements of Aristotelian teachings were ­embedded into aspects of Christian belief. However, while Aristotle coupled materialistic and idealistic approaches to thought in his metaphysics, the scholasticism of the 10th – 14th centuries tended to separate the two. Materialism and idealism were studied in isolation, and the intellectual engagement with the material aspect fell short. In addition to subordinating philosophy to theology, this meant that theology spread out into all areas of thought. The separation of the material world from the dogma of theology necessarily resulted in a speculative treatment of abstract scientific questions and a repression of the importance of sensory perceptions. It was not until the beginnings of skepticism and then the ­Renaissance that an intensive intellectual examination of material reality took place. The rules established by Vitruvius were turned ­ alazzo on their heads, as for example in the P Farnese, in which ­Michelangelo placed heavy upper storeys onto delicate ground floors. ­ ichelangelo, Unlike Filippo Brunelleschi or M many artists of the Renaissance never managed to convert their ideas into actual build-

1900

Describing reality In the 17th century, the quest for knowledge shifted from the metaphysical to the physical plane, from the theologically motivated search for the underlying source of all phenomena to the scientific exploration and description of the world. Freed from the restrictive need to encompass religion and science in a single unifying concept, the search for knowledge could now concentrate on the realities of nature. What concept of self and what systems were now used to describe these realities? An understanding of nature was viewed as the first step towards its dominion (Francis Bacon). In the pursuit of this understanding, the dissection of nature – disseca naturam – was a central tenet: the idea that deconstructing physical processes into component processes and individual actions allows one to understand them. Galileo Galilei used scientific methods to study physical processes in isolation, replacing empirical experiences with scientific experiments and conjecture with mathematically supported claims. This represented a breakthrough in the perception and description of nature. Though paradigms act as guiding principles and aid in orientation, they have also directed and restricted the development of the sci­ ences over centuries. The deterministic observations introduced in the Renaissance, based on causal connections and disseca naturam, the abstraction of systems into subsystems and processes, remain the foundation for ­problem-solving and prediction in civil engineering to this day. The sectioning principle plays a central role in the determination of internal effects.

From natural sciences to engineering sciences Paradigm shifts require courage and curiosity. Research efforts began to organise themselves into academies, beginning in Naples with the Academia Secretorum Naturae, founded in 1560 (and disbanded in 1578 at the behest of Pope Gregory XIII) and with other academies in the urban centres of Europe. The foundations for the engineering sciences were established, among them the reductionist deconstruction of problems, that is, reducing the whole to its parts and “beginning with the simplest and smallest, leaving nothing out” (René Descartes), and following the principle that evidence indicates truth. Galileo Galilei introduced the concept of the experiment, along with the description of quantifiable phenomena of matter; Isaac Newton unified empirically gathered observations into a closed

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mathematical-mechanistic theory, which not only explained these observations but also allowed unknown phenomena to be derived from it. This led to radical abstraction, mathematisation, quantification, and to the predictive potential associated with them. In the natural sciences, further fundamental abstractions led to the development of quantum mechanics and the Theory of Relativity. Phenomena on both atomic and cosmic scales were now accessible. In contrast, the various branches of the more practical engineering sciences use the findings of the discovery-­ driven natural sciences to address only the issues relevant to themselves. Thus, the civil engineering sciences – for example, engineering mechanics – still rely on models and methods based on Newtonian mechanics in absolute space and time, since these are entirely applicable at the scale on which the relevant artefacts exist. “There are no wrong or right theories, but only theories that properly describe specific situations,”4 said the German engineering s­ cientist AUGUST FÖPPL. The focus on N ­ ewtonian mechanics yields no further deepening of our understanding of modern natural science. Does it represent as much of an unnecessary restriction as does increased attention on new descriptors, such as wave-particle duality? Are we lulled by the sweeping success of our use of definite, causal, indisputable, reproducible processes that allow us to analyse and predict accurately? Over time, haven’t the underlying stochastic processes and uncertain values in the semi-probabilistic safety concept been reduced to simple causal links for practitioners, even in the engineering sciences? Aren’t we always discussing how to train engineers to master the intersection of artefact and society even beyond the realm of the causally predictable? Clearly we, too, operate within paradigms and need procedures to question and escape them.

Mathematical and scientific models Abstraction in the engineering sciences relies on models that serve to reduce the complexity of real systems and on the mathematical tools used to describe them. Calculus (René Descartes, Isaac Newton, Gottfried Wilhelm Leibniz) was further expanded by variational calculus to form the mathematical foundations for all physical extremal principles (Leonhard Euler, Joseph-Louis Lagrange), making it possible to describe both the course and the outcome of a process by means of integral and differential equations. The groundwork was laid

On the Education of Engineers

for the mathematical modelling of phenomena through the minimum principle and differential equations; the treatment of problems involving stability, vibration and optimisation now ­acquired a mathematical backbone. But the path to the powerful abstractions of technical and fluid mechanics by way of these model reductions was difficult. Even the development of beam bending theory took over two centuries, from Galileo Galilei to CLAUDELOUIS ­NAVIER. The latter put great stock in the mathematisation of civil engineering, both as a ­teacher at the great French academies, the École ­nationale des ponts et chaussées (founded 1747) and the École polytechnique (founded 1794), and as a practicing engineer. This was a controversial stance; damage to the Pont des Invalides resulting from a burst pipe in a pumping station confirmed the writer Honoré de Balzac in his belief that, unlike in Germany, England and Italy, education in France concentrated too much on theory and too little on practice. Nevertheless, the support of theoretical analysis in France had enormous impact. Napoleon offered a prize for the development of a theory on plate vibrations, which was subsequently worked out in large part by the mathematician Sophie Germain at the École polytechnique. This academy provided fertile ground for further abstractions, such as the separation of structure and materials by ­Augustin-Louis Cauchy und Gabriel Lamé, which allowed continuum mechanics to be applied for any geometry. Armed with the tools of abstracted mechanical-­mathematical models, the Swiss mathematician and engineer Walter Ritz and the Soviet engineer Boris Galerkin developed concepts for using reductive methods to derive approximate solutions from an infinite number of estimator functions, laying the foundations of the modern Finite Element Method. The pathway from problem to possible solution – which proceeds via abstract modelling, estimations, projections and optimisation and culminates in the implementation of a physical artefact that interacts holistically with its real environment – is the essence of engineering. The conscious engagement with each individual step and with its associated responsibilities must not be obscured by the other steps. This is more important today than ever before, since the modern practicus has access to resources whose limits of applicability are known only to the theoreticus.

What about the education of engineers? Traditionally, the central focus of the fields of engineering and their curricula are the artefacts

created by the civil, electrical and mechanical engineering disciplines. Surrounding this core is a careful consideration and identification – as simple as possible and as complicated as necessary – of the relevant disciplines. Since the sciences are in a continual state of development and the artefacts themselves as well as their real-world context are constantly changing, the delineations of the relevant disciplines are subject to perpetual changes. In civil engineering, mathematical and scientific foundations and traditional ­technology-intensive, design- and process-­oriented teaching methods remain paramount. However, contextual developmental needs (societal discourse, the treatment of causally unpredictable risk) as well as ­technology-related requirements ­(digitisation possibilities with cross references to informatics and logistics, Building Information Modelling (BIM)) are becoming increasingly important. In addition, the last couple of decades have seen a veritable explosion in the variety and interdisciplinary relationships of the technical fields. Can a university education be properly completed within the framework and formats that have existed to date? Must the extraordinarily successful path of disseca naturam, created at the end of the 16th century and followed to this day, be adapted in favour of a more holistic approach? What is the best way to integrate new technological topics? While the number of relevant subjects is on the rise, the duration of the course of study remains constant, necessitating a new organisational approach to education. The success of complementary courses of study, in which the topics covered are no longer centred on a given artefact type, but instead on societal challenges (as in environmental engineering), methodologies (as in computational mechanics) or across multiple artefact types (as in general engineering studies or in material science), draws diversely-­motivated students into the engineering sciences who in earlier times might have chosen different disciplines. The two-step system of Bachelor and Master’s degrees can help promote specific talents: a student who begins in one of a small number of introductory and foundational bachelor-level programmes can focus in advanced semesters or in a Master’s programme on a more individualised, talent-based course of study. This approach for the ‘young’ newcomers requires a clear set of rules for the ‘older’ generation who are designing it. Topics of contemporary relevance or topics covering an individual scientist are often either too volatile or too nar-

On Inventors, Entrepreneurs, Problem-Solvers and Designers

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Facing page  The development of the ­research and teaching sectors, as seen through the example of the Department of Civil, Geo and Environmental Engineering at the Technical University of Munich (as of 2017)

1870

1890

1910

1930

1950

1970

1868 Focus Area CONSTRUCTION Materials Science and Testing Metal Structures Concrete and Masonry Structures Soil Mechanics and Foundation Engineering, Rock Mechanics and Tunnelling Timber Structures and Building Construction Mineral Engineering Building Physics Energy-Efficient and Sustainable Design and Building Non-Destructive Testing Focus Area MOBILITY & TRANSPORTATION SYSTEMS Road, Railway and Airfield Construction Urban Structure and Transport Planning Traffic Engineering and Control Modelling Spatial Mobility Transportation Systems Engineering Focus Area MODELLING-SIMULATION-PROCESSES Structural Analysis

together with the Chair of Metal Structures

Hydromechanics Construction Management and Real Estate Management Computation in Engineering Structural Mechanics Construction Law and Project Management

1990

2010

rowly focused to allow for the development of a sustainable, career-spanning skills profile. More than one hundred new designations for courses of study in civil engineering exemplify an undesirable trend in German university education that will need to be reversed. New categories must not be allowed to mask the old practicus versus theoreticus dilemma. Even today, a clear distinction must be maintained between skills that can only be gained through academic study and those that are better attained through on-the-job professional experience. Courses of study should be developed with an eye to the r­esulting skill set, thus avoiding both over-specialisation and overload. The publication Civil Engineering Body of Knowledge by the American ­Society of Engineers (ASCE) is exemplary for its dialogue with engineering practice and for its overall outlook. Its ‘output-oriented’ approach seems more promising than the more ­‘input-oriented’ ideas being debated in Germany, which stipulate that the scope of each subject must be clearly defined. We need to maintain distinctions among academic knowledge, skills and expertise gained gradually by repetitive exposure in diverse formats, and supplement these by a ‘hidden curriculum’, in which experienced professors authentically convey the way engineers think and work. The development of engineering has always reflected an interaction among mathematics, philosophy, observation and practice. Different elements of this interplay were dominant at different times. The success of the causal links of the past few centuries has been exciting. However, previously unintegrated natural and social scientific findings, opportunities arising from digitisation and a stronger regard for individual talents have opened up new possibilities. We require a new broadening of our perspective to encompass a holistic approach, so that changes in technological processes and their associated risks and opportunities can be interlinked with societal processes. Without the creativity of universities, neither the mathematisation of the 19th century nor the digitisation and talent-­d riven expansion of the engineering sciences in the 20th and 21st century would have taken place. The need for universities remains strong!

Computational Mechanics Engineering Risk Analysis Computational Modelling and Simulation Focus Area HYDRO- & GEOSCIENCES Hydraulic and Water Resources Engineering Urban Water Systems Engineering Engineering Geology Tectonics and Material Fabric Hydrology and River Basin Management Hydrogeology Landslide Research Geothermal Technologies Focus Area GEODESY Geodesy Cartography Photogrammetry and Remote Sensing Astronomical and Physical Geodesy Land Management Satellite Geodesy Geoinformatics Remote Sensing Technology Geodetic Geodynamics Signal Processing in Earth Observation

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On the Education of Engineers

Engineering Aesthetics

Structural engineering combines apparent contradictions – science and art, intuition and empiricism – but its full creative potential is often underestimated. Creativity in engineering goes far beyond the usual intuitive interpretations of the basic principles of physics and geometry and of the building code to establish new, non-standard techniques. A structure is often discussed merely in terms of economy and efficiency, but it also incorporates aesthetic factors. The combination of both aspects is crucial, as the Spanish engineer EDUARDO TORROJA has observed: “The functional purpose and the artistic and structural requirements must be considered integrally from the initial conception of the project. The artist should not be required at the last moment to give artistic appearance to what is already completed, and the technician’s task should not be limited to only devising means of keeping the structure up. Both should work together to form an integrated whole.”1 The engineering discipline, at its very best, forms a complex synergy that OVE ARUP called “total design” or “total architecture”, wherein building design, structure, and construction are integrated to form a coherent, intertwined process and project.

to be found imagination, intuition, and experience, and which demands a certain freedom in the creative agent. It adheres, in short, to the same laws as those of artistic creation. Thus it presents to some minds an inconvenience, in that such laws cannot be included in any chapter of the Building Regulations.”2 However, throughout history engineers have not always received the recognition that they deserve as both designers and problem-­ solvers. What is design to an engineer, where do the focal points of innovation lie and what does the creative process of problem-solving look like? What appears in their mind’s eye as they design and what do they want to render visible?3 How do they influence the design of not just the technical elements but of the formal aspects of architecture as well?

In engineering culture there has been a shift in the understanding of structure’s influence on the shaping of form and space, of its relationship to aesthetics and its impact on pragmatic and theoretical concerns. Structures are often presented poetically as an engineering accomplishment, because they both combine and arise from creative and technical thinking. FÉLIX CANDELA, in emphasising efficiency, economy and elegance, noted that “design and structural design, of course, is an intellectual process of synthetic nature in which is

On Inventors, Entrepreneurs, Problem-Solvers and Designers

36

Nina Rappaport

1 Eduardo Torroja: Philosophy of ­Structures. Berkeley 1958. 2 Felix Candela: Toward a New Philosophy of Structure. Student publication, School of Design, NCSU, 5, No 3, 1956. 3 See Eugene S. Ferguson: Engineering in the Mind’s Eye, Cambridge, MA, 1992. 4 Sylvie Deswart, Bertrand Lemoine: L’Architecture et les Ingenieurs. Paris 1979.

Below  The Penguin Pool at the London Zoo (GB) 1935, Ove Arup Opposite, top  Boots Pure Drug Company, Beeston (GB) 1933, E. Owen Williams Opposite, centre  Raleigh Arena, North Carolina (US) 1953, Matthew Nowicki / Fred Severud Opposite, bottom  Spiral ramp inside the Fiat factory at Lingotto, Turin (IT) 1926, Giacomo Mattè-Trucco

Ingenuity A straightforward analysis of etymology yields an interesting fact: The English word ‘engineer’, or in French and German ingenieur, has the same root as the word ‘ingenious’, defined as that which is imaginative and ­creative. The engineer’s work is closely related to creative design, since it involves solving problems in many different fields. Yet engineering is often seen as largely mathematical and empirical rather than aesthetic and intuitive. But the work of the engineer goes far beyond mathematical equations; it is conceptual, drawing on the formal as well as the rational. On the other hand, engineering is not a science, because it is subjective; when two engineers are presented with the same problem, they will provide different solutions. However, the structural feasibility of both approaches can  be tested, and in this way the work is sci­ entific. Some engineers always work with the proven systems known as structural building codes, which are tied to strict parameters, while others use rules of thumb. Some use these rules as a baseline and manipulate them from concept through to implementation with a combination of analysis and intuition. Creativity enters the picture when the manipulation of structure exceeds established norms.

that proved to be more innovative. They experimented with newly available technologies and materials such as iron, steel, and glass.4 This development is evidenced by the introduction of professional engineering courses in architecture schools, but also in the work of early British and French engineers such as Thomas Pritchard, whose Iron Bridge (1779) near Coalbrookdale in England was the first iron bridge ever designed, or in the prefabricated steel bridges and the Eiffel Tower (1889) by GUSTAVE EIFFEL. Structures of glass and steel became a manifestation of a new industrial and technology-based culture. This is especially apparent in the works of JOSEPH PAXTON, who drew inspiration from the giant water lily Victoria amazonica to develop the steel beam structure for the Great Conservatory at ­Chatsworth (1840) and for the Crystal Palace (1851) in ­London. With these accomplishments he shaped the new aesthetics of his time. In the early modern era, engineers experimented with new reinforced concrete systems to develop longer spans and parabolic shells. Examples of this are the works of the Frenchmen FRANÇOIS HENNEBIQUE and ­ UGÈNE FREYSSINET or that of Swiss engineer E ROBERT MAILLART, who designed elegant concrete bridge structures. Experimentation in concrete was also critical for large spans in industrial structures, as seen in the buildings by British engineer OWEN WILLIAMS. Italian engineer ­Giacomo Mattè-Trucco was impressed by the designs of American engineers and experimented with function and spatial structure at the Fiat factory in Lingotto (1926) by building an automobile test track on the roof. PIER LUIGI

Historical context Over the years, there have been critical moments of transformative change in engineering, ushered in by novel materials, new technologies or ingenuity. Especially in Europe during the late 19th century, engineering was considered distinct from architecture both academically and culturally. But by the end of the century, it was often the architectural projects and prototypes designed by engineers

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Engineering Aesthetics

NERVI designed buildings such as the Stadio Artemio Franchi (“Comunale”) in Florence in 1929 using the new material ferroconcrete, a fine mesh of steel wire filled and covered by a thin layer of cement.5 In the mid-1950s, HEINZ ISLER of Switzerland developed thin-walled ­reinforced-concrete shell structures curved on all sides that became true works of art.

The 1950s were a period during which engineering strongly influenced architectural design, and engineers began to collaborate actively with architects. Tecton Architects worked with OVE ARUP, who designed the concrete penguin pool at London Zoo with its thin circular ramps (1934); Fred Severud made possible the unique saddle-shaped design of Matthew Nowicki’s cantilevered roof over the Dorton Arena (1952) in Raleigh, North ­Carolina. Severud’s freeing of the framework to create a non-linear space constituted a break from the rigid normality of grid structures, and served as an inspiration, for example, for Eero Saarinen’s concrete shell over the Yale University skating arena Ingalls Rink (1956) in New Haven, Connecticut. FREI OTTO teamed up with the engineering practice Leonhardt, Andrä und Partner to explore lightweight structures by way of the topographic roof surface of the Munich Olympic Park of 1972. The project exemplifies FREI OTTO’s concept of tensile structures that make use of the economy of largespan membranes. OTTO continued to research these at the Lightweight Structures Institute at the University of Stuttgart. JÖRG SCHLAICH and his team carried on with the investigative work in the Special Research Centre (Sonderforschungsbereich) 64, “Lightweight Planar Structures”, and later on the unit’s leadership passed to Werner Sobek.6 The goal of all of these collaborative efforts was to integrate structure, material and form to shape spaces, synthesising the rational with the creative.

ture, with overlapping responsibilities requiring a paradigm shift from previous eras. Not only are architects today more interested in structure, but engineers have taken on a greater role as designers, blurring professional boundaries, making the design process more flexible and collaborative and greatly expanding the potential for integrated and complex projects. Some reasons for this closely-knit process are the changes in standard design methods; the engineer is involved from the initial planning phase of a project, designing and producing preliminary sketches in collaboration with the architect. Engineers can even take the lead on a project, be awarded commissions and hire an architect to work for them. The engineer’s work is no longer taken for granted but is recognised as a creative endeavour in its own right.

Non-linear structures Engineers are experimenting with new ways to shape space into non-linear forms. Some might call these new forms embodiments of a new structural expressionism8, since they enable new kinds of non-hierarchical spatial experiences. 9 Computer-guided algorithms create a greater potential for non-linear and non-hierarchical projects, allowing for a reproducible form-finding process and a more fluid information exchange. The Japanese engineer Mutsuro Sasaki uses digital models and 3D Extended Evolutionary

Engineers in the designing role Today’s engineers do not just calculate stresses and follow building codes; they test the limits of what is structurally feasible. Of many possible areas of research, two are discussed here: first, an unconventional method of form finding for complex and non-standard or non-linear spatial structures; and second, structures derived from natural forms that give rise to new models, or what could be called ‘deep decoration’,7 a core system of structural purpose and function. Contemporary building practice has transformed the structural design of buildings and infrastruc-

On Inventors, Entrepreneurs, Problem-Solvers and Designers

38

5 Eduard F. Sekler “Structure, Construction, Tectonics”, in: Gyorgy Kepes (ed.): Structure in Art and in Science. London 1965, pp. 89 – 95. 6 As the successor to both Frei Otto at the Lightweight Structures Institute and Jörg Schlaich at the Institute for Construction and Design, Sobek merged the two entities into the Institute for Lightweight Structures and Conceptual Design (ILEK) in 2001. www.uni-stuttgart. de/ilek/institut/ilek-geschichte (25 July 2017). 7 Nina Rappaport: “Deep Decoration”. In: Emily Abruzzo, Alexander Briseno, Jonathan D. Solomon (eds.): Decoration: 306090. Volume 10. New York, 2006, pp.  95 –105. 8 Interview with Greg Lynn. In: Any Magazine, No. 5, Lightness, 1994. 9 Jesse Reiser: Decoration: 306090. ­Discussion at the Architectural League, New York, November 2006.

Opposite  Gardens by the Bay, Singapore (SG) 2010, Atelier One Top  Water Cube – National Aquatics Center, Beijing (CN) 2008, ARUP

Structure Optimisation (ESO) for form finding. Sasaki’s design with curving forms for the Rolex Learning Centre by SANAA at the École Polytechnique Fédérale de Lausanne (2010) is based on principles of self-organisation in nature and offers a non-linear spatial experience. Sasaki’s work on flux structures, shape design, and the structural potentials of flowing forms and spaces reflects an approach without apparent hierarchies.

Deep Decoration – modelling nature Another basis for a new aesthetic is an engineer’s reference to and return to the holistic, spatial structures found in nature that have an internal effect and gain meaning through representative forms. Many engineers are inspired by plants, a spider web, a piece of coral, a beehive, the texture of bone or the interiors of crystals or sponges, all of which provide an understanding of the structure of form. In some projects, these inner structures are clearly visible – their constituent parts, taken together, exist within a network of meaningful and necessary mutual relationships. This is the case, for example, in the bubble structures of the Water Cube National Aquatics Centre, designed for the 2008 Beijing Olympics by the Australian team of Arup and PTW Architects. The structure of ETFE foil cushions forms a connective mesh of cell-like units that connects the surface with the internal structure in

39

one organic whole. The holistic nature of the structure itself becomes decorative. Often the inspiration for formal qualities is metaphorical, as in biomimicry, or an actual physical replica of nature in another material and for a different purpose. The patterns that nature uses to provide shelter can also be adapted to the relationship between climate and contemporary structures. In the Gardens by the Bay project in Singapore by Atelier One and WilkinsonEyre Architects (2012), sustainable methods that mimic nature also harness sun, wind, and water by using trees as climate mediators. These engineering innovations demonstrate that, while architecture has a diverse vocabulary, engineering has a grammar whose ­e lements and syntax can be shifted and ­manipulated to push past the boundaries of the expected, and to make new inventions possible. Thus, engineers do not merely use the pragmatic problem-solving concepts of calculations, economy and efficiency, but also the innovation that allows the limits of spatial and physical structures to be extended to attain ­impressive subtlety and creative expression. The significant and ongoing contributions of present-day engineers blur boundaries within the design professions and create a new ­paradigm that is shaping a future of increasingly complex spaces and our lives within them.

Engineering Aesthetics

Enclosure + Space

Creating Spaces: Linking ­Aesthetics and Structure

The need for protection and security has always been a motivation for the creation of spaces. The cultural and communal goals of different societies are reflected in the way their private and public spaces are designed. At the same time, the designs are often also a demonstration of what is technologically possible. About 200 years ago, exhibition halls and event venues, and later on also aircraft hangars and the enormous spans in railway stations and market halls, represented the vanguard of experimental approaches that led to new geometric forms and innovative uses of materials. Nowadays it is often the smaller projects that lie at the cutting edge. The development of different types of support structure and constructional form is often linked to the use of newly developed materials.

Domes and vaults based on the shapes of tents and huts long dominated structural engineering, until industrialisation and the new material iron allowed the introduction of framework and skeleton structures, which became a new building type and ushered in the era of prefabrication. Though these structures were defined along largely geometric lines, force flows would soon inspire the design of corresponding constructions such as shells (later also ­network and grid shells), folded plate as well as tensile structures (see “Wide and Light”, p. 64).1 In these designs, form finding occurred (and still occurs today) in a number of different ways: through models, simulations, experiments, analytical and mathematical methods or through inspiration drawn from systems and structures of the world’s flora and fauna.

1 Rainer Barthel distinguishes between three categories: geometrically defined structures (orthogonal structures), structures generated from the laws of statics, and free-form structures. See Rainer Barthel: “Form der Konstruktion – Konstruktion der Form.” In: Exemplarisch. Konstruktion und Raum in der Architektur des 20. Jahrhunderts. Munich 2002, pp.  15 – 26

Facing page  ICD / ITKE Research Pavilion 2013 / 14, Stuttgart (DE) Jan Knippers, Achim Menges Left  Centennial Hall, Wrocław (PL) 1913, Günther Trauer, Willy Gehler; architect: Max Berg

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Creating Spaces: Linking Aesthetics and Structure

On the Development of the Zeiss-Dywidag Shell Construction System

What is meant by the terms “Zeiss-Dywidag System” or “Zeiss-Dywidag Shell Construction Method”? How did a Jena-based com­ pany famous throughout the world for the manu­facture of excellent optical systems get involved with the construction company ­Dywidag (Dyckerhoff & Widmann AG), whose own international renown stemmed from its innovative shell and bridge structures? The ­e xciting development of shell construction was made possible through the successful collaboration of highly talented and motivated ­experts and companies drawn from various disciplines, who worked together in order to solve a difficult construction problem.

The invention of the planetarium dome The story began in Munich in 1903 with the foundation of the Deutsches Museum. Its chief creator and first general director was none other than OSKAR VON MILLER, civil engineer and owner of an engineering practice, and a leading light in the water and energy management sectors.1 From the museum’s foundation, MILLER had intended to incorporate an astronomy department with a planetarium. An initial suggestion involved an accessible rotating sheet metal sphere with holes cut into it; when illuminated from the outside, the sphere was supposed to simulate the starry sky as well as the motions of the sun and planets. As this seemed too complicated, an idea was developed to project the image of the night sky onto the inner surface of a sphere.2 Though Carl Zeiss of Jena was predestined to convert this idea into reality, the company did not express much interest in the project at first. MILLER had to make a personal effort to convince them to accept the assignment. Preliminary studies were conducted in Jena from 1912 onwards.3

ENCLOSURE + SPACE  |  Arch and Shell Structures

The project came to a standstill during World War I and Zeiss did not reinitiate its work on the sky projector until July of 1918.4 WALTHER BAUERSFELD, managing director of Carl Zeiss in Jena and himself a mechanical engineer and physicist, delegated the development to one of his employees, who encountered unexpected difficulties during the construction of the light source for the projection of the fixed stars. He wrote a letter to MILLER in which he recommended that the whole project be scrapped. BAUERSFELD was able to prevent him from sending the letter at the last minute. BAUERSFELD decided to take the design into his own hands in order to make his idea of the projection planetarium become reality.5 The highly adept engineer and physicist ­succeeded in developing a projector, but now required a 16-metre diameter domed space in which to test it. Since no appropriate site could be found on the factory premises, the decision was taken to build it on the roof of one of the existing multistorey buildings. This was probably the critical moment that led to the d ­ evelopment of the Zeiss-Dywidag System. The dome structure had to be as lightweight as ­possible in order not to overburden the roof. The decision was made to construct a hemispherical iron lattice, composed of approximately 3,840 rods of 51 different lengths6, which could be ­manufactured with great precision at Zeiss.7 ­BAUERS­FELD’s spatial lattice construction was made of flat bars with cross sections of 8 × 20 millimetres each, connected to one another by a special knot ­consisting of two discs with annular recesses bolted together. At this stage, however, another construction obstacle presented itself: the lattice dome required a covering that was lightweight, weather-resistant on the outside and lined on the inside with a smooth, spherical projection surface.

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Cengiz Dicleli

1 www.wikiwand.com/de/Oskar_von_ Miller (05 May 2017). 2 ibid. 3 www.planetarium-jena.de/90-Jahre-­ Zeiss-Planetarium-Jen.169.0.html (20 May 2017). 4 ibid. 5 The projection planetarium by Carl Zeiss. In: www.deutsches-museum.de/ sammlungen/meisterwerke/meister­ werke-i/planetarium (20 May 2017). 6 Hartwig Schmidt: “Von der Steinkuppel zur Zeiss-Dywidag-Schalenbauweise”. In: Beton- und Stahlbetonbau, 01/2005, p. 87. 7 Bertram Kurze: Industriearchitektur eines Weltunternehmens. Carl Zeiss 1880 –1945. Published by the ­Thüringi­sches Landesamt für ­ enkmalpflege und Archäologie. D Erfurt 2016, p. 64. 8 Walther Bauersfeld: “Die Entwicklung des Zeiss-Dywidag-Verfahrens.” Presen­ tation delivered on 12 December 1942 in Berlin. Printed in: Jürgen Joedicke: Schalenbau-Konstruktion und Gestaltung. Stuttgart 1962. 9 90 Jahre Torkretieren. Torkret AG ­Essen, 2010. 10 see note 6, p. 64. 11 After the Czech civil engineer Josef Melan (1853 –1941), who filed for a ­patent for his process in 1892. 12 www.gdp-planetarium.org/planetarien/ geschichte-der-planetarien.html (14 August 2017).

Facing page, top  Test planetarium in J­ ena (DE) during construction in 1922 Facing page, bottom  Spraying concrete on the planetarium (diameter 25 m, shell thickness 6 cm) in Jena (DE) in 1926

To address this need, in 1922 BAUERSFELD approached the construction company Dywidag, which had already successfully built several projects for Carl Zeiss Jena. August Mergler, one of the engineers from their Nuremberg branch, recalled a process for the “mixing and application of malleable or adhesive materials”8 that had recently been developed in the United States and had been introduced to Germany in 1920 by the company Torkret under the technical term shotcrete, or sprayed concrete.9 It was decided to “cover the structural lattice, after having slightly reinforced it, with a 3-centimetre thick concrete shell using the Torkret process. The smooth inner sur-

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face would be achieved by attaching timber formwork of spherical curvature to the inside of the lattice and spraying the concrete on from the outside….”10 The 3 ≈ 3-metre timber formwork was to be moved as needed as the construction progressed. Of course this meant that the iron grid became encased in concrete and could not be reused. A similar procedure, known as the Melan System, had already been employed in the construction of arch bridges.11 In this application, rigid steel truss girders had been employed both as formwork beams as well as encased in concrete as reinforcement. In 1922, the Carl Zeiss Jena company patented both its “Knot joint connections for iron lattices” (German Reich Patent (DRP) No. 420,823) and the “Procedure for the construction of domes and similarly curved surfaces from ­r einforced concrete” (DRP No. 415,395). In later large-scale constructions, the process was adapted so that the grid was no longer encased in concrete, but was rather used as a framework for the timber formwork, often in two-layer thickness in order to increase the load-bearing capacity of the frame for largespan structures. In 1923, after the planetarium projector had been intensively tested in the trial dome and been publicly celebrated as the “Miracle of Jena”, it was delivered to Munich and officially put into operation at the Deutsches ­Museum in 1925.12 In 1926, projection planetariums opened in Wuppertal-Barmen, Leipzig, ­D usseldorf, J­ ena, Dresden and Berlin, in 1927 in Mann-

On the Development of the Zeiss-Dywidag Shell Construction System

heim, Nuremberg and Vienna, and later also in ­Hanover, Stuttgart, Rome, Moscow, Stockholm, Milan and Chicago.

Dywidag and modern shell construction The origins of modern shell construction described here differ fundamentally from those of historical construction methods for masonry domes. In traditional barrel or dome structures made from natural or artificial stone, the lack of building materials with high tensile strength and a paucity of adequate calculation methods resulted in large cross-­sections. Thus, the Pantheon in Rome, the Hagia ­Sophia in Istanbul, the Duomo in Florence and St Peter’s Basilica in Rome (with a diameter of more than 40 metres and a weight of 10,000 tonnes) all feature domes and walls with thicknesses of a metre or more. The ribbed dome of the Centennial Hall in Wrocław, with its impressive 65-metre reinforced concrete span, weighs 6,340 tonnes. In comparison, the mass of one of the domes of the Leipzig Market Hall,  which has a thickness of 9 to 10.7 centimetres and a span of 80 metres, is a mere 2,000 tonnes. The creation of shell structures of 4 to 8 centi­metres thickness, in which the forces generated are predominantly membrane stresses, was made possible only by the devel­opment of high-strength cements and by advances in reinforced concrete construction and membrane theory. The forces remain relatively constant throughout the cross-­ section and have no components orthogonal to the shell surface. As a result, the cross sections are ­almost completely free of bending moments, with all forces lying within the plane of the shell (membrane forces). The publications by Jürgen Joedicke (Schalenbau – Konstruktion und Gestaltung, 1962) and Franz Hart (Kunst und Technik der Wölbung, 1965) are still good sources for an overview of this topic. During the construction of the test dome in  1922, FRANZ DISCHINGER, an experienced senior engineer at Dywidag, had joined BAUERSFELD’s team in Jena. A year later, having just received his degree from the Technical University of Munich, the highly motivated and ambitious ULRICH FINSTERWALDER became DISCHINGER’s employee. FINSTER­ WALDER’s mechanics professor at the Technical University of Munich, Ludwig Föppl, had awakened FINSTERWALDER’s interest in shell constructions, which led him to write his ­thesis on the theory of lattice shells.13 Therefore he was immediately put to work as ­Dywidag’s liaison in Jena. With BAUERSFELD’s

ENCLOSURE + SPACE  |  Arch and Shell Structures

help he began an intensive investigation of the statics of barrel shells, since it had become clear that these were better suited to covering rectangular industrial layouts than spherical shells. “ULRICH FINSTERWALDER developed the statics of barrel shells (which had previously been advanced by BAUERSFELD and DISCHIN­GER) to perfection. He was able to prove that the original concept of the (DISCHINGER) patent, according to which the advantages of a cylindrical shell take effect only when its crosssection is markedly elevated above the thrust line, was structurally impracticable and that there was an alternate solution. On the basis of his newly calculated bending theory of cross-braced cylindrical shells, he introduced a cross-sectional form of barrel shell that was circular instead of elliptical. […] In 1929, DISCHINGER earned his doctorate at the Technische Hochschule Dresden with a thesis on the load-bearing properties of polygonal domes, while FINSTERWALDER earned his in Munich in 1930 for the above-mentioned theory of rigid shells.”14 Despite their intense internal rivalry15, the long-lasting research done by both engineers made further developments and patents on shell construction possible. Dywidag became the premier company in the field of shell construction. Outstanding engineers such as Anton Tedesco (USA), EDUARDO TORROJA (Spain), FÉLIX CANDELA (Mexico) and many others developed freer forms and created spectacular examples of shell structures all over the world.

46

13 Cengiz Dicleli: “Ulrich Finsterwalder 1897–1988. Ein Leben für den Betonbau”. In: Beton- und Stahlbetonbau, 09/2013. 14 see note 6, p. 69. 15 cf. Dicleli, p. 66.

Above  Test barrel in 1926, Franz Dischinger (left) and Ulrich Finsterwalder (centre) Below  Development of the cross-­ sectional curves of the Zeiss-Dywidag shell vaults.

Form Finding – Graphical Tools, Experiments and ­Models, Numerical Methods

Below  Palazetto dello Sport, Rome (IT) 1957, Pier Luigi ­Nervi, architect: A ­ nnibale Vitellozzi

The publication Graphische Statik (“Graphic Statics”, 1866) by KARL CULMANN presented engineers with a new process for determining forces. PIER LUIGI NERVI used this method to develop his support structures, as did ROBERT MAILLART and ELADIO DIESTE. The characteristic feature of the Palazetto dello Sport in Rome is the self-supported dome, the rib construction of which is visible on its underside. The dome was assembled from 1,620

47

prefabricated reinforced concrete elements in just 30 days. The elements are shaped like flat boxes with slightly protruding edges around their perimeters. When they are put together on the framework the edges form the ribs. The ribs were reinforced and the dome was cast ­directly into its self-supporting form without cumbersome formwork. The loads on the dome are directed via exterior Y-shaped ­supports into the ring-shaped foundation of

Form Finding – Graphical Tools, Experiments and Models, Numerical Methods

prestressed concrete. Structure and form coalesce to form a whole that Nervi referred to as “structural integrity”.

Shell structures – from concrete to wood to steel and glass Shell construction with (reinforced) concrete moved into high gear in the 1960s, with a ­ onstant push to increase span lengths and c

­reduce the thickness of the materials. In addition there was the ongoing issue of the optimisation of the formwork. In their quest for form, engineers such as ULRICH MÜTHER and HEINZ ISLER approached their objective using models and experiments, in which fishing nets and cloth were draped over a desired outline, ­allowed to find their form, and then fixed. As wages rose, shell construction became unprofitable, while at the same time other build-

Top left  Zarzuela Hippodrome, Madrid (ES) 1935, Eduardo Torroja Top right  Félix Candela, Restaurant Los Manantiales, Xochimilco, Mexico City (MX) 1958 Above left  Petrol station at the autobahn rest stop in Deitingen (CH) 1968, Heinz Isler Above right  Parcel Post Hall, Munich (DE) 1969, Ulrich Finsterwalder, Helmut Bomhard, Paul Gollwitzer, architects: ­Rudolf Rosenfeld, Herbert Zettel Left  Bus station in Salto (UY) 1974, ­Eladio Dieste Opposite, top  Great Court, British Museum, London (GB) 2000, BuroHappold, Foster + Partners Opposite, bottom  Elephant House at ­Zurich Zoo (CH) 2014, WaltGalmarini, Markus Schietsch Architekten, Lorenz Eugster Landschaftsarchitektur; digital design: Büro Kaulquappe

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ing materials became more economical to use. The German Democratic Republic (GDR), however, continued to use this building type, since it did not depend on the import of steel. The 1970s saw the rise of timber lattice frames and eventually framework structures of steel and glass. Since the end of the 1980s, these lattice-like roofs have been used especially to cover inner courtyards or other spaces in historical buildings, since they cause only minimal disruptions to the existing building fabric. Today, shell construction is enjoying a renaissance. The development of new tools, technologies, manufacturing and calculation methods has driven a resurgence in experimentation in this building style, causing it to move back into the focus of a diverse range of research projects.

Timber frame roofs Since it is an inhomogeneous building material, wood has only limited suitability for shell support structures. Nevertheless, the choice of which material to use for the Elephant House at Zurich Zoo was never in question. Though in this context, one of the wishes was the use of an organic material, the main motivation was the requirement that the roof have a relatively low self-weight, so that the interior space could be free of supports. The architects and engineers found their solution in flat panel strips that were placed over one another in three layers and brought “into form” only once they were at the building site. The timber roof covers more than 6,000 square metres of open space with span lengths of up to 85 metres. It rests on a ring

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beam hidden within the prestressed concrete. The 271 openings of various sizes, covered with a translucent membrane, admit daylight to the interior and evoke the effect of a giant leafy canopy. The design, structural planning and simulation, as well as the cutting of the timber and the planning of the assembly, all proceeded in a closed digital chain and with the aid of 3D models.

Form Finding – Graphical Tools, Experiments and Models, Numerical Methods

Hybrid shells Reminiscent of the hills of the surrounding countryside on the shores of Lake Geneva, the university building lies on the campus of the École Polytechnique Fédérale de ­Lausanne (EPFL). On a single level, it houses many ­d if­ferent functions: office spaces, a ­library and an auditorium. The basic concept of the structure is a pair of shells, the first a ground-­level waveform with a maximum pitch of up to 30 degrees, and the other a parallel curved roof covering with a span of 85 metres. Fourteen openings with diameters ranging from seven to 50 metres have been made in both layers to create inner courtyards, resulting in an uneven distribution of

ENCLOSURE + SPACE  |  Arch and Shell Structures

forces. Given the desired span lengths, a pure shell structure was not feasible. Eleven arch support structures, which are integrated in especially load-intensive areas into the 80-centimetre­thick plate, make the structural design possible. In the design process, engineers converted the architects’ physical models into digital versions in order to optimise the forms. The building’s floor is concrete, the upper shell steel and timber. The creation of the shells required 1,400 formwork elements of wood as well as hard foam elements. Over a two-week span, the self-compacting concrete was delivered continuously so as to achieve a seamless shell structure.

50

Jan Knippers, Achim Menges

1

Bill Addis: Building. 3000 Years of ­ esign Engineering and Construction. D London 2007.

Below  Palm House, Bicton Gardens, Budleigh Salterton (GB) around 1843, ­ nknown architect (building style based u on John C. Loudon’s constructions)

Computer-Based ­Processes for ­Biomimetic Structures

The profession of civil engineering, as we ­understand it today, was established in the 19th century and was closely linked to the rise of construction with iron. The latter development began towards the end of the 18th century after a series of disastrous fires in the large British spinning mills. A new, timber-­free type of structure, in which the wooden beams were replaced by cast-iron girders and supports (as in e.g. the Ditherington Flax Mill, Shrewsbury, GB, 1797), was supposed to improve safety. Architecturally, however, this new building technique was not yet visually apparent. Bridge-building played an important role in the development of construction with the new material, though at first iron was only used to replace timber and stone in established types of vault and

51

arch structures (see e.g. the Iron Bridge, ­ oalbrookdale, GB, 1799). Only after the sucC cessful completion of these first bridges and buildings was the innate architectural and structural potential of the new material ­explored. Since there were as yet no established conventions in place to guide these ­explorations, the structures that resulted are breathtaking even to this day. The green­ houses in Bicton Gardens in Great B ­ ritain are a prime ­example. The craftsman-like experimental ­approach used here created a superposition of the stiffness of glass, cement and iron ­mullions that to this day can hardly be simulated even with the most modern computer-­based computation methods. The result has a fascinating quality of lightness, transparency and space.1

Computer-Based Processes for Biomimetic Structures

The rapid spread of railways in the second half of the 19th century generated demand for a large number of station halls and ­bridges that could be built quickly and safely. But r­ apid construction was only possible if internal forces and deformations could be predicted reliably on the basis of statics calculations. The early pioneers of iron construction with their trial-and-error approach were unable to provide this. But when mathematics and mechanics were used to develop new design tools for engineers, the new generation to make use of these tools came to see themselves as fundamentally distinct from both architects and the early trailblazers of iron construction. This shift in self-perception gave rise to entirely new structures, such as the well-known two- and three-hinged arches that were used toward the end of the 19th century for practically all large railway and exhibition halls. In striking contrast to the entire history of building and construction, motions allowed by these hinges made safe structures possible by simple calculations of internal forces.2 Many other new structural topologies were developed as well, among them the Schwedler dome, with which numerous gasometers were covered. JOHANN WILHELM SCHWEDLER, a ­Prussian building administrator and an engineer of the new breed, was able to make the remark­able intellectual leap from the rotational symmetry of framework structures to the spatial support of shell structures – and therefore to the archetype of all lattice and framework shells – through analytical studies at his desk.3 This new approach to design allowed for span lengths and loads that had been previously ­unthinkable. At the same time, a multitude of structural forms was reduced to a small set of calculable and standardised typologies that were used again and again and incrementally developed along the way. “Predictabil­ity” ­b ecame the dominant design criterion for ­engineers.

New typologies: bending-active structures Modern structures are designed with the goal of minimising bending deformations as much as possible. The ICD / ITKE (Institute for Computational Design / Institute of Building Structures and Structural Design) Research Pavilion 2010 fundamentally contradicts this approach. Its basic element is an arch with seven hinges, a system that 19th-century arch theory would have declared impossible due to its instability. It could be built here because the arrangement of the hinges, and therefore of the weak points of the arch, varies over the surface of the ­torus.4 In this case, therefore, the geometrical variation of the building elements, made possible through computer-assisted fabrication, is a prerequisite for the stability of the structure. The 6.5-millimetre thickness of the individual plywood strips is such that they can barely support their own weight over more than two metres. Only when they are bent and braced by neighbouring strips do they form a load-bearing structure. The stresses due to these large deformations, and the geometry resulting from them, can be simulated only through methods that have just recently become generally available to practicing engineers. The possibilities inherent in parametric modelling and digital manufacture have been the subject of lively discourse for almost 20 years. Almost always, however, the focus is on the design and implementation of architecturally motivated complex geometries. The

With the introduction of numerical simulation  processes in the 1970s and computer-­ based production chains around the turn of the century, much has changed. Nowadays, multiply indeterminate systems no longer pose a challenge to static computations, and ­customised building elements to be used in complex structural forms can be readily manufactured. But behind it all lie the structural ­typologies of the 19th century – the frames and arches, trusses, triangulated grid shells and similar a ­ rtefacts – merely expressed in a new architectural form.

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2 Werner Lorenz: “200 Jahre eisernes Berlin”. In: Stahlbau, 06 / 1997, pp. 291– 310. 3 Jan Knippers: “Johann Wilhelm Schwed­ler. Vom Experiment zur ­Berechnung”. In: Deutsche Bauzeitung, 04 / 2000, pp.  105 –122. 4 Moritz Fleischmann et al.: “Material ­Behavior. Embedding Physical Properties in Computational Design Processes”. In: Architectural Design, 02 / 2012, pp. 44 – 51. 5 Jan Knippers, Thomas Speck: “Design and Construction Principles in Nature and Architecture”. In: Bioinspiration and Biomimetics, 07/ 2012.

Top  First three-pin frame system, ­ ammer Works II, Bochum (DE) 1865, H Johann Wilhelm Schwedler Below  System sketch, ICD /  ITKE ­Research Pavilion 2010 Bottom  ICD /  ITKE Research Pavilion 2010

pavilion, however, proves that computer-aided processes can also make possible structural forms beyond the common typologies. What would a consistent strategy for the development of new structural forms be if the methods and goals of engineers were determined primarily by computability and the resulting structural typologies?

Robotic fabrication for nature-based ­structures

6

Oliver Krieg et al.: “Biomimetic Lightweight Timber Plate Shells. Computational Integration of Robotic Fabrication, Architectural Geometry and Structural Design”. In: Philippe Block et al. (eds.): Advances in Architectural Geometry 2014. Zurich 2015.

Above  Exoskeleton of a sea urchin ­(Echinoidea) Bottom left  ICD / ITKE Research Pavilion 2011 Bottom right  Dieter Paul Pavilion (formerly Forst Pavilion), Schwäbisch Gmünd (DE) 2013, photograph of the interior. The entire shell has exterior dimensions of about 11 × 19 × 6 metres.

One strategy for developing new forms is to explore structures in nature, since these follow entirely different principles than the technological principles we know. Natural structures consist of a small number of mostly low-mass chemical elements (carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, calcium, etc.) and very few polymeric substances (such as proteins, polysaccharides, fats and nucleic acids), which self-organise to form energetically and materially efficient multifunctional systems. In this way the natural process is diametrically opposed to its technological counterpart, which relies on the assembly of a number of prefabricated components of very different composition and functionality.5 The direct transfer of processes from biology into technology, which is usually what is understood by the term biomimetics, is successful only very rarely, since structures in nature and in technology are subject to completely different sets of requirements. One of the crucial differences, for example, lies in the fact that natural structures grow and must be functional at every stage of their development. At our current state of the art, we are still far from being able to technically depict the complexity of nature down to its most minutely differentiated structures. Nevertheless, an exploration of natural structures is a worthwhile undertaking, not only because it forces us to question our understanding of design and construction, but because it might inspire solutions beyond conventional typologies.

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This concept is neither new nor original. More than 50 years ago, in collaboration with Johann-­Gerhard Helmcke, FREI OTTO studied, among many other things, the exoskeletons of radiolarians, diatoms and sea urchins. The exoskeleton of a sea urchin consists of polygonal plates. It grows by virtue of the fact that each of the plates increases in size. To accommodate the expansion, the plates are interlocked with one another at their edges. This connection is subject to certain static constraints: the edges can relay compression forces orthogonal to and shear forces parallel to their lengths, but are less able to support torsional or tensile stresses. As a consequence, the plates are arranged so that three edges will always meet in one point, yielding a load-bearing shell even though the edges can transmit only compression and shear forces. The adaptation of this structural principle to a free architectural form is demonstrated in the ICD / ITKE Research Pavilion 2011, a structure characterised by changes in curvature, exposed edges and openings. The overarching goal in this project was the development of a construction method for shells made up of prefabricated modules, since the creation of seamless shells from reinforced concrete or other materials has become very costly and, sadly, very rare nowadays. Each individual hexagonal module comprises two 6.5-millimetre thick plywood panels. The contact between modules is ensured by a positioning system consisting of detachable M6 bolts. Transmission of bending moments between modules is not necessary. In collaboration with a timber construction company, this approach was later developed further and adapted to conform to the conditions of modern building practice. The pavilion features a layer of flat plywood panels of birch wood just five centimetres thick. As with the sea urchins, the forces at the edges of the plates are transmitted by interlocked finger joints. In addition, fully threaded bolts accommodate transverse forces at right angles to the shell surface.6 Because the design process was completely computer-based, it was possible to digitally produce all of the building parts of the timber structure, ranging from the 243 different plates to the custom-cut insulation, the water-­ proofing and the exterior surface layer of larch wood sheets. The biggest challenge of the project was the fabrication of the 7,600 geometrically varied finger joints that lend the pavilion its stability and remain visible from the inside of the structure. The robotic production method is the key to the whole process, since it offers a greater degree of freedom than the

Computer-Based Processes for Biomimetic Structures

usual computer-controlled fabrication methods do. Thanks to the completely computer-based design and prefabrication techniques, the entire building was manufactured and assembled in just four weeks.

Innovations in building materials: fibre composites A careful analysis of biological structures reveals that these are very frequently not isotropic but composed of fibres, such as the cellulose in plants, chitin in insect carapaces, collagen in bone or spider silk. A combination of different alignment directions and packing densities allow them to achieve very finely tuned structural ­characteristics. In addition, ­fibre bundles facilitate a multitude of other functions: they transport nutrients, catalyse chemical reactions, recognise signalling substances and act as ­passive actuators (in pine cones, for e ­ xample, drying out or moistening the fibre layers oriented along different directions causes them to open and close in response). Many modern high-performance materials rely on the principle of anisotropic fibre reinforcement but, in comparison to natural structures, make very limited use of the potential for structural and functional differentiation. In general, mats with orthogonally arranged strengthening fibres of glass or carbon are placed in a mould and impregnated with polyester or

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epoxy resin. These fibre composites are used today in all sorts of technological applications in which form or weight are of critical importance, such as in wind energy facilities, in the aerospace industry, on sailing boats and, increasingly, in automobile manufacture. Only in the building sector has their use remained limited to specialised niches, even though they are by no means new to the field. The Monsanto House in California, built in 1957, was the first prototype of a house built from prefabricated sandwich elements with a polyurethane foam core and a facing layer of glassfibre-reinforced plastic. Despite enormous public interest and a series of ­follow-up projects, this “house of the future” never achieved lasting success. In the mid-1970s, the experimentation with synthetic structures ended as quickly as it had begun. A lack of design experience and flaws in implementation had caused structural damage that gave fibre-reinforced plastics a reputation for being inferior materials. But a more salient reason for their decline is probably the fact that an ever more individualistic society found the concept of a serially prefabricated living unit increasingly unattractive.7 Still missing today are approaches for the manufacture and assembly of fibre composites that are adapted to the specific demands of the building industry. In contrast to aeroplane or automobile production, the focus in

54

Above  Comparison of the wing cases (elytra) of flying (left) and flightless ­beetles (right) Below  Frames that can be adapted to given module dimensions are mounted onto two industrial robots with coupled steering. The stationary fibre spool is placed between the robots. The inexpensive glass fibres are drawn through an epoxy resin bath and wound to form ­hyperbolic surfaces. The high-strength carbon fibres are deposited wet on top of this form, following the path of the primary loads. As soon as the resin has cured, the elements can be removed from the frames.

7

Jan Knippers et al.: Atlas Kunststoffe und Membranen. Munich 2010, p. 12ff. 8 Stefana Parascho et al.: “Modular ­Fibrous Morphologies. Computational Design, Simulation and Fabrication of Differentiated Fibre Composite Building Components”. In: Philippe Block et al. (eds.): Advances in Architectural Geometry 2014. Zurich 2015, pp. 29 – 46. Top and bottom  ICD / ITKE Research ­Pavilion 2013 –14. Finite element analysis of the stress curves and implementation into a production-ready force-flow arrangement of the carbon fibre reinforcement (below)

construction is predominantly on the manufacture of custom-made large-scale pieces whose geometry is individually determined. For these, the creation of the usual polyurethane foam moulds is not only very expensive, but also produces a lot of residual waste. In construction, furthermore, criteria such as durability play a major role during both the manufacture and usage phases of the building, while other aspects, like meeting high standards in production tolerances or in mechanical efficiency, are of secondary importance. For the design of the ICD / ITKE Research Pavilion 2013-14, a process was developed specifically for architectural applications that minimises the cost of producing formwork moulds. In a technique known as coreless

winding, robots deposit resin-saturated fibres onto a rotating steel frame.8 The frame is later removed, yielding a rigid and load-bearing fibre structure whose metal content is limited to screws and screw sleeves. The natural inspiration for this was supplied by the wing cases (elytra) of beetles, which protect the hind or flight wings from mechanical damage. The elytra consist of two layers, combined via a special orientation of the chitin fibres into a very light-weight yet robust structure. This concept was transferred to the pavilion in the form of its modular, double-­layered structure of glass- and carbon-­reinforced ­fibres. The 36 geometrically different modules are so light that a single person can carry them. The goal of the research project was primarily to explore the fabrication process

55

Computer-Based Processes for Biomimetic Structures

and to establish its geometric possibilities. The parallel investigation of robotic production processes and biological models led to a completely new structure far beyond the established architectural and engineering ­typologies. Despite its fragile appearance, the structure proved to be extraordinarily robust and dependable not only during its fabrication but also during assembly and use. This process was developed further in a project for a public building client who had functional and economic requirements. The resulting Elytra Filament Pavilion consists of 40 hexagonal modules, connected to form an inclined flat roof surface. It is supported by seven pillars whose funnel-shaped heads are also wound. The internal orientation and density of the fibres is adapted at every point to the static loads on the roof modules and the heads of the supports. The only change to the fabrication process was that just one robot was used to wind the resin-saturated components. The steel frames were removed after winding, and the resulting modules were tempered in an oven. The structural form is computed using a simplified Finite Element Model which represents the open mesh structure as a continuous shell. The primary function of this model is to determine the arrangement and density of the fibres. A numerical prediction of the load-bearing characteristics of the open mesh structure is not possible because of the numerous parameters that influence the load-bearing properties, such as the effects of fibre crossings or the buckling of fibres ­under compression. Therefore, the only way to establish the stability of the structure was by physically testing the components.

­ xploration of its structural and architectural e potential. There is still a lot of ground to cover in achieving its eventual widespread use, both in terms of the materials themselves (fire and UV resistance of the resins as well as the use of resource-efficient organically based raw materials) and also in terms of improvements in the safety and speed of the manufacturing process. As with the construction with iron, however, the critical step will be the development of practically workable and reliable calculation methods for structural analysis that enable the relevant processes to be scaled to larger building projects. If this succeeds, the coreless winding technique could be used in any application in which the transparency of roof or ceiling structures plays a significant role. Due to their small weight, the elements are also ideally suited for situations in which the use of large and heavy building components is impossible, as in, for example, construction in existing buildings or in remote and hard-to-access regions. The only things that would have to be transported to the building sites would be lightweight and compact fibre spools and containers of resin, since the winding itself could be done on site. In the two pavilions illustrated here, the complex geometries and the differentiation in fibre ­layering were possible only via robotic fabrication methods. Simpler building components, however, could just as easily be produced by other technological means, such as by winding about a fixed axis of rotation, or even by hand.

The long road from research to practice: carbon concrete

If one compares this with the development of construction with iron that was elucidated earlier in the chapter, it becomes apparent that construction with fibre composites is still in the early phases of an experimental

Many years of experience with the previously described projects have shown that the path from a promising concept that has been successfully tested in university laboratories to an actual practical application in the building industry is a very long and arduous one. A

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Right  Elytra Filament Pavilion in the ­inner courtyard of the Victoria and ­Albert Museum, London (GB) 2016. The 40 modules have a uniform outer ­dimension of 2.40 m and a height of 0.40 m and are connected by bolts. To demonstrate the process, four elements were wound on-site in London. Opposite, top  Various roof elements Opposite, bottom  Winding of the roof components of the Elytra Filament ­Pavilion Project participants  The illustrated projects were created by the Institute for Computational Design (ICD) and the ­Institute of Building Structures and Structural Design (ITKE) with the par­ ticipation of many research associates, students, colleagues and sponsors. Without their amazing dedication these projects would not have been possible.

good example of this is the case of carbon concrete, the most important and substantial innovation to the most ubiquitous building material of our age, reinforced concrete. In carbon concrete, the steel bars and meshes that typically supply tensile reinforcement are replaced by textiles of carbon fibres. The fibres have approximately the same rigidity as steel, but do not rust. This means that in a given application, the thickness of carbon concrete can be significantly less than that of reinforced concrete, since less material is required to protect the reinforcement. As a consequence, structures of carbon concrete are not only more slender and elegant, but – more importantly – require less cement. The 1,450 °C temperature needed for the manufacture of cement makes the process extremely energy-intensive, and one of the greatest CO2 emitters of our times. Ecologically speaking, this makes a reduction in cement use one of the most important topics in contemporary building research.

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The research and development of carbon concrete has been actively supported for many years; two of the institutions involved were the special research divisions ­ erman R ­ esearch Foundation at the of the G Rheinisch-Westfäli­s che Technische Hochschule Aachen and the Technische Universität Dresden, which were both active in this effort from 1999 –2011. Despite this longterm support and a persuasive concept, carbon concrete has still not found acceptance in building practice, though it is certainly expected i­ncreasingly to supplant conventional reinforced concrete over the long term. The scientific and technological foundations are laid; what is still missing are the subsidy programmes, procurement procedures and building regulations that provide targeted support for the shift from basic research to real applications in the building i­ndustry, and thus encourage building clients, licensing authorities, designers and contractors to give this novel and unfamiliar material a chance.

Computer-Based Processes for Biomimetic Structures

Structural Design and Form Finding Processes

In terms of form, material and construction, the possibilities of structural design have grown tremendously over the course of the 20th century. The beginnings of this change are found in the first designs of KARL ­C ULMANN, KARL ­WILHELM RITTER and others arising from the principles of graphic statics, or the inductive-­ deductive experimental methods such as the legendary hanging chain models of ANTONI GAUDÍ. A source of important inspiration and motivation for these developments were the methodical works of FREI OTTO and his colleagues, who used their visionary designs and successfully realised prototypes to underscore the importance of experiment in the ­design of structures and in form finding.1 The explosive development of computing and of numerical simulation methods created entirely new opportunities for structural engineers, who could now use an interconnected process. A

multitude of parameters could be ­considered using the aid of physical and digital prototypes to develop the right structural form for an architectural concept. The great number of possible solutions produced by these numerical methods requires that users can correctly categorise and assess the results, since they depend directly on the model choices made by the designing engineer. It is relevant in this context to ask how civil engineers see themselves: as scientists, or more as designers looking for ­engineering solutions? Exactly this question lies at the heart of the current discussion about whether it is reasonable to separate the educational careers of engineers and architects2 as well as what the future of said education should be in the context of generative computer-­aided design methods and practical ­processes.

Thrust line

Compression

Tension

Reaction force

F1 ... F2 self-weight Catenary curve

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Christoph Gengnagel

Below left  Example of the link between catenary curve and thrust line in an arch structure made of blocks of differing ­geometries and self-weights Below right (top)  Relationship between the spatial compression equilibrium shape, the thrust network (G), its planar projection as a funicular polygon (primal grid) and the reciprocal force polygon (dual grid) Below right (bottom)  The primal grid and dual grid are related by a reciprocal relationship. The equilibrium of a node in one of them is guaranteed by a closed polygon in the other and vice versa Opposite, top  Photograph of the ­reversed hanging chain model of the Sagrada Família in Barcelona (ES) Antoni Gaudí Opposite, bottom  Multihalle multipurpose hall Mannheim (DE) 1975, Frei Otto. Chain model used in form finding

Form finding as an inductive-deductive method

1

Frei Otto: “Form-Kraft-Masse 5. Experimente. IL 25”. Mitteilung des Instituts für leichte Flächentragwerke. Stuttgart 1990, p. 5. 2 Stefan Polónyi: “Der Einfluss des ­Wissenschaftsverständnisses auf das Konstruieren”. In: Geschichte des Konstruierens, Part 2. Published by ­Sonderforschungsbereich 230 Natürliche Konstruktionen, Universität Stuttgart und Tübingen. Stuttgart 1986, pp. 151–165. 3 Toni Kotnik: “Das Experiment als ­Entwurfsmethode. Zur Möglichkeit der I­ ntegration naturwissenschaftlichen ­Arbeitens in die Architektur”. In: Ákos Moravánsky, Albert Kirchengast (eds.): Experiments. Architektur zwischen ­Wissenschaft und Kunst. Berlin 2011, pp.  24 – 53. 4 Kai-Uwe Bletzinger: “Blobs, Schalen und Membrane”. In: Werner Wagner (ed.): Berichte der Fachtagung Bau­statikBaupraxis 10. TH Karlsruhe 2010, pp. 73 – 84. 5 Rainer Graefe: “Zum Entwerfen mit Hilfe von Hängemodellen”. In: Werk, Bauen + Wohnen, 11 / 1983, pp. 24 – 28.

Form finding as an inductive-deductive process and as a scientifically founded experiment in the generation of forms has intrigued architects and engineers of the 20th century and led to the development of a great number of architectural applications and methodical scientific approaches. Famous examples include ANTONI GAUDÍ’s hanging chain models for the Church of Colònia Güell in Barcelona, HEINZ ISLER’s membrane models for thin-walled shell structures as well as the many works by FREI OTTO and his team at the Institute of Lightweight Structures in Stuttgart.3 In essence, one can use these examples to define two classic form finding methods: the soap film model and the hanging model.4 Until well into the 1970s, spatial design concepts were generated primarily through physical experiments using these methods.

Arch and shell structures: using hanging models to find forms Hanging models are a traditional approach to form finding for arch and shell structures, which are capable of redistributing external forces almost entirely through compression and with little deformation or bending. In 1670, Robert Hooke recognised the relationship between the purely hanging catenary curve of a chain under tension and its inversion into the thrust lines in arches and domes under compression. The famous physical experiments GIOVANNI POLENI performed in 1748 to analyse the dome of St Peter’s Basilica in Rome marked the first time that a scientific finding was directly applied to a large-scale building

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in order to determine its stability. In the 19th c ­ entury, hanging models were used on multiple occasions to design single and double-­ curved structures. In Germany, H ­ EINRICH HÜBSCH5 was the first to use this method in his designs for several churches. However, the logic of the support structure was not extended to architectural spatial composition. Instead, the latter continued to follow a completely geometry-based canon of forms that disguised the form-found support structure. ANTONI GAUDÍ’s hanging model of string and small suspended linen sacks filled with lead shot represented his concept for a church in the workers’ settlement of Güell; it marked the first time that a logically consistent transformation from structural to architectural form was made. It was remarkable for being a complete representation of the entire building in a highly complex, spatial, physical hanging model. In addition to his experimental model method, GAUDÍ, like many others, also employed graphical methods to generate forms and analyse vaulted structures. For frameworks, this very descriptive geometry-based approach, much like the soap film analogy, makes it possible to do form finding independent of material considerations. In contrast to the cable and membrane structures that are subject to purely tensile stresses, the graphical approach is limited to deformation-resistant structures whose geometry reflects a dominant loading condition (usually the intrinsic weight). ­Computer-assisted procedures have opened up this approach to digital form generation for complex spatial structures as well, thus making it usable in modern design and implementation processes. An example for this

Structural Design and Form Finding Processes

is the development of Thrust Network Analysis (TNA).6 In recent years, this approach has been logically refined7 with an eye to user-­ friendliness and further applicability, and has formed the basis for the creation of the spectacular “­Armadillo Vault” stone structure at the 15th Venice A ­ rchitecture Biennale 2016. Unlike those of ­geometry-based methods, numerical simulations of hanging model experiments in continuum mechanics require the input of material properties. Where a bend-free form is desired, completely non-linear calculations become necessary on account of the large

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deformations. The material models used purely to generate forms make it possible to define the distributions of stiffness and the form derivations that can follow from them.

Structures under tension: soap film models in form finding The soap film principle is mainly used to derive forms for tension-only membrane structures. The freedom of the membrane to bend implies an optimal exploitation of the material, but at the same time creates an inseparable link

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URS

Abbildung 4.12: Minimalfläche: Ausgangskonfiguration und Gleichgewichtskonfiguration. 6

between the form and the flow of forces. In

Philippe Block: Thrust Network Analyaddition,der theSeile anticlastic or synclastic curved Three-dimensional diesis. Exploring Membranknoten modelliert,Equi­ womit das Rutschen auf der Membran unmöglich surface must be prestressed to stabilise the Dissertation, Massachusetts librium. ist (siehe auch Abschnitt 2.3.1). Die prinzipiell beliebig definierbare Ausgangskonfiguration form. As a consequence, the strategy for form ­Institute of Technology. Cambridge, MA des2009. numerischen Formfindungsprozesses ist als Vielflächner gewählt worden. Es ist deutfinding is fundamentally different from that for lich7 Matthias zu erkennen, wieFunicular die geraden einzelnen Segelsegmente imconditions Laufe der FormRippman: Shell Kanten derother structures. Boundary and a ­Design.gekrümmt Geometric Approaches to Form findung werden. Diese Krümmung ist notwendig, um das Gleichgewicht angenden chosen state of tension are supplied to Finding (also and Fabrication of Discrete flexiblen seilverstärkten) Rändern herzustellen. Des Weiteren ist ersichtlich, dass an erate a specific spatial form from an arbitrary, ­Funicular Structures. Dissertation, ETH den Stellen der Kehl- und Gratseile sich aufyet Grund der Umlenkkräfte die an diesen Stelmathematically definable ruled surface. Zürich, Departement of Architecture, This approach, though reversed as compared len2016. typischen Knicke in der Membranfläche einstellen. Die komplette Tragwerksgeometrie 8 to theder standard method in structural analysis, ergibt sichWüchner: in diesem Fall also der Interaktion vorgeschriebenen Flächenspannung Roland Mechanik undaus Nume­ der Formfindung und Fluid-Struktur-­ it possible to find a suitable geometry derrikMembran und den Seilvorspannkräften.makes Die tangentialen Membranspannungen sind Interaktion von Membrantragwerken. without taking material properties into considwieder homogen und isotrop. Die Fläche ist durch vierknotige finite Elemente parametriDissertation, TU Munich, Department eration. Mathematically, the problem is related siert, wobei Knoten drei global (siehe of Civil, Geojeder and Environmental Engi- orientierte Verschiebungsfreiheitsgrade aufweist to the field of minimal surfaces.8 Supported by neering, 2006. Abschnitt 4.2). developments in computer technology, over 9 see note 4. the past 40 years various numerical methods 10 Christoph Gengnagel, Holger Alperfor the form finding of lightweight shell strucmann,Anisotrope Elisa Lafuente:Vorspannung “Active Bending in 4.5.2 tures have been established: the Force Density Hybrid Structures”. In: Günther H. Filz, Rupert Maleczek, Christian Scheiber Method and itstechnisch extension, Dynamic RelaxDie Wahl eines isotropen Vorspannungszustands ist für viele relevante Fragestel(eds.): FORM – RULE | RULE – FORM ation, as well as the linearisation methods lungen sinnvoll unmöglich. Aus diesem Grund wurde das hier ver2013. nicht Innsbruck 2014; beziehungsweise Martin Tamke derived from continuum mechanics, such as Materials Bespoke et al.: “Bespoke wendete Verfahren (URS)forfür abschnittsweise orthotrope Vorspannung erweitert. Hiermit the Finite Element Method with the modified Textile Architecture”. In: Conference Newton-Raphson technique or Updated Ref­Proceedings, IASS Annual Symposium 95 erence Strategy (URS). In principle, all these 2016: Spatial Structures in the 21st Century. Tokyo 2016. methods are based on an iterative approach 11 Julian Lienhardt, Jan Knippers: to the equilibrium geometry of the given pre“­ Biegeaktive Tragwerke”. In: Bautechnik, stressed state. What differs from method to 06/2015, pp. 394 – 402. method is the interim difference between the 12 Thomas Hughes, J. Austin Cottrell, existing stress state of the approximation and ­Yuri Bazilevs: “Isogeometric Analysis. the target stress state. In the case of the UpCAD, Finite Elements, NURBS, Exact dated Reference Strategy, which is rigorously ­Geometry and Mesh Refinement”. In: formulated on the basis of continuum mechanComputer Methods in Applied Mechanics and Engineering, Vol. 194, 2005, ics, the iterative process is clearly reflected in pp. 4135 – 4195. its name. The process takes into account iso13 Gregory Quinn et al.: “Calibrated and tropic and anisotropic prestressing and makes Interactive Modelling of Form-Active possible an explicit calculation of the stress ­Hybrid Structures”. In: Conference Prodeviations from the target prestress state in ceedings, IASS Annual Symposium 2016: anisotropically prestressed membranes. 9 In Spatial Structures in the 21st Century. this approach, the surface can be discretised ­Tokyo 2016. Facing page  Armadillo Vault, Venice (IT) 2016, Block Research Group ETH Zurich, ODB Engineering, Escobedo Group Above  Minimal surface: Starting configuration (left) and equilibrium configuration after form finding with the Updated Reference Strategy (URS)

into any of the finite element types – triangles, rectangles, and so forth.

Hybrid structures: form finding as an empirical process based on induction / deduction Form finding in the architectural design process ultimately comprises a juxtaposition of theoretical and empirical expertise linked

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through induction and deduction. In practice this amounts to a search for forms for hybrid structures, a search that succeeds when physical and digital experiments, geometrical and mathematical descriptions and individual aesthetic judgments or considerations are combined in the process. In this interactive method known as “hybrid modelling”, illustrative tools are as important as tools that ensure a sufficiently precise analysis of physical interactions. Processes such as structural optimisation occupy a quantitatively huge experimental space encompassing section, form, and topology optimisation. The foundations for this lie in the many ways in which non-linear load-­bearing characteristics can be numerically simulated. The simulations make it possible to carry out static and dynamic analyses of systems with large deformations, as well as analyses of stability failures, of the effect of non-linear and anisoptropic material responses and of deformation-­d ependent effects. Thus, form finding and form optimisation for mixed systems consisting of membranes and highly flexible rods10, or the development of form-adaptive systems11, are also achievable. In 2005, Thomas Hughes first introduced Isogeometric Analysis (IGA), 12 which has been evolving quickly since. IGA combines the parametric geometric model with the analytical model by way of the Finite Element Method (FEM). The rapid interaction between form generation and analysis that it facilitates yields new potentials for computer-aided structural design. Similar objectives motivate efforts to combine digital generative drawing tools with simulated environments on the basis of ­Dynamic Relaxation (DR). These make it possible to obtain geometric approximate solutions for the form of material systems that take into account large deformations and kinematic conditions during the iteration process.13

Form finding through structural optimisation Numerical processes for structural optimisation are the most common approaches used for arriving at an optimal structural form. The characteristics of the resulting form are determined by an arbitrary number of state variables, optimisation variables, target functions and boundary conditions. In a structural optimisation process with many design parameters, sensitivity analysis is a critical component. It determines the degree to which the target function(s) and boundary conditions of an optimisation task are affected by variations in the design variables. In a form finding problem, these variables are usually the spatial coordi-

Structural Design and Form Finding Processes

nates of the design model control nodes such as the FEM nodes, or the positions of the Non-Uniform Rational Basis Spline (NURBS) control nodes in the IGA. All the outputs of a structural analysis – for example, displacements, stresses or resonance frequencies – are suitable candidates for target functions and boundary conditions. If the goal of optimisation is given as the minimisation of strain energy for a predefined structural mass, the inefficient bending states are removed during the optimisation process in favour of load transfers via membrane stress states, resulting in a structural geometry of maximum stiffness and minimal bending that is comparable to that of a hanging model.14 The form finding process for elastic (prestressed) grid shells differs from traditional form finding for shell or membrane surfaces in that a target geometry

ENCLOSURE + SPACE  |  Arch and Shell Structures

is specified. This can be defined geometrically or determined via a balance of forces in a hanging model. The final generated form of the elastic grid shell reflects an approximation of this “ideal” geometry that takes into ­account the bending and axial stiffness of both the rods and the grid topology.15

A new numerical tool for form optimisation: IGA The shift in timing between the development of computer-assisted imaging and numerical structural analysis has led to the evolution of independent and mathematically divergent descriptions of geometric objects in these fields. The separately performed discretisation of design geometries generally required for computer-aided analysis (“meshing”) is a computation-

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14

see note 4. Christoph Gengnagel, Gregory Quinn: “Große Verformungen. Über das Entwerfen von vorbeanspruchten Gitterschalen”. In: GAM 12. Structural Affairs. Potenziale und Perspektiven der Zusammenarbeit in Planung, Entwurf und Konstruktion. Basel 2016, pp. 169 –189. 16 Michael Breitenberger et al.: “Analysis in Computer Aided Design. Nonlinear Isogeometric B-Rep Analysis of Shell Structures”. In: Computer Methods in Applied Mechanics and Engineering, Vol. 284, 2015, pp. 401– 457. 17 Benedikt Philipp et al.: “Integrated ­Design and Analysis of Structural Membranes Using the Isogeometric B-Rep Analysis”. In: Computer Methods in ­Applied Mechanics and Engineering, Vol. 303, 2016, pp. 312– 340. 15

Opposite, top  Interior vertical view of ­Hybrid Tower One, showing the internal radial restraining system Opposite, below  Hybrid Towers One and Two; far left  Tower One prototype of an 8-metre high tower of bending-active glass-fibre reinforced plastic (GRP) rods and knitted membrane in Copenhagen (DK) 2015. Centre for Information Technology and Architecture (CITA) at the Royal Danish Academy of Fine Arts, ­Department of Structural Design and Technology (KET) at the Berlin Univer­ sity of the Arts; centre  Tower Two simulation of form finding with the FEM for the hybrid system and analysis of the stresses under prestressing and wind loads. KET, 2016; far right  Tower One prototype of an 8.30-metre high tower of bending-active glass-fibre reinforced plastic (GRP) rods and knitted membrane in Guimarães (PT) 2016. CITA, KET, Universidade do Minho, AFF – A. Ferreira & Filhos Above  Simulation of the erection, i.e. shaping, process of the elastic grid shell, KET Below  Prototype of the elastic grid shell: span 10 m, GRP rod diameter 20 mm, wall thickness 3 mm, Berlin (DE) 2013, KET

ally intensive part of the analysis process, and accounts for significant time delays between the generation of geometric design iterations and the assessment of their physical performance capabilities. A typical mathematical description of free forms in CAD systems is implemented via streamlined assembled NURBS (Non-Uniform Rational B-Splines) patches for the surfaces. Using these NURBS surfaces as a common basis for both geometrical description and structural computations makes it possible to integrate the geometrical design and analysis processes.16 It also allows for an avoidance of unwanted geometric differences between the design model and the numerical structure analysis model that arise from approximations based on the discretisation of low-order polynomials. The critical advantage of the Isogeometric Analysis process, apart from the removal of the geometrical conversion step, lies in the possibilities for refining the discretisation of the structural geometry without changing geometric or mechanical parameters. The greater precision of the NURBS initial functions results in better convergence characteristics than those for the polynomials that have been used in Finite Element Analysis to date.17

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Form finding processes are part of structural design. The classical approaches to form finding, such as hanging models and soap film analogies, now play a much diminished role due to their inherent design limitations. The many opportunities for digital experimentation in the context of structural optimisation create new design options for generating forms using a multitude of different parameters. Not only is it thus possible to fully depict the mechanical properties of a structure in a continuum-­ mechanical model; simplified modelling strategies can now be employed that take into account only the most important characteristics of a structure, and allow, for example, kinematic states to direct an iterative approach to a solution. In this way, form ­finding is transformed into a highly complex process characterised by freely chosen parameters and design choices.

Structural Design and Form Finding Processes

Wide and Light

Facing page  National Stadium of Warsaw (PL) 2012, schlaich bergermann partner; architects: gmp Architekten von Gerkan, Marg und Partner, JSK Architekci Below  Olympic roof in Munich (DE) 1972, Frei Otto, Leonhardt + Andrä / Jörg Schlaich; architects: Behnisch & Partner. A 1969 illustration of the roof dimensions in “Architekturwettbewerbe Sonderheft 7” (Architectural Competitions Special ­Issue). Size comparison with existing buildings: 1 Montreal, 2 Tokyo, 3 Tokyo, 4 Stockholm, 5 Yale University, New ­Haven, 6 Raleigh, North Carolina, 7 ­Bremen, 8 Melbourne, 9 Ludwigshafen

Since the times of Greek Antiquity, stadiums have been important venues for competitive sports. With the number of spectators estimated at 30,000, the first Olympic Games held in the 8th century BCE can be viewed as the forerunner of modern large-scale events. In contrast to the ancient stadiums, modern event venues are not only expected to protect against sun, wind, rain and snow, but also have a much broader scope of requirements to fulfil. For example, the light conditions must be such that the media are able to broadcast the events clearly. Excellent visibility and acoustics are critical, as is an overall spatial design that also underscores the emotional side of the communal experience of what is happening on the playing field or on the stage. Since the roof-covered seating capacity of modern stadiums is often above 50,000, the

huge roof surface and the associated span lengths that the stadiums require place enormous demands on supporting framework and structure. Yet these are expected to appear as light and delicate as possible, despite huge loads due to wind, snow and self-weight; they should have a predefined level of translucency and, on top of this, must conform to the most current safety standards. In the planning of stadiums, financial considerations such as investment capital and maintenance costs are as important as the expected construction time and the adaptability of the building for subsequent use, as well as issues of sustainability in general. These types of structures, built primarily for World Cup events or for the Olympic Games, also have a high symbolic value, for the host nation as well as for the other participating countries. The long list of requirements shows that large modern buildings represent some of the most demanding design and construction chal­lenges. It takes a lot of innovation, knowledge and experience to create buildings with extra­ordinary functional, structural and design characteristics. Milestones such as the Olympic Stadium in Munich (1972) set structural and aesthetic developments in motion that still have a significant impact on design and computation methods as well as innovative, highly efficient tools, structures and support systems. Next to other important building tasks that serve to fulfil the basic needs of our society, it is especially the large-span roof structures and modern stadiums that are representative of the high quality of contemporary civil engineering and its extraordinary capacity for invention.

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Wide and Light

Lightweight Textile ­ onstruction – Development C of Simulation Methods from the 1970s to the Present

The visionary force of FREI OTTO was the catalyst in the late 1950s for a new architecture of lightweight textile constructions and, as a consequence, for the development of new methods for shaping and simulating these structures. The work done both at the Sonder­ forschungsbereich 64 (Collaborative Research Centre) at the University of Stuttgart and on the roof of Munich’s Olympic Stadium were fundamental in the evolution of this building technique. They mark the beginning of the age of computers in the design and simulation of lightweight structures in particular, as well as for construction in general. If one examines FREI OTTO’s methods for form finding and for simulations of lightweight tensile structures, the visionary boldness and structural lightness of his prestressed cable net and fabric membrane structures are the

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characteristics that have been most indelibly associated with his name since the Bundes­ gartenschauen (national garden shows) in Kassel (1955) and Cologne (1958). The development of these structures reached the absolute pinnacle at its time with the Olympic roof in Munich. In many respects, the Munich roof defines a milestone in the development and acceptance of these support structures, not least of the static and mechanical calculation methods that were necessary for their design. As far as lightweight tensile structures are concerned, the 1972 Olympic Games in Munich ushered in the computer age. Lying as they do at the intersection of engineering, architecture and computational mechanics, these structures were, and remain, the driving force that underscores the fundamental importance of numerical methods in addressing practical issues in

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Kai-Uwe Bletzinger

1

The Force Density Method was first ­described in K. Linkwitz, H. J. Schek: “Einige Bemerkungen zur Berechnung von vorgespannten Seilnetzkonstruktionen”. In: Ingenieurarchiv 40/1971, pp.  145 –158. 2 cf. E. Haug: “Formermittlung von ­Netzen”. In: Bautechnik 9/1971, pp.  294 – 299. Opposite  Olympic Park in Munich during the 1972 Summer Games Above left  Work on the measurement model of the German Pavilion for E ­ xpo 1967 in Montreal Above right  Measurement of the model of a four-point sail at the measuring table (Frei Otto is on the left)

construction. Since those days, much has happened: textile membrane fabrics are now firmly established as “the fifth building material”, CAD and the Finite Element Method (FEM) have become day-to-day tools in design and computation. Today, many makers of building software sell special program modules for non-linear computation, form finding and precision cutting, defining the state of the art in technology. The future belongs to investigations of coupled phenomena and integrative approaches, such as the numerical simulation of the interaction between temporary wind loads and the large deformations of lightweight shell structures in a digital wind tunnel; the implementation of fabric as a multifunctional facade; or the integration of CAD and FEM for a close interaction between design and computation.

The situation in 1972 and the following years Since membrane structures and cable nets can redistribute neither compression nor bending forces but only tension, their spatial geometry must be determined through a form finding process. The form is a function of the equilibrium geometry of the acting forces. If only the pretensioning forces are given as the form-determining loading condition, the ­result is a typical negative-curvature (i.e. anticlastic) surface. When internal pressure is added, a positively curved (synclastic) surface emerges. Typical examples of this are the fourpoint sail and the pneu. Minimal surfaces arise when the prestressing magnitude is the same throughout the surface. FREI OTTO developed the principle of minimal surfaces as the form-­ determining foundation of architecture to perfection.

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Form finding is a difficult mechanical task. The underlying equations are strongly non-­ linear and, in their discrete form, even singular, which makes simple calculations impossible. This explains the existence of the many different competing solution methods. Up until the construction of the Munich roof, forms were developed exclusively using experimental methods on appropriately scaled-down models. The Olympic roof, however, proved to be too large, and the measured values of the model too inaccurate. The building could be constructed only because a very effective, ­exceptionally robust and computationally efficient numerical method was developed: the Force Density Method for the form finding of prestressed cable nets.1 Indeed, the Olympic roof was the reason that one of the most important numerical methods used in lightweight construction was created at all. It also turned out that shear-flexible membrane fabrics can be modelled quite well with analogue cable nets, particularly when the surface curvatures are not too large. The classic Force Density Method for cable nets is therefore still a mainstay in form finding for fabric membrane structures. Many of the computer-aided technologies and methods for lightweight construction commonly used in the present trace their origins to the Collaborative Research Centre (SFB) 64 Long-Span Structures led by FREI OTTO at the University of Stuttgart, and are still valid, unchanged, today. As an alternative to the Force Density Method, a form finding process was developed based directly on the Finite Element Method (FEM) that links the continuum mechanics of an even stress state to non-linear numerical techniques.2 It was only much later that the Force Density Method was successfully integrated into non-linear continuum mechanics and the com-

Lightweight Textile Construction – Development of Simulation Methods from the 1970s to the Present

monalities between the two approaches were identified.3 SFB 64 was likewise the source of groundbreaking methods for the determination of cutting patterns for cables and membranes. Works by Blum and the material model by Münsch/Reinhardt are part of the current standards for anisotropic textile structural materials. 4 The working group around Argyris

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further developed and implemented FEM on a grand scale for use in fully geometric non-­ linear structural computations in building.5 Other centres of lightweight construction in the early 1970s also made important strides in the development of numerical methods. In London, for example, researchers at the City University first employed Dynamic Relaxation

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3

cf. K.-U. Bletzinger, E. Ramm: “A ­general finite element approach to the form finding of tensile structures by the updated reference strategy”. In: ­International Journal of Space Structures 14 /1999, pp. 131–144. 4 cf. R. Blum: Beitrag zur nichtlinearen Membrantheorie. Universität Stuttgart, 1985; R. Münsch, H.-W. Reinhardt: “Zur Berechnung von Membrantragwerken aus beschichtetem Gewebe mithilfe genäherter elastischer Materialpara­ meter”. In: Der Bauingenieur 70/1995, pp.  271– 275. 5 cf. J. H. Argyris, T. Angelopoulos, B. ­Bichat: “A general method for the shape finding of lightweight tension structures”. In: Computer Methods in Applied Mechanics and Engineering 3/1974, pp. 135 –149. 6 cf. M. R. Barnes: Form Finding and Analysis of Tension Structures by Dynam­ ic Relaxation. The City University, London, 1977. Facing page  Roof of the stadium, Olympic Roof Munich (DE) 1972 Above  Aviary of the Hellabrunn Zoo in Munich (DE) 1980, Frei Otto in collaboration with Ted Happold

in form finding for cable and membrane structures.6 Thus, within a short time period, the three most significant lines of form finding processes were developed: • The Force Density Method and its successors •  Dynamic Relaxation • Linearisation methods derived from continuum mechanics Work originating during that time in Japan and the United States falls under the latter heading. Even then, experts recognised the potentials inherent in an interactive, computer-aided work process and created prototypes for it.

The current state of affairs and development trends Looking back, it is clear that essentially all the critical developments that play a role in the current state of computer-oriented methods for the simulation of lightweight tensile structures were initiated in the 1970s. The breadth and depth of all the methodological evolutions that have occurred since are so wide-ranging that only a few examples can be sketched out

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in key words and with an eye to lightweight fabric construction. Many of these developments are not yet standard in commercial software, but are close to being adopted. For the most part, non-linear simulations of load-bearing behaviour are now integrated into large, universal finite element programs and are available as a worldwide industrial standard. Constitutive formulations specific to many materials in common use, such as foils, woven fabrics and other textiles, are in principle also accessible, though their implementation is not necessarily standardised. Form finding, form optimisation and mesh generation remain a heavily researched field and are typically available only through specialised software. Many different processes exist, among them variants of the Force Density Method or of Dynamic Relaxation. Their critical differences lie in the way they regularise the ambiguous or singular equilibrium equations. In concrete terms, this means that the different methods will occasionally generate ­d ifferent forms even when given the same task. This is the case even when the same

Lightweight Textile Construction – Development of Simulation Methods from the 1970s to the Present

method is implemented in different ways. A survey of current software products regarding this issue revealed an astonishing degree of scatter in the results.7 This is of little concern in practice, since the stress states found in all the identified forms may be different, but are all valid. Pattern cutting methods and special material formulations are available only in very specialised software or as a service. In practice, the broad spread in material parameters usually requires extensive experience with compensation techniques. New pattern cutting methods yield high-quality cuts even for strongly curved surfaces and for extremely stretchable materials like knitted fabrics. Material models geared specifically toward cutting applications have been developed based on the Adaptive Response Surface Method, and can be adapted using standardised measurement data for a large number of different materials.8 Developments in the fields of coupled multiphysical analyses, Computational Wind Engineering or adaptive structures place significant demands on software and hardware. They also require the users of the computational tools to have extensive experience and indepth knowledge of their physical and methodological foundations. The use of commercial software therefore makes sense only in the case of specific installations. The numerical wind tunnel, for example, is used to deter-

mine the correlations between the deformations of lightweight tensile structures and the wind flowing around them (known as the Fluid-Structure Interaction or FSI).9 Since these fields promise to be rich in synergistic effects across the board, they are at present a very active and innovative area for basic research.10 The integration of CAD and FEM is being approached by way of Isogeometric Analysis (IGA). Program upgrades for use with original CAD models are available to practicing engineers, as are special applications for shells and membranes and even plug-ins for individual programs. The history and development of lightweight tensile structures is an ideal example of the way in which innovative building techniques and computation methods serve as mutual inspiration for one another and open up new, fertile fields of research with great potential for the future – fields whose results have effects far beyond their originally targeted aims. The special expertise in lightweight structures developed in civil engineering, for example, is highly sought after for applications in other areas of structural engineering, such as in the construction of high-altitude weather balloons.11 Though it is a fair bet that FREI OTTO never thought of computer-aided simulation methods, his visionary power still affects us here and now.

Numerical wind field

Wind

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7 cf. P. D. Gosling, B. N. Bridgens, A. ­ lbrecht et al.: “Analysis and design A of membrane structures: Results of a round robin exercise”. In: Engineering Structures 48/2013, pp. 313 – 328. 8 cf. B. N. Bridgens, P. D. Gosling: ­“Direct stress-strain representation for coated woven fabrics”. In: Computers and Structures 82/2004, pp. 1913 –1927; F. Dieringer, R. Wüchner, K.-U. Bletzinger: “Practical advances in numerical form finding and cutting pattern generation for membrane structures”. In: Journal of the International Association for Shell and Spatial Structures 53/2012, pp. 147 –156. 9 cf. A. Michalski, E. Haug, R. Wüchner, K.-U. Bletzinger: “Validierung eines ­numerischen Simulationskonzepts zur Strukturanalyse windbelasteter Membrantragwerke”. In: Bauingenieur 86/2011, p. 129. 10 cf. M. Andre, K.-U. Bletzinger, R. Wüchner: “A complementary study of analytical and computational fluid-structure interaction”. In: Computational ­Mechanics 55/2015, pp. 345 – 357. 11 cf. A. Bown, D. Wakefield: “Inflatable membrane structures in architecture and aerospace: Some recent projects”. In: Journal of the International Association for Shell and Spatial Structures 56/2015, pp. 5 –16.

Top left  Soap film model of a four-point sail Top right  Streamlines around a fourpoint sail Bottom left  Numerical wind field above a stadium roof Bottom centre  Schematic sketch of a ­numerical wind tunnel Bottom right  Simulation of the wind pressure distribution on a large sunshade

Knut Göppert

Right  Spoked wheel principle

The Spoked Wheel for Ring Cable Roofs in Lightweight Construction

The spoked wheel, which everyone is familiar with from the bicycle, is an extremely material-­ conserving and clever structure. In the bicycle, tension members known as the spokes transfer the loads between the ground and the axle. To ensure the necessary lateral stability, the spokes are spread apart slightly toward the hub, which allows loads perpendicular to the plane of the wheel to be redistributed as well. These are the properties that are put to use by orienting a wheel horizontally, so that wind and snow loads are transferred out through the flared spokes. But how is it possible for such a delicate structure to withstand such high loads? The answer to the riddle is pretensioning: the many spokes of the wheel are pretensioned between the compression ring (the rim) and the hub. Though exterior loads will change the forces within the spokes, the spokes will always remain under tension. They stabilise the rim, so the support structure can remain slender even though it is under compression. A system tensioned in this way, in which the hub can be replaced as needed with a tension ring, can be used for many building tasks and is especially suited for large-span roof structures. Using a few tricks and keeping in mind the appropriate equilibrium conditions, it is even possible to evolve the form from the circular bike wheel to a curved rectangle. Roofs like this are known as ring cable roofs. There are four main reasons that favour the ring ­cable roof principle: Economy – All interior forces are s ­ hort-­circuited. This represents an elegant solution to a p ­ roblem that commonly arises in lightweight construction: the large cost of the foundations. The building components are defined as purely tensile or compressed structural elements, v­ irtually free of bending moments, so that they can be

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Horizontal spoked wheel

The spreading of the spokes radially outward; two compression rings, one central point

Expansion of the central point to a circular tension ring

The Spoked Wheel for Ring Cable Roofs in Lightweight Construction

assigned optimally utilised cross sections and appropriately high-strength materials. From span lengths of over about 40 metres, ring cable roofs are superior to purely cantilevered roofs if the ground plan geometry supports a sufficiently curved compression ring. If a ring cable structure or a cable structure is furthermore covered with a layered, high-strength but lightweight textile fabric, the result has a further advantage in terms of self-weight. Sustainability – In building, sustainability is primarily defined by energy consumption and the best possible CO2 footprint. A comparison between a cantilever roof for a stadium and a primary structure for a ring cable roof, for example, will show that the CO2 equivalent of the latter is significantly lower, meaning that

it contributes less to the greenhouse effect. In addition, the construction of ring cable roofs obviates the typically high costs for temporary support structures during assembly. This can lead to other savings in steel expenditure of up to 30 per cent. Aesthetics – Spoked wheel constructions are captivating in their structural elegance. The viewer develops an understanding of the load-­ bearing behaviour; the visual airiness and the light-flooded interior are ideally suited to the sporting events being held within. Quick and easy assembly – Cable structures are typically laid out on the ground and attached at predefined points without great difficulty. In a carefully choreographed sequence, the cables

Top left  Olympic Stadium Kiev (UA), new building envelope 2011, schlaich bergermann partner, architects: gmp ­Architekten von Gerkan, Marg und ­Partner; two compression rings / pretensioned cable structure of 80 radial cable trusses Top right  Estádio Maracanã, Rio de ­Janeiro (BR) new construction of the roof 2013, schlaich bergermann partner; one compression ring / a total of three tension rings Left and opposite  National Stadium ­Warsaw (PL) 2012, schlaich bergermann partner, architects: gmp Architekten von Gerkan, Marg und Partner, JSK ­Architekci

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The Spoked Wheel for Ring Cable Roofs in Lightweight Construction

are lifted into their final positions by hydraulic presses and pretensioned. This process can often be completed within two weeks. Based on these considerations, a great many stadium buildings have sprung up in recent years that feature some variant of the ring ­cable roof. But the principle is well-suited even for stadium refurbishments as in Madrid and Rio de Janeiro – up to and including oval and rectangular layouts, in which only a slight reinforcement of the existing support structure is necessary. The planners of the National Stadium in ­Warsaw created a building in which the forces are beautifully balanced – and in combining a permanent roof structure with a convertible ­inner roof, they also satisfied the building ­client’s desire for year-round use. The fixed roof is supported by a ring cable structure that draws its stability from supports, a single compression ring and from anchoring the diagonal struts in the foundations. The structure is complemented by a central needle floating above the middle of the field, and by 60 radial spoke cables that act as load-bearing elements for the convertible, suspended roof. A translucent membrane with a surface area of 8,400 square metres is slid along these cables and stored at the centre with a double fold. The stadium roof can be closed completely

in 17 minutes. In the Warsaw stadium this is done by a system that combines both mechanical and hydraulic operations – cable winches for the long stretches, hydraulic cylinders for the short tensioning distances. The needle serves not only as a compression strut, but also as a substructure for the vertically moveable garage in which the folded membrane can be parked to protect it from the weather. In addition, it supports the four attached video screens with their combined weight of 190 tonnes.

National Stadium Warsaw (PL) 2012; membrane garage (above); view from below the fixed membrane roof and the 10-metre wide circumferential glass roof, which is supported by the radial ­cables (left)

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Lightweight Construction in Motion

Assembly over the Thames. London Eye, London (GB) 2000, Jane Wernick (Arup), Marks Barfield Architects

The London Eye on the South Bank of the Thames has a diameter of 135 metres, making it the tallest Ferris wheel in Europe and the fourth-­ largest in the world. The 32 fully glazed compartments are fixed to the outer edge of the wheel and thus permit an unobstructed view of the city. A single rotation takes 30 minutes. Erected in the British capital on the occasion of the millennial celebrations, it was meant to symbolise the “turn of the millennium”. Though it was originally designed to be used for a limited time only, the structure has since become one of the great landmarks of London. Unlike other Ferris wheels, the London Eye has spokes like a bicycle wheel and is supported on one side only. Two inclined struts anchored in the ground transmit the weight of the wheel hub downward and away, while two spherical roller bearings in the hub, each 2.62 metres in size and up to 6 tonnes in mass, turn the wheel over the Thames. There was little room for a construction site on the South Bank, and the time allotted for the entire building process was quite short. Since conventional construction methods would have taken too long, the designers developed a plan in which the individual prefabricated elements of the structure and the cabins were delivered by way of the Thames and assembled on site. The real difficulty then lay in raising the structure from the horizontal into the vertical. The two large spherical plain bearings in the struts, whose actual function is to compensate for wind-­ induced micromovements, made it possible to pivot the wheel into its final position. Since the construction process was venturing into new territory and no data existed for comparison, this step was undertaken in several stages and with interruptions to allow engineers to rerun their calculations and to make any necessary adjustments.

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Lightweight Construction in Motion

Exploring New Dimensions with Timber

Timber is one of the most versatile and, simultaneously, most efficient building materials. It is renewable, sequesters CO2 and is available in many regions of the earth. High strength and low weight, good processing characteristics, high heat resistance as well as moisture-­ regulating ability are just a few of its positive material properties. A large range of building products can be manufactured using solid wood or wood composites. The multitude of uses to which timber can be put is similarly enormous, ranging from support structures, exterior walls, roofs and cladding on one end of the scale to interior design, furniture and everyday artefacts on the other. Aside from its architectural applications, timber is also used in the construction of towers, masts, bridges and other such works, as well as in the erection of large-span support structures. Even the formwork that shapes the building elements made from other materials such as concrete or reinforced concrete is often made of wood.

  Building site operations    Steel / reinforcement  Concrete   Timber   TOTAL

Greenhouse potential [lb/sq ft]

80

60

40

20

For millennia, timber has ranked among the most important building materials. Yet the attention it has been given in recent years in research, development and building programmes has been more pronounced than ever, thanks to the increasing need for ­resource-efficient, sustainable construction. Newly developed methods for digital design and building, for example, have laid the foundations for precise construction saving both time and costs. S ­ ystem-oriented modular construction methods allow for the ­implementation of adaptable buildings. Thanks to novel computation, production and assembly processes, the use of timber has been expanded into unexplored or barely explored domains, such as innovative support structures or high-rise construction. In the latter, the structural and physical properties of timber – more and more often in combination with other building materials – are coming into their own, with enduring results.

Facing page  Centre Pompidou Metz (FR) 2010, Arup (roof structure); architects: Shigeru Ban Architects and Jean de Gastines Architectes with Philip ­Gumuchdjian Architects (digital development/ establishment of the reference ­geometry for the roof) Left  Ecological balance of the CO2 emissions in the construction phase. Timber Tower Project (residential high-rise based on the DeWitt Chestnut Apartments in Chicago), SOM

0

-20

Conventional building type

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Timber hybrid building type

Exploring New Dimensions with Timber

Hybrid timber construction: Life Cycle Tower (LCT One) prototype Fire protection is considered the most significant issue in timber construction – especially in Germany, where a wood support structure is permitted only for buildings with a top floor maximum height of 22 metres. The Life Cycle Tower (LCT One) in neighbouring Austria, for example, has eight storeys and is 27 metres tall overall (the top floor height is 21.97 metres). This is possible because of a hybrid construction system, in which the load-bearing structure comprises prefabricated facade elements (support structures of

untreated wood, clad in aluminium) and the ceilings are made of a timber-concrete composite. The interior is free of pillars; only a rigid staircase core of in-situ concrete supports the system. The individual storeys are strictly separated from one another by a non-flammable layer of ribbed slabs made of a timber-concrete composite. To create these slabs, wooden beams were placed into an 8.10 × 2.70 metre steel formwork and cast in concrete. Double columns of timber in the plane of the facade carry the vertical loads. Owing to the high degree to which the ceiling and wall elements were

LCT ONE, Dornbirn (AT) 2012, architects: merz kley partner, Hermann ­Kaufmann Architekten (top left), prefab­ rication at the factory and assembly on site (left). The original research project was developed in collaboration with the timber construction company Rhomberg as well as Arup and is based on the concept “timber buildings up to 100 metres high”. The FEM model and the colour-­ coded dynamic deformation due to wind loads to determine possible building movements are shown for a 20-storey timber structure (top right) Opposite, top left  Illwerke Zentrum ­Montafon (IZM) in Vandans (AT) 2015, ­architects: merz kley partner, Hermann Kaufmann Architekten Opposite, top right  Student residential high-rise in Vancouver (CA) 2017, architects: Acton Ostry Architects, Hermann Kaufmann Architekten Opposite, bottom  Active House, first ­realised in Winnenden / Stuttgart (DE) 2016, Werner Sobek

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prefabricated, the whole construction process proceeded very efficiently. Work that began as an interdisciplinary research project evolved to produce the Illwerke office building, which boasts 10,000 square metres of usable space and also features ceilings of timber-concrete composite ribbed slabs. In the construction system employed in the 18-storey student residence in Vancouver, meanwhile, the glued laminated timber (glulam) columns are joined to the cross-laminated timber ceiling panels via standardised steel plug connections.

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Prototypes of lightweight construction The self-imposed goals for the Active House were as little energy expenditure as possible during fabrication, and subsequent single-type disassembly and recycling capabilities, all packaged in an aesthetically appealing design. These move-in-ready residential boxes of post-and-beam construction are insulated with 28-centimetre thick fibreboard panels and clad in a waterproof larch wood shell. The prefabricated boxes can be delivered by truck; only the foundations must be poured in concrete. Use of a standardised connection technology makes it possible to assemble the individual

Exploring New Dimensions with Timber

Centre Pompidou Metz (FR) 2010, Arup (roof construction); architects: Shigeru Ban Architects with Jean de Gastines ­Architectes and Philip Gumuchdjian ­Architects, Design-to-Production (digital development/ establishment of the reference geometry for the roof). The meshlike structure is inspired by a traditional Chinese straw hat, the hexagonal weave of which was translated here into a load-bearing frame of glulam timber beams. Top row 3D model of the roof and different geometries of the roof elements, far left individual parts of the roof structure and left view into one of the conical feet during assembly.

units in different arrangements as needed. The system is also especially well-suited for temporary or short-term uses.

From form finding to fabrication In 2010, a subsidiary of the famous Parisian Centre Pompidou was built in the city centre of Metz. Its free-form 8,500 square-metre roof structure spans three exhibition boxes as well as event and restaurant areas. The resulting interior space reaches heights of up to 37 metres. At night, the pattern of the timber construction shows clearly through the translucent roof membrane. The roof is fixed to a central mast and to the exhibition boxes with large steel rings. Four funnel-shaped columns descend from it organically and support it on the ground. The free-form roof would not have been possible without digital tools. The architectural concept had to be developed into a buildable form, and the form had to be translated into a structure. The task required close collaboration among architects, engineers, programmers and join-

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ers. A critical component of the development process was a complex digital 3D model which was used to compute the geometry of every single building element: the roof is composed of almost 1,800 doubly curved, individually CNC-milled laminated wood segments – a total of about 18,000 ­lineal metres – in three variants that can be bolted to one another. Right (top)  Visualisation of the support structure. Timber Tower Project – residential high-rise based on the DeWitt Chestnut Apartments in Chicago (US) 2013, SOM Right (bottom)  Visualisation of the support structure. Office and commercial building HoHo Vienna (AT) projected completion 2018; architects: RLP ­Rüdiger Lainer + Partner; engineers: RWT plus ZT, Richard Woschitz

Timber soars to new heights The high demand for raw materials in the face of increasingly scarce natural resources makes new approaches necessary. Renewable resources play a critical role in these considerations, leading to the development of stronger material constructs. Timber has always been an important building material, but now ideas for its uses are being expanded. All over the world, prototypes have been springing up in which timber is replacing less sustainable materials, in an effort to reduce the high CO2 emissions that the manufacture of cement and steel entails. One approach involves hybrid constructions of timber and reinforced concrete, where each material assumes the tasks for which it is best suited. While fire safety regulations are complicating the development of such buildings in Germany, countries like Sweden are implementing strategies to promote the use of timber in construction. In the town of Växjö, the load-bearing structures of 50 per cent of new construction must comprise mostly wood by the year 2020, and a few eight- and nine-storey residential buildings have already been completed. In the centre of Stockholm, a 34-storey residential tower is due to be ­finished by 2023. The high-rise features an exterior of timber, a concrete core and steel supports sheathed in wood. High temperatures will cause steel to buckle, while charred timber maintains its static properties for extended periods. The most recent “timber high-rise” record is held by HoHo in Vienna, currently under construction. The 24-storey building is projected to reach a height of 84 metres. The hybrid construction of concrete and timber comprises three parts, each braced with vertical access cores and wall slabs made of concrete.The “Timber Tower” by SOM, on the other hand, is purely a research project. In 2013, SOM was investigating the possibility of reproducing the 42-storey DeWitt Chestnut Apartment Building in Chicago (1966) using a timber hybrid construction method. Compared to the 1960s-era (steel) building, the construction of the wood version would produce only one quarter of the CO2 emissions.

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Exploring New Dimensions with Timber

Material and Design – Is Hybrid the Future?

Hybrid construction will determine the future. As a matter of fact, it has already determined the past and has been the norm – notwithstanding the modernity of the phrase “hybrid construction” – ever since humans began to build cities. Foundations and cellar vaults made of stone, with a masonry ground floor above and timber framing with clay infill: that was hybrid construction. So were the masonry buildings of the Gründerzeit (the German era of rapid industrialist expansion), which had ceilings and roofs of timber. The extraordinary churches of the Middle Ages were created as hybrid constructs of natural stone and wood, as well as the occasional forged tie rods or metal connectors. Even the impressive railway stations of the 19th and 20th centuries, such as the Copenhagen train station, are frequently hybrids of cast iron, masonry, timber and glass. The traditional division of the different building specialities into concrete, masonry, steel or timber construction represents a significant oversimplification. At most, it can be seen as a categorisation of structures according to their principle building material – yet it leads to the inevitable question of how ‘principle’ is determined: by weight, volume, area, cost? Many uses have always been found for materials that were locally available, financially affordable and easiest to extract, process and build with at the desired building site. Materials have influenced form finding and structural design, and have spurred master builders of various epochs to make optimal use of their physical characteristics. In this sense, from its very beginnings the building industry is and has been indebted to the concept of efficiency, from the arch structures of the Romans to HANS ULRICH GRUBENMANN’s bold timber bridges and ROBERT MAILLART’s equally auda-

cious reinforced-concrete bridges on to the high-rise buildings of our time.

Innovative uses for materials Just as the natural materials stone and timber have influenced design, the new, artificially manufactured materials such as steel, glass and reinforced concrete have done so to an even greater degree. A novel material fires the imagination; it must be tried and tested, and its limits in terms of both design and technology beg to be explored. A critical need governing building materials – apart from the desire to try them out and to discover their limitations – is a scientifically based description of their material, strength and stiffness characteristics as well as the associated development of new fabrication and computation methods. As a consequence, new materials and forms also introduce new testing methods, computation techniques and standards.

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Stefan Winter

Below  Central railway station in Copenhagen (DK) 1911, architect: Heinrich Wenck Facing page, top  Various timber beams and trusses developed by Otto Hetzer (“Hetzer trusses”): left a parabola-shaped composite beam (Patent No. 163144, 1903), right various trusses (Patent No. 225687, 1907) Facing page, bottom  Saldome 2, salt warehouse of the Riburg saltworks, Rheinfelden (CH), Jürg Fischer, SIA

The material itself is not the only driver of technological development, however. Its ­s uccessful implementation also requires an ­engineering model and the capability to manufacture and use the material at an affordable cost. From time to time, a new fabrication process makes it possible to use an ‘old’ material in completely new applications. The present precision of prefabricated timber buildings, for example, is due entirely to the millimetre-scale precision achievable through CAD and CAM design and manufacturing processes. And the recent development of additive fabrication (3D printing) is opening up entire new domains to building with concrete, steel, plastics and wood-based materials. But new building processes like 3D printing in turn require new design systematics, new building process organisation, altered construction schedules and, as always, continuing education for all parties involved.

Taken together, architecture and material ­determine the structural design. The strength and stiffness of the material, its weight and the available geometrical dimensions impact the static systems and structural forms: arches and domes require materials that are pressure-­ resistant and rigid in compression, cables and membranes must exhibit tensile strength and stiffness, plates and bending rods must show bending resilience, etc. The available technical options for connection technologies further influence fabrication processes and the overall size of the structure. In steel construction, the evolutionary progression went from forging to riveting to bolting to welding. Modern steel bridges are fully welded structures, no longer assembled from small cross-sections and thousands of rivets. In reinforced concrete construction, prefabricated building components of precast concrete are joined together using high-performance grouting mortar. A modern timber building is virtually unthinkable without bonding, high-precision joining of 3D connections or the use of fully threaded screws. Together, the careful selection of the right materials and the design of the support framework result in structures that are sufficiently robust and long-lasting to function well in their environment.

Efficient building Like hybrid construction, making efficient use of available resources is not a new invention. Whether the reasons have to do with cost or availability, for centuries the goal of master builders has been to achieve the best possible effects with the least possible means. So has everything already been invented? Are there no exciting developments to look forward to? Is it enough for architects and

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Material and Design – Is Hybrid the Future?

civil engineers to just add a little spice to centuries-­old traditions – say, in the form of those new materials (like carbon) that globalisation seems to have made available in near-limitless quantities – and just keep building as before? No, because nowadays there ­ dditional considerations that have an are a increasing influence on material choice and therefore on structural design. The most important issue is energy efficiency. In addition to the energy expended in the operation of buildings – passive houses or plus-energy houses have in many cases ­already become standard in this regard – more intensive consideration is now being given to how much energy our buildings consume in the manufacture of their components, during construction, and eventually during their demolition and reprocessing. The so-called Life Cycle Assessment (LCA) illustrates the environmental impact of buildings. It shows that, thanks to recent optimisations in the energy efficiency during the use phase, energy expenditures during the construction and demolition phases of buildings now predominate. Coupled with this are the long-term prospects for the availability of building materials. Many materials are manufactured from finite resources, some in highly energy-intensive processes. Concrete is composed of gravel, sand, cement and water. Sand that is suited to the production of concretes is becoming quite scarce in some regions of the earth. The manufacture of cement, which is fired from limestone and clay, is the source of about seven per cent of the world’s CO2 emissions. The process by which aluminium is smelted from bauxite is extremely energy-consuming, etc. In comparison, a sustainably managed forest will supply wood today, and will continue to do so for the next 1,000 years. Another question that arises because of the increasing scarcity of building materials is that of reusability. In Germany, the amount of material in buildings alone is a staggering 14.72 billion tonnes.1 Given an expected building lifetime of 50 years, the recovery of materials from these buildings – a process known as ­urban mining – will take on great significance (at present, “only” about eight million tonnes are recycled annually). The building industry must learn to adapt its construction methods to ensure recyclability so that, ideally, the resulting buildings can be dismantled into their constituent materials without great (energy) expenditure. The catch is that this requires people to do and pay for things now from which they will not themselves profit. Building owners and, by extension, their designers must proceed like foresters in putting long-

term, generation-spanning plans into action. A further consideration influencing the choice of materials is the possible contamination of air through substance emissions. Materials can also impact room temperature and relative humidity via their thermal and hygric properties. Thanks to their visual and haptic effects, building materials represent critical elements in design. As hybrid building substances, they will be able to do even more. It is possible, for example, to modify concretes so that they function as solar cells and produce electricity, or so that they serve as switches for interior lighting. Building components can be activated to deliver heating or cooling or they can be integrated to supply ventilation – all hybrid technology. None of this, of course, is possible without a qualified labour force. Modern and traditional building materials require extensive knowledge – the mason must know how to lay high-quality exposed brickwork, the concrete worker must be expert in reinforcement, the welder must have mastered of welding sequences, the joiner must be conversant with the many new timber materials and with computer-assisted fabrication methods. Taken together, these demands make the case for transferring more work from the construction site to industrial prefabrication venues, where the environment can be better controlled to ensure safety and quality.

Timber as the building material of the future Many of the considerations discussed above support the rapid renaissance of timber construction: timber is the only sustainably-­sourced building material that is available worldwide in the necessary quantities and with the required properties and dimensions. It grows in forests, which in Europe, at least, are all managed according to a sustainability principle introduced by Hans Carl von Carlowitz more than 300 years ago. The timber harvested every year corresponds at most to the annual growth. Compared to other building substances, wood has the best power-to-weight ratio (relationship between strength and bulk density), and its low weight allows for large prefabricated elements. Since the development of large-scale, bulk cross-laminated timber, wood and reinforced concrete are the only building substances from which rods and slabs can be fabricated as construction elements. The structural system with supports, girders, beams and decking is identical, and combining the materials to form timber-concrete composite ceilings and walls is one way to implement a hybrid construction process.

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1 Umweltbundesamt (ed.): “Kartierung des anthropogenen Lagers in Deutsch­ land zur Optimierung der Sekundärroh­ stoffwirtschaft”. UBA Texte 83/2015, Dessau-Roßlau 2015

Opposite  Student residential high-rise in Vancouver (CA) 2017, architects: Acton Ostry Architects, Hermann Kaufmann ­Architekten

In the past few years, timber has been visibly reclaiming the city, both in tall buildings and in approaches to urban densification. The latter represents one of the most important challenges to present-day construction, and wood is especially well suited to tasks such as adding storeys to existing houses, closing gaps and creating building extensions. Should all future construction use timber ­exclusively? Not quite – as with all building materials, its distinctive peculiarities must be taken into account. One of these is the pronounced anisotropy of timber. Its structure can be likened to that of a bundle of tubes, with high strength along the grain but a factor of ten less in the orthogonal direction. As a consequence, it has a tendency to split or form cracks. Similar pro and con arguments can be made regarding its building physics (acoustic and moisture insulation), fire safety, its effects on the indoor climate and its need of wood protection measures. Timber construction must be based on expert knowledge and a solid understanding of the material. Is there even enough timber available in forests to cover the increasing building industry demand? The answer to that, for our sustainably managed forests, is an unqualified “yes”, though this is predicated on a reduction in conifers and an increase in hardwood harvests due to climate-induced forest conver-

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sion. Since hardwoods are stronger and stiffer, and therefore facilitate the production of more slender and efficient building components, this forest conversion in turn opens up new perspectives and opportunities. Added to this are the ever-increasing possibilities for modifications of timber. Just a few of these include the manufacture of thermowood, mineralisation, magnetisation or adaptations in electrical conductivity. Can timber be considered the building material of the 21st century? Yes, but not exclusively. The important thing is that more sustainably sourced materials be used in construction. Timber and timber construction will make their contribution to this effort, and will inspire many exciting developments along the way. Combining wood sensibly with other materials will foster the hybrid construction of the ­future, in which each material finds the optimal niche for its own characteristic strengths. The art of building, of architecture, of civil engineering lies in finding and developing synergistic combinations, and in presenting people with solutions that are long-lasting, robust, safe and – in the best of all worlds – beautiful to their users. Buildings with appeal will be cared for and preserved, and that – independent of material – is the most sustainable approach to building!

Material and Design – Is Hybrid the Future?

Aiming High

1

Rainer Graefe, Murat Gappoev, Ottmar Pertschi: Vladimir G. Šuchov. 1853 –1939. Die Kunst der sparsamen Konstruktion. Stuttgart 1990, p. 18. Facing page  Burj Khalifa, Dubai (AE) 2010, 828 m, Bill Baker / SOM Below (left to right)  Eddystone Lighthouse, Plymouth (GB) 1759, 22 m, John Smeaton Eiffel Tower, Paris (FR) 1889, 301 m, Gustave Eiffel in collaboration with ­Maurice Koechlin and Émile Nouguier Shabolovka radio tower, Moscow (RU) 1922, 150 m, Vladimir Shukhov Stuttgart TV tower, Stuttgart (DE) 1956, 217 m, Fritz Leonhardt

One of the prerequisites that allows engineers to meet the challenges set by societal needs is the willingness to transcend limits. The motto “higher, faster, farther” is transformed to “more complex, more delicate, more flexible”. The technologically thinkable becomes the doable, covering the full spectrum from the sensibly rational to the emotional power of the monumental. Challenge and experiment go hand in hand. The first manned mission to the moon on 16 July 1969 was a much greater accomplishment than merely setting foot on an earth satellite. It was also more than the culmination of a political race: it opened up a perspective on Earth that had never before existed.

Information spreads throughout the world Before height became habitable, towers were transmitters of information: lighthouses on coasts or lookout and watch towers on land using signals to relay messages. Though for a long time, limits existed on how tall such structures could be, the creation of the Eiffel Tower in 1889 changed this. The tower was a vision made manifest of a structure taller than any that had gone before, and a successful

demonstration of what is technologically possible. In the ensuing decades, the modern world became more turbulent; revolutions, political upheavals and, later on, the Great Depression all preoccupied the public. Electrification was introduced, movies suddenly had colour, and the new medium of radio conquered daily life. Towers now took on new significance: as transmission masts they broadcast information to an increasingly networked society. VLADIMIR SHUKHOV’s Shabolovka radio tower, built in Moscow in 1922 and dubbed the “trumpet of the radio revolution”,1 is a prime example. It represents a new type of structural framework, SHUKHOV’s hyperboloid lattice tower. Because it was easy and quick to build, the structure was subsequently often used, not only for broadcasting but also for water towers or high-voltage pylons. A similar revolution in the world of tower construction occurred when Fritz Leonhardt built the Stuttgart television tower in the 1950s: it marked the first time a tower was made of concrete, and soon copycats cropped up all over the globe. By this time, the battle between residential towers for a place in the record books had become practically routine. Thanks to new methods for transmitting data, meanwhile, towers continued to decline in functionality and importance, while the technological muscle-flexing and showiness they once embodied have long since become the purview of the supertalls.

Milestones on the way up The high-rise is the innovative building type of the 20th century and a New World invention. In his 1927 book New Backgrounds for a New Age, Edwin Avery Park writes that it “represents the first real contribution by America to the history

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Aiming High

of architecture. ”The figurative fuse for high-rise construction was lit when the fail-safe elevator was introduced. In a spectacular demonstration, using himself as a test subject, Elisha Otis presented his epochal invention at the 1853 World’s Fair in New York. Otis’ new lift was first installed in 1857 in the E.V. Haughwout Building. What followed over the next 150 years was a skyrocketing progression from high-rise to skyscraper to the supertalls that are now approaching the one-kilometre mark. On the way up, the engineers of the 19th century drew inspiration from the bridge builders; other influences on the increase in height and cubage came from technological and structural innovations as well as materials and also, ultimately, the zoning codes of the cities. The next steps on the rise to the top were first made possible by the use of iron for the internal support structure, and later steel for the load-bearing frame. The ‘dissolution’ of the supporting exterior stone walls came next, removing the last barriers to rapid upward growth. Thanks to the introduction of electric light into cities, even rooms that the layout had relegated to the deep interiors of buildings could now be utilised more effectively.

The first high-rises built in Chicago after the great fire of 1871 were still encased in a stone facade to provide protection from fire. This changed in the middle of the 20th century, when engineers adopted the use of the curtain wall, common in industrial buildings, for their facades. Covers made of thin metal profiles and glass were suspended like curtains, independent of the support structure, from mounts on the outer edges of the buildings. In the second half of the 20th century, civil engineers concentrated mostly on efficient load-­ bearing structures, which were, in the main, steel construction. Today, composite systems of concrete and steel are once again in vogue, presenting a challenge to concrete technology, which is developing flowing (high slump) concrete in response. Flowing concrete is very strong and fast-curing and can be pumped easily to great heights. Though initially highrise buildings were generally used to house department stores and offices,2 soon residing in a tower established itself as a popular way of living – first in America and, much later, in Europe as well. One example of such a tower is Marina City, which was the highest residential building in the world when it opened in 1962.

2 Chicago’s first generation of high-rises (second half of the 19th century) are now known as ‘Chicago Commercial’. For more on this, see Robert Bruegmann: “Myth of the Chicago School”. In: Charles Waldheim, Katerina Ruedi Ray (eds.): Chicago Architecture. Histories, Revisions, Alternatives. Chicago 2005. pp. 15 – 29. Daniel Bluestone: “Preservation and ­Renewal in Post-World War II Chicago”. In: Journal of Architectural Education. Vol. 47, No. 4 (May 1994), pp. 210 – 223.

Below  Selection of a few buildings that represent technological and structural ­innovations and that influenced the ­development of the high-rise (stated height is the architectural height of the building).

800 m

up to 400 m

up to 200 m

up to 100 m

Scale 1:3,000

1885  Home Insurance ­Building, Chicago (US), 55 m. William Le Baron Jenney. At ten storeys, it is considered one of the first high-rises in the world.

1894  Chicago Stock ­ xchange Building, Chicago E (US), 57 m. Sullivan & Adler. The foun­ dation principle of bridges (the caisson foundation) is first used in high-rise ­construction.

ENCLOSURE + SPACE  |  Towers and High-Rises

1895  Reliance Building, ­Chicago (US), 61 m. Architects: John Wellborn Root / Charles B. Atwood. Skeleton construction, and one of the first buildings without load-bearing walls. Facade with extensive ­window elements.

1931  Empire State Building, New York (US), 381 m. William F. Lamb, Homer G. Balcom. The cubage of this skyscraper, which narrows with height, dates back to the 1916 New York Zoning Act.

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1952  Lever House, New York (US), 92 m. SOM / Gordon Bunshaft. One of the first high-rises with a curtain wall.

M 1:3000 alle bis auf burj

Annette Bögle, Christian Hartz, Bill Baker

Pushing the Limits

Humans have always experienced the desire to build upwards. Evidence for this can be seen in the story of the Tower of Babel, in the Dynasty Towers of San Gimignano in Tuscany and in the many Gothic cathedrals and churches of Europe. Often considered statements by the builder or the user, towers and tall ­buildings provide a view over great distances

that can serve a functional need or evoke an emotional experience. Now, however, economic considerations likewise favour the construction of high-rises in inner cities, to create denser urban centres in support of both urban development and ecological goals. In the process, new height records are continually being pursued and established – a trend that may to some extent be viewed critically, but nevertheless brings with it important technological developments. High-rises must fulfil two essential technical requirements: they must incorporate a vertical supply system – specifically, functioning building services and a reliable means of vertical transport – and their structural support system must handle the increased height-dependent loads and redirect them safely into the foundations.

Use and supply

Scale 1:6,000

Scale 1:3,000

1965 DeWitt Chestnut Apartments, Chicago (US), 120 m. Fazlur Khan / SOM. First use of the “framed tube”, a bending-resistant system of columns and spandrel beams within the building facade.

1973 U.S. Bank Center, ­ ilwaukee (US), 1983 m. M Fazlur Khan’s “outrigger system” becomes one of the most important support structures. A stiff, storey-high construction connects the highrise core with the load-bearing outer columns.

M 1:6000

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2010 Burj Khalifa, Dubai (AE), 828 m. Bill Baker /SOM. With a “buttressed core” support structure, this building represents the first successful completion of a tower exceeding 800 m in height.

M 1:6000

M 1:5000

The use of a high-rise would be unthinkable without Elisha Otis’ invention of the fail-­ safe ­elevator (also known as the ‘vertical railway’). The implementation of lifts takes up a significant proportion of a building’s square footage. Putting in a single lift is not enough; since large numbers of people use a high-rise, the building requires a sophisticated system consisting of both express elevators that service only certain levels and local elevators that stop at every level. To give an example, the ­average percentage of non-marketable floor space in a Chicago high-rise is 15 per cent, while in the Burj Khalifa (2010), currently the tallest skyscraper in the world, that number is 35 per cent. Included in this total are not ­only the lifts themselves but also rooms for ­energy supply, maintenance and waste disposal. These and all other aspects of sustain­

Pushing the Limits

ability demand more urgent attention in skyscrapers than in smaller structures, because of their outsized dimensions and their (exposed) ­design.

Tall and taller The taller a building or the longer a bridge, the more important it is for the structure to be ­supported by an efficient framework. The current records in high-rise construction, for example, are only possible when the small self-weight of the structure allows for large live loads. In addition to the self-weight and live loads, all buildings – but most especially high-rises – must be capable of withstanding wind loads and the forces that occur during earthquakes. Viewed on a large scale, a tower, and therefore also a slender skyscraper, is essentially a ­giant, vertical cantilever, a statically determined, easy-to-calculate system. As an efficient structure, it must be engineered so that it does not buckle under vertical loads and simultaneously limits horizontal movements, or oscillations, to an acceptable degree to guarantee the building’s usability. The magnitude of wind loads and their effects (oscillations) are directly correlated with the building characteristics: its height, its external form and its internal structural system. The fine art of skyscraper design lies in composing this complex interrelationship, and only a perfect composition makes tall – and the tallest – buildings possible.

To reach the limits of the possible, the trick is to reduce the unavoidable shear deformations to a minimum. For example, for a long time, the ‘bundled frame tube’ structure of the ­Willis Tower in Chicago was considered highly efficient because, of all the deformations it was subject to, under 30 per cent were shear deformations. This value was, however, reduced down to ten per cent for the structural system called the ‘buttressed core’ used in the record-breaking Burj Khalifa.

Torsional forces Forces due to wind and earthquakes pose a challenge because they can act on all sides of a building. In such cases, the building not only bends, but tends to twist – i.e. experience torsion – about its vertical axis. This can represent the controlling load case, especially for seismic loading. To counter this type of stress, the building must possess torsional stiffness. As a general rule, the geometry of closed cross-sections results in a much greater torsional stiffness than that of open cross-sections. The structural systems of high-rise buildings fulfil these requirements with shear walls that brace the building core (lift shafts, stairs, toilets, utility rooms, etc.) or through a closed frame in the exterior facade.

Horizontal forces Going higher not only causes the sum of all horizontal forces to rise but also increases their individual magnitudes. The engineering approach to horizontal forces, which result primarily from wind and rise with height in a non-linear fashion, is reflected in the development of high-rise support structures. In the cantilever, horizontal loads cause bending and shear stresses. As a result of the bending stresses, the tower will experience tension forces on its windward and compression forces on its leeward side. Shear forces develop as each individual floor level becomes distorted while transmitting the horizontal loads toward the ground storey by storey. Since the horizontal forces add up on the way down, the distortions also increase toward the foundation. Despite the simple analogy to the cantilever, the support structures of high-rise buildings are very complex. This means that the bending and shear deformations are superimposed, and the shear deformations cannot be neglected as they are in the simplified beam theory.

ENCLOSURE + SPACE  |  Towers and High-Rises

Willis Tower (formerly Sears Tower) ­during construction, Chicago (US) 1973, 443 m. Fazlur Khan / SOM (left); a bird’s eye view reveals the staggering of the ­individual ‘tubes’ (above). The architect Bruce Graham compared the appearance of the tower to that of a newly opened pack of cigarettes, from which the cigarettes project unevenly. Opposite  Construction of the John ­Hancock Center in Chicago (US) 1969, 344 m. Fazlur Khan / SOM

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New systems out of growing challenges The primary demands on skyscrapers have given rise to different structures. However, significant strides in the development of structural systems depend not only on these demands, but also on technological options, particularly available materials. The First Leiter Building (1879) in Chicago is considered one of the first modern high-­ rises. It still has load-bearing walls, but also features a skeleton structure of cast iron. In these types of structures, the transfer of horizontal loads goes through the frame, and the achievable building heights are correspondingly limited. The next developmental step is combining the frame structure with an internal core. Because its walls have very few openings, the core has high shear and torsional stiffness, but as the height increases

it becomes too slender to ensure the necessary stability. For this reason, the innovation known as the outrigger system combines a building core with a series of outriggers. In this arrangement, outriggers placed at regular intervals and attached rigidly to the core connect it with the outer columns, so that the structural elements placed farthest away from the neutral axis can resist bending moments. The outrigger levels generally house the mechanical services. Ideally, the entire building surface is utilised to resist the loads. The distinctive, visible outer frame of Chicago’s John Hancock Center makes the structure one of the first framed tubes. When these are bundled, the result is the unique staggered arrangement of the aforementioned Willis Tower. The denser the outer frame lattice is, the more efficient the load-bearing behaviour of the tubes becomes. In the Burj Khalifa, the options available at the time of its construction were combined in a new way – only this allowed the leap from about 500 to the new record height of approximately 800 metres. The structure is a ‘buttressed core’, a hexagonal core braced by three vertical wings. Though the core is torsionally stiff, it is much too narrow to be able to stand on its own. Therefore it is supported by the wall-like wings, whose forms follow the bending curvature, much like the buttresses in Gothic cathedrals.

On to new records Today’s towers are getting more and more slender, which means that they are growing ever taller in relation to their base width. The narrower a building is, the easier it is for wind to cause it to swing. This behaviour relates to the aerodynamic properties of a tower. Wind blows, and when it encounters a building its flow is disturbed. The disturbance generates alternating eddies on either side (vortex shedding), which exert lateral forces on the building. The resulting alternating forces on the building cause it to undergo horizontal oscillations. The duration (period) of an oscillation, as well as its intensity, are critical factors in the design of a structure. Both depend on wind speed, the effective building width and the building’s position relative to the wind. To avoid the occurrence of oscillations or to minimise their effects on the structure as much as possible, the footprint and the shape of the building are tuned to the prevailing winds so that a targeted ‘disturbance’ of the uniform wind flow results in asynchronous vortex

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Pushing the Limits

Free end

Wind load

l

Fixed end

W

Self-load Gravity weight diagram

shedding. In the Burj Khalifa, for example, this is achieved through the variations in geometry between different storeys, markedly reducing the lateral wind forces. Thus it is possible for a support structure to influence active wind loads. The aerodynamic properties of a building not only impact its structural safety, but affect the well-being of the people inside as well. For example, during extreme wind conditions, the John Hancock Center in Chicago can experience deformations of up to 70 centimetres at its tip. It is important to differentiate here between horizontal and torsional oscillations, as people are significantly more sensitive to rotational motions. For this reason, any occurring oscillations must be damped as much as possible. This can be done either through choice of structure and/or through the building material. Reinforced concrete frames exhibit larger damping effects than reinforced steel walls or steel X-braces. The dynamic characteristics can also be changed by using additional mechanical dampers.

Wind Wind ­moverturning oments diagram

Self-weight Combined gravity and wind wind load diagram: one wind direction

1st mode period = 11 seconds

2nd mode period = 10 seconds

In the wind tunnel Wind tunnel tests are performed to predict aerodynamic behaviour. In these tests, the normalised frequency and the corresponding dynamic responses of the building are measured for different wind speeds. A significant danger to the building occurs when the frequency of vortex shedding approximately coincides with the eigenfrequency of the structure, which is the frequency of its easily excitable typical eigenforms. The resulting self-amplifying effect is known as resonance, a state in which the amplitude of the oscillations builds up rapidly in a sort of feedback loop. Compact and slender buildings exhibit interesting differences in their behaviours. Compact buildings with a high degree of

ENCLOSURE + SPACE  |  Towers and High-Rises

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Potential Potential tall building buliding form form

3rd mode period = 4 seconds

the physical limits of simple over-compression to counteract any existing tensile forces. Consequently, tensile forces must be taken into consideration in the design of the foundation, which not only makes the foundation more complex but also more costly. Ultra-slender buildings, for example 432 Park Avenue in New York City, are therefore built only in extremely dense urban areas.

What is next? Opposite, top left  Structural diagram of a fixed vertical cantilever beam Opposite, top right  Form finding for tall buildings Opposite, bottom  Characteristic diagram of the first three important eigenmodes with their periods for the Burj Khalifa Right  432 Park Avenue, New York (US) 2015, by WSP Cantor Seinuk in collaboration with schlaich bergermann partner (architect: Rafael Viñoly Architects). The roof height is 426 m, with a widthto-height ratio of 1:16

stiffness lie above the resonance interval for all wind events, so the dynamic force contribution tends to be small. Narrow structures, on the other hand, cannot be clearly positioned, and their resonance interval lies somewhere in the middle of possible wind events. This can lead to substantial movements of the structure and usually requires the use of additional vibration dampers – expensive and high-­maintenance elements. A well-designed structural system can potentially avoid the need for such dampers.

Safely set up The stresses on a high-rise are concentrated at its base. The bending stresses resulting from the horizontal loads create a force coupled with a compression and a tension component. It is significantly easier to lay out a foundation just for compression forces than to carry possible tensile forces into the ground. Ideally, the tension component is counteracted by the self-weight of the tower, as in most structures. The magnitude of the tension or compression component for a given bending stress depends on the size of the building footprint. The narrower and taller a structure is – that is to say, the more slender it is – the greater the forces. Today’s very slender buildings exceed

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Despite the 2001 attacks on the World Trade Center in New York, numerous technological developments have prompted and emboldened high-rise designers to explore new dimensions. Most of the tall and tallest buildings are located in Asia and the Near East within a dense urban context, since the development of megacities there is coupled with high population growth. As a result, these ­skyscrapers are no longer unique representative buildings of a corporation, for example, but rather part of a three-dimensional urban space. In this context, profitability, structural efficiency and considerations of reproducibility (a rapid construction process) become paramount. The geographical locations of many high-rises are often coupled with complicated regional conditions, such as earthquakes or extreme wind or weather conditions. The climate in particular is a driver for the continual increase in building sustainability demands. Given this complex assortment of requirements, there is no single approach to an optimised structural system, though for the first record heights this goal was one of the preponderant criteria in the design. In order to vouchsafe the further development of sustainable high-rise systems, a number of disparate, in many instances even mutually exclusive considerations must be addressed. This requires the development of completely new, hitherto unknown structural typologies that will stand out for their geometry-dependent efficiency alone. Critical to this effort will be new optimisation algorithms as well as tried-andtrue knowledge (graphic statics, the Rankin method, Michell structures), broadening the expertise of even experienced structural designers. Ideally, the new findings will have applications in different building tasks as well. In parallel with these developments, nuanced (site-specific) critical discussions must be held, in which the ecological, functional and creative justifications for projects take centre stage – for a given location, what is a reasonable and appropriate upper limit for the height of a highrise building?

Pushing the Limits

The Buttressed Core

Engineers, architects and owners are in constant pursuit of ever taller buildings. At 829.80 metres, including its antenna, the Burj Khalifa is currently the tallest skyscraper in the world. One hundred and sixty three of its storeys are usable, while the top eight leading to the tip of the building house only mechanical facilities, which are accessed by a narrow staircase. Two outdoor terraces for visitors are located on the 124th and 148th floors, at a height of over 555 metres. The multifunctional tower comprises about 280,000 square metres of floor space, accessible via 57 lifts and eight escalators. Apart from retail stores and a hotel, the building is used mainly for office space and residences. The tower has a Y-shaped ground plan, formed by three building wings attached vertically to the central hexagonal core. The wings are stepped upward so that their combined setback pattern forms a spiral. The 120° angles between the building wings not only maximise the views, but provide residents with the requisite degree of privacy, as the arrangement eliminates direct sightlines into neighbouring flats. The shape of the building’s footprint combined with the upward progression in the floor layouts serves to provide rigidity to the tower. Its new structural type, the “buttressed core”, is characterised by extraordinary lateral and torsional stiffness. An especially difficult challenge in the reinforced-­c oncrete construction was the ­development of a flowing concrete that was capable of being pumped up to heights of over 600 metres in a single work step without losing its consistency. Two of the world’s largest high-performance pumps were used to achieve this feat.

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Burj Khalifa, Dubai (AE) 2010, Bill Baker, architect: Adrian Smith (SOM). The diagram (below) illustrates the allocation of the storeys to different functional use sectors as well as an example floor plan from each sector.

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The Buttressed Core

Water + Energy

Water in Cities

In Germany, the average daily consumption of water is approximately 125 litres per person, of which only about 1.3 litres are used for drinking. In all, 85 per cent of water consumption in Germany is attributed to commercial uses in industry and agriculture. Every day, enormous quantities of high-quality water must be supplied, and the wastewater must be collected, treated and recycled. The supply and drainage of water from districts and cities are of fundamental importance for public and environmental health, and present a challenging task for civil and environmental engineers. The processing, purification and collection of water are just three of the functions of modern water networks. The conversion of old sewage canals, as for example in Emscher Park, ­creates new landscapes that very often result in an overall improvement in the quality of the

living environment. Open waterways that constitute part of the drainage system are now perceived as attractive green spaces that provide opportunities for local recreation, energy production and climate regulation. As a consequence, they have become a core component of urban development projects, necessitating a multitude of design and construction processes. While the primary challenge about 150 years ago was to improve the sanitary conditions for the population at large, today’s designers are faced with a much more complex set of requirements. Increasingly scarce resources and a rise in the incidence of extreme rain events, together with demographic changes and urbanisation, demand focused attention. The solution lies in flexible modular systems that address technical concerns while simultaneously providing sustainable approaches to confront and facilitate the water and energy transition. Facing page  Groundwater well, Frastanzer Ried, Feldkirch (AT) 1980 Left  Sewer system for Hamburg (DE) from 1856, William Lindley. After a great fire that destroyed almost a third of the Hanseatic city in 1842, the city council voted in favour of implementing a design submitted by canal construction engineer Lindley shortly after the disaster. The plan for the reconstruction of the city and its sewage system also included a public water supply as well as washand bathhouses. In the following years, the first network of sewers on the ­European continent was established, which Hamburg residents call the ­Sielnetz.

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Water in Cities

Water Transitions in Cities of the Future

A historical review of urban water supply and wastewater disposal The supply of water and the disposal of wastewater have been a challenge for human settlements from time immemorial. For this reason, early settlements tended to be located near water: on river banks, near springs, or on lake shores. Because of their steadily growing populations and densely clustered buildings, me­ dieval cities were characterised by highly unsanitary conditions. All refuse, including human and animal faeces, ended up in the streets or ­ xisted, in in ditches or frequently, if these e ­rivers and streams. This did not deter people from withdrawing water from those same water sources and using it to cook food, wash dishes, or brew beer, for example. A ­directive

issued by the mayor of Munich in the 13th century states that “no one is to throw their refuse out of their door, but rather dump it into the town creek.”1 This partially closed water cycle had serious consequences for public health, and resulted in a multitude of diseases and ­epidemics. As early as 1836, the physician and hygiene expert MAX VON PETTENKOFER pointed out the connection between the constantly ­recurring plagues (especially of cholera) and the poor water supply and disposal practices of the citizens of Munich. However, it was not until the late 19th century that this connection was scientifically understood and unambiguously substantiated. In the cities of the mid-19th century, growing urbanisation and industrialisation caused the

WATER + ENERGY  |  Water Supply and Wastewater Disposal

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Jörg E. Drewes

1Rolf Meurer: Wasserbau und Wasserwirtschaft in Deutschland. Wiesbaden 2000.

Below  Joseph Bazalgette (top right in the photograph) on the construction site of the northern sector of the sewers beneath the Abbey Mills pumping station in London, 1862

Top left  Cross section drawing of the Emscher Brunnen (“Imhoff tank“) by Karl Imhoff (1907). The vessel is used for the initial mechanical clarification of sewage in water treatment plants. Top right  Sewer profiles for the Mannheim sewer system. William Heerlein Lindley (1853 –1917), son of English ­canal builder William Lindley, was given the general directorship for the construction of the new urban sewer network in the city centre. Below  Water treatment plant Essen-­ Rellinghausen (DE), the site of the first operational activated-sludge basin in 1914 (biological wastewater clarification was first introduced to the European continent in 1912). The prerequisite for this was the Imhoff tank

situation to become dramatically worse. At this point, a targeted effort was begun to install ­underground sewers in the streets that would transport waste and rain water out of the cities. This water-based sewer system improved city sanitation, but resulted in significant contamination of the waterways. In 1842, work on a sewer system as we know it today was started in London. The first modern sewer network on the European continent was begun in Hamburg in 1856. Though a cholera epidemic in Munich in 1854 prompted a reassessment of the situation, it was only in 1862 that work on a citywide sewer system was initiated under the leadership of the civil engineer and architect ARNOLD ZENETTI. Through research visits to northern Germany and various large Euro­

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pean cities, ZENETTI had set in motion a knowledge transfer, the insights of which have left their mark on the water supply and wastewater disposal of Munich to this day. Where once untreated wastewater was discharged straight into nearby bodies of water, little by little it ­began to be mechanically processed in treatment facilities before being discharged, so as to ­reduce water pollution. In 1869, JAMES ­HOBRECHT, a civil engineer and urban planner, laid the foundation stone for the city sewer system of Berlin, in which radially arranged discharge and pumping systems transported wastewater out to sewage farms outside the city. The concept of wastewater irrigation was also adopted in Gdánsk, Dortmund and ­Münster. In Manchester in 1914, the chemists Edward Ardern and W.T. Lockett developed the activated sludge process, a treatment step in which microorganisms clean the water by utilising the matter in wastewater as a growth medium. This biological method remains the backbone of wastewater treatment throughout the world to this day. Another pioneer in wastewater technology, KARL LUDWIG IMHOFF, was instrumental in advancing this and other important processes further. IMHOFF , who studied civil engineering at the Technical University of Munich and the Karlsruhe Institute of Technology, is considered the founder of wastewater treatment in Germany and has left an indelible mark on the field. These pioneers are largely to thank for the characteristic linear systems in cities that draw their water from protected watersheds into urban areas. In these, the water is usually used once, collected in the sewer system and flushed with its waste products to central water treatment plants, where it is processed before being reintroduced to surrounding bodies of water. The system led to dramatic improve-

Water Transitions in Cities of the Future

Sewage

Water in

Waste­ water treatment

Bodies of water

Water out

Water treatment

Run-off

ments in hygiene and public health and is considered one of the ten most important engineering achievements of the 20th century.

Present-day challenges The construction of a centralised water supply and a sewer system with central treatment plants in cities required comprehensive engineering expertise and substantial financial means and took many decades to develop. In addition, the operation of these systems is associated with complex maintenance requirements and high costs. In the fast-growing cities of Asia, Africa or South America, such resources are often only available on a limited basis. The traditional water supply and wastewater removal concept familiar to us in European cities may not be the only available choice, despite the benefit of substantial improvements in public health that it provides. Furthermore, as an ever-increasing number of people live in cities (a projected 70 per cent of the world population by 2030), an enormous demand for clean potable water as well as a drastic increase in wastewater in highly urbanised centres are the inevitable consequence. Precisely those locations where water is already scarce will likely experience serious water shortages. As a consequence, approaches that allow wastewater to be treated for local reuse take on special importance. A change in thinking is occurring even in the European and North American cities characterised by centralised water supply and waste­ water removal systems. Here, the challenge arises from aging infrastructure that is in urgent need of renovation. If investments in these projects are made too late, the consequences include water losses from pipes, or leaks in the sewer system that can cause groundwater contamination. Demographic changes are reflected in a population exodus

from rural areas, growing urban regions and a shift in age structure. These changes affect the supply of potable water via centralised networks, since falling consumption in rural areas can lead to stagnant water in the pipelines and associated sanitation problems. If sewer systems lack the minimum level of wastewater to function properly, deposits will accumulate and cause odour nuisances and corrosion. Even climate change has immediate impacts on water supply: the availability of fresh­ water resources at previous levels is no longer secure, and extended dry periods, as for example during extremely hot summer months, can lead to local water shortages. Water is also closely coupled to the energy sector. Not only is water necessary for the production of energy (in the mining of minerals or as a coolant), but the supply and treatment of water itself is energy-intensive. In the past, the energy required for the treatment of water was of secondary importance, but now that we live in a world of steadily growing ­energy prices, a change in thinking towards more energy-efficient processes is called for. In this context it should be noted that, due to the organic residues, the energy content of a communal wastewater flow is approximately 1.6 kilowatt-hours per 1,000 litres, which is more than the energy required to clean it at the current state of the art. Consequently, there is significant potential for extracting ­energy from wastewater, an approach that is already being partially implemented at many modern treatment plants. Furthermore, the requirements for wastewater purification have shifted. While the priorities at the outset lay in reducing organic content, nutrients and pathogens, today’s focus has turned to the progressive reduction of organic trace substances such as pharmaceuticals, household chemicals, endocrine-active substances, antibiotics

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Above  Traditional urban water supply and wastewater removal concept Facing page  “Everything Flows – A ­German Water Balance”: an overview of water flows in Germany (2013)

190 km3

307 km3

Evaporation

Precipitation

Volumes of water

that flow across borders and the coast via large rivers

Where water is scarce in Germany

13

(km3/year)

Many regions in Germany use a lot more water than they are able to obtain themselves within their territories (yellow and orange areas on the map). The reasons for this include highly concentrated economic and settlement structures, features of the natural landscape and contamination of the groundwater. That is why Stuttgart and the surrounding area, for example, take their water from sources such as Lake Constance, which is more than 100 km away.

6

28

Baltic Sea inflows

Elbe

Weser

4 Ems

Natural water flows Germany is a country rich in water resources. While it is true that three fifths of the rainwater evaporates again, 117 km3 remain and a further 71 km3 flow in from neighbouring countries. This means that – in theory – 188 km3 of water are avail­ able, enough to fill a two-metre-deep swimming pool covering the area between Cologne, Hamburg, Berlin and Dresden. However, the natural water supply is not distributed equally across the country: in the mountainous regions of southern Germany between 10 and 20 times more water is available than in Brandenburg.

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Rhine

Pipe diameter of the long-distance pipelines: >4m 1 to 4 m Almost one fifth of the water available