robust resilient resistant: Reinforced Concrete Structures 9783955535476, 9783955535469

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robust resilient resistant REINFORCED CONCRETE STRUCTURES

REINFORCED CONCRETE STRUCTURES



Contents

004



RESEARCH AND TECHNOLOGY 010 Folded Plate Structures: an Ingenious and Efficient Construction Principle 020 Ultralight ­Formwork System for Thin, Textile-­reinforced ­Concrete Shells 028 Folded Plate Floor Slabs in Prestressed Concrete

034 D  igital C ­ onstruction – 3D Concrete Printing 040 Semi-­Finished Products in Structural Carbon ­Prestressed Concrete 

ROOFS 048 Concert Hall in Blaibach 060 Tram Stop at Berlin Main Railway Station

066 High-speed Railway Station in Montpellier 076 Chalice ­Columns for Stuttgart 21

MULTI-STOREY BUILDINGS 088 Single-family House in Gordola 098 Administration and Conference Building in Garching 110 Station Hall with Multistorey Parking Garage in Bordeaux 118 ESO Supernova in Garching

126 Schlotterbeck Residential and Office ­Building in Zurich 134 BioBío Regional Theatre in Concepción 142 taz Publishing House in Berlin 150 Office Building in Lyon

BRIDGES AND INFRASTRUCTURE BUILDINGS 160 Two Stations on the ­Budapest Metro 170 De Lentloper Bridge in Nijmegen 180 Railway Viaduct over the ­Almonte River near Cáceres

192 Hagneck ­Hydroelectric Power Plant 202 Demolishing Major Bridges. A Job for Engineers 208 Bridge Construction, Quo Vadis?

APPENDIX 218 Authors 220 Image Credits

005



222 Project Participants 224 Imprint

Foreword Jakob Schoof

Top Performer in Flux

006



Concrete is the material which makes possible the greatest heights and farthest depths of construction. Neither the 828-m high Burj Khalifa, the world’s tallest building, nor the Gotthard Base Tunnel, reaching 2,450 m below the central Alps, could have been achieved without reinforced concrete. However, concrete also has high and low points in the context of design: the same material that expresses the extreme slenderness of the shell roofs of Heinz Isler and Ulrich Müther, also identifies with concrete panel structures from the postwar era and the economics-driven design of motorway bridges that cut through so many river valleys with the most Brutalist possible monotony. Not by chance, a – cautiously expressed – ambivalent view of concrete developed out of this: the uninterrupted fascination of many engineers and architects with concrete stands in contrast to its rejection by broad sections of the public. Both sides base their judgements on the architectural experiences of the last 150 years, although concrete is far older. The material used by the ancient Romans stood the test of time, not only in the world-­ famous dome of the Pantheon in Rome but also in numerous arched structures and as the core material in multi-skinned walls. Following the end of the Roman Empire, concrete construction was largely ­forgotten in Europe until the late modern period. After Joseph Monier was awarded the first patent for ­concrete reinforced with iron in 1867, the material advanced step-by-step to become the leading technology of modern construction. The works of engineers and architects such as Francois Hennebique and Le Corbusier were crucial, revolutionary contributions to the rationalisation and aestheticisation of concrete. Their successors, on the other hand, have left us a problematic inheritance of defective, “maintenance-­intensive” concrete structures, the repair and replacement of which keep today’s engineers continuously busy. It is crucial that we learn from the mistakes of the past. In many situations, reinforced concrete remains indispensable, even today, because no other material comes anywhere near it in terms of protection against fire, noise and moisture. Its design diversity is likewise unbeatable – the structures discussed in this book bear witness to this fact. However, sustainable reinforced concrete construction today requires not only material-efficient and durable load-bearing structures, but also careful consideration of what should be built, where and when. To do anything other would be environmentally and economically i­ rresponsible. If the global cement industry were a country, it would occupy third place behind China and the USA in the CO2 emissions league table. It accounts for between 4–8% of global emissions, depending on the method of calculation and production processes involved. Although binders with a much more favourable greenhouse effect, such as ground granulated blast-furnace slag from iron ore smelting and fly ash from coal-fired power plants, are now also available, the supply is unlikely to be anywhere near sufficient to satisfy even the world’s current hunger for concrete. Finding a way out of this dilemma requires pioneering work in many areas: in the development of new, more efficient load-bearing structures, in basic research into new concrete mixes and processing methods and, last but not least, in dealing with the concrete heritage of the past. Our book “robust ­resilient resistant” gives insights into the many facets of this work, from 3D printing with reinforced concrete to the refurbishment and demolition of road bridges and experiments with new types of arched structures, and from multi-storey buildings to semifinished products of prestressed carbon reinforced concrete. It also shows in detail some of the most impressive concrete structures of recent years, including the roofs of the new below-ground station at Stuttgart Hauptbahnhof and the TGV station in Montpellier, the metro stations in Budapest and an office building in Lyon with column cross sections describing, in an exaggerated form, the increasing vertical loads from top to bottom of the building. We hope you find them a rich source of inspiration for your own work with reinforced concrete and a cause for some moments of critical reflection over a material in flux that is absolutely certain to exercise a powerful influence over construction in the future.

007



Research and Technology

008

FOLDED PLATE STRUCTURES: AN INGENIOUS AND EFFICIENT CONSTRUCTION PRINCIPLE

010

ULTRALIGHT FORMWORK SYSTEM FOR THIN, TEXTILE-REINFORCED CONCRETE SHELLS

020

FOLDED PLATE FLOOR SLABS IN PRESTRESSED CONCRETE

028

DIGITAL CONSTRUCTION – 3D CONCRETE PRINTING

034

SEMI-FINISHED PRODUCTS IN STRUCTURAL CARBON PRESTRESSED CONCRETE

040

009

Text Stephan Engelsmann, Valerie Spalding

Folded Plate Structures: an Ingenious and Efficient Construction Principle A folds in nature: the leaf structure of the fan palm

010

ESSAY

In construction, the term folded plate structure describes a three-dimensional loadbearing structure assembled from thin-walled elements with flat surfaces. Folds that improve load-bearing properties are found not only in engineering but also in nature, for example in the leaf structures of flora (fig. A). GEOMETRY: FROM FOLDING STRUCTURES TO FOLDED PLATE STRUCTURAL FORMS An almost unlimited number and diversity of shapes can be created through folding. In most cases, folded plate structures follow geometric principles. A folded surface can be

A

described as a folding structure. A load-carrying structure based on a folding structure is a folded plate structure. A folding structure developed in a plane forms a folding pattern (fig. C). Longitudinal folds and reverse folds are basic forms of fold (figs. D, I). Examples of reverse folds include diamond folds (fig. O) or herringbone folds. The folding structure has a fundamental effect on the folded plate structural form – not every folded structural form can be generated with every folding structure. Folded plate structures with curved global geometries can, for example, be constructed using diamond or herringbone folds. The folded structural form, on the other hand, influences the load-bearing behaviour. When designing folded plate structures, these parameters must be matched optimally to one another at an early stage in order to create an ­efficient load-bearing structure. During the development of the ­geometry, the designer must also ensure that all components drain and do not form a local low spot with no outlet. THE STRUCTURAL PRINCIPLE OF THE FOLDED PLATE STRUCTURE In terms of structural typology, folded plate structures are three-dimensional plate ­structures. The individual components of the folded plate structure are thin-walled, flat members that in themselves have only limited stiffness but when configured suitably in three ­dimensions become highly efficient load-bearing structures. The structural principle at the heart of these folded plate structures is based on increasing the effective structural depth by folding, which gives the structure its geometric stiffness. Structural form, fold depth and the geometry of the individual surfaces together determine the load-bearing behaviour of folded plate structures. Not every folding form leads to a structure that has the advan­tageous load-bearing behaviour of a folded plate structure. Compared to 011

Folding – an efficient construction principle

three-dimensionally curved plate structures, such as shells, folded plate structures have the great economic and practical advantage that they can be assembled out of industrially manufactured semi-finished products, for example. The individual panels of folded plate structures are usually loaded with normal ­ oments are superimposed on normal section forces in the same way as plates. Bending m section forces because the external forces acting at right angles to the plate surface are transferred by plate bending in the individual ­panels to the outside edges of the plates, which are formed by the shared edges of the elements. The bearing forces are transferred via the shared edges into the adjacent surfaces and create normal forces in the plane of the individual panels. For the arrangement to be structurally effective, the edges must be joined by a shear-resistant connection that ensures compatibility of deformation and prevents relative displacements. This force-transmitting connection between the ­individual panels is an important character­istic of folded plate structures. Particular attention must be paid to the structural engineering ­design of the free edges of folded plate structures because they are only inadequately restrained and could change shape considerably. The design of folded plate structures is very challenging. Looked at in terms of global ­geometry, in many cases these folded plate structures are the structural equivalent of traditional load-bearing systems such as beams, frames or arches. Today’s numerical methods of analysis allow engineers to design folded plate structures with complex ge­ome­tries. In addition to traditional folded plate structures, there are a large number of special forms, for example hybrid structures which, in terms of their geometry and load-bearing behaviour, have the features of shells and folded plate structures or are folded plate structures stabilised with cables and/or tie rods. MATERIALS AND JOINTING TECHNIQUES The materials most suitable for the construction of folded plate structures are concrete, wood and plastic. Today, many different industrial semi-finished products manufactured as boards or composite elements are available for the design, analysis and construction of folded plate structures. Structural form and material are interdependent with respect to folding structure and the dimensions of the ­individual panels, load-bearing behaviour, jointing technology, manufacture and arrangement. The lower the stiffness of the individual panels, particularly in the context of stability failures, the smaller they have to be. Unless the material is thermally insulating, such as is the case with composite materials with an adequate core layer thickness, folded plate structures normally require external insulation. Except in monolithic concrete folded plate structures, jointing techniques have a crucial role to play in constructional as well as in architectural form, because the edge jointing – except at the support points – is the only detail of construction and therefore has a large effect on design aesthetics. Jointing technique depends on the material used and the options offered by the cross section of the individual panels. Basically, the connections can be permanent or detachable. Precast concrete components are structurally connected by prestress and/or additional in-situ concrete. They can also be joined together by cast-in steel components. Transport restrictions must be considered when determining their geometry and hence the component sizes. The connection of the edges of timber folded plate structures is normally by means of edge timbers that are bolted to one another. If the cross section is sufficiently thick, the connection can be formed directly in the panel cross section. Folded plate structures manufactured in plastic are normally bolted at their flanges, while folded plate structures in metal can be welded, bolted or riveted together. FROM CONCRETE TO PLASTIC FOLDED PLATE S ­ TRUCTURES The principle of folding for carrying loads found application very early in reinforced con­ crete structures. One example is Eugene Freyssinet’s airship hangars at Paris-Orly, which measured 300 × 100 m (constructed 1924) and obtained their strength from their folded surfaces (figs. E, F). To counteract buckling of the shell under asymmetric loading, the surface was divided into wide trapezoidal ribs. The webs are not planar in this structure. Reinforced concrete folded plate structures constructed using in-situ concrete with large individual panel sizes and parallel edges were used for roof constructions with 012

Essay

C

D

F

E

G

C fold pattern, folding structure and folded plate structure

D longitudinal folds

013

Folding – an efficient construction principle

E, F airship hangars, Paris-Orly. Project design / Structural design: Eugène Freyssinet

G UNESCO Headquarters, Paris. Project design / Structural design: Marcel Breuer, Bernard Zehrfuss, Pier Luigi Nervi

St. Paulus Church, Neuss-Weckhoven. Project design: Fritz Schaller, Christian Schaller Structural design: Stefan Polónyi

014

Essay

015

Folding – an efficient construction principle

H

I

J

H  Paketposthalle, Munich. Project design: Ober­ postdirektion München: ­Rudolf Rosenfeld, Herbert Zettel

K

Structural design: Dyckerhoff & Widmann: Ulrich Finsterwalder, Helmut Bomhard

K  sulphur recovery plant, Pomezia /Rome. Project design: Renzo Piano Building Workshop

L new town centre Gaiberg / Café. ­ Project design: Ecker Architekten. Structural design: Engelsmann Peters

016

Essay

I t he principle of reverse folding

M  Mülimatt Sports Centre. Project design: Studio Vacchini. Structural design: Fürst Laffranchi

J Zu den Heiligen Engeln Church, Landsberg. Project design: Josef Wiedemann. Structural design: A. Hillenbrand

long spans. Individual panels of in-situ concrete folded plate structures can afford to be very large in comparison with those of plastic or steel folded plate structures, because he individual components are not industrially prefabricated semi-finished products and buckling is less of an issue than it is with very thin-walled panels. Folded plate structures constructed from the 1950s onwards broke away from the use of comparatively simple prismatic shapes and exploited the geometric and architectural potential of folded plate structures. The UNESCO Headquarters in Paris has a long-span concrete folded plate structure with folds that fan out in plan (fig. G). A particularly expressive example is St. Paulus Church in Neuss-Weckhoven (fig. p. 14 /15). Up to the 1970s, a series of concrete folded plate structures with very sophisticated geometries were constructed, before the construction of concrete folded plate and thin shell structures came to a standstill, apart from a few exceptions. One of the few present-day examples can be found in the

L

M

new town centre in Gaiberg. A ceiling continues the folded theme of a rear wall formed in folds to span the column-free interior of a small café. The folds in the inside faces of the wall and ceiling are designed to benefit their structural action and create an expressive interior effect. Concrete folded plate structures can also be made of precast components. In this case transport restrictions must be taken into account when ­determining their geometry and hence the component sizes. Modular designs are most suitable for prefabricated ­construction methods, especially if the panels are repeated and formwork can be used a number of times. In contrast to in-situ construction, the precast components of a folded solution require a suitable jointing technology to transfer their applied loads. A famous hybrid folded plate and shell structure made from precast concrete units is the 146-m span barrel shell roof of the Postpakethalle completed in 1969 in Munich, which was designed by Ulrich Finsterwalder and Helmut Bomhard (fig. H). Timber folded plate structures were built from the late 1950s. They are often constructed out of large-format plywood or cross-laminated timber panels. Folded plate structures built of large laminated panels with an internal post and rail construction and external finishing l­ayers were used, for example, to form the ­radially folded plate structure of the Zu den Heiligen Engeln Church in Landsberg (fig. J). Experimentation with plastic folded plate structures began in the early 1960s. Folded plate structures are one of the forms of construction particularly suitable for plastic, because the low stiffness of the plastic can be compensated for by the ease of optimisation of its three-dimensional shape. In terms of manufacturing, the modular geometry of many 017

Folding – an efficient construction principle

folded plate structures is an advantage, because the expense of mould-making can be justified economically on the grounds of multiple uses. Plastic folded plate structures were once almost exclusively designed as modular, three-dimensionally shaped fibre-glass reinforced plastic (GRP) elements, which were bolted together. One successful example is the plastic folded plate structure of the sulphur recovery plant in Pomezia / Rome (fig. K). EXPERIMENTS AND PROTOTYPES Engineering developments mainly in the field of materials and jointing can be seen in many of today’s examples. The Mülimatt Sports Centre is a contemporary example of a concrete folded plate structure with some highly challenging aspects of engineering. It consists of large, prestressed, prefabricated units assembled to form a structural frame. The frame cross section is made up of pillars and beams, which are manufactured as ­individual components matching the building’s grid dimensions and connected together on site (fig. M). An interesting area with potential for folded plate structures is thin-walled prefabricated components made from ultra-high performance concrete (UHPC), which are assembled to form a folded plate structure. Folded plate structures made from metals can be designed only as small-scale folding structures, because of stability problems with their thin-walled plates. The potential of the mate­rial has been shown by the design in stainless steel of an open-fronted shelter for an industrial company – a free-standing, cantilevering folded plate structure in structural steelwork (fig. N). For larger plates, one successful approach has been to use multilayer welded steel panels or, an option which may be ­simpler to manufacture, laminated plates. An example of appropriate use of material is the plastic folded plate structure at the Stuttgart State Academy of Art and Design, which uses a specially developed jointing technique (fig. P). The experimental fully plastic construction consists of translucent polycarbonate laminated panels, which are joined using a combination of fixed and detachable connections based on hook and loop fasteners. An innovative jointing technique for timber folded plate structures was developed by the Laboratory for Timber Constructions (IBOIS) at the École Polytechnique Fédérale de Lausanne (EPFL). Revisiting traditional carpentry connection techniques, researchers have fulfilled the technical requirements in a particularly efficient way and allowed the use of double-skinned folded plate structures (fig. Q). The AKA Wippe, a free-standing piece of open-air furniture, whose singly curved roof consists of herringbone folds constructed ­using laminated GRP elements with an extremely low self-weight, is an example of a folded plate structure in lightweight construction (fig. R). A special kind of folded plate structure is the reversible, i.e. folding type. The 3D geometry and arrangement of the panels and the construction of the edge connections allow the object to be folded together. A successful example is the famous Canary Wharf Kiosk in London, which can be opened and closed by an electric motor (fig. S). CONCLUSION Folded plate structures with the right kind of geometric design allow the realisation of complex spaces, expressive forms and self-supporting building envelopes using comparatively little material. Experimental prototypes have demonstrated new development opportunities. For the future, the development of a continuous digital process chain that covers everything from the parametric creation of the geometry to structural design with finite element programs right up to fabrication is within reach. The potential of the ingenious and material-saving construction principle of folded plate structures and its architectural design freedom have yet to be fully exploited.

N Free-standing, cantilevering steel folded plate structure. Project design: ­FATLAB. Structural design: ­Engelsmann Peters

O diamond folds

018

Essay

P  plastic folded plate ­structure, Stuttgart State Academy of Art and Design.

Project design /  structural design: Stephan Engelsmann, Valerie Spalding, Gerlind Baloghy, Melanie Fischer with the support of Engelsmann Peters

Q jointing techniques for timber folded plate structures. Project design / structural design: IBOIS, EPF Lausanne

R  AKA Wippe, Stuttgart State Academy of Art and Design. Project design / structural design: Stephan Engelsmann, Valerie Spalding

S C  anary Wharf Kiosk, London, Project design: make. Structural design: Arup

019

N

O

P

Q

R

S

Folding – an efficient construction principle

Text  Tom Van Mele, Tomás Méndez Echenagucia, David Pigram, Andrew Liew, Philippe Block

Ultralight ­Formwork System for Thin, Textile-­ reinforced ­Concrete Shells 020

ESSAY

HiLo is a research and innovation unit for lightweight construction and smart and ­adaptive building systems. Construction began in 2018 on this two-storey innovation hub and collaborative working space on NEST, EMPA’s modular research building in Dübendorf, Switzerland. The roof of the unit is a double-layered, doubly curved, carbonfibre­reinforced concrete shell structure with integrated hydronic heating and cooling and a thin-film photovoltaic system on top. With a total height of 7 metres, the roof covers an area of 120 square metres and has a total surface area of 160 square metres. A full-scale prototype of the bottom layer of the concrete roof was built at the Robotic Fabrication Lab of the I­nstitute of Technology in Architecture at ETH Zurich as a dress rehearsal for its innovative construction system. The base of the system is composed of ­reusable scaffolding elements that support a set of timber edge beams. A cable net spans between the beams and the lower ­supports, and a fabric on top serves as shuttering for the sprayed concrete. The

cable net is comprised of custom-cut steel cables connected by rings and brackets and is d ­ esigned such that it deflects under the weight of the wet concrete into the correct ­final geometry, which it then supports until the shell has cured. To achieve this, the cable net must be precisely tensioned at the correct angle from specific anchor points on the CNC-milled edge beams. CABLE NET DESIGN The anticlastic shape of the concrete shell structure is the result of a custom-developed, multi-criteria optimisation process that balances architectural and functional constraints, such as possible touchdown regions, headroom clearances and solar orientation, with structural and fabrication requirements. 021

Formwork System for Thin, Textile-­reinforced ­Concrete Shells

Through a best-fit form-finding procedure, the specific non-uniform prestress of the cable net that would allow it to deform into this target shape under the 20 tonnes of wet concrete was then determined. The topology of the cable net was defined to best reflect the features of the anticlastic target shape, while minimising the required number of cable elements, controlling the sizes of the faces and dealing with the concentration of cables in the funnelling parts. Allowable forces were constrained during the form-finding process to limit the required sizes of the cable net components. The specific node design ensured that all cables have the necessary degrees of freedom to conform to the required shell geometry (axial, in-plane and perpendicular rotation). It incorporates features to align and attach the fabric shuttering, to fix the textile ­reinforcement at the correct height, to register the concrete thickness and to facilitate as-built measurement from below with two spherical markers on the nodes’ central axis.

This method requires far less material than earlier methods of constructing double-curved concrete formwork. It uses mainly reusable components and allows access to the area beneath the forms. The result is a shorter construc­ tion time on site.

The developed construction system was d ­ esigned to compensate for unavoidable ­deviations from the theoretical model, for ­example due to fabrication and assembly ­tolerances of the edge beam and the supporting scaffolding structure, by means of an adaptive control system. Tightening or loosening the cables at the perimeter alters the forces within the cable net, steering the shape of the shuttering from an imperfect starting point towards the desired shape. An algorithm was implemented to determine the precise adjustment to be applied at each boundary cable to best direct the cable net towards the intended form while respecting maximum cable stress constraints. PROTOTYPE CONSTRUCTION The construction process consisted of erecting the scaffolding and edge beams; ­hoisting and installing the cable net and fabric, followed by tensioning the cable net according to the control system process; placing the r­ einforcement and spraying of the concrete. The cable net was assembled on the ground in sections that were light enough to be carried by hand. The main spine of the net was hoisted and installed, followed by the sections. Once the cable net installation was complete, the custom-made fabric was rolled and hoisted onto the net’s spine. From this position, it could be unrolled and installed in the correct location by anchoring it to the nodes through precut holes in the fabric. The carbon-fibre textile reinforcement was patterned and cut before being attached, one strip at a time, above the fabric by spacers on each node. 022

ESSAY

The low-pressure sprayed concrete mix was designed to stick to the fabric shuttering, which was almost vertical in places. Liquid admixtures meant that the concrete was mixed on site. Workers manoeuvred aerial working platforms from strategic locations to access the entire surface. Close proximity was required to enable the workers to use vibrating trowels to locally liquify the concrete to ensure that it completely consolidated around the carbon-fibre reinforcement without leaving any gaps. The concrete was sprayed in one continuous process to form a monolithic shell. After curing, the shell is capable of supporting its own weight without the aid of the cable net. It was decentred by releasing the tension on the boundary cables and removing them from the edge beams. The beams and scaffolding were removed, revealing the concrete shell. AN EFFICIENT PROCESS The completion of the prototype demonstrates the efficacy and practicality of this novel flexible formwork system. The process uses significantly less material than conventional approaches to constructing doubly curved concrete formwork, employs primarily reusable scaffolding, preserves access beneath the formwork, proves the capacity of the adaptive control system to deliver improved accuracy and achieves the required tolerances.

A

B

C

A structural system ­components: supporting scaffold, formwork ­system and textile-­ reinforced concrete shell (from bottom to top).

B, C cable net nodes

023

Formwork System for Thin, Textile-­reinforced ­Concrete Shells

The formwork system improves upon con­ventional methods for constructing doubly curved concrete shells in numerous ways. Construction time is reduced due to less re­liance on subtractive machining or on-site craft. Material use and waste is minimised, since a stiff shuttering surface that needs to be supported from below is no longer needed. Furthermore, with the cable net only supported at the perimeter, the need for internal supports is minimised, or can be located external to the perimeter, along with any additional foundations these supports may have required. This opens up the possibility of building across rivers, roads or railway tracks without interrupting normal traffic or operation, as well as allowing worker access to the area below during construction and ­curing. The system incorporates features to ­attach reinforcement, concrete depth indicators, shear connectors and measurement aids. This functional integration reduces time on site, minimises error and increases accuracy, even for structures with complex, doubly curved geometry.

D

024

ESSAY

E

F

G

H

F  carbon-fibre reinforcement fixed to a spacer at a node

H  shuttering fabric and ­cable net from below

D installation of the cable net using aerial working platforms

E  fastening the shuttering fabric onto the cable net

025

Formwork System for Thin, Textile-­reinforced ­Concrete Shells

G a  pplication of sprayed concrete and localised compaction using electric vibrating trowels

026

ESSAY

027

Formwork System for Thin, Textile-­reinforced ­Concrete Shells

Text  Andrea Pedrazzini

Architects: C  orinna Menn, Chur / Zurich (CH) and Mark Ammann, Zurich (CH)

Folded Plate Floor Slabs

in Prestressed Concrete

028

essay

The load-bearing structure of the Namics ­office building in St. Gallen, Switzerland, is constructed almost entirely of reinforced and prestressed concrete. Relatively thin concrete floor slabs span transversely as folded plates across the entire width of the building, allowing the open spaces below them to be uninterrupted by intermediate vertical supports. Flat slabs are preferred for the circulation cores at each end of the building and for the whole of level -2. At the top of the building, level +4, the roof is supported by a longitudinal steel hollow box girder with simple, lightweight steel framed ribs cantilevering on each side. The building’s overall structural system consists of a pair of transverse walls at each circulation core and the frames of the two longitudinal facades. The whole structure rests on a slab foundation, which is thickened locally under the most heavily loaded walls. The transverse walls and facade frames together with the slabs, which act as diaphragms, provide the resistance to horizontal forces. STRUCTURE, ARCHITECTURE, BUILDING SERVICES Taking into account the building use and the disposition of internal spaces, the architect decided to adopt a concept of a “space-generator” building characterised by open spaces. A further requirement was that the entire depth of the building had to be naturally lit. The architectural demands were satisfied with a folded plate system capable of spanning the transverse distance of nearly 13 m between the facades without any intermediate supports, with a low construction depth and self-weight. The light loads from the floors ­allowed the longitudinal facades to contain generously proportioned windows. In addition to these advantages, the folded plate shape creates extra space to accommodate building services equipment (electrical, network, sanitary, heating and ventilation) ­below the raised floors. Heating and cooling of the rooms are ensured by a thermally activated building system (TABS), with the pipes being embedded in the ­concrete cover to the underside of the slabs, where the minimum cover of 20 mm was increased to 50 mm.

3.80

3.80

39.40 31.80 = 6 ≈ 5.30

3.80

a

a

a

a

4.00

12.87

39.40 31.80 = 6 ≈ 5.30

12.87

3.80

prestressing cables 3 or 4 strands Y1860s7-15.7

+4

+2 +4 26.45

22.45 4.00

+3

+1 +3

26.45

22.45

±0 +2

-2 ±0

structure plan of typical storey, ­longi­tudinal and cross section scale 1:500

029

-1 +1

-1 -2

Folded Plate Floor Slabs in Prestressed Concrete

FOLDED PLATE STRUCTURE Each of the 5 folded plate floors is composed of 6 V-shaped “waves”. The floors are ­horizontally bounded by the flat slabs of the circulation cores and are tied into edge beams, which also act as the beams of longitudinal ­facade frames. This structural system is supported vertically by the facade columns and by the transverse walls along the short edges of the open interior spaces. The flat slabs of the circulation cores and the facade beams considerably improve the load-bearing behaviour of the folded plate floor by providing horizontal support along the short edges of the floor and longitudinal edge stiffening. Thus, the folded plates can act as a series of transverse arches resisting vertical load by membrane action, i.e. in compression, thus reducing the transverse bending moment. A

B

The folded plate slabs are contiguous and inclined vertically in the opposite sense to one another, which allows them to share some of the vertical load. In terms of its in-plane load capacity, each folded plate element was idealised as a deep beam with a span of 12.87 m. Commensurate with the resulting stresses, its thickness varies from 15 cm at midspan to 23 cm at the end supports at the longitudinal facades. The strengthened ribs at the crests and troughs of the waves act as compression and tension chords respectively. In order both to limit the thickness of the t­ension (lower) ribs and to improve the structural behaviour under serviceability limit state loading by reducing deformation and controlling cracking, each element of the folded plate system was post-tensioned with bonded prestressing tendons consisting of 3 or 4 150-mm2 strands. Each folded plate wave has four 4-strand polygonal tendons; each flat slab in the circulation cores has two 3-strand tendons (1 straight and 1 polygonal) and each facade beam has two 3-strand straight tendons. ROOF STRUCTURE The top storey had to be set back and hence was narrower than other levels, due to local planning regulations. Since the folded plate slab forming the ceiling to level +3 would be unable to support the loads from the roof structure, the engineers rotated the d ­ irection of span of the principal load-bearing member through 90°, i.e. lengthwise, and adopted a longitudinal girder (39.45-m long) resting on the four transverse end walls. A steel structure consisting of a welded hollow box girder with a trapezoidal cross ­section (1.30 m high, 22 – 85 cm wide) with steel framed ribs projecting laterally to each side at 2.65 m centres 030

essay

6  14 / 125 bottom 6  14 / 125 top

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46  10 / 250

24  12 / 125 bottom 24  12 / 125 top

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10  18 2≈ 5  10 / 250

4  18 2≈ 2

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A installing the raised floor

B f ormwork construction with TABS pipework, ­reinforcement and ­prestressing tendons

031

Folded Plate Floor Slabs in Prestressed Concrete

C reinforcement arrangement in the folded plate floor slabs longitudinal section, cross section scale  1:50 6  14 / 125 bottom 6  14 / 125 top

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46  10 / 250

24  12 / 125 bottom 24  12 / 125 top

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1  14

1  14

1  14

1  30 16  top 18 r. spacer h = 220 mm

1  181  18

 10 / 125 1  18

 10 / 250 26  14 / 125 2≈ 13  10 / 250

 10 / 250

20

 12 / 250 horizontal stirrups1  18

 12 / 125

 12 / 125

32  14 / 125 2≈ 16

r. spacer 100 mm 26  14h/ = 125 2≈ 13

4  14 reinforcement spacer h = 70 mm

1  14

1  14

4  20

reinforcement spacer h = 70 mm

bottom r. spacer h = 50 mm

16  18  12 / 125

 10 / 250 horizontal 12 / 250 stirrups  10 / 125

12 10//125 125

 10 / 125

20  14 / 125 10/ 125 322≈  14 2≈ 16

bottom 4  30 r. spacer h = 50 mm reinforcement spacer r. spacer h =mm 140 mm h = 30

 10 / 125

 12 / 250

 12 / 250

 12 / 250 14  12 / 125 2≈ 7

 10 / 125

20  14 / 125 2≈ 10  12 / 250

 10 / 250 horizontal stirrups  10 / 250

Support section t = 230 mm

 12 / 250 horizontal stirrups  12 / 125

1  18

2  16

1  14

1  14

1  14

1  14

1  14

2  18 1  18 16  18

 10 / 125

26  14 / 125 2≈ 13

2  30

1  14 1  14

4  30 reinforcement spacer h = 140 mm

Midspan section t = 150 mm

4  20

4  14 reinforcement spacer h = 70 mm

 12 / 250

30

 12 / 250 horizontal stirrups  10 / 125

 12 / 125

 12 / 125

32  14 / 125 2≈ 16

r. spacer h = 100 mm

bottom r. spacer h = 50 mm

 12 / 125

 12 / 250

 12 / 125

20  14 / 125 2≈ 10

4  30 reinforcement spacer h = 140 mm

 12 / 250

230

 12 / 250

C

230

150

14  12 / 125 2≈ 7

Support section t = 230 mm

2 2

r s h

satisfied the need for a lightweight solution that would fit in with the planned construction phases. This particular shape of girder cross section was chosen for its aesthetic appeal and for sound structural engineering reasons. The ­engineers wished to make full use of the plastic moment of the section and thus narrowed the width of the bottom flange in order to avoid it buckling prematurely at the two internal supports. Furthermore, the closed cross section provides the necessary torsional stiffness to resist asymmetric live loads. With spans of 3.70 m, 31.80 m and 3.70 m, the reaction forces at the two outermost supports are negative (uplift) for all load cases. For this reason, the box girder has been anchored down to the external walls by cast-in threaded rebars. CONSTRUCTION PROCESS AND MATERIALS The construction of the folded plate slabs for each floor was carried out by laying V-shaped timber formwork over the entire floor area a ­ fter the relevant supporting walls and columns were in place. The formwork was reused for all 5 above-ground floors of the building. This was followed by the TABS pipes, bottom reinforcement, prestressing tendons and top reinforcement. The tendons were tensioned 14 days after pouring and then grouted. The formwork was removed for use on the floor above, leaving temporary props to distribute the loads to the lower floors. Concrete class C30/37 with a maximum aggregate size of 32 mm was used for the whole structure. The consistency of the fresh concrete for the folded plate slabs (maximum slope 17 %) had to be stiff enough to dispense with the use of top-surface formwork. The steel reinforcement is grade B500 B; the structural steelwork in the roof is grade S355. The reinforcement content of the horizontal structural system elements (folded plates, flat slabs and facade beams) is 288 kg/m3, to which the prestressing tendons add 17 kg/m3.

plan of typical storey with open space scale 1:500

032

essay

D

Swiss panel SP 40/183, t = 1,25 IPE 140

RRW 70.70.5,0

3.70

19.8 mm

9.6 mm

7.5 mm

E

L 220.85.8

31.80

D cross section of the ­hollow box girder and framed ribs of the roof construction scale 1:50

E longitudinal structural system – blue: box girder theoretical deflection at installation of windows (considering: precamber; self-weight of structural elements and a part of

033

Folded Plate Floor Slabs in Prestressed Concrete

self-weight of non­ structural elements) and red: box girder envelope deflection during the whole service life (considering: precamber; selfweight structural and

non-structural; snow load; wind load and thermal action)

3.70

Text  Viktor Mechtcherine

Digital ­Construction 3D Concrete Printing A

A  Methods based on selective material deposition, such as filigree printing with industrial robots, are currently the most ­frequently used for 3D concrete printing.

034

Essay

From CAD to digital production: the technological and economic potential of digital construction in concrete in the precasting yard and on site is indisputably high. Productivity increases, costs fall, construction is faster and more flexible. Design freedom over component geometry increases. The potential for ­developing new architectural forms and structural concepts such as “form follows force” is high. Digitisation can also contribute to solving existing problems and challenges in construction production, for example the global shortage of qualified construction workers and dwindling material resources. Advantages also arise in relation to environmentally compatible construction: from dispensing with the use of formwork and its disposal to material-saving component geometry and the minimisation of waste. It also minimises the number of separate construction operations and improves working conditions in difficult-to-access, dangerous areas or in remote regions.

B

C

D

E

B  oven concrete benches, w XtreeE

C  Wonder Bench, University of Loughborough

035

Digital ­Construction – 3D Concrete Printing

D T  he 2.5-m long, 2-m high concrete wall was printed in approximately 5.5 hours.

E  filigree printing with ­coloured 3D mortar

SELECTIVE MATERIAL DEPOSITION Methods based on selective material deposition are currently the most frequently used for 3D concrete printing. A premixed material is extruded through a nozzle at preset ­printing rates at specific coordinates. Material deposition is as continuous as possible and completed with very few interruptions. The deposited filament’s width and height largely determines design freedom. Extrusion-based additive manufacturing methods can be divided into three categories depending on the associated special printing strategy: ­filigree printing, contour crafting or concrete wall printing. FILIGREE PRINTING Filigree printing is particularly suitable for the manufacture of decorative elements with non-linear geometries and textured surfaces as well as complex, bionic load-bearing structures. Examples include the 3D printing concept of the University of Loughborough ­ aumit and Cebe (figs. A – E). A and objects made by companies such as XtreeE, Sika, B ­filament of fine mortar or concrete with very finely graded ­aggregate about a centimetre wide and a few millimetres thick is deposited using a special print head. The process is normally performed by a 6-axis industrial robot. An accelerator is usually added at the print head for faster speed and higher productivity. CONTOUR CRAFTING In the contour crafting (CC) concept developed at the University of Southern California, the fine concrete filaments are a few centi­metres wide and between a few ­millimetres to a few centimetres high (figs. F, G, H, I). To stiffen and hence increase the structural stability and load-carrying capacity of the object, material is deposited fresh-on-fresh in wavy or zigzag patterns between contoured shells. Printed shells can also be used as integrated formwork. In this case, the (reinforced) concrete poured into the formwork fulfils the load-bearing function and the structural design can be done using normal technical standards. Chinese company Winsun manufactures 3D-printed buildings (fig. I) – anything from a ­toilet block to a five-storey building or an office building for the Museum of the Future in Dubai. The structures consist of prefabricated components produced on a stationary portal crane-based 3D concrete printer and installed with a slewing crane. This approach is most efficient and cost-effective for relatively complex geometries, e.g. the first 3D-printed cycleway bridge, which was designed and produced by TU Eindhoven and BAM (fig. G). The deck segments were manufactured as prefabricated components using a portal crane printer and connected ­together by post-tensioned steel bars. A special feature was the steel wire reinforcement embedded in some of the printed strips by a roller attached to the print head. CC can also be used on site. US-based Total Kustom used an in-house designed portal crane printer to manufacture a villa in a ­hotel complex in the Philippines. Apis Cor, a company from Russia, developed a mobile 3D printer that works like a slewing crane (fig. H). The complete s­ ystem was demonstrated by printing a small house in Moscow.

036

Essay

F

G

H

I

H  mobile 3D concrete ­printer in use on site

I 3  D-printed houses at Winsun’s headquarters in Suzhou, China

F c  ontour crafting at TU ­Eindhoven

G c  ycleway bridge constructed from 3D-printed segments post-tensioned together

037

Digital ­Construction – 3D Concrete Printing

CONCRETE WALL PRINTING An example of concrete wall printing is the CONPrint3D technology developed at TU Dresden. This method allows monolithic cross sections several decimetres wide to be printed in a single working operation (fig. J). It ­uses mobile concrete pumps or cranes redesigned for concrete printing. Concrete complying with currently applicable standards, e.g. mix recipes and hardened properties, acts as the “ink”. It is currently being lab-tested at the Institute of Construction Materials, TU Dresden. The first practical applications took place at the end of 2019. Unlike the methods described above, CONPrint3D is designed specifically for manufacturing today’s architectural forms and building dimensions, i.e. with sharp corners, straight-line geometries and solid cross sections. Geometric freedom is limited to benefit productivity and compliance with standards. Also involved with concrete wall printing is the Chinese company HuaShang Tengda Ltd., which has designed a system for steel-reinforced concrete walls. The process starts with steel reinforcement mesh being fixed in position. Concrete is then deposited layer by layer on each side to surround the reinforcement. A special print head design was developed to accomplish this: the forked nozzle deposits and compacts the concrete simultaneously on both sides of the reinforcement (fig. K). INCLINED AND HORIZONTAL ELEMENTS While building vertical elements with a 3D printer using selective material deposition is comparatively easy, the manufacture of ­inclined and horizontal elements presents a special challenge. One way of doing it is to stagger the filament deposition relative to the vertical axis (fig. N). However, this calls for particularly high requirements for shape stability of the freshly deposited filament and the layers below. Other approaches which can also be used to manufacture horizontal components include: the localised use of thin formwork elements integrated into the component, e.g. a thin plate of textile-reinforced concrete as a window or door lintel; adaptive formwork structures that automatically adjust to the printed geometry; temporary 3D-printed support structures made of materials that can be dismantled and recycled; the printing of horizontal components on a separate platform, which are then lifted into place conventionally by crane. Selective bonding, yet another 3D printing method, can be used without difficulty to manufacture inclined or horizontal elements. This involves first placing the dry materials in a thin layer (bed) on a platform and then delivering a binder or activator to specific coordinates. The next layer of dry material is spread on top of this and a further quantity of binder /activator applied. The process is repeated. The printed element “grows” from bottom to top and is supported by the unbonded dry material. After completion of the manufacturing process, the remaining dry material is ­removed. The word “selective” signifies that the dry material is hardened only at the positions at which the activator or binder has been applied. Without doubt, the method offers the greatest possible geometric freedom, but its application is very complicated and therefore it would be seldom used in construction. ­However, it could prove to be the best choice for applications with very complex geometries i­nvolving high-definition features (fig. M). One of its first applications in construction was Enrico Dini’s D-Shape robotic building system. A 3D-printed footbridge designed at the Institute of Advanced Architecture in Catalonia was inspired by the works of Antoni Gaudí (fig. L). The “print resolution”, i.e. the dimensional accuracy of the printed object, depends mainly on the grain size of the dry material and the flow characteristics of the activator /binder in the spaces between the grains of the dry material. The highest resolution is achieved if cement is the coarsest constituent and water is the activator. If sand or rounded or crushed aggregate is used as the bed material, cement mortar should be the binder. REINFORCEMENT OF PRINTED COMPONENTS Most of the earlier concepts for concrete printing concentrated on the placement of the concrete, while solutions for integrating reinforcement progressed at a much slower pace. Because the use of (steel) reinforcement is ­obligatory in most concrete structures, there is an urgent need to advance reinforcement technology in 3D-printed structures. Until now, the approaches have taken the following directions: a) conventional bar or wire reinforcement is placed between printed layers or in voids, b) conventional steel reinforcement is enclosed by “printed concrete”, c) concrete is placed in a dense reinforcement 038

Essay

mesh m ­ anufactured using a generative process and d) fibre reinforcement is added in the form of short fibres, yarn or textile. The latter offers plenty of scope for innovation, particularly with respect to its tensile behaviour and the ductility it offers to high-strength cement-based composites. Fibre reinforcement can significantly reduce the tendency to crack while increasing load capacity and ductility of printed concrete components. However, it can never completely replace steel reinforcement. The use of fibre reinforcement with 3D-printed concrete appears very interesting in relation to geometrically complex objects and for the integration of fixings and services installations.

J

L

K

M

N

L 3  D-printed segmental footbridge in Madrid

J Concrete wall printing: one example of this is CONPrint3D technology. Mobile concrete pumps were converted to concrete printers for this.

K  Print head with forked nozzle, which deposits concrete on both sides of the reinforcement at the same time.

039

Digital ­Construction – 3D Concrete Printing

M “Digital Grotesque” by architects Michael ­Hansmeyer and Benjamin Dilenburger, both ETH Zurich:

a complex, fine-resolution structure manufactured using selective bonding

N  layers deposited in offset steps to create inclined surfaces

Text Josef Kurath

Semi-Finished Products in Structural Carbon Prestressed Concrete 040

ESSAY

Since 2016, following 14 years of research, complete prefabricated bridges have been built out of CPC (Carbon Prestressed Concrete) panels. Because the carbon is prestressed, ­only a minimum amount of the material is ­required as reinforcement. Carbon, an efficient, lightweight, sustainable but expensive material, is therefore capable of ­competing with steel reinforcement. Carbon is chemically resistant. It suffers no ­fatigue before it reaches its fracture strength. In comparison to other textile fibres, carbon is very stiff and exhibits no longitudinal thermal expansion. However, the disadvantage of the material lies in its high price. Although the price of the basic material, carbon fibre rovings, has come down by a factor of 40 over recent decades, carbon is still much too expensive compared to steel reinforcement for the equivalent structural performance. Processing rovings into fabric further increases the price. At the moment, carbon cannot generally be used as a substitute for steel reinforcement. Carbon’s corrosion resistance plays no role in conventional building construction. Our fire tests at Zurich University of Applied Sciences (ZHAW) in Winterthur have shown that concrete reinforcement cover and therefore the thickness of CPC panels cannot be reduced from that of steel-reinforced concrete panels. The present methods of producing carbon ­fibre rovings offer no sustainability advantage compared to steel reinforcement. Because the stiffness of a carbon rod made from conventional carbon fibres is less than that of the same cross-sectional area of steel, and no significant increase in stiffness is achieved even with high-stiffness fibres, the very high stiffness of carbon cannot be exploited if the rods are unstressed when the concrete is poured. Our calculations show that the price for carbon reinforcement would have to be between 1/60th and 1/20th of what it is now in order to be competitive with steel reinforcement. This does not appear likely in view of today’s technology for the manufacture of carbon ­fibre rovings. COMPETITIVENESS BY PRESTRESSING To compensate for the price disadvantage of carbon, new forms of construction or methods of building must be found. We have been pursuing such an approach for the last 14 years in our research. The result is a completely novel way of constructing using concrete. With the newly developed CPC panels, 1– 2 mm thick carbon strands at 15 mm intervals are ­prestressed and cast into thin concrete panels; the strands are arranged parallel to one another in the X and Y directions to form an orthogonal reinforcement mesh. The concrete cover to the strands is between 6 and 8 mm. The result is a concrete panel prestressed in the two principal directions. This semi-finished product can then be further processed. Openings cut out within the panels or at their edges have no adverse effect on the prestressing: measurements have shown that full force transfer between carbon and concrete still takes place even with a cut edge passing within one centimetre of a strand. 2-cm thick panels are reinforced with 2 layers of strand; thicker panels to resist higher loads have correspondingly more layers. In the near future, panel thicknesses of up to 8 cm with eight reinforcement layers will be available. The length and width of the panels are determined by logistics requirements. For highway applications, the semi-finished panels are cut to a maximum of 13 m × 3.50 m out of considerably larger production panels. In the same way as with timber construction, the concrete quality is tailored for the specific areas of use: fire protection, lightweight, thermal insulation or resistance to salt. Once a decision about the method of ­construction has been made, the semi-finished products can be manufactured in great numbers in a factory environment. Thanks to their low self-weight, they can be inexpensively transported over large distances and are simply stored by stacking. Building with CPC would be a particularly attractive o ­ ption for areas such as the Middle East or in underdeveloped countries where resources are sparse.

041

Semi-­Finished Products in Structural Carbon ­Prestressed Concrete

A panel dimensions W / L / D in mm

number of layers of carbon strands

permissible deflection

permissible uniformly distributed load

permissible point load

1000/6000/24

4

w = B/300

3.9 kN/m2

2.7 kN/m2

requirement not met 1 

12.5 kN/m2

3.9 kN/m2

w = B/300

3.5 kN/m2

8 kN/m2

requirement not met 1, 2

11 kN/m2

10 kN/m2

2000/3000/40

8

  use as e.g. balcony slab or facade panel   use as e.g. staircase steps, traffic surfaces for pedestrians, cyclists and maintenance vehicles

1

2

B

C

1

D

2

3

6 15

20

6 15 15 15 15

A The load-bearing capacity of CPC panels as ­single-span, simply supported beams on end bearings increases by 20–40 % when continuity is taken into account.

B fractured face of a two-layered CPC panel

042

ESSAY

15

15

15

15

C s chematic construction of a 20-mm thick CPC panel

15

15

D prefabrication in the ­factory: CPC panel after being cut to length

1 concrete (quality according to ­requirements) 2 top reinforcement ­layer, Ø 1.2 mm carbon strand

3 bottom reinforcement layer, Ø 1.2 mm carbon strand

At first glance, one of the great advantages of in-situ concrete construction, the high ­flexibility and the ability to cast concrete to complex geometric profiles, would appear to be lost. However, most components for load-bearing structures in the mass market ­ lmost all straight, planar items. In the open for buildings and in bridge construction are a air, where no fire protection requirements ­apply, CPC panels can be designed as steps or platforms, spanning as simply-supported slabs on a substructure or as balcony slabs in prefabricated steel frames. The possibility of adding these panels into complex load-­ bearing structures also makes semi-finished precast components an attractive option in bridge construction. Digital design software and automated CNC machines in weather­ protected production halls allow the components to be manufactured to precise dimensions and quickly assembled on site as dry construction. We based the idea of creating individual building components from semi-­finished products on the practices adopted in modern timber construction and its use of glued boards. Over the last 200 years or so, cast components have largely been superseded by semi-finished products in structural steelwork too. THE LIGHTEST CONCRETE BRIDGE IN THE WORLD The capabilities of the new method of construction were proved in practice for the first time in 2016: the 7.85-m long, 2.44-m wide pedestrian and cycleway bridge over the River Eulach in Winterthur, Switzerland. The existing bridge had to be replaced because the main steel beams were no longer capable of safely carrying the applied loads. Over the years, rainwater had flowed through gaps in the 120-mm thick concrete planks comprising the bridge surfacing and over the main beams, which led to serious corrosion damage. The steel beams were retained in the new bridge only to act as supports for the existing pipework under the deck. The new bridge deck consists of a single large-format, 40-mm thick CPC panel with a continuous milled-out drip rebate on the u ­ nderside near its edge. Smaller, 40-mm thick panels glued to one another back-to-back in pairs form a continuous supporting edge beam frame, which is glued to the ­underside of the large panel to form a combined structural unit. The depth of the frame in the abutment area is 320 mm, which is derived directly from the level of the top of the existing bearing and the carriageway surface on the approach to the bridge. The transverse beams of the new deck had cut outs made in them to accommodate the existing pipes. The top surface of the longitudinal beams was cut to a radius of 218 m to create an effective structural depth at mid-span of 354 mm, where the greatest bending moment occurs. The falls thus created ensured water would drain off the bridge deck surface. A pocket was created along the whole length of the ­underside of the longitudinal frame beams by milling out the surface of one of the smaller panels to accept a 10-cm wide carbon strip, which was glued into place as additional reinforcement. The top layer of concrete of the deck panel forms the running surface and is designed to be the wearing course. There is no corrosion risk. The concrete resists freezethaw action and the carbon reinforcement cannot corrode. The prestressing ensures the deck is crack free and therefore relatively watertight.

043

Semi-­Finished Products in Structural Carbon ­Prestressed Concrete

E

conventional in-situ concrete bridge

dimensions/weight • concrete • reinforcement • total eco-indicator points EIP • concrete • reinforcement • total • percentage construction costs excl. design (CHF)

carbon concrete bridge

Variant I t = 350 mm 14 700 kg 385 kg 15 085 kg

Variant II t = 280 mm 11 800 kg 525 kg 12 325 kg

CPC t = 76 mm 3200 kg 14.5 kg 3214.5 kg

1 896 300 935 550 2 831 850 100 %

1 522 200 1 275 750 2 797 950 99 %

412 800 189 950 602 750 21 %

77 000

77 000

39 500

F

G 5

6 4

7

1

7

2

E life cycle analysis of the CPC bridge compared with reinforced concrete alternatives

F completed bridge in place

G–I cycle bridge campus T in Winterthur 2016. Planning and design: Staubli, Kurath und Partner

G longitudinal beam

section scale 1:20 1 bridge deck CPC panel 7815 × 2370 × 40 mm C65/75 four-layer reinforcement

2 support frame made of 2× 40 mm CPC, cambered top of longitudinal beam

3 carbon strips glued into groove: h = 100 mm l = 7800 mm

4 structural connection of running surface slab to support frame and counter-sunk sleeves stainless steel M8 Ø 24 mm, glued

5 handrail and strengthening for cast-in parapet rail CPC panel 40 mm four-layer reinforcement

6 stainless steel tube Ø 26.9 × 2.6 mm 7 concrete adhesive

J Future application: use as structural floor in building structures, CPC panel as semi-finished component.

K CPC panel used as a balcony slab, milling out of narrow recesses

3 H

I

044

ESSAY

H support frame below bridge deck panel

I erection of the bridge on site with crane

LIFE CYCLE ANALYSIS AND ECONOMIC EFFICIENCY The life cycle analysis of this bridge sets new standards. The CPC panels, being prestressed, require only small quantities of ­carbon. The weight of carbon is well under the limits for organic contamination of the concrete. This allows old CPC components to be directly processed into recycled concrete or sent to landfill, without having to separate the reinforcement from the concrete. At 190 kg/m2 of usable deck surface, the construction is four times lighter than a comparable RC deck: the equivalent of a light steel bridge. In terms of life cycle analysis, the CPC bridge is five times better than its conven­tional concrete rival. An alternative solution for the deck replacement in which two additional steel beams were inserted would have cost an estimated CHF 22,000; one with additional in-situ concrete beams CHF 27,000. Another alternative was a replacement new bridge in concrete using a similar design to the existing one. The estimated cost for this was CHF 77,000. The constructed design with CPC panels was completed for CHF 39,500 and in terms of quality is as good as a new build.

J

K

USE IN BUILDING STRUCTURES AS LOST FORMWORK An interesting application in building structures would be the use of a composite slab as a floor slab. In this, the CPC panels would act as lost formwork and would contain the bottom layer of reinforcement. These composite floors are considerably stiffer than reinforced concrete floors. Instead of 100 kg of steel r­ einforcement, we would need only 2.5 kg carbon to keep deflection below the specified limiting value. A master’s degree study of f­atigue behaviour, bending and shear stresses with various surface roughnesses between the CPC formwork and the applied in-situ c ­ oncrete showed that this type of composite deck complied with all the applicable standards and could be designed in accordance with Eurocode 2. CPC panels placed on both sides of in-situ concrete wall elements replace both reinforcement and formwork. However, the costs for these applications are still too high but, if enough of them were constructed as part of a project, the solution would become increasingly economic.

045

Semi-­Finished Products in Structural Carbon ­Prestressed Concrete

Roofs

046

ESSAY

CONCERT HALL IN BLAIBACH

048

TRAM STOP AT BERLIN MAIN RAILWAY STATION

060

HIGH-SPEED RAILWAY STATION IN MONTPELLIER

066

CHALICE COLUMNS FOR STUTTGART 21

076

047

SEMI- FINISHED PRODUCTS IN STRUCTURAL CARBON PRESTRESSED CONCRETE

Architects  Peter Haimerl, Munich (DE)

Structural engineers  a  .k.a. ingenieure, Munich (DE) Thomas Beck

Concert Hall in Blaibach

048

049

The concert hall in Blaibach, recently opened and the centrepiece of various urban design measures aimed at revitalising the town centre, looks like a monolith dropped from the sky, stuck at an angle within the newly designed pavement of the town square. Vertical joints between facade elements indicate tectonic intent to the expert eye, and the granite surface is reminiscent of the local stonecraft traditions. The inclined cube constitutes the conclusive response to the sloped construction site and the building’s function as a concert hall. The inclined floor of the closed box supports the rows of seats of the auditorium and covers the exterior stairs of corresponding width that lead from the town square to the underside of the cube. This is where the foyer and its auxiliary rooms are situated, providing ground-level access to the garden in the rear of the building. Visitors are guided past the wardrobe and bar, around the auditorium, and finally into its interior. The atmosphere of the concert hall is characterised by the exposed concrete surfaces of the walls and ceiling, structured into horizontal bands. The texture of the

aa

4

3

a

1

5

a

5

a

2

4

site plan, scale 1:5000

section, floor plan scale 1:400 1 entrance 2 musicians

3 cloakroom a 4 bar 5 stage

3

1

050

Concert Hall

2

concrete extends beyond many of these “folds” and emphasises the appearance of a monolithically cast space. It is illuminated by indirect light provided by hidden LED bands along the underside of the tilted concrete ­surfaces. Despite its sculptural quality, the complex form of the interior is most of all the result of the precise calculation of acoustic properties. Aside from lighting tracks, bass absorbers are hidden within the folds of the walls and the floor of the auditorium. The porous surface of the lightweight concrete can also absorb mid-range frequencies. The inclined floor slab features ­reinforcement, electrical wiring and ventilation ducts. Just enough space remained to connect the steel cantilevers that allow the filigree lattice shell seats to seemingly float above the floor. Burkhard Franke

051

Blaibach (DE)

052

Concert Hall

053

Blaibach (DE)

Text  Thomas Beck

B

A

C

D

E

A  complex geometry of the interior wall surfaces of the auditorium, 3D model wireframe illustration

B side wall of the auditorium prior to removal of formwork / toothed joint with rear wall reinforcement bolt

054

Concert Hall

C v entilation ducts inlaid ­into the reinforcement ­prior to pouring concrete of inclined auditorium floor slab

D mounting boxes for sound absorption, air distribution and LED lighting E acoustically effective cavities in finished concrete

STRUCTURAL SYSTEM AND GEOMETRY The building consists of two structurally separate elements: the basement including foyer and restrooms and the inclined cube housing the actual auditorium. The basement that surrounds the auditorium on three sides is a solid concrete construction made of waterproof concrete and poured on site. It consists of a continuous ceiling, exterior and interior walls, and the inclined surface beneath the open staircase that serves as a retaining wall. The structural design of the auditorium can be described as an inclined box. Along its lower edge, it rests on the floor slab and on a recessed retaining wall set back along its upper edge. The roof slab spans laterally and is supported by the side walls. The upper front wall comprises a shear wall spanning between the cantilevered side walls. The lower front wall is placed on top of the floor slab. The lower inclined surface to which the aisles are connected

is supported by the floor slab, the retaining wall and the upper front wall, from which it is suspended. Similar to the basement, all elements function as shear walls and support horizontal loads created by tilting the cube. As a geometrical object, the inclined cube comprises an ­unusual form that still enables sufficient control. However, with their different inclinations and partially undercut surfaces, its interior walls lead to a very complex geometry that no longer permitted visual representation in two-dimensional drawings in a sensible way. A 3D model of the entire building volume was used to generate sections and working drawings. Yet, they were of limited use on site. This is why communication with the builders was in part based on “operative instructions” mostly focused on individual construction components.

INTEGRATION IS THE RULE A special feature of the wall, floor and ceiling construction is that all the important elements for concert hall performances are integrated into the folded concrete structure. For example, fresh air is delivered through oblong distribution ducts and ventilation outlets integrated into the concrete. The folds are intended mainly to distribute the sound correctly in the room – with some help from almost hidden but highly effective tubular base absorbers cast into the

055

Blaibach (DE)

concrete behind the folds. The porous quality of the concrete surface also has an acoustic effect by absorbing the mid-to-high frequencies. Even the lighting is integrated in the form of linear LED elements built into the concrete folds.

PROCESS: CONCRETE WORKS Creating the folded interior wall surfaces of the auditorium monolithically in concrete required complex formwork and sophisticated logistics. Creating the formwork on site was soon recognised as too complex. Instead, all concrete ­surfaces were subdivided based on an orthogonal grid to create formwork elements 2.50 by 3.00 m in size using a digital 3D building model. The formwork consisted of folded plywood formwork boards that were subdivided into ­triangles, mitered at various angles, and buttjoined (fig. H). The panels are supported by ­vertical plywood ribs (figs. K, L). The box-shaped bass absorbers were pre-­installed facing the formwork boards. The roughly 130 different formwork elements required distinct identification markings and had to be delivered on site in the appropriate sequence. Not a traditional carpenter, but ­instead an Austrian vehicle manufacturer was contracted who had the experience and expertise in dealing with complex three-dimensional forms and who could guarantee the required precision by use of CNC-­ supported production. The formwork elements

2 ∅ 28 3 ∅ 28 3 ∅ 28 ∅ 10/15

staggered stirrups 73 ∅ 10/15/1.06

3 ∅ 28 Q524A

Q524A 2 ∅ 28 3 ∅ 28 ∅ 10/15

25

F

were used as infill liners between two standard formwork components used for large surfaces. After erecting the interior formwork wall, the actual formwork elements were connected to it (fig. I). Conical millings ensure continuous and precise connections between elements. After reinforcing the 25-cm thick load-bearing wall surface, the “spiky” volumes facing the interior were reinforced as well. To prevent the use of hundreds of different spacers due to the continuously varying depth, reinforcement bars of identical length were placed into the welded wire fabric reinforcement of the “spikes”, and the excess part was bent back into the wall surface (fig. M). The large formwork panels ­received anchor bolts according to grid dimensions and openings were covered with elliptically shaped plugs. Bolt holes were filled after stripping the formwork. Pouring the concrete walls took place in multiple steps from bottom to top (fig. N). After creating the seating level, a formwork table was created up to the underside of the ceiling and served as support for the formwork used to pour the roof.

G 3 ∅ 28

3 ∅ 28

∅ 10/15

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25

F  details of flush face ­column  scale 1:20

G reinforcement plan of ­auditorium side wall  scale 1:200

056

Concert Hall

c

c

b

b

L

J

M

15 30

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I

N

Bent back in on site

I reinforcement of ­loadbearing wall layer

057

Blaibach (DE)

J formwork elements with bass absorbers attached on site

K, L axonometric illustrations, prefabricated formwork elements (front panel of large-scale formwork omitted in the figure)

30 15

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∅ 8/25 ∅ 8/25 ∅ 8/25

H  manufacturing of ­formwork elements

Anchors positioned on site 21 mm plywood

15

60

15

Bent back in on site

60

H

M o  n-site bending of ­reinforcement into folds

N  section, formwork ­composition with largescale panels and inlaid formwork element  scale 1:50

FACADE ELEMENTS The production and assembly of the curtain wall facade with its natural stone panels was highly complex. The production of facade elements took place directly next to the construction site. Since the stone patterns were supposed to extend continuously beyond individual panels, the facades were drafted along a carefully levelled area and subdivided according to planned joints (fig. O). The granite stone was laid out in order to exclude weak spots and cracked elements (fig. Q). Joints were infilled to one-third with sand. The reinforcement was placed on top (fig. R), the steel components were set, and finally, the panels were cast in place. A steel truss hoist (fig. P) served to erect and lift the panels measuring up to 3 m × 10 m and weighing 19 t.

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In order to achieve closed corner elements without visible joints, the border elements of the two front facades were erected after curing, set into the formwork of the ­corresponding border areas of side walls, and orthogonally cast in place ­together (fig. S). Steel components were integrated along the upper border of each element. Their connectors transmit loads into the building structure and are cast into the ceilings at precise dimensions, forming a closed roof ring. This ensured the precision required to join the inbuilt elements and the facade panels during assembly: concrete construction with the production accuracy of steel!

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O formwork plan for ­facade elements, ­individual panel a ­ rrangement and ­layout direction for stone panels;

058

steel edge sections define the joint width. Textfeld Loremwidth Joint Ipsum = 2 cm

162.8

form height = 25 cm Textfeld Lorem Ipsum

element F14 illustrated as example for position of inbuilt steel ­element

Concert Hall

P assembly of inclined facade element by use of hoist

Q–S different work steps in manufacturing ­facade elements

2 3 4

1

5

Q 6

7

R 6 7

S section scale 1:50

059

Blaibach (DE)

1 liquid sealant 20 mm scattered gravel 19 –140 mm reinforced screed; separation layer bituminous roof sealant 450 – 950  mm lightweight concrete

2  heat and smoke vent

5 150 mm natural stone ­embedded 100 mm deep in 200 mm reinforced concrete bituminous sealant layer 250 – 950  mm lightweight concrete

6 b  ass absorber, steel sheet metal with insulation

3 inbuilt roof border ­element; steel

7 LED strip

4  inbuilt facade steel element

Architects Gruber + Popp Architekten, Berlin (DE)

Structural engineers schlaich bergermann partner, Stuttgart (DE)

Tram Stop at Berlin Main Railway Station

060

061

Elongated, slightly curved reinforced concrete shells shelter the two platforms of the tram stop north of Berlin Hauptbahnhof central station. From the walls to the main stairwell to the metro below, the wings rise gently to their delicately proportioned tips. The roadside flanks of each of the four roof wings rest on five steel columns. The architects and engineers worked together on this project from the competition stage. In order to be able to realise the unusual roof form, as thin as 7.5 cm at the ends, and keep the self-weight down,

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section, plan  scale 1:400

062

tram stop

3.00

the engineers chose to use a high-strength lightweight concrete. While the connection points of the roof wings at the stairwell core walls are conventionally designed, the column heads have to transfer high bending moments, which requires special steel components, additional stirrups and punching shear reinforcement to be installed. To keep deflection due to self-weight, shrinkage and creep as low as possible, the concrete was kept in the formwork for 28 days before being subject to load. Andreas Gabriel

063

Berlin (DE)

a substantial curvature – shell action

A

b low curvature – load transfer by bending

a b

B

C

660

115 30 70 3070 30 70 3070 30 115

28

300 660

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100 100 100100 100 100 300

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400 400 53 310 37 310

aa 28 1228 5

125

A  To achieve the very thin edges to the cantilever roof, the section was reinforced with 2.5-m wide strips of stainless steel reinforcement. 

064

 he high-strength lightT weight concrete with ­porous aggregate (LC 45/50, 1600 kg/m3) has higher strength than normal lightweight concrete. Relatively stiff in

tram stop

4

125 28 28

4

125

terms of flowability, it ­requires expert ­handling. Tests in advance verified the strength and flowability characteristics.

B Bending moments of around 200 kNm have to be transferred into the column heads, which are designed for truck impact, via special steel inserts.

C column head ­components vertical section, ­horizontal section scale 1:20

065

Berlin (DE)

Architects Marc Mimram Architecture & Associés, Paris (FR) Atelier Nebout, Montpellier (FR)

Structural engineers Marc Mimram Ingénierie, Paris (FR)

High-speed Railway Station in Montpellier 1.45

8.42

16.

1.30

8.27

16. 066

2.78

1.45

8.42

2.97

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1.30

8.42

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aa

bb

a

11

10

b

12

b

9

8 3 4 2 7

13

5 1

6

6

a

5 customer service 6 offices 7 rental area 8 food & drink 9 transport operators

site plan  scale  1:25 000 sections, plan layout scale 1:1000

1 main entrance 2 station hall 3 access to platforms 4 kiosk

068

High-speed Railway station

10 car hire 11 left luggage 12 waiting room 13 tram station

A new type of railway station designed for the Mediterranean climate is being built in Montpellier, southern France. Its unusual roof structure creates a pleasant space and ­climate inside the station and takes the visitor by surprise with a special lighting effect. High-speed trains travelling between Paris, Marseilles and Barcelona make frequent stops at this station. It is located in the middle of a development zone in the transition between city and open countryside. The station hall, which can be seen from a great distance away, spans the wide expanse of the platforms and offers a raised podium with extensive views over the surrounding landscape. Lifts and escalators lead down from there to platform level. Instead of a glazed hall, the objective of the design team working around Marc Mimram was to create a space with a roof that would filter the light and ­provide shade. To achieve this, they designed a refined, modular structure of thin, perforated, precast concrete elements that not only fulfilled the architectural, acoustic and climatic requirements but also brought the interior to life with an interplay of reflected light at floor level. The designers referred to the vaulted roof ­elements by the nickname “palms”, making reference to the feeling of being protected by a leafy canopy while waiting in the station hall. Station users are now able to experience this for themselves, with the first train arriving in July 2018. Andreas Gabriel

069

Montpellier (FR)

Text  Marc Mimram, Michele Bonera

A

B compression 

taut stress

D

2.97

C

1.30

E

1.30

2.97

1.30

8.27

1.30

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1.45

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8.42

2.78

16.84

8.42

High-speed Railway station

1.45

8.42 16.84

070

8.42

16.84

1.45

COMPLEX ROOF STRUCTURE The roof of the new high-speed train station in Montpellier consists of a perforated concrete structure of 115 modular, precast “palm” units of white, ultra­-high performance concrete (UHPC).

These doubly curved elements offer permanent protection against the sun and rain. Open gaps ­between the elements allow n ­ atural ventilation of the hall.

OVERALL STRUCTURE The load-bearing structure of the station has four main layers: the lowest is the reinforced concrete plinth, which has a grid of 18 × 19.45 m determined by the arrangement of the platforms. The second layer includes all the reinforced concrete constructions above the station hall

floor. The third structural layer is a multi-span welded steel column and beam frames (5 spans of 19.45 m longitudinally, 2 spans of 18 m and 36 m transversely). The fourth structural layer is the modular roof ­elements spanning between the steel main girders.

STRUCTURE OF THE ROOF ELEMENTS The palms are self-supporting precast units with a span of 16.84 m. They consist of a variable cross section central rib prestressed by four T15S cables and a doubly curved and perforated shell with edge upstands and are only 40 mm thick. The four reinforced corner bearings of each roof element rest on support brackets attached to the steel girders. The palms behave as statically determinate beams with pinned bearings at one end and longitudinally sliding bearings at the other. They do not provide any stiffening to the overall structure. In addition to their selfweight, they also carry maintenance access, snow, wind, temperature changes and earthquake loads. The extremely delicately proportioned shape of the elements required the design of a new UHPC mix, which incorporated a high proportion of stainless steel fibres (Ductal B3 FI 1.75 %).

A cross and longitudinal section of the structural steelwork, static system

B isometric view of a roof element showing compression and tension zones

071

Montpellier (FR)

C isometric view of ­tructural steelwork

Connecting the compression-loaded top edge to the pretensioned bottom edge by the thin, perforated shell, allowed each palm to act as a vaulted Vierendeel girder. The more highly loaded ends of the shell have fewer perforations. A transverse rib at the ridge prevents the V-shaped cross section from folding in on itself. As a result, the elements are very stiff. Their maximum deflection under self-weight including creep is 14.6 mm at the ridge, i.e. only 1/1200 of the span. The analysis using Sofistik took into account nonlinear behaviour in arriving at the design of the c ­ omplex geometry of the system and allowed crack widths to be limited to 0.01 mm. The high density and low porosity of the UHPC e ­ nsures that the elements are ­waterproof. Glass inserts seal the openings in the palms. The model of the whole roof indicated that the structural steel frames would ­deflect a maximum of +/- 28 mm laterally under earthquake loads, from which the joint width of 70 mm was derived.

D isometric view of support brackets on main girder

E v ertical section of type 3 roof element scale 1:100

F vertical section, plan of type 5 roof element  scale 1:100

G

I

H

J

K

5

0.07

1

0.98

2 0.24 3 4

0.36

2.42 K vertical section of roof  scale 1:25 1 40-mm UHPC (ultrahigh performance ­concrete)

G  isometric view of a roof span, each of the five roof spans consists of a group of four elements of different shapes at each end and 15 identical elements ­between the end groups

H–J production, site storage + installation of roof ­elements

072

High-speed Railway station

2 400/160-mm opening with glass cover 3 UHPC rib 4 pretensioned element with  4 T15S cables

5 aluminium plate, powder-coated

VARYING DEGREES OF TRANSPARENCY The number of transparent openings in the palms above the hall reduces from north to south, which limits the amount of light and heat admitted. In addition, the density of the openings is less on the west-facing parts to ­reduce the entry of afternoon sun. The proportion of

6

transparent openings varies from 8 % in the southwest to 25 % in the northeast. The elements in the external roof projection over the forecourt are thicker and evenly perforated to create a gentle transition between indoor and outdoor lighting conditions.

7.00 5.98

L 0.60

0.40 7

0.61

6

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0.14

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0.14 8

1.20 c

c

0.81

9

1.40 cc

5.98 0.40

1.20 c

7.00

0.81

9

1.40

L vertical section of roof edge, horizontal ­section of column scale 1:20 6 UHPC roof element 7 1200/600-mm beam

­welded out of 50-mm steel plate 8 UHPC cladding 9 1400/810-mm column welded out of 65/55-mm steel plate

073

Montpellier (FR)

0.10 8

074

High-speed Railway station

075

Montpellier (FR)

Architects ingenhoven architects, Düsseldorf (DE)

Structural engineers Werner Sobek, Stuttgart (DE)

Chalice Columns for Stuttgart 21

076

077

Text Roland Bechmann, Angelika Schmid, Torsten Noack

1

A

B 4

2

1

3

C

D

078

CHALICE COLUMNS FOR STUTTGART 21

2

3

Stuttgart 21 is a transportation and urban ­development project to redesign Stuttgart’s major rail interchange. Key to the project is the reconstruction of the old 16-platform, surface rail terminal in Stuttgart to form a below-ground, eight-platform, through station. Completion of the station is scheduled for 2025. Taking up the surface-level tracks and demolishing signal boxes will release around 100 hectares of land for new green space and the expansion of the urban centre. The design for the new station was ­originally prepared by Christoph Ingenhoven in conjunction with Frei Otto; this design emerged as the winner from the 126 participants in an ­international competition held in 1997. Structural engineering firm Happold was initially responsible

for the structure. This role was later taken on by Leonhardt Andrä und Partner. Consulting engineers Werner Sobek assumed responsibility for the design of the structure and facade in 2009. At this point, the task was to modify the design and take it forward into the approval and execution planning phases. This updated design was based on the applicable DIN standards at that time. From 2014, the design has used ­Eurocodes. The high external loads (for example from the earth fill), difficult ground conditions, complex geometry of the reinforced concrete structure and long spans demanded a completely digital approach to the design and many new i­nitiatives at the interface of design and construction.

STRUCTURAL TROUGH WALLS AND CHALICES The 420-m long, 80-m wide and up to 12-m high platform hall currently being built is a monolithic, reinforced concrete structure constructed out of white, fair-faced concrete consisting of a “trough” topped with a shell roof. The roof with its multiple curves is carried by 28 chalice-­ shaped columns, which are crucial to the station’s striking appearance (figs. A, B). Some 23 of the 28 columns are “standard” chalices. They consist of a foot, a shell and a “scoop”; then a semi-circular upstand beam is added to stiffen the shell roof at the huge skylight or “light-eye”. A further four “flat” chalices have no edge stiffening and there is one large special chalice. The latter is turned through 180° compared with the other chalices so that it opens to provide access to the inner city. In addition to the total of 28 full chalices, there are also 18 “partial” chalices. Once complete, all these elements will be connected to one another by filling the shrinkage gaps between them with reinforced concrete. The trough structure is founded on bored in-situ concrete piles and driven piles, which generally end above the underlying gypsum beds. These

A  3D model of a chalice 1 scoop 2  chalice shell 3  chalice foot

B 3D model of the shell roof 1  edge chalice 2  inner chalice 3  partial chalice 4  shrinkage gap

079

Stuttgart (DE)

C T  he geometrically highly complex shell roof was designed completely in 3D. The same data was ­also used for the reinforcement detailing.

bands of gypsum act as a barrier to the water in aquifers below them. The chalice columns are founded on the ground slab of the trough. The edge and partial chalices are connected to the outside walls by a moment connection. Due to the topography of the Stuttgart Basin as well as the complex project restraints and conditions, for example the underground S-Bahn and light rail tracks that run above and b ­ elow the new tunnel, the distance between roof and trough, and therefore the height of the chalices, varies along the length of the platform hall. The design concept envisaged a structure loaded purely in compression with as little steel reinforcement as pos­sible. Even though this could not be 100 % achieved due to imposed movement strains, seismic and earth pressure loads, the form chosen for the structure considerably reduced tensile forces and bending moments. The ­result is spans up to 36 m and comparatively little ­reinforcement. The thickness of the shell roof varies b ­ etween 45 cm in the interior and 130 cm at the edges.

D  Reinforcement fixing ­underway on a standard chalice: An unusual feature is the scoop, an upstand along the top of the chalice that surrounds and carries the light eyes.

This area had to be ­reinforced like a beam.

E

E  freestanding reinforcement of a chalice foot before erection of formwork

080

Chalice ­Columns for Stuttgart 21

SOAP FILMS AND SUSPENDED MODELS The development of the geometry of the chalice is based on methods Frei Otto used in projects such as the German Pavilion at the 1967 World’s Fair in Montreal. He created a membrane surface using soap film and suspended models to arrive at an isotropic, even flow of tension forces under self-weight. The light eyes transfer the forces from the support points in the membrane surfaces without causing peaks of stress at the load introduction points. The geometry derived

from the suspended models was “frozen” and then turned upside down to give the required form of the compression structure. Even though the basic shape of the chalice was modified over the course of the design, it is still essentially the same. Due to their shape and the openings in the top, the chalices reflect daylight far into the platform hall. Ventilation flaps in the steelglass structure, which close the top of the light eyes, allow natural ventilation and airconditioning.

EXTENSIVE FINITE ELEMENT MODELLING Because the complex geometry cannot be clearly expressed in 2D drawings, the design of the load-bearing structure was based on a 3D model from the very beginning (fig. C). The model included precise detailing of the reinforced concrete structure and showed all the shell’s joints, in-built components and ducts. The structural design used various finite element models (FEM) based on the geometric model. These models were capable of simulating all the stages of construction and load cases, including seismic effects and structure/earth interactions. The critical load cases for the design were those

involving self-weight, fill on top of the structure, seismic effects, temperature and other imposed strains. The 3D model not only contained the geometry but also all the information about the load-bearing structure with coordinates. The 600 or so structural drawings for the shell roof were based on the model, which was also used as the basis for their data by many design and construction partners in other disciplines. The contractors used it for designing their formwork, and the structural engineers for the reinforcement design and detailing.

HIGH DENSITY OF REINFORCEMENT The complex reinforced concrete structure has a high density of reinforcement in some areas. In typical parts of the shell roof, each face has four layers of bar reinforcement. To make maximum use of the internal lever arm and to ensure adequate concrete cover, the bar reinforcement had to closely follow the component geometry. This resulted in four different basic bent bar forms. The structural engineers used their ­in-house 3D software to determine the precise geometric line of each bar. This data was then converted into actual reinforcing bars using a 3D reinforcement design program. Generating the bent forms took into account the elastic-­ plastic behaviour of the reinforcing steel and the technical limits of bar-bending machines. This 081

Stuttgart (DE)

revealed at an early stage in the design that ­certain bent-bar shapes could not be manufactured. The number of complex shapes, such as bars that had to be bent in different planes, could then be deliberately reduced to a minimum. A typical inner chalice with around 300 tonnes of reinforcement required 350 DIN A0 reinforcement drawings. A total of 12,000 such drawings were needed to detail the reinforcement for the complete shell roof. The 3D reinforcement model also proved useful on site: the contractors could check individual bar positions and fixing details against the design at any time in the drawing container.

THE SCOOP An unusual reinforcement feature is the scoop (figs. A, C), a strengthening upstand running ­partially around and over the top of the chalice. The scoop surrounds and carries the light eye. The forces from the steel/glass structure of the light eye are picked up by the scoop and transferred into the surounding concrete of the shell. This area has to be reinforced like a beam, which leads to local high concentrations of ­reinforcement. 32-mm diameter closed stirrups were arranged in a large ring surrounding the

scoop (fig. D). To be able to fix the tangential-­ running reinforcement conveniently from above and avoid having to painstakingly thread it into position, the ­stirrups were left open at the top and closed only a short time before concreting. Special U ­ -shaped stirrups were designed for this task: their ends each had a steel plate to allow the stirrups to be simply closed using a transverse bar (figs. F, G).

FORMWORK AND CONCRETING The formwork design was also based on the 3D model. All the chalice columns are cast ­using three sets of formwork in which the ­individual ­elements can be varied according to the desired geometry. Around 600 glued timber board elements were manufactured by CNC milling, sanding and reinforcing with intermediate layers of GFP-reinforced resin. In addition to the complex geometry of the formwork elements, another challenge was to remove all the air from around the formed surfaces during concreting. The flowing consistency (F5) of the specially developed concrete mix, optimisation of concreting speed and intensity of vibration all helped prevent the formation of voids. A sample chalice was constructed to demonstrate the feasibility and provide a cast surface for reference as the work progressed. This took the form of a full-scale partial segment of a typical inner chalice. During steel fixing, the

necessary vibrators and concrete hoses were integrated into the reinforcement cage and then pulled out as the concreting progressed. A video camera monitored the behaviour of the concrete as it rose up the forms in the areas not ­directly visible. Any breaks in the concreting process would have shown up as pour marks at the surface. To ensure this could not happen, a second batching plant was always on standby. Stripping the forms from the chalice columns normally started after about three days. This ­ensured that the concrete surface came into contact with oxygen as soon as possible to keep any blue colouration to a minimum. Temporary 12-m long props were put in place around the chalice after stripping (fig. H). These temporary steel props had a square cross section with ­varying wall thicknesses. They prevent possible deformation along the edges of the chalice until the shrinkage gaps are closed.

F scoop stirrup with steel special construction in transport template

H 12-m long temporary props prevented any ­deformation of the chalice edges between stripping and closure of the shrinkage gaps.

082

Chalice ­Columns for Stuttgart 21

G scoop reinforcement fixed in place showing special steel components

F

G

H

083

Stuttgart (DE)

084

Chalice ­Columns for Stuttgart 21

085

Stuttgart (DE)

Multi-Storey Buildings

086

CHALICE COLUMNS FOR STUTTGART 21

SINGLE-FAMILY HOUSE IN GORDOLA

088

ADMINISTRATION AND CONFERENCE BUILDING IN GARCHING

098

STATION HALL WITH MULTISTOREY PARKING GARAGE IN BORDEAUX

110

ESO SUPERNOVA IN GARCHING

118

SCHLOTTERBECK RESIDENTIAL AND OFFICE BUILDING IN ZURICH

126

BIOBíO REGIONAL THEATRE IN CONCEPCIóN

134

TAZ PUBLISHING HOUSE IN BERLIN

142

OFFICE BUILDING IN LYON

150

087

STUTTGART (DE)

Architects Nicola Baserga, Christian Mozzetti, Muralto (CH)

Structural engineers Pedrazzini Guidotti, Lugano (CH)

Single-Family House in Gordola

088

089

This single-family house is nestled into a sloped site in the community of Gordola in Ticino. The stunning natural landscape was a significant theme of the design. The new house is positioned on the ridge line and is raised above the ground by just two support pillars. A paved pathway leads from the parking space with its striking roof at the access road to the entrance ramp. The bridge-like concrete structure of the house determines its interior organisation. The two continuously glazed longitudinal facades of the building connect all rooms with the valley as well as the mountains. Individual rooms are situated behind the

bb

aa

2 1 a 3

4 b

4

5

b

6

4 3

a

cross section longitudinal section floor plan section scale 1:400

1 parking 2 rustico (existing) 3 access ramp

4 bedroom 5 living room 6 kitchen

090

Single-Family House

closed end walls of the building. The open concept kitchen /living room comprises the centre of the house. The exterior concrete surfaces of the building were created using straightforward wood formwork. Together with the simple corner details, they emphasise the striking character of the structure. This creates an exciting interplay between lightness and solidity. With its controlled ventilation, the building conforms to the Minergie standard. Andreas Gabriel

091

GORDOLA (CH)

092

SINGLE-FAMILY HOUSE

093

GORDOLA (CH)

Text Andrea Pedrazzini

Überhöhung Durchbiegung t0 Durchbiegung t∞A

5

a

B 6

a

Überhöhung Durchbiegung t0 Durchbiegung t∞

5,875

7 2

1

4

b Verformung Träger a [mm]

b

60

40 7

C

60

Verformung Träger a [mm]

30

40 7

5,875

6

a 60

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3,50

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5,875

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3,50

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1 40

30

10

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60

Verformung Decke b [mm]

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10

7 b

30 Verformung Decke b [mm]

D

1

4

67

2

3

1

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67

2

3

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a

5

a 10

b

9 8

b

E 10 10

1

13 12

1 1

13 13 12 12

A, B cross sections structural system

C deformation diagram section structural system scale 1:200

a deformation beam [mm] b deformation floor slab

Überhöhung camber Überhöhung bending t0 Durchbiegung t00 Durchbiegung bending t∞ tt∞∞ Durchbiegung

094

SINGLE-FAMILY HOUSE

D section structural system scale 1:200

11

E facade section scale 1:20

11 11

A PRESTRESSED STRUCTURE MADE OF REINFORCED CONCRETE The entire construction is suspended by two longitudinal beams at roof level measuring 1100 × 300 mm. They are connected to two ­lateral beams supported by two pillars set apart by 21 m and extend outward by 6 m. The main beams include 12 prestressed concrete cables with a cross section of 150 mm2 . The main beams support the roof slab spanning between them as well as the floor slab of the house. The latter is suspended along the end walls and four tie beams tilted towards them and visibly integrated in the facade. The tie beams divide the middle zone of the floor slab between the pillars

1 1100/300 mm edge beam, reinforced steel 2 multi-strand cable Ø 76 mm steel pipe 3 mono-strand cable ­Ø 21 mm steel pipe 4 compression reinforcement

5 shear stud 6 tensile reinforcement 7 comp. reinforcement 8 column base, pinned connection 9 column base, fixed ­connection

095

Gordola (CH)

10 roof construction: liquid plastic ­waterproofing 230–300 mm ceiling slab, reinforced ­concrete 120 mm thermal ­insulation, foam glass

into three areas. To ensure the rigidity of the tie beams, they feature two integrated mono-strand cables. The two support pillars ensure the stabil­ ity of the entire structural system. One pillar is pin-ended in ­order to prevent longitudinal stress and prestress loss. To limit deformations of the building volume, it was necessary to provide a ­negative camber of 60 mm for the cantilevers and a positive camber of 30 mm in the mid-­area of the house. The construction of the f­olded shell roof of the parking area also consists of ­reinforced concrete.

metal framing for hung ceiling with ­mineral wool layer 12.5 mm gypsum board

11 15 mm wood parquet 25 mm subfloor OSB 80 mm framing 80 mm thermal ­insulation, foam glass 220 mm floor slab, exposed ­concrete

12 triple glazing in ­aluminium frame 13 sun blind

7

200

35 65 65 35

25 3000

400 575 700

20

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+2.18 55

40 135 135 40 106125 2 350

9510 95 5 509 40 120 45

10 3000

90 150 60

220

2≈ SWISS GEMI Ø 40 290

H = 25 200

100

H = 43

150 70

100

H = 61

550

800 H = 79

550 H = 94

25 125

10 65 20 255

100

200

2≈4 PECO 13 L = 75 5 125 25

100 10 100

H 200 = 93

H = 90

5

100

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40 120 40

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100

2≈ SWISS GEMI Ø 50

10 20 140 20 10

40 70 70 40

125

45 120 40

7 100

100

82

110

28

875

10

H = 87

F

H = 83

2≈8 H =PECO 80 19 L =

50 100 100 100 100 100 100

10

200 165

255 20 65

H

23

45

22

800

300

100 100 100

25

999 1001100

5

10015 190 15 100 10

55 215

F facade layer scale 1:100

G lateral beam roof level scale 1:100

H  mono-strand tens. member, facade plane scale 1:20

I section lateral beam scale 1:20

096

Single-Family House

5

J steel connection ­longitudinal  /lateral beam scale 1:20

400

10

90

220 80 80

35 25 180

50 5 85 20100 10

35 25 180

61°

G

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18 88

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125 575

25

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292

20 3

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114

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5095

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100 H = 83

100 H = 87

100 H = 90

100 H = 93

10 100 H = 94

100 H = 79

100 H = 61

100 H = 43

100 H = 25

290

292

114

3

2≈ SWISS GEMI Ø 50

90 150 60

300

200

+2.18

610

7

700

2≈ SWISS GEMI Ø 40

200

220

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120

114

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88

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18

340

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165

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9510 95

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350

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20 140 20 10 200 J

Gordola (CH)

220

250

120 60

30 250

200 200

550

3000

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10 20

800

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097

255 20 65

15

25 125

15

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200

2≈4 PECO 13 L = 75 5

9510 95 40 120 45

10 20 140 20 10

15

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95 10 95

200

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5

5

3000

250

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100

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7

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550

2≈8 PECO 19 L = 125

120

100 250

25 25

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22

50 100 100 100 100 100 100 100 50

30 800 50

7

450

150 70 120 60

25 25

340 40 120 160 20

200

Architects Auer Weber, Munich (DE)

Structural engineers Mayr | Ludescher | Partner Beratende Ingenieure, Munich (DE)

Administration and Conference Building in Garching

098

099

Rising numbers of staff and Member States of the European Southern Observatory (ESO) required an extension to the administrative headquarters located in the Garching Research Centre, TU Munich. The existing Fehling+Gogel building built in 1980 comprised segments of a circle in which office units are arranged around open-plan, communal areas. Auer Weber returned to and re-interpreted this ­architectural vocabulary for the 270-workplace extension: three circular buildings – amalgamated on

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5 cafeteria 6 lightwell 7 meeting room 8 internal courtyard 9 office

sections, floor plan 1st floor scale 1:1000

1 link to existing ­building 2 connecting bridge 3 technical services 4 conference room

100

Administration and Conference Building in Garching

the upper floors – accommodate continuous cellular offices around the façade, a conference chamber, a cafeteria and meeting rooms. A large continuous edge cantilever of about 5 m gives the building a perceptible lightness. The sophisticated, efficient load-bearing structure goes hand in hand with the architectural concept and was developed during the competition phase by close cooperation between the two disciplines. Andreas Ordon

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GARCHING (DE)

Text  Lars Schiemann

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Administration and Conference Building in Garching

CANTILEVERING STOREYS – EFFICIENT 3D SOLUTION The important design criteria were the circular floor plan, the continuous 2-storey cantilever (fig. A) and the column-free intermediate areas. The intended architectural impression of a ­building floating above the ground was to be achieved with a recessed plinth storey and a funnel-shaped support arrangement. A suitable

load-bearing system had to be integrated into this scenario. A number of different design ­options for the 2-storey cantilever were explored: inclined ground-floor columns (fig. B) to reduce the cantilever and three different 2D and 3D structural actions.

SYSTEMS WITH 2D STRUCTURAL ACTION With both 2D options, the moment from the ­cantilever is carried by thickened slabs. In the case of the “table structure” option (fig. C), this is done by the ceiling slab over the ground floor storey while with the “roof structure” option (fig. D), the roof slab performs this function.

A–D  design options for the 2-storey cantilever

E structural system bulkhead wall structure

F  bulkhead wall structure showing flow of forces

­ ension columns at the end of the cantilever T ­connect the intermediate storey slabs to the roof slabs. Both options only partially create the desired impression of a floating building with thin exposed external faces to the slabs.

axonometrics from 3D structural analysis model:

G  foundation zone and inclined compression columns H bulkhead walls 2nd floor

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Garching (DE)

I  resulting hoop force Rz and cancellation of forces

J

1 1

2 2

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2 2

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J reinforcement drawings bulkhead wall structure scale  1:100 /1:400

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bulkhead wall interior column tension column compression column inclined column

Administration and Conference Building in Garching

SYSTEM WITH 3D STRUCTURAL ACTION: “BULKHEAD WALL STRUCTURE” Unlike the other two options, the “bulkhead wall structure” (fig. E) uses a 3D system consisting of the deck slabs, the tension and compression columns on the 1st floor and the bulkhead walls on the 2nd floor to transmit the loads to the foundations. The tension columns (red) on the 1st floor are set back 50 cm at the end of the cantilever and connect the cantilevering ceiling slab above the ground floor to the bulkhead walls positioned above on the 2nd floor to transmit the loads to the foundations. The bulkhead walls act as deep beams inside the building and rest on the 1st floor compression columns and on the ­inclined columns of the ground floor (blue). Connecting the roof slab to the 2nd storey floor slab by bulkhead walls creates a 3D struc-

tural system. The cantilever moment of the bulkhead wall is picked up as a horizontal couple by the two circular slabs and transmitted to the stiffening stairwell walls. This load transfer is made even more efficient by the ­circular building geometry. Using the hoop stress formula for circular structures, the resulting annular tensile hoop force Rz in the slab can be calculated from the radial load Z and the radius of curvature r (fig. I). The symmetrical arrangement of the bulkhead walls ­allows the continuous floor slab, cast without joints, to cancel out the radial loads. The end result is an extremely efficient 3D system with very thin slabs (d = 26 cm) that achieves the architectural effect of a “floating” building and uses the least material.

STRUCTURAL SYSTEM FOR THE COLUMN-FREE AREAS ON THE GROUND FLOOR A further objective of the architectural design was to have the whole office and conference building supported in three concentrated areas only – all inside building sections I, II and III (see floor plan on p. 100). A ribbed reinforced concrete slab structure spans a maximum of 22 m over the column-free area on the ground floor between building sections I/II and II/III. ­Tension anchors connecting the columns and the bulkhead walls to the floor slabs conduct the vertical loads from the slabs into the ribbed

105

Garching (DE)

slabs at roof level. In the longitudinal direction, the ribbed slab with its grillage type structure rests on ­vertical columns and walls in the edge areas of building sections I, II and III (fig. K). In the transverse direction, the cantilever loads are transferred through a Vierendeel structure comprising the bulkhead walls, the tension columns and the ribbed slab. The ribs, including the roof slab itself, have a depth of 1.50 m and a width of 0.75 m.

K

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Building section I

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Administration and Conference Building in Garching

CONSTRUCTION METHOD AND SEQUENCE The construction method for the 3D structural solution differs only slightly from that of conventional reinforced concrete buildings. One difference compared to the “table structure” is the temporary support of the cantilever during construction. Only once all the structural members

are effectively connected to one another and have achieved the minimum specified strength can the props be removed. In the meantime, the tension columns function as compression columns, which presents no problems because they are reinforced concrete.

UNITY OF FORM AND CONSTRUCTION The design and implementation of the ESO office and conference building in Garching ­provide a successful example of early, effective and sustained interdisciplinary cooperation ­between architects and structural engineers. The criteria relating to architecture, building use

K structural system for ribbed slab and column­ free areas

L 3-dimensional structural model with ribbed slab

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Garching (DE)

M reinforcement drawings ribbed slab structure scale  1:75 /1:400 1 tension column 2 edge ribbed slab 3 ribbed slab

and load-bearing structure are combined into an extremely efficient overall system. The architec­ tural concept, high-quality continuous cell office space on two floors, is integrated ­into the 3D load-bearing system.

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Administration and Conference Building in Garching

10

facade section scale 1:20   1 planted roof 100 mm ­gravel bed; non-woven ­filter drainage 2-layered bitumen waterproofing

180 mm insulation waterproofing 260 mm RC 2 80 mm triple glazing in aluminium frames 3 300 mm reinforced ­concrete bulkhead wall

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Garching (DE)

4 Ø 300 mm reinforced concrete tension column 5 Ø 300 mm RC concrete compression column

6 corridor partition wall: 2× 12.5 mm GFRP panels 75 mm insulation 2× 12.5 mm GFRP 7 15 mm cementitious building board metal substructure

120 mm insulation, 260 mm RC 170 mm suspended floor with adjustable height substructure 35 mm cement screed 10 mm carpet

  8 20 mm cementitious building board   9 500/300 mm inclined reinforced concrete column 10 115 mm plastered ­masonry

Architects SNCF Gares & Connexions, Paris (FR) Agence Duthilleul, Paris (FR) AREP, Paris (FR)

Structural engineers MaP3, Paris (FR)

Station Hall with Multistorey ­Parking Garage in Bordeaux

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structural sections  scale 1:500 layout scale 1:1250

1 concourse 2 entry  /exit to parking decks 3 station platforms 4 reception hall 5 shops and restaurant area

112

Station Hall with ­Parking Garage

  6 services and waiting area   7 bicycle parking   8 subway to the ­platforms   9 parking deck 10 overhead void reception hall

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The refurbishment of the historic Saint-Jean railway station in Bordeaux was undertaken in conjunction with the new section of high-speed train line to Paris, which opened in the middle of 2017. At the same time, a ­ arage above it was constructed on the opposite side of further station building with a multistorey parking g the tracks. This new structure, with its concourse, 360 bicycle parking places and a ground floor passenger hall with restaurants and shops, acts as an additional reception building for the station and serves the adjacent urban quarter of Belcier. The connection to the main building and access to the platforms are through a new subway. Above the spacious reception hall are six partially staggered parking decks for a total of 850 vehicles. From almost any point on the upper decks, unique views open up across the old town and the surrounding countryside. This all-round vista is made possible by dispensing with a solid facade and using a delicately proportioned load-bearing structure of elegant precast concrete units in conjunction with a vehicle impact barrier made from slender posts and prestressed steel cables. Roland Pawlitschko

113

Bordeaux (FR)

Text  Emmanuel Livadiotti

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A–C parking deck, precast concrete edge slab section, view from ­below scale 1:25

D assembly of prefabricated concrete units

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Station Hall with ­Parking Garage

E  ontinuity reinforcement c before in-situ concrete casting

b

LOAD-BEARING STRUCTURE The objective of the design was to incorporate a railway station hall and shops into an unclad concrete parking garage. The structural concrete components also form the ceiling ­inside the shops and the reception hall. The multi­ storey parking garage extending along a residential street was designed to allow the penetration of daylight through its volume. The designers strove to achieve the thinnest possible slab edge while assuring the highest quality surface finish. The confluence of these objectives quickly led to a prefabricated solution, with high-density concrete reaching strengths of at least 70 MPa. Standardisation allowed the design of elaborate shapes and profiles, the cost being absorbed by the large quantity of modular elements. To avoid the appearance of a structure completely assembled from individual parts, in-situ concrete was used to connect separate components together to give the appearance of a monolithic structure. The structural grid measures 7.80 × 9.90 m. The floors extend beyond the perimeter column line with a cantilever of 3.80 m. Hollowcore floor slab units, efficient and cost effective, are used for the middle bays spanning 9.90 m. These, in turn, are surrounded by shallow in-­situ concrete beams aligned with columns every 7.80 m. The in-situ beams create belts connecting the columns together and increase earthquake resis­ tance.

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Bordeaux (FR)

The edges of the building are constructed of 3.80 × 7.80 m precast concrete slab panels ­tapering in depth from 55 to 11 cm. These ­elements are shaped to incorporate the trapezoidal section of the longitudinal beams at the leading edge of the element and support the hollowcore units before they are concreted in. Incorporated into each element are ribs ­designed to connect to the columns and a ­thickened edge that forms the joint between ­elements. This area allows the integration of a prestressing cable, which prevents micro cracking and eliminates long-term deformations. The in-situ concrete reinforcement continues into the 5 cm structural in-situ concrete screed cast on top of the hollowcore units to transfer the positive bending moments into the vertical supports. 40 cm diameter columns, originally designed as prefabricated concrete components, were changed to in-situ concrete elements to simplify the construction. Some columns include stainless steel drainage pipes connected to floor gutters. The exterior safety stairs are isolated from fire by the concrete walls used to increase horizontal stiffness. Steel K bracings with their ends cast into the concrete floors provide stiffness in the vertical plane.

ACCESS RAMP A semi-circular helicoid ramp connects all the levels. The ramp is supported by a two­ dimensional grid formed by inclined steel posts. These posts connect the upper and lower floors as diagonal truss members. A cable v­ ehicular

impact barrier is fixed to these posts. The posts provide structural redundancy by preventing the damage or collapse of the entire construction in the event of a ­severe vehicular impact.

VEHICULAR IMPACT PROTECTION The vehicle impact barrier is provided by two 15 mm cables, tensioned between steel posts positioned at 7.80 m intervals on the prefabricated edge ribs. The cable deformation absorbs the kinetic energy of the vehicle, which reduces the force applied on the structure by a factor of five. The steel post bases are constructed from a single folded 12 mm plate, without welds, improving resistance to metal fatigue under the

116

Station Hall with ­Parking Garage

daily random loading due to vehicles touching the cables. Three 10 mm diameter cables are added to support stainless steel wire netting, transforming the car barrier into a pedestrian railing. This system, entirely designed by our team was used for the first time in France, and has been tested under the supervision of Centre Technique et Industriel de la Construction M ­ étallique (CTICM).

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Bordeaux (FR)

F, G vehicle impact protection, detail scale  1:20

H T  he calculated deflection of the steel cables under impact is 10°.

The perpendicular force acting on every cable is 2.3 t. The longitudinal force on the cable is 12.6 t.

Architects  Bernhardt + Partner, ­Darmstadt (DE)

Structural engineers Bollinger+Grohmann, Frankfurt / Munich / Vienna (DE / AT)

ESO Supernova in Garching

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The European Southern Observatory (ESO) is the leading intergovernmental organisation for astronomy in Europe and, according to its own literature, “the most productive astronomical observatory in the world”. Opened in 2018, the ESO Supernova is surrounded by fields on the outskirts of Munich, adjacent to TU Munich‘s Garching Campus. ESO Supernova is a donation from the Klaus Tschira Stiftung, a German non-profit foundation based in Heidelberg, and traces back to an idea of the physicist and SAP co-founder Klaus Tschira (1940 – 2015). The state-of-the-art planetarium with 109 seats and a 2,200 m2 interactive exhibition over three floors, is intended to communicate the fascination and importance of astronomy and astrophysics to the public. The special shape of the building represents a merging double star system shortly before it explodes. The breaking open of the outer skin symbolises the start of the mass exchange. Its surface

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longitudinal section floor plans scale 1:1000

1 entrance and foyer 2 planetarium 3 under-roof void 4 ramps 5 glass dome 6 roof terrace 7 seminar rooms

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120

ESO ­Supernova

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consists of 1,400 different 4 mm thick aluminium panels that have double and, in some cases, triple curvature. The precisely prefabricated sheets were installed onto the reinforced concrete building carcass with spacers. The architects arrived at the design for the two glazed facades of the foyer through a digital form-finding process that would allow the desired free-form shape to be constructed using flat glass panels. The vertical room-defining and load-bearing elements consist of curved concrete strips that follow the architectural principle of the supernova and join together to create free-form shells and shell segments. Various large openings and gaps arising from the offsetting of components allow views between the exhibition rooms and into and out of the building. Visitors access the building from the foyer on the ground floor. Heike Kappelt

121

GARCHING (DE)

Text  Moritz Heimrath, Adam Orlinski

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ESO ­Supernova

EFFICIENT STRUCTURAL ACTION Shells, decks and ramps together form a three-dimensional structure with high vertical and horizontal stiffnesses. Two series of segmented shells are arranged around the two cores to form the vertical structure. Circulation ramps and the decks of the exhibition spaces span between the inner and outer series of shells. Balconies project into the interior of the

cores. Some of the shell segments are stiffened with vertical lesenes between which the building services installations are integrated. Hollowcore slabs with reduced self-weight and a thickness of 0.5 m span up to 13 m ­between the two cores. All structural components are made from reinforced concrete.

THREE-DIMENSIONAL AND PARAMETRIC The complex geometry of the project meant the design of the building carcass – from the first digital sketches to the formwork design – was completely based on and represented by a 3D model. Using the NURBS modelling package Rhinoceros to model areas and volumes and the Grasshopper graphical programming interface, the basic architectural concept was expressed parametrically in all the room-defining elements from the very ­beginning. Gradually, the dimensions of all the structural components, building services shafts and openings were precisely ­defined and coordinated. Based on the updated

A  boundary curves in FE model

B complete building model

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Garching (DE)

C flow of forces: compressive stresses in FE model

D a  utomated drawing production: isometric views and coordinate points

parameters of space contents and dimensions requiring change, the 3D model was regenerated according to the previously programmed logic. The visual programming environment ­allowed the workflow to link building geometry with building information. Interdisciplinary ­communication and ­exchange of information between the various trades was exclusively by 3D objects with a ­ ppropriate parameters, ­attributes and annotations. The building carcass, building services ­installations, fitting out and facade were integrated into the same model.

E s tructural model without outer shells

F  art of building carcass p drawing with coordinate points

G inner and outer shells H r einforced concrete with spacers for facade panels

TAILORED INTERFACES During the approval and detailed design phases, the visual programming environment (Grass­ hopper) enabled tailored interfaces to be used for the transfer of the 3D building ­geometry between the modelling and calculation tools and the various programs used by the participating design teams. So as not to exceed the size limits of the FE analysis software when importing and manipulating the free forms, the complete axial surface model for shells, ramps and decks was

derived for the calculation from the digital ­building carcass model. Joints, points, lines, curves, penetrations, materials and component thicknesses are defined in an Excel table, which precisely depicts the complex geometry using ordinary spreadsheet functions. This information was calculated using predefined rules so that it could transfer smoothly into the programming environment of the ­calculation tool and generate the geometry automatically.

SPECIAL FORMWORK: EVERY ELEMENT IS UNIQUE High requirements applied to the formwork for the inclined, curved walls. Every concrete pour was different, every formwork element unique. Adigital workflow was developed specifically for the formwork design. Each one of the 200 segments was automatically generated as an isometric view including lettering together with the development of their inner and outer surfaces, sections and complex ­connections. To achieve an optimum process flow, all horizontally connecting components were integrated into the ­reinforcement design and the relevant informa-

tion required for their manufacture and fixing shown directly on the shell surfaces: actual lengths, reinforcement diameter, anchorage lengths, geometry of the sleeve connectors, etc. Then the whole geometry including the complex, three­dimensional working joints were transferred as a 3D model to the formwork ­manufacturer. Slatted timber and steel frame subconstructions were used to create the curved formwork panels. The slats defined the shape of the substructure to which a thin, coated plywood board was bent and attached.

REINFORCEMENT AND CONCRETE The vertical shell elements were completed first. The horizontal components – ramps with beam and slab decks – were connected later using sleeve connectors and continuity reinforcement. The shell elements were marked in the factory with coordinate points, which were also recorded on the formwork drawings. A total station

124

ESO ­Supernova

correctly positioned every element on site using these coordinate points. Temperature sensors allowed the stripping time to be shortened to 3 days. Directly after completion of the building carcass, the prefabricated aluminium panels and spacers were attached precisely and efficiently to the reinforced concrete.

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I  reinforcement connection: ramp to wall shell

J – L  formwork for inclined, curved outside segments

K l oad-bearing formwork frame supporting the form and 8 mm plex board

M unique shell elements

N Positioning formwork using a total station

125

Garching (DE)

Architects Giuliani Hönger Architekten, Zurich (CH)

Structural engineers Dr. Lüchinger+Meyer ­Bau­ingenieure, Zurich (CH)

Schlotterbeck Residential and Office ­Building in Zurich 126

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site plan scale 1:7500 plans, sections scale 1:1000

1 garden apartment 2 office / commercial space 3 commercial  / exhibition space

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Residential and Office Building

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Ground floor a 4 maisonette 1 5 commercial / office 6 standard apartment 7 panorama apartment

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With its tower-like extension, the conversion and extension of the former Citroën garage – originally completed in 1951 to a design by architects Suter & Suter – references the neighbouring high-rise blocks of Zurich’s Heiligfeld housing estate, which was also built in the same decade. The project to convert the building into a residential complex for high-density city living has created a new urban design landmark, without renouncing the building’s past. The design for the conversion by architects Giuliani Hönger on the existing building footprint added storeys to the circular access ramp and garage structures. It also offered space for 104 owner-occupied housing units of various types – from garden lofts to maisonettes – from condo patio apartments to flats in the tower. The garage structure was increased in height generally by one storey and at the southern end by four storeys. Partialheight light wells bring daylight into the depth of the building. The cylindrical residential tower rises to a height of over 40 m and is built on top of the listed access ramp structure. Its circulation core supports the nine storeys above as a mushroom-shaped plinth and leaves the existing ramp structure largely untouched. The double helix ramps are retained in their entirety. The lower part is used for bike parking, with commercial activities occupying the areas above. Offset walls in the upper storeys create the space for column-free panorama apartments. The mushroom-headed supports of the garage structure are retained and appear as single columns in the apartments. The three-dimensional concept of precisely intermeshing the existing and new structures was linked from the beginning with the special solutions proposed by the structural engineers at Lüchinger+Meyer. Andreas Gabriel

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ZURICH (CH)

Text Hans Seelhofer

8

+ 28

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2900

10099 260

4401

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100

60

Pos. Brüstungselement

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11675

+2

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1450 2825

+21

Halfen HTA 28/15 Einlage 35/100

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compression rings F tower shaft haunch

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C isometric view of tower shaft with decks

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RESIDENTIAL AND OFFICE BUILDING

G temporary supports and foundation reinforcement

H radial deck reinforcement

I construction of haunch

J panorama apartment tower

THE NEW RESIDENTIAL TOWER The structure is divided into the circular building, main building and the additional floors on the tower and the southern end of the complex. The new nine-storey tower stands on a cylindrical shaft, which transmits the loads into the foundation through the eye of the listed ramp structure. Five residential units with reinforced concrete load-bearing partition walls are arranged radially on each floor. The floor plans are offset by 36° relative to one another, with the decks, which are s­ upported by the radial walls, spanning 9 m at their outer edges (fig. A, B). This led to very economic deck thicknesses. The radial walls are designed as deep beams cantilevering from the outer cylindrical wall of the circulation core. Equilibrium is ensured by the horizontal edge shear forces in the walls being transferred into the decks. The forces from the walls immediately above and below a deck act in opposite directions and cancel one another out. The deck slabs are also subject to transverse bending moments, mainly due to the offset positions of the radial walls. Large bearing forces in the radial walls require them to be inset into the shaft wall. At the top of the tower, the forces are taken out by a tension ring in the deck slab.

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Zurich (CH)

A prestressed upstand beam spanning 18 m runs as a support along the slab edge of the top deck, which in turn is prestressed with concentric monostrands (fig. D). The prefabricated concrete balustrade panels in the plane of the ­facade are rigidly connected to the decks and are designed as single-span beams with a span of around 9 m. The continuous circumferential corridors required for circulation mean that the ­external core wall has a larger diameter than the tower shaft. A chalice-shaped haunch adjusts for this difference in the transition area. At its upper edge, the outward-acting force components are less than the edge shear forces in the partition walls in the residential units, which creates a compression ring. A compression ring is also formed at the foot due to the opposing inward­acting force component on the haunch (figs. C, F). A combined micro-pile and slab foundation was used to transfer the loads into the deeper gravel and moraine layers. To construct the 2.8 m thick foundation slab, it was first necessary to support the internal columns of the ramp with a steel support structure on micro-piles (fig. G).

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Residential and Office Building

EXTENDED MAIN BUILDING In addition to extending the building vertically, the basement of the main building underwent significant expansion. The existing individual foundations did not have the capacity to carry the additional loads, which meant strengthening measures were necessary. In the areas without an existing basement, the higher individual foundations were strengthened and the loads from them transferred ­into the foundations for the adjacent ­extended basements. Groups of piles were driven from above the existing foundations to extend down to the new micro-pile foundation slabs. In the case of the foundations for the basement supports, the existing and new wall panels were used to transfer the additional loads to new micro­pile foundations (fig. K). Two longitudinal walls that supported the ­earlier uni-axially spanning deck were ­demolished to extend the basement for use

as a parking garage. Steel beams supported on new concrete transverse walls took over their function (fig. L). Although the overall concept aimed to minimise deck loads through the use of ­lightweight materials, there was a significant ­increase compared to the original design. In ­addition, compensation had to be made for the weakening of the structure by new deck openings. This took the form of widespread strengthening using dowelled-on concrete and steel plates bonded onto deck soffits (figs. O, P). Only five columns in the basement ­required banding by means of an additional jacket of self-compacting concrete (figs. Q, R). On the newly built 3rd storey, new reinforced concrete walls transferred the loads from the floors and the suspended 2nd floor into the existing columns (figs. M, N).

ADDITIONAL FLOORS AT THE SOUTH END Four additional storeys were added to the main part of the building, which required an independent structure to be installed within the existing one. To transmit all the loads into this internal structure, the partition walls in the apartments were incorporated into a 3D concrete panel structural system. Horizontal forces from

K foundation strengthening with load-transfer ­serrations

L strengthening measures in basement

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Zurich (CH)

M, N 2  nd floor deck suspended at new walls 3rd floor

O deck strengthened with dowelled concrete

the wall panels are transmitted ­directly into the decks, with the 6th floor ­being centrally ­prestressed (figs. S, T). The new columns pass through the main building and transmit their high loads via the micro-piles into the ground.

P d  eck strengthened with glued steel soffit plates

Q, R  column strengthened with self-compacting ­concrete jacket

S, T  prestressed structural ­elements, southern rooftop extension

Architects Smiljan Radic, Eduardo ­Castillo, Gabriela Medrano Santiago de Chile (CL)

Structural engineers B y B Ingeniería, Santiago de Chile (CL) Pedro Bartolomé

BioBío Regional Theatre in Concepción

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section, floor plans scale 1:1000

1 main1entrance 2 foyer 3 cloakroom 4 multifunctional rooms

136

BioBío Theater

5 front stalls of large ­auditorium 6 stage 7 dressing rooms 8 small auditorium

Clearly visible from a distance, the new theatre for the BioBío region stands near the bank of the river bearing the same name in Concepción, Chile. The city was severely damaged by an earthquake in 2010. The dazzling white building forms the focus of a newly created public square and is the cultural centre for the whole region. Concealed behind a horizontally folded textile skin, an orthogonal grid frame of concrete columns and beams, as simple as it is strong, forms the load-bearing structure of the building. Cut out of the regular pattern of frame members, a large auditorium capable of seating 1,200 occupies the centre of the building alongside a smaller 250-seat auditorium, the underside of which forms the ceiling of the foyer at a height of 12 m above ground level. This public space clearly illustrates the design idea of stairs and walkways passing through a three-dimensional grid structure of identical sequences of parallel, matching elements. The architect intended the structure to reference the scaffold normally hidden behind the stage and to strip away the edifice of some of its associated elitism. During the day, the lightweight, ephemeral building skin draws the eye to the idiosyncratic, asymmetrically folded volume. At night, on the other hand, the textile building turns into an inviting, luminous sculpture reflecting in the river like a giant Chinese paper lantern. Burkhard Franke

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CONCEPCIóN (CL)

Text  Francisco Bartolomé

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A  main stairs with stiffening central wall

B black-painted timber beams in the expansion joint area

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BioBío Theater

C cross section scale 1:400

D, E  detailed sections of ­concrete member joints, composite construction and conventional reinforcement scale 1:50

ORTHOGONAL GRID FRAME IN REINFORCED CONCRETE The structure of the theatre is an orthogonal grid frame consisting of reinforced concrete ­columns and beams forming a cuboid laid on its longest side with dimensions of 114 × 31 × 28 m (L × W × H). The beams follow a 3.90 m grid, have a 30 × 30 cm cross section and were all cast in-situ. Wall panels and floor slabs in the grid planes define the exterior of both auditoriums and cut their volumes out of the structure. In addition, the exposed concrete surfaces of the stairways and walkways finish flush with the tops of the structural beams and reinforce the abstract atmosphere of the spaces. Concrete columns transfer the vertical loads. Because of the close spacing of the columns and the poor underlying soils, the whole building rests on a continuous 50 cm thick foundation slab. The ­location on the earthquake-prone Chilean west coast called for the building to be designed to resist seismic horizontal forces of 20.2 % of its self-weight. These forces are much more determinant for the transverse stiffening than the horizontal forces arising from wind. A large proportion of the solid ­areas within the structure are used to stiffen it. The floors and walls of the large auditorium form a rigid body in the centre of the building. The roof surface is overspanned with steel girders and stiffened diagonally. 45 cm thick piers and beams stiffen the 19.50 m high

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Concepción (CL)

wall surfaces of the auditorium and offer adequate installation depth for the black timber acoustic elements. The open space of the foyer under the small auditorium was a challenge to the structural engineers. Diagonals were added locally to the grid structure to transfer the seismic horizontal forces from the body of the auditorium down to the level of the first floor. Comprised of IPB-160 steel sections acting compositely, they were used instead of conventionally reinforced bracing. These elements transfer the forces into the continuous surrounding gallery decks of the first floor and from there into the central wall of the main stairwell and two further wall panels at the outer corners. In addition, the striking, continuous peripheral, truss-like bracing composed of inclined concrete members transfers the horizontal forces from the first floor into the foundation slab. An expansion joint between the two ­auditoriums divides the long building into two ­independent parts. In front of the back wall of the large auditorium, black-painted timber members are used in the central access corridor and for the horizontals to each side. Although structurally unnecessary, these elements ­emphasise the design idea of a continuously ­repeated spatial grid.

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5 6 F section scale 1:100 1 PTFE coated textile 2 steel section ­substructure 3 300 × 300 mm ­reinforced concrete

cantilever ­bracket 4 300 × 300 mm reinforced concrete beam 5 300 × 300 mm ­reinforced concrete column

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BioBío Theater

6 300 × 450 mm ­reinforced concrete diagonal 7 300 mm reinforced ­concrete floor slab

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G The climate envelope of the building consists of the glass facade on the ground floor and the lightweight PTFE membrane skin appearing to float above it. This mem-

brane is stretched over a substructure of steel members, which in turn are supported on cantilever­ing concrete brackets. The climatic requirements on the

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Concepción (CL)

facade are ­minimal, therefore additional thermal insulation, for example the area of the concrete surfaces, can be dispensed with, allowing the architec-

tural idea to be expressed clearly in the absence of cladding.

Architects E2A Piet Eckert und Wim Eckert Architekten, Zurich (CH)

Structural engineers Schnetzer Puskas Interna­tional, Basel (CH)

taz Publishing House in Berlin

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143

Newspaper publisher taz moved into its new building at Friedrichstrasse 21, just a couple of hundred ­ ccupying a special metres away from its former location in Rudi-Dutschke Strasse, in autumn 2018. O b corner position, the new building mediates between the traditional Berlin block style development and the stand-alone buildings in southern Friedrichstadt completed as part of the International Building 2 3 10 10 Exhibition (IBA) in 1987. 8 of Architects 1 Swiss architects E2A won the competition o ­ rganised by taz and the Berlin Chamber 5 9 9 the street, in 2014. With simple, striking volumetrics, the architects took up the development plan, making a a corner and courtyard an urban d ­ esign leitmotif. 11 At first glance, a continuous mesh of 6 steel members appears to support the new building. In 12 12 7 fact, this filigree layer is only a front. The actual load-bearing structure consists of diagonal reinforced concrete struts placed d ­ irectly behind the glass facade, thus dispensing with the need for any additional columns within the building. 4 13 9 8 14 13 9 8

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1 cafe 2 bar 3 exhibition 4 back office

5 kitchen 6 foyer / taz.shop 7 editorial room 8 open-plan office

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taz Publishing House

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First floor

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Concrete, glass and 13 m deep office floors create a workshop atmosphere and allow various modes of working. The architects have taken the wish of the newspaper’s editorial board for hierarchy-free organisational structures and transferred it directly into the publishing house building. Red studded flooring in the conference and editorial room makes reference to the taz branding. It also characterises the heart of the newspaper offices on the first and second floors. In the centre, behind glass, a spacious, double staircase links the storeys together. Half-landings and continuous narrow balconies offer space for impromptu meetings. Architecture, facade and the intelligently integrated, lowmaintenance building services systems combine to ensure excellent user comfort with individual climate control. Heike Kappelt

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BERLIN (DE)

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Text  Tivadar Puskas, Kevin M. Rahner

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taz Publishing House

vertical sections scale 1:25

2 320 × 320 mm struts (blue) 3 floor slabs  /  landings (grey) 4 edge beams with (red) and without (pink) prestressing

5 concrete ribbed deck slabs (yellow) 6 flights of stairs (brown) 7 deck cut-outs, wells (cyan)

C section through a precast ribbed floor element 1 prestressing cable pretensioned in casting bed before concreting

D normal forces from ­transfer of vertical floor loads E normal forces from ­hori­zontal  loads (wind)

The reduced load-bearing structure of the new taz building is reminiscent of the Schabolowka Radio Tower by Vladimir G. Sukhov from the early 1920s, which achieves its required load ­capacity with very little material and is a symbol of a system without a hierarchy, one in which each element has equal significance. All components make a contribution but only together do they achieve stability. The new taz building essentially comprises two basement storeys, a ground floor and six almost geometrically identical upper floors. The top

storey is defined by a double-height section of the building. Double-storey spaces are also found on the ground and first floors. One of these is the large editorial conference room on the first floor, which, because of its size and position, is an easily recognisable central forum. The floorplan of the building is divided into three: a southern part separated by a continuous firewall from a future neighbouring building, a northern part and a middle part in which the main access staircase is located.

FLOOR SLABS AND BEAMS The floors consist of precast reinforced concrete TT slabs. The ribs on the underside of the precast units were prestressed in the factory to counteract deflection. A layer of in-situ concrete transforms the floor elements with the edge beams into a monolithic, solid component (fig. C). The floor construction is 500 mm deep. The ­individual TT slab units are 2.1 m wide and span a clear 12.5 m. The continuous in-situ concrete

edge beams are also prestressed. Reinforced concrete brackets cast onto the edge beams act as supports for the notched precast concrete floor units (fig. A).

VERTICAL FLOW OF FORCES Unlike conventional skeletal frame structures, the vertical flow of forces does not take place through columns within the building but rather in a way similar to the Schabolowka Radio Tower: almost completely via a mesh of slender, V-shaped reinforced concrete struts in the plane of the facade. In conjunction with the in-situ concrete edge beams, the struts combine to function in the vertical plane as a mesh of strong triangles. Inside the building, the edge beams are additionally supported by the two ­circulation shafts (fig. B). These consist on one side of a solid, 5.1 m long wall stiffened by narrow lateral walls. On the opposite longitudinal side, there is a drop beam in every floor on which the deck elements of the middle building section rest. The in-situ concrete circulation shaft walls are 25 cm and 30 cm thick.

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Berlin (DE)

A firewall and circulation core terminate the building on the southern side. The core walls working in conjunction with the diagonal struts carry the vertical loads. The structure has a high degree of redundancy and all the strut elements contribute to load transfer. For example, should settlement of the renowned Berlin foundation soils occur, the load can be diverted through the stiff triangular elements. The internal walls are constructed in masonry or, in case of the circulation area along the firewall, in 20 cm thick reinforced concrete. The floor over the basement rooms is conventional reinforced concrete. The basements extend below groundwater level and are fully waterproofed.

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taz Publishing House

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1 pretensioning cable 2× 6-4 Y1860 2 connection plate 3 shear stud 4 base plate 5 top plate

HORIZONTAL STIFFENING The triangular elements of the diagrid in the plane of the facades stiffen the building horizontally (fig. E). At every floor, the triangles ­comprise two diagonal concrete struts and the continuous edge beam. The prestressing in the edge beams can be relieved or intensified in ­individual elements or over a whole series of ­elements. The floor slabs between the triangular ­elements can act as diaphragms, thanks to the layer of in-situ concrete, and couple the

s­ tabilising triangles rigidly together. All the floor loads are collected along the facade plane and at the two circulation cores containing the building services equipment. Therefore, bored piles founded at depth were the most obvious and ­efficient foundation. The building stands on 97 Atlas piles which are 56 cm in diameter and 7.65 m in length. The piles are an a ­ verage of 3 m apart at ground floor level.

COMPLEX CONNECTING NODES The reinforced concrete struts in the plane of the facade were prefabricated and delivered to site. The prestressing in the edge beams is designed such that they are always in compression under the permanent vertical loads. The prestressing cable follows a parabolic line in the vertical plane, with the high points defined geometrically by the intersections of the edge beam with the struts (fig. G). The profile of the cable is also determined by the vertical load ­distribution and the deflections of the long canti­ levers at the corners, where the prestressing cables’ anchor heads are installed. Complex

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Berlin (DE)

nodes are necessary to transfer forces at the ­intersections of the struts and the T ­ T deck ­elements. Cast-in steel components transfer the normal forces from the struts, the horizontal force component from the diagonal struts and the vertical loads from the floors. The ­geometry of the connections made them very challenging to construct. The struts themselves behave as pin-ended members. The vertical floor loads are transferred by shear studs into the cast-in steel components and through them into the pin­ended struts below.

Architects Christian Kerez, Zurich (CH)

Structural engineers Batiserf ingénierie, Fontaine (FR)

Office Building in Lyon

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La Confluence, a district in the centre of Lyon, France, is currently being transformed from former industrial land into a lively quarter of the city. Based on the masterplan by architects Herzog & de Meuron and lan Michel Desvigne, a total of eight 21,00 buildings – public and private housing, offices, a children’s 6,85 6,10 6,85 Îlot A3. nursery and a sports hall – now stand on plot The investors in the office buildings called for retail premises on the ground floor and seven floors of flexible office space. The building design demonstrates a perfect implementation of this neutral room 2 programme for tenants who are unknown at this stage and yet the building has its own unique character.

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This is achieved not only by using exposed concrete surfaces in the interior of the building but also, and more significantly, by creating an exposed concrete load-bearing structure with columns, some of which stand outside in front of the facade. All the storeys share the same form of construction. While the column grid is repeated on each floor, the appearance and diameter of the columns change. Rammed concrete was used for the columns on the lowest three storeys, in-situ concrete on the middle three and precast spun concrete for those on the top three storeys. The diameter of the columns reduces with building height to reflect the reduction in vertical loads, while lending the building an impressive elegance. Roland Pawlitschko

153

LYON (FR)

Text  Nicolas Roger

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B o  ffice storeys with columns made from spun concrete (top), in-situ ­concrete (middle) and rammed concrete (bottom)

Office Building

C s tep-by-step completion of a storey with rammed concrete

D horizontal section of a rammed concrete column scale 1:40 300 130 120 50

A  overview of structural components: staircase and lift cores, columns, external structure with window lintels, floor slabs

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CONCRETE AS A CONSTRUCTION MATERIAL The internal and external appearance of this office building is defined fully and completely by its load-bearing structure and the structural material concrete. Long spans with very few structural elements were every bit as important to the architects as the aesthetically reduced yet meaningful conciseness and the durability of the already “finished” concrete surface on stripping. This makes any easily damaged ­additional cladding superfluous and therefore minimises maintenance costs. Reinforced concrete is not only used for the frame structure outside the building envelope but also for the spandrels and lintels. With the exception of the prefabricated spun concrete columns in the upper three sto-

reys, all the vertical and horizontal structural ­elements consist of uniformly light-grey, site-cast exposed concrete, which is given a hydrophobic, transparent matt finish and anti-graffiti coating. The load-bearing structure is in complete accord with the simple building volume. The similarly shaped columns and slabs share the same footprint on each floor, which creates large, column-free office areas that can be flexibly ­divided or horizontally connected as required. The building, which measures 52.50 × 21 m in plan and has a total of eight storeys, is monolithic and was built completely without expansion joints.

STIFFENING CORES The two freestanding reinforced concrete stairwell cores (a third set of stairs was built using dry construction) and the rectangular lift shaft extend through the full building height and ­consist of vertical, in-situ concrete walls with a

thickness of 25 – 32 cm. They provide adequate stiffening of the building to ­resist horizontal wind and earthquake loads and are connected to one another by the ­reinforced concrete floor slabs acting as horizontal plates.

THREE TYPES OF COLUMNS In addition to the circulation and lift cores, the building has reinforced concrete columns, which are all circular in cross section but with different diameters. The 4 × 8 columns per floor are arranged in an orthogonal grid and form seven 7.33 m bays longitudinally and three 6.10/6.85 m bays transversely. Their d ­ iameters decrease in steps floor by floor as the load they carry reduces with height. The way they were constructed and their surfaces also vary, depending on where they are in the height of the building. On the ground floor and on the 1st and 2nd floors they were constructed in rammed concrete with diameters of 80, 70 and 65 cm and were cast in 50 cm high climbing forms in 16 cm layers. Pneumatic hammers were used to

155

Lyon (FR)

compact each layer in succession. The steel ­reinforcement in the columns had to be designed to allow enough room between individual vertical bars and between the reinforcement and the formwork for the manually operated compaction tools to be inserted and work effectively. The rammed concrete has a compressive strength of 16 N/mm2 and a water-cement ratio of 0.3. The exposed concrete columns on the 3rd and 4th floors were cast in circular timber forms and have diameters of 45 and 40 cm. ­Precast spun concrete columns with very smooth surfaces and diameters of 30, 28 and 26 cm were used in the top three storeys.

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E vertical section of facade with fixed glazing units scale 1:40

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Office Building

1 vertical section ­concreting stage 1 2 vertical section ­concreting stage 2 3 horizontal section

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EXTERNAL LOAD-BEARING STRUCTURE Circular reinforced concrete columns are used not only inside the office storeys but also outside directly in front of the facade. These outer columns in combination with a continuous 1.26 m wide, 25 –30 cm thick external reinforced concrete slab and a lintel form an external load-bearing structure. The concrete spandrels do not contribute significantly to the strength of the structure. They are there to provide privacy and improve the thermal properties of the facade. The external structure carries vertical load from the floor slabs. This is achieved by connecting the reinforced concrete slabs spanning between the external columns directly to the main floor slabs over a length of about 1.50 m in the plane of the column axes. The ­remaining sections between the main floor slab

edges and the external reinforced concrete slabs are thermally and structurally separated to minimise cold bridging. The external columns had to be designed and built not only to carry their vertical loads but also to accommodate reinforced PVC rainwater downpipes. Their diameters are 60 mm on floors 5 – 7 and 80 mm on the other floors. The downpipes carry roof water and collect rainfall from the external reinforced concrete slabs. The in-­situ concrete, non-structural spandrels were cast using timber board formwork after the whole external part of the structure was f­ inished.

FLOOR SLABS WITHOUT DOWNSTAND BEAMS The in-situ concrete floors between the load-­ bearing cores and columns act as a continuous slab without downstand beams. The internal slabs were all 30 cm thick to satisfy the r­ equired strength, sound and fire protection criteria. The exposed concrete internal slab soffits have 5 cm deep grooves into which flush­finished acoustic elements were installed during the fitting-out stage. To achieve the monolithic appearance so ­important for this project, the projecting parts of the floor slabs and the reinforced concrete lintels in the facade were poured together – timber boards being used for the lintels and 157

Lyon (FR)

­ lywood board formwork for the slab soffits. p Subsequently, the concreting of the internal floor slabs was completed in two separate shifts, with a construction joint between pours. All exposed concrete components were carefully protected from subsequent damage during the construction phase so that the concrete structure visible in the interior today – as originally planned – has a finish quite close to the appearance and precision of normal internal ­fitting out standards.

Bridges and Infrastructure Buildings

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OFFICE BUILDING

TWO STATIONS ON THE BUDAPEST METRO

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DE LENTLOPER BRIDGE IN NIJMEGEN

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RAILWAY VIADUCT OVER THE ALMONTE RIVER NEAR CÁCERES

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HAGNECK HYDROELECTRIC POWER PLANT

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DEMOLISHING MAJOR BRIDGES. A JOB FOR ENGINEERS

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BRIDGE CONSTRUCTION, QUO VADIS?

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LYON (FR)

Architects sporaarchitects, Tibor Dékány, Sándor Finta, Ádám Hatvani, Orsolya Vadász, Budapest (HU)

Structural engineers Uvaterv, Főmterv, Mott MacDonald Budapest (HU)

Two Stations on the Budapest Metro

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The Budapest Metro is considered the world‘s second oldest subway line, with the London Underground being the oldest. The “Millennium-Line” M1 began service in 1896 and has remained an integral part of the subway network ever since. In 2014, the M4 line with its ten new stations was included. It connects ­Buda, the part of the city located west of the Danube, to Pest, the part of the city along the eastern banks. Until recently, the public transportation system in Hungary was planned ­exclusively by engineers and traffic planners. Inspired by the urban planning director at the time and the local architects‘ chamber, a competition initiated in 2003 was intended to explore the potential of architectural design for future subway stations. The aim was to ­improve the image of the subway system. It was not very popular, also due to the spatial deficits of a technocratic type of planning that was implemented during the past decades and originally influenced by the Soviet Union. In collaboration with a group of engineering firms, the Budapest-based office sporaarchitects designed the two stations on the line located at its deepest points: Szent Gellért tér and Fővám tér. They are located along the banks of the Danube, roughly 40 m below ground. The stations resemble twins and

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1 entrance 2 streetcar 3 void 4 elevator 5 ventilation

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 6 gallery   7 control room   8 transformer rooms  9 platform 10 tunnel 11 skylights

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Two Stations on the Metro

6

follow the same principle: a small footprint on the surface blends in unobtrusively with the historic buildings of Budapest. Below ground, it accesses a cavernous space that is all the more impressive. The striking exposed concrete structure defines the space. This connection between architecture and engineering produced a proud statement in terms of how contemporary architecture in Budapest can present itself. At more than 40 m below ground, the second subway station, Fővám tér, is at the deepest point of the M4 Metro line. Descending via the escalator becomes a journey through the impressive concrete structure. The intersecting exposed concrete beams reflect the dynamics of the traffic flows and symbolise their interweaving and traversing character. Daylight reaches down to the platform via the large-scale glazing of the skylights and the open structure above. At Fővám tér, this dramatically enhances the station‘s enormous depth. The design features exposed concrete, glass and oxidised steel sheet metal. Natural stone flooring, lighting and technical equipment follow uniform design specifications for all stations. Andreas Ordon

163

BUDAPEST (HU)

Text  Gergely Pataki 11 A

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A  section scale 1:200

B  the architects’ schematic sketches show the principle of the cut -and-cover method and the tunnel construction

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Two Stations on the Metro

C  artial reinforcement p plan for the intermediary level (level -4) scale 1:200

CONSTRUCTION PROCESS AT FŐVÁM TÉR STATION Fővám tér is a local public transportation hub. The subway line intersects with a tram line that is situated one level below ground. The limited size of the site located between the Danube and the historic structures of Corvinus University permitted only a small building volume for the station. The construction of the track required building tunnel platforms. The cut-and-cover method proved ideal under these circumstances. The diaphragm walls that circumscribe the station volume consist of interlocking 120 cm thick reinforced concrete panels. Panel construction featured the following steps: excavation of (bentonite slurry stabilised) trenches, installation of reinforcement cages and concreting (fig. B1). Street traffic and tram operation continued shortly afterwards (fig. B2). From top to bottom, levels for bearing horizontal loads were cast in concrete and the soil below was excavated

(fig. B3). The horizontal beams resist soil and water pressure caused by the Danube. They are connected by a continuous ring beam typically 2 m wide and 1,2 m deep. It is held in position by steel profiles connected to the diaphragm wall. Wateproof concrete was used for the diaphragm and inner walls. The construction of the tunnel platforms began after completion of the lowest level (fig. B4). Geotechnical surveys discovered fault lines and the lowest beam level had to be dimensioned anew. The tunnel had to be repositioned away from the Danube towards the University (fig. B5). Ground freezing with liquid nitrogen prevented water from intruding. Finally, the connections to the nearest stations approximately 10 m below the Danube and 20 m beneath the historic city of Pest were excavated (fig. B6).

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D detail section BB scale 1:50

1 diaphragm wall, waterproof reinforced concrete 2 PU resin sealant 3 steel profile for ­securing position of horizontal ­levels

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­Budapest (HU

4 interior construction wall, waterproof ­reinforced concrete 5 ring beam

5

HORIZONTAL BEAM STRUCTURE Horizontal beams that are encircled by a ring beam support the diaphragm walls against the horizontal pressures deep underground. The ­arrangement of beams follows no strictly construction-oriented logic and therefore departs from the conventional grids of similar construction types. The structure was optimised step by step in a simultaneous process of calculation and design. The amount of reinforcement is very high in order to achieve beams and intermediary slabs that are as slender and slim as possible. Up to three beams intersect at extreme points. This was only possible by arranging different ­reinforcement levels and related overview plans became necessary. In addition, the arrangement

G detail sections, concrete beam, different reinforcement layers scale 1:50

E diagram, horizontal loads, concrete beams of level -4

F reinforcement plan for beam B04 scale 1:200

166

Two Stations on the Metro

of reinforcement had to ­provide sufficient space for pouring concrete. Thus, the dense arrangement of the reinforcement bars became one of the greatest challenges in realising the project. Extreme dimensions of structural members ­required special concrete mix designs and diligent treatment after curing. The arrangement of beams did not offer room for delivery and ­removal of material and soil. Therefore, some beams were declared “secondary structure” and they don‘t have any load-bearing function. The ­reinforcement connectors had already been planned for these beams. Later, however, they were added as supplemental loads to the primary construction.

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Two Stations on the Metro

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­Budapest (HU

Architects & structural engineers Ney-Poulissen Architects & Engineers, Brussels (BE) Laurent Ney

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The transverse forces acting on the bridge superstructure are ­transferred into the piers with each pair of piers acting as a frame with the superstructure.

De Lentloper Bridge

The capacity of watercourses in many parts of the Netherlands is being increased to prevent flooding. A sharp bend in the river Waal near Nijmegen was constricting the flow, so the dyke was moved 350 m outwards. This created the space for a secondary channel and formed an elongated island. The main access to the island is provided by the De Lentloper Bridge, which carries mainly pedestrians and cyclists, and, as an exception, cars are also allowed. The municipal authorities had requested a bridge that did not simply provide a connection: it should also act as a local attraction with spatial features above and below the bridge deck. Ney-Poulissen Architects & Engineers drew up a preliminary design in 2011 that formed the basis for a design, build & maintain tender. The final architectural and structural engineering design, including the details, was completed by Ney-Poulissen working closely with the main contractor. This ensured that full consideration was given not only to construction methods and details but also the construction programme and future maintenance. Different levels on the bridge separate vehicles from pedestrians. The central carriageway rises towards the middle of the bridge, while the foot/cycleways along the sides drop lower towards the middle of the bridge. Transversely sloping surfaces connect the different levels. This forms an omega-shaped cross section that varies along the length of the bridge. With two transverse connecting platforms under the carriageway to allow cyclists and pedestrians to change sides, the De Lentloper Bridge represents a new, extraordinary type of bridge. Andreas Gabriel

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NIJMEGEN (NL)

Text  Laurent Ney, Thijs Van Roosbroek, Bart Bols

A

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B perspective showing ­longitudinal prestressing tendons

A  Structural system showing positions of post-­tensioned tendons. 2× 6 tendons each with 22 strands were installed longitudinally.

4-strand tendons were used transversely. The connecting platforms each have 4 tendons with 22 strands.

174

De Lentloper Bridge

C–E reinforcement of the monolithic pier / superstructure connection

F detail of dense ­reinforcement

CONCRETE SCULPTURE WITH AN OPTIMISED LOAD-BEARING STRUCTURE The bridge has an overall length of 220 m and 5 spans of 30, 52, 56, 52 and 30 m. The increasing level difference between the footway and carriageway results in the maximum structural depth of 3.5 metres being achieved at the middle of the bridge – precisely where it is needed most. At the ends, on the other hand, the structural depth is only 0.6 m. The shape of the concrete deck with its sloping surfaces ensures the carriageway and

footway parts act together and lend the cross section an arch-like character. Transversely, the deck is mainly subject to compressive forces. This allows an extremely efficient use of materials and a reduced thickness of 30 cm at the edges and up to 58 cm at the centre of the carriageway. Longitudinal and transverse prestressing tendons were installed and post-tensioned to prevent long-term deformations.

OPENINGS The openings in the inclined sides are not only designed for the efficient flow of forces, they also allow access to the pedestrian platforms below the carriageway. Pedestrians and cyclists

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NIJMEGEN (NL)

can move from one side of the bridge to the other and take a look at the inside of the concrete section.

The concrete has a very smooth, light-coloured surface to reflect the water on the underside of the bridge deck. This required a detailed analysis of the cracking behaviour of the bridge and careful measures to limit cracking. Numerous sample concrete surfaces were produced. The time for each pour was reduced and much attention paid to the details of the formwork design. The incremental casting of the complex ­geometry was possible only because of close cooperation between designers and constructors and a precise, thoroughly prepared construction phase. Finally, in addition to transverse and longitudinal prestressing, the designers specified relatively high-strength grades of concrete (C45/55 for the bridge deck and C50/60 for the piers and platforms). It was extremely ­important to limit stripping times to the minimum, because concrete darkens if it spends too long in the form. A concrete mix design had to be found that would provide the high surface quali-

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ty with the required strength. At the same time, the concrete around the incorporated elements such as the prestressing ducts had to be adequately compacted, even at a 30° incline. The choice fell on a concrete mix with a short hardening time, which would result in a rapid gain in temperature and an increased risk of cracking during the initial hardening phase. By careful analysis of this phase in preconstruction trials, it was possible to adequately limit crack formation. Very smooth timber formwork with carefully prepared construction joints and varnished form faces were used. Great emphasis was placed on cleanliness in the preparations for concreting. The harmony of architec­ tural form and structural concept led to an ­integrated structure that efficiently fulfils all its required functions. The designers based their search for a geometry that would make the most efficient use of all the materials involved on the “form-giving forces” acting in and on the structure.

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De Lentloper Bridge

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CONCRETE TECHNOLOGY

4 tendon with 22 strands Y 1860S7 (Ø 150 mm2) 5 200/85/65 mm brick paving sand bed drainage mat ­waterproofing

6 Ø 80 mm stainless steel drainage pipe

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Nijmegen (NL)

Architects & structural engineers Arenas & Asociados,Santander (ES) IDOM, Madrid (ES)

Railway Viaduct over the ­Almonte River near Cáceres

180

181

Trains operating on the new Madrid–Lisbon line cross the Almonte River near Cáceres in Extremadura, Spain. The viaduct carrying them is 996 m long, spans 384 m over the river, has a deck supported on 20 piers 36 –45 m apart and is the largest reinforced concrete arch in the world carrying high-speed trains. No part of the substructure – not even temporary works – could be located in the river because of strict environmental protection rules. This required a very detailed investigation of the various possible

elevation scale 1:6000

construction phases for the erection of the arch approach structures scale  1:10 000

182

Railway Viaduct

bridge types and how they could be constructed. The deck is designed as a continuous beam with sliding bearings on the piers and a fixed bearing at the arch crown. The arch performs all the critical functions in the transfer of the dynamic forces generated by trains travelling at speeds of up to 350 km/h. The arch was erected from both sides of the river as cantilevering arch segments supported by temporary cables. Andreas Ordon

183

ALMONTE NEAR CÁCERES (ES)

Text  Guillermo Capellán, Pablo Jiménez Guijarro, Pascual García Arias

A

fixed bearing

release of the fixed bearing

fixed bearing

sliding bearing release of the fixed bearing

fixed connection at the crown of the arch 2,95 B

17,20 2,95

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A s tructural systems: changes in the method of support during the construction phase

B  detail of the foundation anchorage (grid point P16) scale 1:500 C foundation anchorage

184

Railway Viaduct

SELECTION OF BRIDGE TYPE During the initial stages of the project, several alternative bridge types were analysed in a ­detailed feasibility study, which considered the behaviour of the bridge during erection and in its completed state. These alternatives included cable­stayed, skeletal frame and ­variable-depth truss deck solutions. Various forms of cantilever constructions and a central steel section lifted into place were among the options considered for the erection procedure. The multi-criteria analysis highlighted the concrete arch solution as the most economical, the best in terms of durability and maintenance, and the one that would perform best in resisting dynamic load effects and wind. This focus on service life prevailed during ­design and construction with the aim of creating an ouvrage

d’art that will resist the passage of time with the minimum of maintenance. The choice of concrete, the arch geometry, the method of design and the specifi­cation of an erection procedure that would avoid cracking the concrete all contributed to achieving this ideal. The arch solution is the most appropriate in several respects: the long span, the constraints of the location, the elevated alignment, the presence of highly competent rock for the foundations and the special demands of highspeed rail (HSR) bridges. Railway bridges have to carry much greater traffic loads than road bridges, are subjected to greater dynamic loads caused by passing trains, as well as significant horizontal loads and fatigue effects.

DESCRIPTION OF THE STRUCTURE ELEMENTS The viaduct has a continuous, prestressed concrete box girder deck. It was constructed in-situ using a movable scaffolding system. The superstructure is 14.0 m wide and carries two HSR tracks. The arch has a hollow octagonal section in its central 210 m and was designed to have good aerodynamic properties. Its cross section splits transversely into two inclined feet at the springers, increasing the stiffness of the structure in this direction. The piers and spandrel ­columns have a variable octagonal section.

185

Almonte near Cáceres (ES)

The deck is fixed at its junction with the crown of the arch. This transmits the horizontal braking and acceleration forces from the deck into the arch. During the construction process, the position of this fixed point and the bearings of the continuous beam deck varied (fig. A). The arch, piers and abutments are founded directly on rock. The concrete foundations for the arch are benched into the rock and were constructed within temporary peninsulas higher than the ­anticipated maximum flood level in the river.

STRUCTURAL ANALYSIS AND DETERMINING THE IDEAL SHAPE OF THE ARCH The design had to fulfil very stringent dynamic, serviceability and safety criteria. Given the type of structure, the construction method and the serviceability requirements, the complex calculations involved an iterative determination of an ideal antifunicular arch shape that took into account the dynamic amplifi­cation of railway

D

loading. Next followed a ­detailed analysis of the construction stages, nonlinear modelling of the serviceability and ultimate limit states and a detailed dynamic analysis. Wind tunnel tests on a reduced model confirmed the calculated performance of the structure in wind and the aero­elastic ­behaviour of the bridge.

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D, E movable scaffolding ­system for the continuous beam deck

F – I travelling formwork for the arch

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Railway Viaduct

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ALMONTE NEAR CÁCERES (ES)

CONSTRUCTION Bridge construction began in July 2011 and the structure was ready for use by the end of 2016. Following completion of their foundations, the abutments and piers were constructed, the latter using climbing formwork. A movable formwork system supported the decks on both sides of the bridge during construction. The piers were tied back to anchors drilled and grouted into the rock to counterbalance the forces in the temporary cable stays supporting the arch cantilevers. These anchors were tested and monitored by instrumentation. The erection procedure for the arch was a cantilever method with cables stays attached to two temporary steel towers over the piers at the springers (P6 and P15), each following the same construction sequence. The arch is ­divided into 32 segments on each side plus the key central segment. It was constructed using 80MPa self-compacting concrete, a special mix designed for the potentially high setting temperatures on this project. Arch construction started with the erection of the first pair of segments on each side supported on heavy-duty falsework. Travelling formwork was then assembled and attached to these segments in order to begin the construction of the arch using the successive ­cantilever method. These travelling formwork units were very complex devices that allowed the variation of every single dimension to adapt to the changing arch shape. For segments 3 to 15, two travel-

J View of arch from below and sequential cross ­sections through the arch  scale  1:3000, 1:750

K section through the crown of the arch and development of the arch cross section  scale 1:750

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Railway Viaduct

L construction phases for the erection of the arch  scale  1:10 000

ling forms were used on each side to build the arch. Once the single-section part of the arch was reached (P8 and P13), their configuration changed into a single travelling form on each side to close the arch. The temporary steel towers constituted structures in themselves, rising to a height of over 50 m above the deck and pinned at their ­bases. The temporary towers were assembled on their sides, then rotated into the vertical ­position. Once the arch was closed, the temporary stays were released and disassembled to allow the 8 spandrel columns to be constructed on the arch. Then the sections of deck over the arch were constructed, starting from each side and progressing symmetrically towards the crown. The shape of the arch was monitored during construction to ensure that the bridge would function in accordance with the design. Precamber was applied to correct for the d ­ eflections due to the travelling formwork and the movement induced by tensioning the ­cable stays prior to casting each segment. The range of instrumentation for continuous monitoring ­included inclinometers, accelerometers, strain gauges, wind and temperature gauges etc. ­Recording these values allowed engineers to detect displacements or changes in the structure’s vibration frequencies and thus provide warnings of behavioural change or anomalies.

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Almonte near Cáceres (ES)

CONCLUSION The viaduct over the Almonte River presented a real challenge to its designers and constructors. It is notable for several reasons, not least its ­exceptional span, which makes it the largest ­railway bridge in Spain and the world’s largest concrete HSR arch bridge. The quality of its ­engineering design brought together structural efficiency, out-of-plane stability (as required by HSR deformation limits), improved response against cross-wind effects (verified in boundary

M

layer wind tunnel tests) and aesthetics. Its ­environmentally friendly design will have lasting advantages in terms of durability and maintenance. The use of high-performance self-­ compacting concrete (HAC-80), the complex erection procedure and the specific development of one-off temporary works, in addition to a complete control and monitoring system, were essential to ensuring the success of the project.

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M, N erection of the temporary steel towers for ­tying back the arch ­segments

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Railway Viaduct

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P reinforcement drawing of the arch temporary connections for the ­tie-back cables  scale 1:100

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Almonte near Cáceres (ES)

Q construction phases for the erection of the arch deck  scale  1:10 000

Architects & structural engineers  Penzel Valier AG, Zurich / Chur (CH)

Hagneck ­Hydroelectric Power Plant

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3 Hagneck canal (upstream) 4 new Hagneck power plant 5 weir bridge

6 boat transport system 7 Lake Biel ­(downstream) 8 fish ladder

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­Hydroelectric Power Plan

sections weir / turbine plan at level + 12.65 (2nd floor turbine hall) scale 1:1000

  9 entrance area 10 visitor centre 11 headroom turbine hall

12 weir piers 13 weir bridge 14 weir abutment

Completed in 1878, the Hagneck Canal connects the Aare river and Lake Biel and is used to manage flood levels in the Bern area of Switzerland’s Seeland region. Around 110 years after the first hydroelectric power plant, which is still operating today, a second run-of-the-river (ROR) plant has been built on the site of an old weir at the mouth of the canal, where it enters the lake. The client, Bielersee Kraftwerke AG, defined the technical requirements of the plant (two Kaplan axial turbines on the right, a four-channel weir on the left, and a hydrau­lically efficient profile) and issued a design competition held under the Swiss Society of Engineers and Architects (SIA) rules. The design submitted by architect Christian Penzel and engineer Martin Valier won the competition. The proposal – which also included new bridges, one upstream of the sluice channel and the other on the weir, and a new fish ladder– embedded this impressive landmark into the natural surroundings with remarkable sensitivity. One distinctive feature is the use of pigmented fair-faced concrete. Another was the decision to support the weir bridge on the downstream side walls of the weir channels, and have it cantilever forward to act as a viewing platform. So with this relatively low overall profile, the designers succeeded in creating a structure that, despite its massiveness, appears extremely graceful from the canal or from the lake. The viewpoint of crossing pedestrians and cyclists on the weir bridge is slightly above the upstream water level, which means they get a particularly good impression of the volumes of water flowing over the weir. The widened deck on the upstream side of the bridge between the weir piers ­allows access for mobile cranes to be set up from time to time to maintain the works. Roland Pawlitschko

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Hagneck (CH)

Text Martin Valier

A

B

C

support against water pressure

D

water pressure pretensioned anchor keying into rock self-weight

upstream water level mean lake level Weir

Control room

Cut-off key beam Secant wall

A 3D model of concrete components and steel mounting plates

B suction tube formwork

C completed suction tube with turbine

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HYDROELECTRIC POWER PLANT

D plan horizontal supports section uplift supports scale 1:1500

The new hydroelectric power plant at Hagneck did not present the engineers with the usual challenge of creating a structure that had to be as small and as economically efficient as possible. On the contrary, Hagneck needed to be much more: a massive and heavy structure planned and designed with a great deal of

emphasis placed on the aesthetic qualities of the engineering works, whilst complying with all the applicable regulations and standards. It required a close partnership between architects and engineers and all the contractors involved from the start of the competition concept to final commissioning.

PLANNING AND DESIGN A comprehensive 3D model was used for the planning and design of the hydroelectric plant at Hagneck. All the works were integrated into the model, which resulted in hardly any errors during construction – in spite of complex geometric relationships between the individually completed sections, formwork requirements, reinforcement and the components of the plant itself. All measurements were based on absolute coordinates not relative dimensions.

All specialist designers and companies had access to the 3D model, which they could download, edit and coordinate with others, while on site the images of the model helped interpret the complex formwork and reinforcement requirements (fig. A) and in the visualisation of the various construction stages. Block planning was used to optimise the concreting sequence based on the readily accessible quantities information, so that the scheduled dates and budgets would be met.

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HAGNECK (CH)

e

AAR SUSCEPTIBILITY AND COLOURED CONCRETE The power plant design envisaged that the concrete should achieve the closest possible match in terms of its colour to the natural beige and ochre of the surrounding molasse rock outcrops of Jurassic chalk. In the competition, we proposed a concrete mix composed of crushed beige chalk aggregate, white cement and a pigment additive. After the project started, however, it became clear that it was not possible to manufacture a concrete resistant to alkali-­ aggregate reaction (AAR) using white cement and chalk aggregate. Following an ­extensive series of trials, we were able to find a warm and light-coloured cement (CEM III-B), which, with a minimum addition of 1 % yellow and 0.5 % black

pigments, achieved the desired colour using the locally available ­aggregates and possessed the required AAR resistance. Initial doubts about possible workability difficulties with this concrete incorporating CEM III-B cement were not confirmed in practice. On the contrary, all the concreting stages, many with high aesthetic requirements, were successfully poured without complications. Because of the long curing times, the temperature of the concrete never rose above 45 °C, even in the massive components up to 300 cm thick, which meant that no cooling measures of any kind were necessary.

STILLING BASIN FOUNDATION At the time of the original design, the stability of the stilling basin (the weir’s downstream foundation slab) was to be ensured by a continuous concrete beam cast into the molasse, which would also act as the impermeable ­curtain to resist the upstream water pressure. However, during excavation of the first section (on the lefthand side in the area of the second weir channel), a geometrically unfavourable, 4 – 5 m deep, gravel-filled scour hole was found. The stability of the weir in this situation was achieved by spanning the stilling basin slab over this hole and casting it into the sound molasse rock on

the left-hand side. On its right-hand side, the stilling basin was extended under and “suspended” from the power plant. The lower floors of the power plant are fully anchored into the molasse. The impervious curtain is provided by a 150 cm diameter secant wall with 12 m long piles bored at least 6 m into the unweathered molasse. At the places in the area of the weir piles where the vertical connection between the stilling basin and the molasse bedrock is interrupted, vertical load transfer is continued by similarly sized large diameter bored piles.

UPLIFT AT THE CONTROL ROOM The foundation of the control room is around 20 m (normal head across the weir) below the maximum upstream water level and 9.5 –13.2 m (minimum/maximum lake water level) below the surface of the lake. With the inlet and suction tube filled with water, the self-weight of the structure is enough to provide the necessary safety factor against uplift with the turbines in operation. However, the critical uplift load case was found to be during commissioning. Only then are the two inlets and suction tubes empty, while there is yet no applied 198

­Hydroelectric Power Plan

load from the two turbines and generators. In spite of embedding the lower floors into the molasse, it must be assumed that the water held back by the weir flows down through ­fissures in the rock. This water pressure cannot be assumed to be relieved before it flows into the downstream body of water. There is therefore the risk that the full uplift pressure of the upstream water, about 20 m head, will be developed. We selected a combined means of ­counteracting this uplift load case. The power plant foundation slab was cast into a continuous

groove around its edge in the bedrock molasse to form a connection capable of resisting loads in all directions. To provide the reserve of resistance in the most unfavourable uplift load case,

110 11.5 m deep rock anchors (Swiss Gewi 43) pretensioned up to 400 kN were installed in the inner bay of the control room.

UPSTREAM AND WEIR BRIDGES a

The upstream bridge crosses the upstream channel at an angle of 45°. It has a span of 56 m a and must be capable of carrying heavy machinery components weighing 90 t. At the slope side, the bridge is bolted into a foundation box, which in turn is supported on in-situ concrete bored piles. The opposite a end ofbthe bridge cantilevers 13 m beyond the This cantilevering projection creates a abutment. b a high support moment at the sliding bearing, which relieves the sagging bending moment in a the large b span and allows an extremely slender prestressed bridge deck cross section. a

b

a

b

b

The weir bridge provides a pedestrian route and the standing area for 70 tonne mobile maina b b tenance cranes. From the lake side, the deck appears to have a very slim profile, ­tapering down from the deepest part of its cross section to expose only a 35 cm deep edge. The bridge is divided into several lengths of deck, each of c d which is prestressed with three cables. Each deck acts as a two-span continuous beam and c d is prevented from tipping by the upstream balustrade, above all under the variable load case of the operating crane. c d c

c

c

c

c

d

F

aa

bb

dd

cc

G

a a

a a

199

c

b

c

b

b b

Hagneck (CH)

c F bridge sections scale 1:200

c

d d

d d aa south abutment: fixed bearing bb deck void cc north abutment: sliding bearing dd extension beyond north abutment

G plan, section upstream bridge scale 1:400

d

d

200

­Hydroelectric Power Plan

201

Hagneck (CH)

Text  Gregor Schacht, Ludolf K ­ rontal

Demolishing Major Bridges A Job for ­Engineers 202

Essay

The demolition of bridges over narrow valleys or close to superstructures carrying traffic requires new demolition concepts. As with new bridges, the structure to be demolished must be investigated, analysed and its structural stability verified. For structural engineers, this presents new challenges that demand ­innovative approaches and a combination of computer analyses and experimental investigations. EFFICIENT AND VIABLE INFRASTRUCTURE Germany’s economic success is crucially ­dependent on having a viable railway, road and water infrastructure. In the case of German motorways, this mainly involves extending and widening the present road network. Existing bridges complicate road widening. Because these structures were not designed for today’s loading requirements, they are usually replaced by new ones. However, conventional explosive demolition is ruled out for bridges over valleys, in nature conservation areas or crossing other transport routes or rivers. In these cases, engineers employ the sort of temporary support structures that were earlier used only for the construction of new bridges. Launching girders are particularly effective for the demolition of long bridges over deep valleys. INCORPORATING THE EXISTING STRUCTURE INTO THE DEMOLITION PLAN The demolition of bridgeworks is very much like building within the fabric of an existing building. The stability of the structure in the various states of demolition is determined from record drawings and expert on-site a ­ ssessments. Engineers must understand the development of bridge design and the “childhood i­llnesses” of early prestressed concrete structures. They must know the method and date of construction, design codes and calculation models applicable at that time, the diverse range of stressing systems and their constructional details. Any changes to the existing structure or ­repair works must be incorporated into the ­final demolition plan. The engineer must think “backwards” in order to arrive at dem­ olition states in which the existing cross sections and reserves of strength are structurally adequate.

A

A  Lahntal Bridge in 2007

B conventional demolition with excavators within the launching girder

203

Demolishing major bridges

B

DEMOLITION OF THE LAHNTAL BRIDGE, LIMBURG The first Lahntal Bridge on the A3 motorway was blown up shortly before the end of the war. A temporary truss bridge allowed traffic to cross in one lane in each direction before the construction of a prestressed concrete bridge began in the 1960s. The Lahntal Bridge was one of the first major valley bridges to be designed to have a post-tensioned continuous concrete deck consisting of two individual single-cell box girders and constructed using the balanced cantilever technique (fig. A). The third Lahntal Bridge was ­officially opened for traffic at the end of 2016, allowing demolition of the old bridge to begin (figs. B – D). The Lahntal Bridge was demolished using a launching girder (figs. C, D). Compared with conventional demolition concepts, such as “cutting down” segments of the bridge, this method has the advantage that the traffic routes below can continue to operate almost without any restriction. The launching girder is erected under the superstructure and spans between two temporary supports that stand on the foundations of the bridge piers. The section of the deck to be demolished sits in the launching girder and is then cut away from the remaining bridge deck (fig. C). The special point here was that the structure during demolition differed greatly from the structure during erection, which meant that the reinforcement had not been designed for many of the demolition stages (fig. E). The main problem was cutting through the prestressing bars because they were essential for the structural stability of the remaining ­superstructure.

The smooth pretensioned bars and the uncertainty about the actual effectiveness of the grouting of the pretensioned member meant it was possible to verify structural stability only by theoretical modelling and in-situ testing of the grout condition. It was necessary to assume that the prestressing bars were anchored into the concrete by composite action up to the next demolition cut (fig. E). The smooth surface of the ­DYWIDAG prestressing steel and the uncertainties about their grouted condition meant this assumption could only be verified through complex theoretical modelling and in-situ ­investigations. The anchoring behaviour was checked at defined demolition cutting points (figs. F, H). In the case of existing structures, the partial safety factors for deadweight can be considerably reduced by accurate measurement of the geometry and weight determination. To do this, the box cross section was measured and cores taken at points along the superstructure.

204

Essay

C

D

C  construction sequence for the section-by-section demolishing of the east superstructure with launching girder

D launching girder with temporary supports standing on the bridge pier foundations

205

Demolishing major bridges

The design codes for new structures cannot generally be applied to this sort of structural problem. A satisfactory analysis is possible ­only with a combination of engineering models and experimental testing. The risk lies with the structural engineer and requires a good relationship with public-sector clients, expert construction companies as well as structural and materials testing engineers. Much work is going on at different levels i­nto devising some universally applicable rules for the demolition of major bridges. The first demolition conference took place in January 2018 at Leibniz Uni­versity Hanover.

E

direction of construction  ...

no composite action

 segment 2

 segment 1

direction of construction   segment 2

...

direction of demolition segment 2

segment 1

F

 segment 1

direction of demolition ...

segment 2

G composite action

direction of demolition

direction of demolition segment 2

segment 1

...

E  action of the prestressing bars for different directions of demolition – in the same or opposite ­direction to the superstructure’s construction

F hollow box section at one of the cutting points

G bar bell anchorage with sleeve coupling and grouting duct

H effective (composite ­action up to cut face) and non-effective (steel drawn back into concrete) anchorage of prestressing bars

206

Essay

segment 2

H

207

Demolishing major bridges

Text  Ludolf Krontal

Bridge Construction Quo Vadis? 208

Essay

On 14 August 2018, the Morandi Bridge in Genoa collapsed and 43 people fell to their deaths. With so many lives lost, this collapse is a frightful tragedy and of almost traumatic significance for structural engineers working in bridge construction. We do not know exactly what occurred, but we have many questions. How could that happen? What risks do structures of this generation hold in general? What can we do, what must we do, to guarantee their safety? As yet, there are no official answers but suspicions about the causes and the knock-on effects for bridge construction are intensively discussed among industry professionals. These events are a painful reminder to engineers of the great responsibility they carry with their work and everyday decisions. There is no doubt, despite its collapse, that the Morandi Bridge was a masterpiece of engineering and a milestone of bridge construction when it was built in the early 1960s. The design philosophy of bridge construction has changed a great deal over recent decades in response to new knowledge and experience. Structures designed today have as little in common with those of the 60s and 70s as cars of that era have with the latest generation of vehicles. The requirements in bridge construction have grown considerably over recent d ­ ecades just as they have in automobile construction. In the early period of development of prestressed concrete, the focus was on prestressing the cross section in the most effective way both physically and in terms of cost. Much less emphasis was placed on achieving robustness, e.g. by providing additional conventional reinforcement. Deficiencies in the design codes at that time (temperature effects, shear) and in reinforcement detailing guidelines, not to mention the enormous increase in traffic loads, have led to many bridges being strengthened or renewed.

A

B 202.267 OD

64 80 90 87 87 87 87 104

A  Queensferry Crossing near Edinburgh, Scotland: the failure of one cable cannot lead to the collapse of the structure. Modern cable-stayed bridges have many more

209

tensile cables and therefore considerably higher in-built redundancy than for example the Morandi Bridge.

223

650

B elevation scale  1:20 000

BridgE Construction, quo vadis?

210.717 OD

650

202.267 OD

223

104 101,5

The latest generation of engineering structures can hardly be compared with their earlier predecessors. The demands placed upon structures have intensified extraordinarily because of rising traffic volumes and changed design requirements, but most of all the desire for continuous availability combined with minimal time and cost spent on maintenance. Can modern design concepts for bridges with robust and multiple statically indeterminate systems incorporating high degrees of redundancy better fulfil the wish for long service life structures than those designed by earlier generations of engineers? Only time will tell. At the moment, we cannot predict what the transport systems of the future will look like – however, we can be sure that they will function in the long term only with a flexible, reliable and durable infrastructure. RESOURCE-CONSERVING DESIGN AND CONSTRUCTION Today’s designs should be based on the experience and knowledge of both earlier and historical bridge construction. Younger engineers are usually unfamiliar with historical bridges, their builders and design concepts – whether that be through disinterest or lack of coverage during training and education. This is precisely where there is still much potential for advancing bridge construction and building better structures through tried and tested but perhaps forgotten design approaches. Important criteria from today’s point of view are durability, robustness, timeless architecture, conservation of material resources, appropriate use of materials and more effective deconstruction and recycling. Modern structural analysis software enables engineers to precisely check their designs and helps them find the optimum solutions. However, the new digital world and highly specialised methods of analysis and design alone cannot initiate new developments in bridge

We should ensure that all the money, energy and material that we invest in bridge building is reflected not only in the quantity but also the enduring quality of the results, while conserving valuable natural resources. Some important projects in the recent past have proved that this can be successful. construction. This can only happen through our knowledge of what is feasible and our ­creativity in handling these tools. In recent years, the number of projects involving the maintenance, assessment and strengthening of older and historical bridges has greatly increased. Existing bridge stock not only has a historical and cultural value, it was built at considerable financial cost and consumed great quantities of energy and materials. From the view of resource conservation alone, the retention of bridge structures is one of the most important tasks now and in the years ahead. The operator’s question of how long a bridge can continue to be used must be put another way in future: What must be done for a structure to fulfil its requirements over the long term? Completely different questions to those applicable to the design of new bridges are relevant here.

210

Essay

C

D

E

F

C  orandi Bridge in Genoa, M which collapsed in summer 2018, was designed to have very little redundancy in terms of structural behaviour. D – F  The replacement LangeFeld-Straße railway bridge, Hanover, is a new type of bridge for Deutsche Bahn AG: the extremely skewed steel trough deck was

211

BridgE Construction, quo vadis?

connected monolithically with the abutment to ­optimise the construction depth for the span and avoid using com­plicated bearings with tensile anchors.

G

H

I

G Structures from the 1950s: Stennert Bridge over the Lenne in Hagen was one of the first balanced cantilever bridges in Germany. The bridge is

in good structural condition and should continue in operation for many years. It was not possible to prove by calculation that the bridge would

H Sensors and a monitoring system were installed in June 2018 to provide continuous prognoses of possible prestressing wire breakages.

I, J  Examples of the new ­generation of bridges and winners of the German Bridge Building Prize 2012 and 2014: the Gänsebachtal (fig. I) and Scherkondetal bridges

212

Essay

show any tell-tale changes in behaviour in the event of prestressing steel deteri­oration.

(fig. J) are two of the first large integral and semi-­ integral valley bridges in the Deutsche Bahn highspeed rail network.

J

STRUCTURAL DIAGNOSIS USING SOUND EMISSIONS Structural diagnosis using non-destructive m ­ aterial testing, structural analyses combined with load tests and bridge monitoring already offer a range of options for assessing existing bridge stock. We can look forward to having better and more efficient methods of assessment and analysis available to us in the future. They will not, however, come about of their own accord, they will have to be researched and brought to market readiness by engineers. It is ideal when universities work on this with infrastructure operators and engineering consultants. Our office is presently cooperating intensively with a number of project partners on practical research topics linked with structural diagnosis. These include detecting broken prestressing wires by monitoring sound emissions with special sensors distributed at regular intervals over the length of a structure. This enables a realistic prognosis of a structure with tensioned elements at risk of developing stress corrosion cracking (SCC). Ideally, this monitoring regime would allow some bridges to continue to operate without strengthening works. The behaviour of the Stennert Bridge in Hagen (figs. G, H), the first such pilot project in Germany, is being measured and recorded using sound emission monitoring equipment to detect any occurrence of prestressing wire breakage. In recent years, numerous assessments of bridges with prestressing steel at risk of SCC have been carried out in Germany. Bridges from the 50s, 60s and 70s that looked completely intact have been demolished and replaced, simply because their good condition could not be verified by calculation. A ­financial time bomb is ticking, particularly in cities with many prestressed concrete structures built during this time, because local ­authorities do not have the money to replace this type of “at-risk” structure. “INTELLIGENT” BRIDGES Electronic monitoring systems will become an important part of the assessment of structures. The “intelligent” bridge is still a vision but, with increasing digitisation in construction, new measuring systems and assessment techniques, we will be in a better position to understand what is happening inside structures and to detect critical conditions at an early stage. Deutsche Bahn AG and the German Federal Highway Research Institute (BASt) are currently running research projects on the intelligent networking and anal­ysis of digital and analogue information to allow predictive maintenance based on improved prognoses. These systems will help us to better determine and understand the condition of structures. However, they cannot replace the engineer. Not only do we need the expertise of consulting engineers, but also adequately skilled and informed partners in public works authorities and infrastructure operators. For many years now, these bodies have invested a great deal of time and energy into inviting tenders for professional services. Tendering for these projects devours huge amounts of office resources. Many suitably skilled and highly capable consulting engineers no longer take part in these tenders, because the time spent is out of all proportion to the possible gains. Unfortunately, we are also noticing that very large consultants often seem to be preferred in these tenders and the contracts for design services are awarded to them. It is questionable whether having a large turnover or employee count is a prerequisite for good bridge design. The tried-and-tested structure of independent owner-managed engineering consultancies built up over time in Germany could suffer long-term damage through this trend.

213

BridgE Construction, quo vadis?

VDE 8 ENHANCES BAUKULTUR The construction industry in Germany is currently very competitive, which is also having its effect on bridge engineering. We should ensure that all the money, energy and material that we invest in infrastructure and bridge building is reflected not only in the quantity but also in the enduring quality of the results, while conserving valuable natural resources. Some important projects in the recent past have proved that this can be successful. One example is Deutsche Bahn’s popular new and upgraded railway line between Berlin and ­Munich, known as the German Unity Transport Project 8 (VDE 8). It offers a real alternative to travelling by car or plane. These ecological transport concepts will lower CO2 emissions. Bridges across the Scherkonde, Gänsebach, U ­ nstrut and Stöbnitz valleys are unique in their form and language and demonstrate that this sort of infrastructure project also enhances Baukultur – the built environment and how we perceive and interact with it.

L

M

M

K–M  Stöbnitztal Bridge (fig. M) and Unstruttal Bridge (figs. L and K) with one (fig. K) of four 116 m span strut-framed arches are

two more of the integral and semi-­integral valley bridges on Deutsche Bahn’s VDE 8 project.

214

Essay

K

215

BridgE Construction, quo vadis?

Appendix

216

ESSAY

AUTHORS

218

IMAGE CREDITS

220

PROJECT PARTICIPANTS

222

IMPRINT

224

217

BRIDGE CONSTRUCTION, QUO VADIS?

AUTHORS FRANCISCO BARTOLOMÉ Francisco Bartolomé is an engineer with B y B Ingeniería in Santiago de Chile and was responsible for the structural engineering design of the Theatre BioBío in Concepción. ROLAND BECHMANN Roland Bechmann is ­managing director of Werner Sobek and has been ­responsible for the design of the new below-ground station at Stuttgart Hauptbahnhof since 2009. THOMAS BECK Thomas Beck is a structural engineer and since 1999 managing partner of a.k.a. ingenieure in Munich. He was responsible for the structural engineering design of the concert hall in Blaibach. PHILIPPE BLOCK Philippe Block is professor of architecture and struc­ ture at ETH Zurich, where he founded the Block ­Research Group (BRG). He is also ­director of the Swiss National Centres for Competence in Research (NCCR) – ­Digital Fabrication. BART BOLS As a project engineer at consulting engineers Ney & Partner, Bart Bols was responsible for the “De Lentloper” Bridge in ­Nijmegen. MICHELE BONERA Michele Bonera is a structural engineer and was ­responsible for the engineering design of the roof structure of the highspeed railway station in Montpellier. 218

GUILLERMO CAPELLÁN Guillermo Capellán ia a ­consulting engineer and technical director at bridge design consultants Arenas & Asociados, which, together with IDOM Consulting, ­Engineering, Architecture, designed the high-speed railway viaduct over the ­Almonte near Cáceres. STEPHAN ENGELSMANN Stephan Engelsmann is a structural engineer. He is professor of structural design at the Stuttgart State Academy of Art and Design and managing partner of Engelsmann Peters. BURKHARD FRANKE Burkhard Franke is a freelance architect, editor and photographer. He is a ­frequent author of articles for Detail and structure – pub­lished by Detail. ANDRES GABRIEL Andreas Gabriel, who is an architect with extensive practice experience, was an editor at Detail until 2018, where he was involved with the conception and implementation of themed publications, specialist books and new journal profiles.

­ ollinger+Grohmann in B Vienna. He is a specialist in parametric structural ­engineering design, working in particular on the ESO Supernova project in ­Garching. He is also a ­development team member for the “Karamba3d” analysis software.

ANDREW LIEW Andrew Liew is a structural engineer and was post-­ doctoral researcher in the Block Research Group (BRG) at ETH Zurich. Today he is a lecturer at the University of Sheffield.

HEIKE KAPPELT Heike Kappelt is a civil ­engineer. She started in the Detail project team in 2016 and almost two years later joined the editorial team for structure – published by Detail. Since January 2020, she has been a member of the Detail editorial team.

VIKTOR MECHTCHERINE Viktor Mechtcherine is the Director of the Institute of Construction Materials and a full professor at Technical University (TU) Dresden. One of his main areas of ­research is 3D printing of concrete.

EMMANUEL LIVADIOTTI Emmanuel Livadiotti is a structural engineer and was PABLO JIMÉNEZ responsible for the struc­ GUIJARRO tural engineering design Pablo Jiménez Guijarro is the engineering manager for of the parking garage in Bordeaux. In 2001, together construction area III at the with Taha Aladine, he found­ Spanish national railway company ADIF AV, the client ed the engineering consultancy MaP3, which de­ for the high-speed railway signed the engineering viaduct over the Almonte ­details for the architect. near Cáceres.

TOM VAN MELE Tom Van Mele is co-director LUDOLF KRONTAL Ludolf Krontal is the manag­ and head of research and ing partner of Marx Krontal development of the Block Research Group (BRG) at consulting engineers. The office specialises in design­ ETH Zurich. ing bridgeworks on existing and new bridges and planned TOMÁS MÉNDEZ the demolition of the Lahn- ECHENAGUCIA PASCUAL GARCÍA ARIAS tal Bridge in Limburg. Pascual García Arias is the Tomás Méndez Echenagucivil engineering manager cia is an architect and was JOSEF KURATH at IDOM Consulting, Engipost-doctoral researcher in Josef Kurath teaches struc- the Block Research Group neering, Architecture – Madrid, which, together with tural engineering, strength (BRG) at ETH Zurich. Today bridge consultants Arenas & of materials and construc­ he is Assistant Professor at tive design at Zurich Uni­ Asociados, designed the University of Washington. versity of Applied Sciences high-speed railway viaduct ZHAW in Winterthur, Switzer- MARC MIMRAM over the Almonte near land. He is head of the fibre- Marc Mimram is an archi­Cáceres. reinforced plastics research tect, structural engineer group. He is a founding MORITZ HEIMRATH and the founder of the Marc partner at Staubli, Kurath Moritz Heimrath works Mimram Architecture & und Partner AG consulting as an architect and office ­Ingénierie consultancy. He engineers in Zurich. partner at consultants was responsible for the

APPENDIX

structural engineering ANDREA PEDRAZZINI design of the high-speed Andrea Pedrazzini, a railway station in Montpellier ­structural engineer, is the owner and founder of the LAURENT NEY Pedrazzini Guidotti engineer­ ing consultancy in Lugano. Laurent Ney is a structural engineer and architect. He is He was responsible for the head of the engineering the structural engineering consultancy Ney & Partner design of the Namics office and was responsible for the building in St. Gallen and design and structural engithe single-family house in neering for the Lentloper Gordola. Bridge in Nijmegen. DAVID PIGRAM TORSTEN NOACK David Pigram is co-founder Torsten Noack has been and director of the architecdeputy project manager at ture firm supermanoeuvre Werner Sobek working on and a senior lecturer at the the design of the new below-­ University of Technology ground station at Stuttgart Sydney (UTS), Australia. Hauptbahnhof since 2009. TIVADAR PUSKAS ANDREAS ORDON Tivadar Puskas is partner at Andreas Ordon is an archi- the engineering consultancy tect and works for StollenSchnetzer Puskas Internawerk Architekten. From tional in Basle and was 2014 to 2017, he was a free- ­responsible for the struc­ lance editor for the maga­ tural engineering design zine structure – published of the taz publishing house by Detail. in Berlin. ADAM ORLINSKI Adam Orlinski works as an architect at consultants Bollinger+Grohmann in Vienna. He is a specialist in parametric structural design and is a member of the ­development team for the structural analysis software „Karamba3d“. GERGELY PATAKI Gergely Pataki is a struc­ tural engineer. He joined Uvaterv Engineering Consultants in Budapest in 1999, working in particular on the two stations for the Budapest Metro. ROLAND PAWLITSCHKO Roland Pawlitschko is an ­architect as well as an author, architecture critic and translator. He has been working as a freelance editor with the Detail ­editorial team since 2007. 219

KEVIN M. RAHNER Kevin M. Rahner is partner at the engineering consultancy Schnetzer Puskas International in Basle and was responsible for the structural engineering design of the taz publishing house in Berlin. NICOLAS ROGER Nicolas Roger is a civil ­engineer and worked with a team of engineers from consultants Batiserf on the structural design of the office building in Lyon. THIJS VAN ROOSBROECK As a project engineer at consulting engineers Ney & Partner, Thijs Van Roosbroeck was responsible for the “De Lentloper” Bridge in Nijmegen.

AUTHORS

GREGOR SCHACHT Gregor Schacht is a struc­ tural engineer and has worked for consulting ­engineers Marx Krontal in Hanover since 2014. He is the project manager ­responsible for planning the demolition of the Lahntal Bridge in Limburg. LARS SCHIEMANN Lars Schiemann is Pro­ fessor of Structural Engineering and Design at the University of Applied Sciences, Munich. As the project manager at Mayr | Ludescher | Partner, he was the engineer responsible for the structural planning of the ESO building in ­Garching. ANGELIKA SCHMID Angelika Schmid has been project manager at Werner Sobek working on the design of the new belowground station at Stuttgart Hauptbahnhof since 2009. JAKOB SCHOOF Jakob Schoof has been an editor since 2009 and deputy chief editor of Detail since 2018. Among his ­responsibilities during this time were magazines and books in the Detail Green series on sustainable build­ ing. He also edited the maga­zine structure – pub­ lished by detail. HANS SEELHOFER Hans Seelhofer is a member of the management board at Dr Lüchinger+Meyer ­Bauingenieure – consulting engineers for structural ­engineering facades and lightweight structures in Zurich. He was respon­ sible for the structural ­engineering design of the Schlotterbeck development.

VALERIE SPALDING Valerie Spalding is an ­architect and works at the engineering consultancy ­Engelsmann Peters. Her ­dissertation focused on folded plate structures. MARTIN VALIER In 2008, together with Christian Penzel, Martin Valier founded the archi­ tecture and structural ­engineering consultancy Penzel Valier, which was ­responsible for the build­ ing of the Hagneck hydroelectric power plant.

IMAGE CREDITS RESEARCH + TECHNOLOGY

ROOFS

 OLDED PLATE F STRUCTURES: AN INGENIOUS AND EFFICIENT ONSTRUCTION PRINCIPLE Page 11: Konstanze Gruber / Adobe Stock Photos Page 13 centre left: Association Eugène Freyssinet Page 13 centre right: from: Eugène Freyssinet: Les hangars à dirigeables de l‘aeroport d‘Orly. In: Bulletin Technique de la Suisse Romande N° 22 of 2 November 1929, pp.  255 –257 Page 13 bottom: from: Marcel Breuer / Bernard Zehrfuss / Pier Luigi Nervi, UNESCO: Preliminary Project, Paris 1953, p. 15 Page 14/15: Florian Monheim Page 16 top: Stefan Müller-Naumann Page 16 bottom left: Siegfried Wameser Page 16 bottom right: Courtesy of Fondazione Renzo Piano 1966, Mobile Structure for Sulfur Extraction, Pomezia (Rome), Italy Studio Piano, architects Page 17 left: Brigida Gonzalez Page 17 right: René Rötheli Page 19 top left: FAT LAB Page 19 centre left, bottom left: Engelsmann Peters Page 19 centre right: Christopher Robeller, IBOIS / EPFL Lausanne Page 19 bottom right: Make Architects

220

ULTRALIGHT FORMWORK SYSTEM FOR THIN, TEXTILE-REINFORCED CONCRETE SHELLS Page 21, 26/27: Block Research Group, ETH Zurich | Photo credit: Michael Lyrenmann Page 23 bottom right, 24, 25 top left, 25 bottom: Block Research Group, ETH Zurich | Photo credit: Naida Iljazovic Page 25 top centre, 25 top right: Block Research Group, ETH Zürich FOLDED PLATE FLOOR SLABS IN PRESTRESSED CONCRETE Page 28, 32, 33: Roger Frei, Zurich Page 30: ingegneri pedrazzini guidotti Page 31: Corinna Menn & Mark Ammann

APPENDIX

DIGITAL CONSTRUCTION – 3D CONCRETE PRINTING Page 34, 35 top left and right: XtreeE Page 35 top centre: University of Loughborough Page 35 bottom: Sika Page 37 top left: Project Milestone Page 37 top centre: TU Eindhoven /BAM Page 37 top right: Apis Cor Page 37 bottom: Zigor Aldama Page 39 top left: TU Dresden Page 39 top centre: HuaShang Tengda Page 39 top right: © ACCIONA. Bridge designed by IAAC and printed with DShape® technology Page 39 bottom left: voxeljet / ETH Zurich Page 39 bottom right: University of Innsbruck

CONCERT HALL IN BLAIBACH Pages 49, 54 top and centre left, 57 top, 58, 59: Karl Landgraf Page 51, 52/53, 54 bottom, 57 bottom: Edward Beierle Page 54 centre right: Peter Haimerl . Architektur TRAM STOP AT BERLIN MAIN RAILWAY STATION Page 61, 64: schlaich bergermann partner Page 63: Hanns Joosten Page 65: BEGA HIGH-SPEED RAILWAY STATION IN MONTPELLIER Page 67, 72 bottom, top left and centre: Dronestudio Page 69: Hisao Suzuki Page 72 top right, 73, 74/75: Erieta Attali

CHALICE COLUMNS FOR STUTTGART 21 Page 77, 78 bottom and 83 centre: Achim Birnbaum Page 78 centre: SEMI­FINISHED PRODUCTS Werner Sobek IN STRUCTURAL CARBON Page 80, 84/85: ingenhoven PRESTRESSED CONCRETE architects /Achim Birnbaum Page 40: Christian Page 83 top: Ed. Züblin AG Weidmann, Silidur Page 83 bottom: HG Esch Page 42–45: cpc-AG

MULTI-STOREY BUILDINGS SINGLE-FAMILY HOUSE IN GORDOLA Page 89, 96: Pedrazzin i Guidotti Page 91–95: Nicola Roman Walbeck ADMINISTRATION AND CONFERENCE BUILDING IN GARCHING Page 99, 104, 106: Lars Schiemann Page 101: Aldo Amoretti Page 109: Roland Halbe STATION HALL WITH MULTISTOREY PARKING GARAGE IN BORDEAUX Page 111, 114 top and bottom left, 117: MaP3 Page 113, 114 bottom right: Didier Boy de la Tour Page 116: Mathieu Lee Vigneau ESO SUPERNOVA IN GARCHING Page 119: ESO / TUMFSD&ESO supported by Autel Robotics Page 121: ESO / P. Horálek Page 122 (renderings, drawings): Bollinger+Grohmann Page 122 bottom right: ESO Page 125 very top, very bottom: Axel Müller, Bernhardt+Partner Architekten Page 125 top and bottom left: Doka Page 125 bottom right: Bollinger+Grohmann

BRIDGES AND INFRASTRUCTURE BUILDINGS BIOBÍO REGIONAL THEATRE IN CONCEPCIÓN Page 135, 141: Cristobal Palma Page 137, 138 top, 139: Iwan Baan Page 138 bottom, 140: Roland Halbe TAZ PUBLISHING HOUSE IN BERLIN Page 143: E2A Page 145, 148 bottom: Rory Gardiner Page 148 top: Schnetzer Puskas Page 149: Yasutaka Kojima

DE LENTLOPER BRIDGE IN NIJMEGEN Page 171, 173, 177–179: Thea van den Heuvel / DAPh Page 175: Johan Roerink / Aeropicture

RAILWAY VIADUCT OVER THE ALMONTE RIVER NEAR CÁCERES Page 181, 184, 186 top, centre right, bottom, 187, OFFICE BUILDING IN LYON 188, 190 bottom, 191 left Page 151, 156: Batiserf and centre: Page 152, 153, 154 top, 157: Arenas & Asociados Seite 186 centre left: Maxime Delvaux Rúbrica Ingeniería Page 154 bottom: Page 183, 190 top, Christian Kerez GmbH 191 bottom right: FCC Construcción

SCHLOTTERBECK RESIDENTIAL AND OFFICE BUILDING IN ZURICH Page 127: Hans Seelhofer Page 129–132: David Willen

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TWO STATIONS ON THE BUDAPEST METRO Page 161, 163, 166–169: Tamás Bujnovszky Page 165: Uvaterv

IMAGE CREDITS

HAGNECK HYDROELECTRIC POWER PLANT Page 193, 196: Dominique Uldry Page 195: Hannes Henz Page 197–201: Kuster Frey DEMOLISHING MAJOR BRIDGES. A JOB FOR ENGINEERS. Page 203 left: Wikimedia Commons / Oliver Abels Page 203 right, 206: Marx Krontal GmbH Page 205, 207: Thyssenkrupp Infrastructure

BRIDGE CONSTRUCTION, QUO VADIS? Page 209: Transport Scotland Page 211 very top: Wikimedia Commons / Davide Pap Pages 211 top, centre and bottom, 212, 214 bottom: Marx Krontal Partner Page 214 top: Ludolf Krontal Page 215: Frank Kniestedt

PROJECT PARTICIPANTS RESEARCH + TECHNOLOGY

ROOFS

FOLDED PLATE FLOOR SLABS IN PRESTRESSED CONCRETE (Office Building in St. Gallen) Architects: Arbeitsgemeinschaft Corinna Menn, Chur / Zurich (CH) and Mark Ammann, Zurich (CH) Structural engineers: Ingegneri Pedrazzini Guidotti, Lugano (CH) in collaboration with Borgogno Eggenberger, St. Gallen (CH) Client: asga Pensionskasse, St.Gallen (CH) Main Contractor: DIMA & Partner AG, Glarus (CH)

CONCERT HALL IN BLAIBACH Architects: Peter Haimerl, Munich (DE) Structural engineers: a.k.a. ingenieure, Munich (DE): Thomas Beck Client: Gemeinde Blaibach (DE) Acoustic engineering: Müller-BBM, Munich (DE) Concrete and formwork, facade: Fleischmann & Zankl, Viechtach (DE) Formwork, interior: Gföllner, Fahrzeugbau und Containertechnik, St. Georgen (AT) Acoustic systems: Akustik & Raum AG, Olten (CH)

SEMI­FINISHED PRODUCTS IN STRUCTURAL CARBON PRESTRESSED CONCRETE (CPC research project) Start up: CPC AG Andelfingen (CH) Development partners: Silidur AG, Andelfingen (CH): Philipp Steiner Zurich University of Applied Sciences, Winterthur (CH) Department A, specialist group for composite plastics: Josef Kurath, Antje Sydow Sponsoring: Innosuisse – Schweizerische Agentur für Innovations­ förderung, Bern (CH)

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TRAMSTOP AT BERLIN MAIN RAILWAY STATION Architects: Gruber + Popp Architekten, Berlin (DE) Structural engineers: schlaich bergermann partner, Stuttgart (DE) Building Contractor: ARGE Matthäi + Glass, Berlin / Munich (DE) HIGH-SPEED RAILWAY STATION IN MONTPELLIER Architects: Marc Mimram Architecture & Associés, Paris (FR) Atelier Nebout, Montpellier (FR) Structural engineers: Marc Mimram Ingénierie, Paris (FR) Client: SAS Gare de la Mogère General Contractor: François Fondeville, Montpellier (FR)

APPENDIX

MULTI-STOREY BUILDINGS CHALICE COLUMNS FOR STUTTGART 21 Architects: ingenhoven architects, Düsseldorf (DE) Structural engineers (Work phases 3–8): Werner Sobek AG, Stuttgart (DE) Client: DB Projekt Stuttgart –Ulm, Stuttgart (DE)

SINGLE-FAMILY HOUSE IN GORDOLA Architects: Nicola Baserga, Christian Mozzetti, Muralto (CH) Structural engineers: Pedrazzini Guidotti, Lugano (CH) Clients: Tiziano Minghetti, Gordola (CH) Monica Rossi, Gordola (CH) Landscape architect: Giorgio Aeberli, Gordola (CH) Shell construction: Marchesini G. SA, Mezzovico (CH) ADMINISTRATION AND CONFERENCE BUILDING IN GARCHING Architects: Auer Weber, Munich (DE) Structural engineers: Mayr | Ludescher | Partner Consulting engineers, Munich (DE) Client: ESO (European Southern Observatory) – Europäische Südsternwarte Garching (DE) Landscape architect: Gesswein Landschafts­ architekten, Ostfildern (DE) naturaplan, Gauting (DE) STATION HALL WITH MULTISTOREY PARKING GARAGE IN BORDEAUX Architects: SNCF Gares & Connexions Agence Duthilleul AREP, alle Paris (FR) Structural engineers: MaP3, Paris (FR) Client: SNCF Gares & Connexions, Paris (FR)

BRIDGES AND INFRASTRUCTURE BUILDINGS ESO SUPERNOVA IN GARCHING Architect: Bernhardt + Partner, Darmstadt (DE) Structural engineers: Bollinger+Grohmann, Frankfurt (DE) /  Munich (DE) / Vienna (AT) Client: ESO (European Southern Observatory) – Europäische Südsternwarte Garching (DE) Facade and dome: Frener & Reifer, Brixen (IT) Formwork: Doka, Maisach (DE) SCHLOTTERBECK RESIDENTIAL AND OFFICE BUILDING IN ZURICH Architects: Giuliani Hönger Architekten, Zurich (CH) Structural engineers: Dr. Lüchinger+Meyer Bauingenieure, Zurich (CH) Client: Schlotterbeck-Areal, Zurich (CH) Building services design: Haerter & Partner, Zurich (CH) WSM, Zurich (CH) Building physics: Wichser Bauphysik, Zurich (CH) Facades: GKP Fassadentechnik, Aadorf (CH) Outdoor works: Kuhn Landschafts­ architekten, Zurich (CH)

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BIOBÍO REGIONAL THEATRE IN CONCEPCIÓN Architects: Smiljan Radic, Eduardo Castillo, Gabriela Medrano, Santiago de Chile (CL) Structural engineers: B y B Ingeniería, Santiago de Chile (CL): Pedro Bartolomé TAZ PUBLISHING HOUSE IN BERLIN Architects: E2A Piet Eckert und Wim Eckert Architekten, Zurich (CH) Structural engineers: Schnetzer Puskas International, Basel (CH) Client: taz, die tageszeitung. Verlagsgenossenschaft, Berlin (DE) Concrete and masonry work: Hochtief Infrastructure, Berlin (DE) Steelwork: Dörnhöfer Stahl-Metallbau, Kulmbach (DE)

TWO STATIONS ON THE BUDAPEST METRO Architects: sporaarchitects, Budapest (HU): Tibor Dékány, Sándor Finta, Ádám Hatvani, Orsolya Vadász Structural engineers: Uvaterv, Főmterv, Mott MacDonald, Budapest (HU) General architects of the M4 line: Palatium Stúdió, Budapest (HU): Zoltán Erő, Balázs Csapó Clients: Budapest Transport Ltd. DBR Metro Project Director, Budapest (HU)

DE LENTLOPER BRIDGE IN NIJMEGEN Architects and structural engineers: Ney-Poulissen Architects & Engineers, Brussels (BE): Laurent Ney Client: City of Nijmegen (NL) General contractor: OFFICE BUILDING IN LYON Consortium i-Lent / Architects: Dura Vermeer, Christian Kerez, Zurich (CH) Rotterdam (NL) AFAA (Site management), Ploegam BV, Oss (NL) Lyon (FR) Structural engineers: RAILWAY VIADUCT OVER Batiserf Ingénierie, THE ALMONTE RIVER Fontaine (FR) NEAR CÁCERES Client: Structural engineers Icade Promotion and architects: (Private developer), Arenas & Asociados, Issy-les-Moulineaux (FR) Santander (ES) SPL Lyon Confluence IDOM Consulting, (Public developer), Lyon (FR) Engineering, Architecture, Main contractor: Madrid (ES) Léon Grosse, Bron (FR) Client: ADIF Alta Velocidad, Madrid (ES) Contractors: FCC Construcción, Madrid (ES) Conduril, Ermesinde (PT)

PROJECT PARTICIPANTS

HAGNECK HYDROELECTRIC POWER PLANT Structural engineers and architects: Penzel Valier AG, Zurich / Chur (CH) Client: Bielersee Kraftwerke AG, Biel (CH) Power plant design: BKW Energie, Bern (CH)

IMPRINT EDITOR Jakob Schoof

DESIGN strobo B M, Munich (strobo.eu)

EDITORIAL TEAM Roland Pawlitschko, Charlotte Petereit

TRANSLATIONS Raymond Peat PROOFREADING Meriel Clemett REPRODUCTION Repro Ludwig, AT– Zell am See

© 2021 DETAIL Business Information GmbH, Munich detail-online.com The FSC-certified paper used for this book is manufactured from fibres ­originating from environ­ mentally and ­socially compatible sources.

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IMPRINT

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Bibliographical informa­ tion published by the German National Library. The German National Library lists this publication in the Deutsche National­ biblio­grafie; detailed biblio­ graphical data is available on the internet at dnb.d-nb.de. 

PRINTING AND BINDING Eberl & Kœsel GmbH & Co. KG, DE – Altusried-Krugzell PAPER Luxoart samt 1,08-f. Vol. 115 g/m2 (content) Peydur Neuleinen 135 g/m2 (cover) ISBN 978-3-95553-546-9 (print) ISBN 978-3-95553-547-6 (e-book)

Reinforced concrete is the Swiss army knife of modern construction: no other structural material lends itself to ­being moulded so well or has similarly excellent noise and fire protection properties. This book illustrates the versa­ tility of the material with around 25 example buildings and ­essays by experts in the fields of building and structural ­engineering. The contributions also portray a fundamental change in concrete construction. Rising ecological re­ quirements, digital design methods and increasingly competent concrete mixes mean that reinforced concrete has little in common with the material used by the pioneers of modern architecture 100 years ago. At the same time, the refurbishment and maintenance of historic reinforced concrete structures continues to be a major task for us ­today. The book also casts a critical glance at how we use this building material.

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