slender. high. long.: Steel Structures 9783955535216, 9783955535209

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STEEL STRUCTURES



slender high long STEEL STRUCTURES

Contents



ROOFS 010 Matmut Atlantique Stadium in Bordeaux 020 Central Railway Station in The Hague 030 Technology Center in Chicago

040 Quai de la Moselle Sports Hall in Calais 048 Coal Drops Yard in London 058 Jewel at Changi Airport in Singapore

BRIDGES 070 Motorway Bridge in Sundsvall 082 Isarsteg Nord Bridge in Freising 088 Queensferry Crossing near Edinburgh

098 Pedestrian Bridge in Be’er Sheva 106 Kienlesberg Bridge in Ulm

BUILDINGS 118 Intesa Sanpaolo High-Rise Block in Turin 128 Morpheus Hotel in Macau 138 Experimenta Science Center in Heilbronn

150 Oodi Central Library in Helsinki 162 Arena Office Building in Herzogenaurach

SPECIAL STRUCTURES 176 Observation Tower in Brighton 184 Lausward Power Plant in Düsseldorf 194 Meixi Urban Helix in Changsha

204 Vessel in New York 214 The Shed Cultural Centre in New York

APPENDIX 226 Authors 228 Image credits

005



229 Project participants 232 Imprint

Foreword Jakob Schoof

Elegant ­ and ­Efficient

006



“Cast iron was, effectively, an entirely new construction material, the first one since the Romans introduced concrete on a wide scale. There were no precedents, no standard designs, no design rules.” This is how British structural engineer Bill Addis describes the situation at the birth of modern iron archi­ tecture at the end of the 18th century. Since then, iron and steel have been used for all sorts of purposes in construction. Its tensile strength exceeds that of other traditional building materials; it has relatively good fire protection properties; high potential for large-scale prefabrication and speeds up construction processes. It is therefore not surprising that Addis’ German colleague Richard J. Dietrich once described steel as the “material of possibilities”. Iron and steel, however, were always expensive and in limited supply. Their early use in construction was therefore largely dictated by thoughts of efficiency and their dimensions calculated by engineers. The lack of regulation of their design and use described by Addis, soon gave way to modern construction principles and industrial product standards developed using scientific methods. This was one way in which iron and steel construction set itself apart from older forms of building, which were based on empirical knowledge accumulated over centuries. The first golden age of iron construction at the start of the 19th century went hand in hand with many inventions, such as the I-beam and the truss, which still figure significantly in the structural engineer’s repertoire today. The construction of Joseph Paxton’s Crystal Palace in London in 1851 signalled the birth of industrial, standardised, mass prefabrication in building construction. Pioneering bridge structures, such as the Brooklyn Bridge in New York and the Forth Bridge to the north of Edinburgh, would also have been impossible to realise without iron and steel. Engineers of today must consider new aspects, such as designing modern steel structures for ease of deconstruction and the recyclability of their materials. Steel, according to one pertinent observation, is only used and not consumed. The fascination that steel structures exert shows no sign of waning: delicately proportioned roofs and daring cantilevers can be built in steel just as well as in all other mass construction materials. This was convincingly demonstrated by Frei Otto with his Olympic roof in Munich and Jean Nouvel with the Culture and Congress Centre in Lucerne. Steel structures can define the external appearance of buildings, such as the Hearst Tower in New York or the Morpheus Hotel in Macau, which will be extensively discussed in this book. Steel structures can also be extravagant, for example the Atomium in Brussels, the Guggenheim Museum in Bilbao or New York’s large-scale sculpture, the Vessel, which also features in this book. The title “Slender High Long” alludes to steel’s uniqueness: steel almost always has a key role to play in slender towers, long-span bridges and audacious cantilevers. Twenty-one pioneering structures from past years – including bridges and skyscrapers, stadiums and station halls – are presented in detail on the following pages. We hope that they can be a source of real inspiration for your own designs. The development of digital design and analysis methods allows us to believe that the limits of innovation with respect to structural design are nowhere close to being reached. This prognosis, however, applies not only to steel construction and ingenious structural design, but has long since led to efficient utilisation of the strengths of all available materials. “Slender High Long – Steel Structures” is therefore only the starting point for a three-book series. Two other volumes about structures in reinforced concrete and in timber are already in preparation and will appear in the coming months.

007



MATMUT ATLANTIQUE STADIUM IN BORDEAUX

010

CENTRAL RAILWAY STATION IN THE HAGUE

020

TECHNOLOGY CENTER IN CHICAGO

030

QUAI DE LA MOSELLE SPORTS HALL IN CALAIS

040

COAL DROPS YARD IN LONDON

048

JEWEL AT CHANGI AIRPORT IN SINGAPORE

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009

Architects Herzog & de Meuron, Basel (CH)

Structural engineer Cabinet Jaillet-Rouby, Orléans (FR) Structures Ile de France, Montrouge (FR)

Matmut Atlantique Stadium in Bordeaux

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Matmut atlantique Stadium

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The new stadium stands on the northern edge of Bordeaux. The multifunctional arena for up to 42,000 spectators can host football and rugby matches as well as concerts and social events. The clear, orthogonal geometry of the structure is also visible inside the arena, not least from the rectangular opening over the pitch. All functional and event rooms are located in the plinth surrounding the playing area, which supports the lower spectator stands on its inner side and provides the base for a continuous circulation level. An alternately stepped outer strip of auxiliary rooms defines the external limit of this level. The upper spectator stand forms a single unit with the 44 m cantilever roof, which has a neutral appearance from below so as not to distract from the action. The internal space is as reticent as the building’s exterior is expressive. The complex stepped surface of the bottom of the upper spectator stand is supported on a dense, in some places randomly arranged network of thin, white columns, through which spectators pass on their way up the steps into the stadium. The interplay of these columns with the cubic overall form and the prominent plinth evokes the image of a white, filigree temple. Burkhard Franke

section floor plan level 3 scale 1:2000

1 outdoor steps 2 continuous circulation level 3 access to upper stand

013

Bordeaux (FR)

4 lower stand 5 kiosk 6 toilets 7 pitch (level 0)

Text Burkhard Franke, Munich (DE)

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C plan of whole structure showing division into 12 structurally independent sections

A axonometric structure west stand

B axonometric structure north-west corner

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MATMUT ATLANTIQUE STADIUM

D perspective digital 3D model division of whole structure

E stand steelwork on concrete plinth

F moment joints in steelwork

LOAD-BEARING ELEMENTS The rectangular building has overall dimensions of 233 × 210 × 37 m. Its cross-section d ­ ivides into three components: the four-storey plinth (with the extensive outdoor steps on the long sides, the lower spectator stands and the surrounding continuous “snake” with the auxiliary rooms), the upper spectator stands and the roof. In the plans, the structure is divided into 12 structurally independent sections extending from the plinth to the roof and connected by ­expansion joints (Fig. C). At these points, bracket-­ like supports with neoprene compression elements transfer only vertical loads to the neighbouring beams, but allow horizontal movements of up to 5 cm resulting from expansion or seis-

mic loads. Except for the plinth construction in reinforced concrete on the two long sides, the whole loadbearing structure is made from steel.

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G section west stand scale 1:500 H section south stand scale 1:500

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Bordeaux (FR)

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I structural principle west stand

J structural principle south stand

K axonometric corner roof trusses with stiffening longitudinal beams

016

MATMUT ATLANTIQUE STADIUM

M installation of roof modules with heavy-lift crane

N installation of perforated corrugated acoustic sheets as roof soffit cladding

O side elevation roof of module with 44.5 m cantilever

BASIC STRUCTURE AND STIFFENING The spectator stands are supported on columns, each roof truss rests on a main support at the top of the upper spectator stands above the highest row of seats. The moment from the cantilever on the inside of the stadium is resisted by a tension column at the outer edge of the roof. The system is balanced in such a way that the roof transmits only minimal compression to the outer supports, even in the case of uplift from strong winds. The supports on the foundation and on the concrete plinth construction generally have hinged bearings. Stiffening is provided by ­moment connections of the columns with

the roof slab and the spectator stand beams (Figs. I, J). The high number of columns ­creates a complex multiple frame effect. In the roof area, the columns extend up to the underside of the top chord of the roof truss. Because these trusses are also connected to one another in the plane of the supports by a lattice girder ­stiffener (Fig. K), each column is restrained in both directions. Their buckling lengths are also reduced. The spectator stands and roof represent an annular “table” on the plinth structure.

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L section east stand roof scale 1:100 1 tension column, Ø 508 × 8 mm ­circular ­section

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Bordeaux (FR)

2 stiffening for hinged connection to tension column, welded steel plate 3 non-structural column, Ø 406 × 6 mm circular s­ ection with

locating pin 4 main column, Ø 711 × 12 mm ­circular section 5 moment connection to steel beam upper stand

6 column upper stand, Ø 610 × 12 mm ­circular section 7 stiffening for roof truss tip, welded steel plate

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MATMUT ATLANTIQUE STADIUM

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Excitation frequency [Hz]

VIBRATION DAMPING Vibration analyses examined how the structure responds dynamically to the movements of the spectators, whose influence can be modelled as a periodic, non-harmonic function. This can be expressed as a Fourier series, of which only the first three harmonics are relevant. Assuming a damping ratio of 1.3 % for vertical and 0.4 % for horizontal dynamic excitations, it was shown that vertical vibrations are within the permissible

range. Piston dampers on 8 of the 12 movement joints minimise horizontal vibrations (Figs. R, S). These dampers can accept loads of up to 60 kN and movements of up to 10 cm.

NON-STRUCTURAL COLUMNS As well as structural columns, a number of non-structural columns were introduced for

R

architectural reasons. They also act as drainage pipes and cable ducts (Fig. T).

S

T

P horizontal acceleration of north stand without vibration dampers

Q horizontal acceleration of north stand with vibration dampers

019

BORDEAUX (FR)

R damper locations

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S piston damper for stands

T cross-section of non-structural column with media ducts

U steel sheet cladding to stand soffit

Architects Benthem Crouwel Architects, ­Amsterdam (NL)

Structural engineer Sweco Nederland, De Bilt (NL) [formerly Grontmij, De Bilt (NL)]

Central Railway Station in The Hague

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a Ground floor

Upper floor

2 sections floor plans scale 1:1500 site plan scale 1:6000

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1 station hall 2 office ­building ­(existing) 3 trams 4 light rail station 5 bus station 6 entrance

 7 shops   8 train platform access   9 tram platform access 10 bus station access 11 train platforms 12 light rail access

Central Railway Station

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After the railway stations in Rotterdam, Utrecht and Amsterdam, architects Benthem Crouwel have recently completed a further infrastructure project: the central station in The Hague. Den Haag Centraal is a terminal station for ­national and international railway services and an essential transportation node close to the Dutch government quarter. The light and airy station hall, constructed in steel to ­replace a dark concrete building, connects an existing office block and is crossed by an elevated tram line. West of the hall at street level is another tram connection, to the south – one floor above the railway platforms – are the bus station and the new terminus of the light urban railway designed by architects Zwarts & Jansma for the national passenger transport authority. The station hall is open on all sides, functions like a covered square and is therefore closely tied to the city. With so many different means of public transport in and around the building, spatial organisation and ease of orientation were ­important elements in its design. Daylight streams through the transparent roof and glass façades. In sunlight, the rhomboid roof panels create an interesting interplay of light and shadow – they serve three functions simultaneously: lighting, ventilation and acoustics. Supported by elegant 22 m high tree columns, they are important design elements in the 120 m × 96 m hall. Andreas Ordon

023

The Hague (NL)

024

Central Railway Station

025

The Hague (NL)

Interview  Bas van Ooijen, Sweco Nederland, De Bilt (NL) [formerly Grontmij, De Bilt (NL)]

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A structural system at ­section aa (p. 22)

B structural system at ­section bb (p. 22)

C roof section scale 1:50 1 rainwater gutter 2 insulation glazing

3 smoke / ventilation flap: aluminium element 70 mm insulation 4 tapering HEB beam 5 perforated aluminium plate, 70 mm insulation

026

Central Railway Station

6 tree column ­connection 7 200/125 mm hollow steel section 8 luminaires

D steelwork details tree column – branch scale 1:50

E steelwork details, connection of branch and roof beam scale 1:50

F steelwork details, tree column base scale 1:50

TRANSPARENCY AND OPENNESS FOR PASSENGERS Andreas Ordon: The tree columns and the striking roof construction are the main structural and architectural elements of the railway station. How do the steelwork connections and the load transfer system work? Bas van Ooijen: Each of the eight tree columns has an encastre support at the foundations. They mainly carry the vertical loads from the roof. The four branches are each connected to the column by moment connections. Tapering HEB beams intersect to form a welded cruciform joint, which is attached by a pinned joint to the ends of the branches by a cast steel connection, and is capable of transmitting bending moments. The HEB 500 beams span the intermediate space to the next tree column. The applied bending moment determines the cross-section of the beams. Smaller rectangular 200/125 mm steel

tubes within the rhomboid panels function as secondary steelwork. The roof surface consists of glass and ventilation elements. The roof construction and the columns work as parallel systems. The roof members carry tensile forces up to 3000 kN, while the branches are loaded in compression. This requires the member axes at the connection to meet precisely at one point, so that no bending moments can arise from eccentricities. If this were not the case, the beams would have needed to be much larger. In turn, this would have led to greater bending of the roof members. Was the oval shape of the columns a purely architectural decision or were structural engineering considerations involved? By building the columns into the foundations, they can also carry wind loads, but their oval

t = 35 t = 35

435 915

= 30 t = t30

2000 20002000 t t = 80 = 80 t = 80

4000 4000

915

2000 2000

HEB900 HEB900 HEB900 2000 2000 t = 80 t = 80

t = 50 t = 50 t = 50

435

t = 35 t = 35 435

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=100 35HEB900 ≈ 100 HEB900 2≈ t = 2≈ 35 t≈2≈ t = 35 ≈ 100

435

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t = 30 t = 30

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937

937

= 35 t = t35

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Ø 200 Ø 200 Ø 200 =≈ 35100 ≈ 100 2≈ t2≈ = t35

= 50 t = t50

= 35 t = t35

Ø 200 Ø 200

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THE HAGUE (NL)

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Cast steel

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Gussstahl Gussstahl Ø 330 Ø 330

Gussstahl Gussstahl Ø 330 Ø 330

Ø 80 Ø 80 t = 25 t = 25

237 237 Ø 80 Ø 80 471237 237 = 25 471t = t25 237237 237237 471471

shape was exclusively in accordance with the wishes of the architect. The orientation of the oval relates to the north-south direction of the branches. The physical dimensions of the columns, on the other hand, are determined to suit structural engineering requirements. What role does the facade construction play in the stability of the roof? The rhomboid roof construction is flexible in both directions because the absence of triangular panels means there are no rigid areas. Moreover, the beams and columns are relatively slender. The roof can deform not only through the bending of the roof beams but also from quite small rotations of the tree columns. Wind loads in the principal wind directions are therefore carried locally in the plane of the facades. Wind bracing performs this task in the southern facade. The forces from wind from the east or west are transmitted by the roof beams into this bracing. They therefore also affect the columns. The ground floor columns of the east and west facades are built into the foundations to ensure facade deformations are kept to a minimum. Additional steel members in the rhomboid roof panels near the east and west facades prevent the roof beams folding together like a concertina under the action of wind loads (Fig. I). The first row of rhomboid panels at the east and west facades therefore acts like a horizontal beam. The exact flow of forces ultimately depends on member stiffnesses. The upper columns in the east and west facades are carried by a beam over the ground floor level. Why is there this intermediate step? The architects wanted a minimum of columns on the ground floor to increase the transparency and openness for the visitor. This was resolved by the introduction of a steel beam in the facade

and connecting it to the upper and lower columns by bending moment connections. At points where these connections are close to one another, the beam must also be capable of accommodating torsional forces and is tubular in order to increase its stiffness. How does the connection to the existing office building contribute to the overall structure? In addition to the tree columns, the south facade and the connection to the bus platform, the structural system is also stabilised in the horizontal direction by being connected to the adjacent office building. The existing building – a column and slab construction with a stiffening stairwell core – also carries a small proportion of the vertical load from the roof. Inclined connecting members at the edges of the station hall are designed so that they compensate for deformations caused by temperature changes and ensure the stability of the roof by accommodating the tension and compression forces in the tubular steel profiles from wind in the northsouth direction (Fig. K). Additional connections to the central core of the existing office block carry wind loads from the east-west direction (Fig. L). These were introduced to reduce the deformation of the station building, but are not essential for overall stability. The deformation of the roof without these connecting members would be twice as high and architecturally unsatisfactory. To what extent has the later connection of the light urban railway designed by Zwarts & Jansma architects and Knippers Helbig influenced the design of the structure? Its effect has been very minor. In the design, we assumed that a certain volume of the building could be severed from the rest at some time in the future. It contributes no additional loading however.

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I deformation under wind loads

G part section structure south facade scale 1:1000

H part section west facade scale 1:1000

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CENTRAL RAILWAY STATION

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J axonometric structure

K horizontal / vertical section, lateral connection to existing building scale 1:100

L horizontal / vertical section, central connection to existing building scale 1:100

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Stichthage Office building 1 1

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1 Ø 55 mm steel rod 2 oval 650/450/18 mm steel column encastre 3 RC slab 2 × 1 m 4 bracing 5 wind bracing 6 connection rod (Fig. L)

7 connection rod (Fig. K) 8 600/220/20 mm steel column south facade 9 800/300/20 mm steel column west facade 10 HEM 1000 beam on side

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THE HAGUE (NL)

2890 2890 1825 18251065 1065

11 Ø 200/100/12.5 mm steel connection member 12 300/300/14 mm beam 13 concrete facade element (existing) 14 steel plate t = 20 mm

15 HEB 400 beam connection to stairwell core

2590 2590

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1825 1825

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Architects Barkow Leibinger, Berlin (DE)

Structural engineer Knippers Helbig, New York (US) / Berlin (DE)

Technology Center in Chicago

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Technology Center

site plan  scale 1:4000 sections, plan scale 1:1000 1 showroom 2 delivery area

3 lobby 4 café 5 terrace 6 office space 7 courtyard 8 training room

Machine and laser manufacturer Trumpf’s new Technology Center is a combined workshop and exhibition hall. The facility, which is ­accessed directly from the road, consists of two large buildings with gently sloping roofs and is surrounded at the rear by lawns, open groups of trees and a small artificial lake. The showroom facing the road and the northern building component with offices, training rooms and a café connect at a corner and define two external areas: the car park and main entrance to the southeast and a large curving terrace facing the green space in the northwest. The continuous mono-pitch roof is 12 m high at the southern facade, a steel-glass construction which presents a series of display windows to the road. In the showroom, networked machine tools in product lines demonstrate the process chain required to manufacture complex sheet metal components. A striking roof structure comprising eleven 44 m long, up to 3.6 m high Vierendeel steel trusses welded out of laser-cut sheets spans the interior space and, at the same time, showcases the company’s expertise. An open skywalk crosses the trusses at a height of 6.5 m, offering an impressive overview of the machinery and allowing the visitor to enter and appreciate this special roof structure. With its facades of corten corrugated steel sheets, extensive glazing and a careful choice of material and detailing, the complex combines industrial character with corporate elegance. Andreas Gabriel

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Chicago (us)

Text Thorsten Helbig and Boris Peter, Knippers Helbig, New York (US) / Berlin (DE)

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local bending moment diagram e–h optimisation of the girder geometry to suit the applied load effects

A development of the girder form (schematic)

a single-span girder under uniformly distributed load b shear force diagram c global bending moment diagram

034

TECHNOLOGY CENTER

B beam elevation scale 1: 250

REINTERPRETATION OF THE VIERENDEEL PRINCIPLE The design of this walk-in “roof space” over the showroom revisited a girder concept first used by the Belgian engineer Arthur Vierendeel (1852 –1940) in 1897 at the Congrès International des Architectes in Brussels. Vierendeel developed the “bridge girder without diagonals” as an economic alternative to the riveted steel truss girder, which at that time could not be accurately analysed and therefore required very high safety factors to take into account secondary stresses. The static forces in this new type of truss for the Trumpf building were reliably cal­ culated based on the principles of the theory developed by Vierendeel, which led to an even more economical design. The girder system allows the roof to span over an area of 2,425 m2 without intermediate supports, which provides design freedom on the ground floor. The full storey height girder system, borrowed from bridge construction, allows flexible use of the showroom roof space generated between the top and bottom chords

in which footbridges and p ­ latforms can be ­installed. In addition to the generally uniformly distributed vertical loads from the roof, the robust girders carry the comparatively high ­localised loads from the footbridges and ­platforms.

STRUCTURAL SYSTEM /  CROSS-SECTION MAKE-UP The 11 girders, placed parallel and 4.88 m apart, span the 44.2 m gap between the north and south facades. The girders are supported on columns standing inside the building at the facades. The top chords are stiffened horizontally at roof level. The girder chords and verticals are ­rectangular in cross-section and are made up of steel sheet in ASTM A50 steel (equivalent to S355). The sheet thicknesses used for the top and bottom chords are mainly 20 mm and for the verticals 10 mm. The vertical cover sheets ­visible in elevation are 10 mm throughout.

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Chicago (us)

The vertical sheets project beyond the horizontal sheets at the joints, which allows fillet welds to be used for all the connections and avoids the need for expensive reworking.

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Technology Center

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Chicago (us)

DEVELOPING THE STRUCTURAL FORM The structural form is derived from the requirements under uniform vertical loads. Because of the constantly increasing shear force and the resulting higher frame ­moments towards the girder ends, the spacing of the verticals decreases and the width of the chords increases continually. The chords are deepest at mid-span, where their normal forces are highest. The vertical distance between the chords, which is greatest at mid-span, where the maximum main bending moment occurs, re­duces with the distance to the girder end. The girder dimensions required to resist

local bending moments further homogenise the resulting design chord forces (Fig. A). A consistent degree of utilisation of the cross-section over the length of the girder can be achieved with constant sheet thicknesses of only 10 to 20 mm. The comparatively thin sheets allow minimum weld sizes to be used. The girders have a self-weight of approximately 75 kg/m2 of over-spanned floor area; an economically ­efficient value for a roof structure of this span carrying footfall loads.

PREFABRICATION AND INSTALLATION The girders were prefabricated in three sections stiffening roof panels were connected to the top each 15 m long and lifted on site onto the previ- chords (Figs. D, E). ously installed columns. The sections are connected by integrated bolted end plate butt joints in the chords. With the main girders in place, the

FACADE The facades are defined by the glazing construction, which consists of up to 11.50 m high vertical beams fabricated from weathering steel. The standard rolled profiles at a spacing of 1.63 m transfer the horizontal loads from the connected aluminium-glass facade into the foundations or the roof plane. Cleats attached to the cover profiles provide this connection. Measuring up to 3.83 m in height, the glazing

­ lements were inserted from inside the building. e The 63 mm wide posts are spaced to coincide with the vertical beams on the outside of the facade (Fig. F).

C isometric illustration of cross-section segmentation. The trapezoidal widening of the verticals at the chord connection to

accommodate local frame moments is typical of a Vierendeel girder.

D butt joint detail of secondary beams scale 1:20

E section and  partial elevation of Vierendeel beam scale 1:50

F horizontal and vertical sections of facade scale 1:10

1 aluminium mullion with custom mullion cap

2 corten I-beam section as column to support curtain wall system

3 insulating glass in alumi­nium curtain wall framing system

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Technology Center

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1' - 0"*

3'- 9 21/32"

5'- 0"

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E R 1/2" Ø,TYP

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3'- 2 127/256"

1'- 2 155/256" 1'- 3"

3'- 11 225/256"

3'- 0 51/64"

4'- 65/32"

4'- 331/256"

1'- 3"

11°

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28"

73/21

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1'- 3"

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2' - 7"

8 27/256" TYP

1'- 0 7/16"

6'- 3 95/256"

6' - 5

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1'- 3"

1'- 3"

- 3 203/256"

Architects Bureau faceB, Lille (FR)

Structural engineer Bollinger+Grohmann, Paris (FR)

Quai de la Moselle Sports Hall in Calais

040

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On the Quai de la Moselle in Calais, France, stands a new sports hall with seating for around 1500 spectators. It forms part of an urban development programme to revitalise the former docklands and is primarily known as a venue for professional basketball games and tournaments. Clubs and neighbouring schools and colleges also make use of the facility. The hall is hexagonal in form and has extensive glass facades on all sides, which make it look ­inviting and open to all. The building’s position on a piece of sloping ground adjacent to the Quai de la Moselle allows visitors a good view down into the interior from the main entrance area up at street level. The impression of lightness is above all thanks to the steel catenary roof, which, together with the two opposing spectator stands, forms a single, integrated unit. In addition to further entrance and circulation areas, beneath the reinforced concrete spectator stands are locker rooms, washrooms, technical rooms and offices, all of which act as an acoustic and thermal buffer.

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sections, floor plans scale 1:1000

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The underside of the white-painted steel catenary roof is left unclad so that the whole construction, including the stiffening grid of diagonal secondary beams, remains visible to the visitor. Steel connection details and the transition of the roof structure into the spectator stands are also left exposed and make clear the flow of forces.  Roland Pawlitschko

043

calais (FR)

Text Agnes Weilandt and Klaas De Rycke, Bollinger+Grohmann, Paris (FR)

A

1

2

3

B tension

tension

tension

compression

compression

A structural elements:

1 main beams in catenary

2 secondary beams curved in the opposite direction

044

QUAI DE LA MOSELLE SPORTS HALL

3 reinforced concrete spectator stands acting as supports for the main beams

tension

B structural system

ROOF STRUCTURE The appearance of the new sports hall is largely determined by the hexagonal plan ­layout and gently curving catenary roof. In close cooperation with architects from faceB, Bollinger+Grohmann designed a lightweight roof structure that combines the building’s floor plan and the opposing spectator stands into an integrated component of the overall structural system. The roof surface is saddle-shaped, i.e. double curved. Its geometry, a hyperbolic parab-

oloid, was designed to have the main beams take up the shape of a catenary under load ­between the spectator stands. By adopting this shape, the members are subject to hardly any bending moments. In the transverse direction, the roof takes an opposite curvature. This drains rainwater off the roof to the sides of the building and stabilises the catenary roof under un­evenly distributed loads.

DIAGONAL BEAM GRID The roof is stabilised transversely by a diagonal high transverse bending moments do not occur. grid of secondary beams that reduce the bend- A trapezoidal profile sheet roof skin does not ing moments and deflections of the main beams contribute structurally to the overall system. to an acceptable level when the roof is subject to unevenly distributed wind loading. The grid runs from east to west over the whole roof surface and is connected to the two external edge main beams (Fig. A). The edge main beams are in turn connected at the connection points of the secondary grid beams ­vertically to columns in the plane of the facades. The edge beams are not made continuous but are pin-jointed at the connection points so that

MAIN BEAMS Nine main steel beams with spans between 39 and 65 m are arranged parallel to one another at 6.06 m centres. Fabricated out of welded I beams pre-profiled to the curved shape of the roof, they vary in structural depth between 500 mm at the ends and 920 mm at mid-span in order to make good economic use of the crosssection over the whole deck. The main beam bearings are bolted onto the spectator stands such that the vertical and horizontal loads arising from the catenary shape of the roof are transferred through the spectator stand struc-

045

calais (FR)

tures into the foundations (Fig. B). Each main beam was delivered to site in at least three ­segments for assembly in its final position at roof level on temporary supports.

1575

925

SPECTATOR STAND STRUCTURES

650 300

350

c

50 n mi

The spectator stand structures consist of con450 tinuous, inclined, reinforced concrete panels sloping at up to 45° with seating banks cast onto their upper surface. Vertical and horizontal 50 min forces are transferred ontoc a grid of beams and columns. The inclined panels transfer the horizontal loads from the roof structure downwards. This reinforced concrete structure divides the rooms and circulation areas under the spectator stands. Additional shear walls contribute to the stiffness of the building in this area. Like the rest of the reinforced concrete components of the building, the spectator stands were cast in situ. They were built in two stages: The first stage was to construct the inclined basic 400

50 n mi

50

90 40 310

CONCLUSION roof is fully visible to the visitor after completion. The roof and supporting structure therefore still define the appearance of the sports hall from the inside and outside.

260 270

65

40 310

By the clever arrangement of spectator stands and alignment of the roof structure on the plan axes, the designers were able to develop an elegant and efficient load-bearing structure. By deliberately dispensing with any cladding to the underside of the deck, the construction of this 10 40

120 150

150

90

150

150

390

100

120

50

m in

100

panels – without the use of a front-face form. Vertical formwork was used in a second concreting stage to cast the steps and seating banks. The reinforced concrete surfaces of the spectator stands were reworked after the formwork was stripped to expose the aggregate that gives the concrete the colour of the nearby beach. At three beam end support points, the roof span starts clear of the spectator stand. For this reason, additional supports are incorporated in the form of steel frames to transfer the roof loads. They are anchored into the reinforced concrete structure horizontally at the level of the circulation area floor.

30

300

350 650

D 40

20 40

15

300

250

80

15

20 40

 300

C

126 40

C exaggerated deformation diagram of the roof under the half-sided suction wind load case

D detailed section, steel pin connection at roof beam end scale 1:10

E detailed section, roof beam/spectator stand joint scale 1:20

30

cc

046

QUAI DE LA MOSELLE SPORTS HALL

86

460 520

40

30

E

1575

925

650 300

350 c

400

50 n mi

50

50 min

50 n mi

450

c

90 40 310

65

40 310

10 40

260 270

120 150

150

90

150

150

390

100

120

50

m in

100

30

300

350 650

20 40

15

 300

40

300

250

80

15

20 40

126 40

30

047

calais (FR)

86

460 520

40

30

Architects Heatherwick Studio, London (GB)

Structural engineer Arup, London (GB)

Coal Drops Yard in London

048

049

With an emblematic roof sculpture, the newly opened Coal Drops Yard shopping centre in Kings Cross, London, invites visitors to drop in, shop and stroll. Two elongated 150 m and 120 m long 19th century warehouses lying at a slight angle to one another underwent extensive renovation and conversion works in the realisation of this project. London’s coal was originally brought here by train for storage and distribution. In recent decades, the increasingly disused buildings housed workshops and clubs. The objective of the redevelopment was to turn this somewhat wasted land back into a living part of the city, link the two buildings together and create a roofed public courtyard that can be used for concerts and other events, while retaining as much of the original building fabric as possible. Earlier considerations of bridging the two blocks with a third element could not be reconciled with the original buildings’ double-pitched roofs and the need to keep any new supporting structures discreet. Eventually, Heatherwick Studio designed an intriguing ­solution in which the two inner pitched roof surfaces appear to peel off from their buildings, arch upwards as freely curving ribbons that touch one

4

4

2nd floor

1 2 3

site plan scale 1:5000 floor plan scale 1:1500

1 former warehouse with retail floors 2 viaduct 3 public courtyard 4 anchor store

1 2 Ground floor

050

Coal drops yard

3

another at a point in the middle. The thoroughly provocative shape may break every commonly accepted rule and precedent of architecture, yet it is not completely divorced from the location’s historical context. The new roof cladding of blue-grey shingles is sourced from the same quarry as the original and therefore represents a link to the history of the place. In terms of function, the structure simultaneously creates a bridge between the two buildings and a focus for the whole development. The redesigned space has a butterfly-shaped floor plan, with the two wings joined only at the short line of contact. Visitors on the bridge enjoy interesting views through the scalloped glazing. Burkhard Franke

051

London (GB)

Text Ed Clark, Arup, London (GB)

A

B

C

D

6100 6 100

E

6100 610

6100 6100 6100

6100

6100

6100 6100

6100

6100

6100 6100

6100

F 6100

6100

6100

6100 6100

6100

6100 610 6100

B suspended deck, but rafters outside the roof

diagrams A – D development of the supporting structure and roof shape

A roof and deck 2nd floor separate, no “floating deck” over the courtyard

052

COAL DROPS YARD

6100

C rafters visible from below and too flat

D final solution: rafters not visible, only local discontinuity

E layout of roof structure scale 1:1000 F section through structure scale 1:1000

ADDITIONAL SUPPORT SYSTEM Early in the design, the individual components of the two buildings were assessed for their load-carrying capacity. There were a variety of forms of historical construction, such as ­masonry arches and timber roof trusses, ­riveted steel beams and cast-iron columns, up to 150 years old. The majority of the original structures were retained or repaired, always with the aim of ensuring that the spatial qualities of the building fabric were not adversely ­affected.

The architectural concept envisaged a complicated roof construction set on the old buildings. At the same time, it was clear that no a ­ dditional loads could be introduced into the old structures. Therefore, the new roof has its own independent support system consisting of steel columns that pass through the existing buildings without limiting the usability of the space.

BALANCED OVERALL STRUCTURAL SYSTEM The structural engineers faced a particular challenge: how to integrate a supporting structure into the sculptural roof that would not have the appearance of an independent structure. An A-frame supports the two curved ribbons of roof where they touch in the middle at their highest points (Fig. H). It consists of two inclined, cross-braced rafters – “giraffe beams” – tied together at their bases by Y-form connection pieces and a primary tie fabricated from steel plates. The two roof ribbons themselves are designed as three-chord trusses and can be considered as two inclined arches leaning against one another. Their ends are also tied to create a closed two-directional system that transfers no horizontal forces onto the existing structures (Fig. G). The geometric intersection point of the two halves of the A-frame lies outside the roof surface (Fig. B), therefore the massive “kissing point”, two V-shaped connection pieces, was ­introduced at this position. The kissing point is fabricated from heavy steel components that transfer the considerable compression forces below this theoretical apex around the actual ­intersection of the A-frame rafters. This arrange-

053

London (GB)

ment was the best way to allow the roof surfaces to touch so delicately at their contact point (Fig. D). The roof fulfils the true role of a bridge and carries more than its self-weight alone: it also supports the storey spanning over the courtyard. The deck spans the courtyard-facing walls of the existing buildings and is suspended from the two curving roof ribbons by steel rods. The ribbons tend to twist under vertical loads due to their curved and inclined geometry. However, as the floor hangers connected to the deck are suspended from the bottom chord of these ribbon trusses, they ­introduce an eccentric force, a counter-torsion that works against the twist of the roof ribbons. The result is a carefully balanced overall structural system.

H

G

tension compression

J

I

K CHS 508.0 ≈ 12.5 PLT 35 ≈ 459

PLT 40 ≈ 788 CHS 219.1 ≈ 8.0

CHS 610 ≈ 124.5

I, J, K roof ribbon trusses

G diagram showing closed system of tension and compression forces

H axonometric illustration of primary A-frame structure roof ribbon trusses

054

COAL DROPS YARD

I welding during fabrication

J supported on temporary steel trestles during assembly

K segment of a roof ribbon truss scale 1:100

STRUCTURAL STEELWORK The roof ribbon trusses make full use of the space within the roof, increasing in height from approximately 5 m at the ends to 7 m in the middle. ­Circular hollow sections were ­used to achieve the complicated geometry ­using standard steel products. Their diameters are 610 mm in the chords, 508 mm in the ­verticals and 219 mm in the diagonals. The chords are singly curved in order to simplify fabrication. Each truss consists of four prefabricated segments, which were bolted together on site by circular end plates and lifted into their final position using a crane. They were supported on temporary steel trestles during assembly.

L

The kissing point joining the two A-frame halves has to transmit a considerable bending moment and weighs almost 100 tonnes. The height of the section tapers from 1300 mm in the middle to 900 mm where it meets the ­A-frame rafters and is made of welded steel plates up to 80 mm thick.

M

N

O 301

36

5

3883

3906

5

1

36

298

38

60

05

33 9

19

5

17

8

2750

8 17

17

4500

713 151 632

46

8537 12609

2048

L, M, N the “kissing point”: fabrication and on-site installation of steel node

O elevation of steel node scale 1:100

055

London (GB)

2024

DEFLECTION IS A CRUCIAL FACTOR The floor suspended from the roof construction spans about 40 m. The theoretical selfweight deflection was 40 mm. The anchor store required a level floor and therefore it was designed to have a pre-camber of around 80 mm.

During erection on site, the actual geometry was compared with the design geometry and corrected where necessary.

GLASS FACADE A glass facade follows the curved, toothed edge of the suspended deck. The glass panels are up to 8 m high and 2 m wide and stand on the deck plate. The scalloped geometry of the glass surface adds to its stiffness and requires no mullions. Small pin bearings under each glass

panel transform the deflections of the deck plate into vertical movements. Silicone joints ensure the required flexibility and an ­extensive, unobstructed view out onto the courtyard.

P suspension of the 2nd storey deck from the ­bottom chord of the roof ribbon truss

056

Coal drops yard

Q deflection of the roof ­ribbon trusses and the 2nd storey deck (red = high value)

P

057

Q

LONDON (GB)

Architects Safdie Architects, Singapur (SG)

Structural engineer Buro Happold Engineering,­ ­New York (US) RSP Architects Planners & ­En­gineers, Singapur  (SG)

Jewel at Changi Airport in Singapore

058

059

4

2 3

4 2

1 4

205

5 4

154

6

5

5 4 5

Level 3

4

2 3

4 2 location plan scale  1:25 000 schematic floor plans scale 1:2500 Level 1

060

Jewel at Changi Airport

1 4 1 waterfall 2 garden access 3 lounge 4 shopping centre 5 atrium access 6 elevated railway

An elliptical volume in the shape of a flattened, glass torus forms the new centre of the airport at Singapore. The recently completed “Jewel Changi Airport” acts as the connecting element between three existing terminal buildings. The new build is situated in front of Terminal 1, to which it has a direct underground link, and between Terminals 2 and 3, which visitors reach along elevated, glazed bridges. The five above-ground storeys contain airport facilities, restaurants and food outlets, resting and relaxation areas, a hotel and retail space arranged around a common centre. This part of the new build provides the main attraction: a terraced tropical garden similar in form to a five-storey amphitheatre is roofed with apparent ease by a glass dome with triangular elements made up of slender steel profiles. Towards the middle of the roof, the surface curves downwards to form a 12 m diameter oculus, which is sealed with a continuous ETFE cushion. Some 40,000 litres of water per minute cascade down in the form of a “waterfall” to the lowest level through the annulus between the load-bearing structure and the cushion. The continuous column of water is fed in part by monsoon rain and helps to cool the surrounding glazed interior space. In addition to its role in the airport’s passenger circulation system and its commercial significance for the airport, the space’s spectacular ambience is intended to make the Jewel a destination to visit in its own right. Burkhard Franke

061

Singapore (SG)

Text Cristobal Correa, BuroHappold Engineering, New York (US)

A

B spline curve

level 1

tangent ellipse

27,27°

R2

0,0 7

10,95

ellipse

21,30

3,07 11,1 11,11

roof

33,06° arc 33,06° 29,55°° curve 29,55

81,74

C

typical shell compression ring inverted cone oculus inverted cone compression ring typical shell

C sectional axonometric illustration showing the different gridshell zones. The change to a curtain-wall facade is not apparent from outside.

A section

B diagram section geometry scale 1:1500

062

JEWEL AT CHANGI AIRPORT

D structural system

ring beam

THE BUILDING FORM The defining design element of Singapore Airport’s Jewel, a new build which opened in 2019, is the filigree gridshell with a central oculus for a waterfall. The building envelope and structure are combined in a single unit. The overall form is a horizontal elliptical toroid up to 200 m long and 150 m wide with a cross-section based on circle geometries (Fig. B). The elongated shape increases the curvature of the shell in some areas and reduces

the risk of creating flat, badly drained roof surfaces. The visitor scarcely perceives that the geometric centre is eccentric in order to accommodate the existing elevated railway that passes through the building longitudinally and had to be enclosed during construction. The four accesses around the building take the form of ellipsoid atriums and are cut out of the five above-ground storeys without interrupting the external envelope (Fig. E).

ENVELOPE GEOMETRY The surface of the torus is divided into triangles so that flat glazing elements, which are more cost efficient to produce, can be used. The balance achieved between the glass panel size and the structural depth of the envelope creates a lightweight, translucent structure. The triangular grid is created by horizontal rings at a spacing of approximately 2.60 m and two families of beams running at an angle to them. This geometry

becomes denser from the outside towards the centre and would normally have become opaque and structurally inefficient in the area of the oculus. To ensure that the triangles were all more or less of the same size, the engineers thinned out the number of grid shell elements from the outside towards the centre in two stages. A noticeable change in the otherwise straight direction of the rods occurs at two elliptical rings (Fig. E).

D

gridshell facade

063

SINGAPORE (SG)

064

Jewel at Changi Airport

065

Singapore (SG)

89,40

E

65,20

53,39°

3,31 18,47

a=

39

,92

98,16

36,61° a = 2,94 4,95 66

102,60

E view on the gridshell from below (left) and the geometry of the access atriums (right) scale 1:1500

F axonometric schematic of a gridshell panel with nodes

G axonometric schematic of a node

066

Jewel at Changi Airport

a = 50,47

21,00

6,04

,99

ellipsoid east gate

HYBRID SHELL The profiles making up the gridshell are all 120 mm wide but their depth depends on their position in the structure. The flattened form of the torus allows a traditional shell, which carries only longitudinal forces, to be used. Therefore, the central zone of the roof is supported by a ring of 14 groups of 12 m high columns arranged on the inner edge of the top floor. Each of them consists of four columns leaning outwards from a common base. No two groups of columns are alike because they are dimensioned to suit the local grid geometry (Fig. E). Outside the ring of column supports, the roof acts as a typical gridshell. The depth of the structural profiles here is about 350 mm and the curvature creates mainly compressive forces. Inside the ring of column supports, the depth is only 250 mm. This part of the structure is an inverted cone, which is mainly subject to tensile forces and creates a compression ring directly over the columns. This area is the most complex

part of the gridshell: the compression forces occur in combination with the forces from the columns that act perpendicular to the gridshell. To be able to resist the resulting bending moment, the profiles here are up to 750 mm deep. The three-zone shell is supported on its outer edge by a ring beam at the top level of the structure. Below this, the building envelope is a curtain-wall facade.

NODES The design achieves an uncluttered look for the profiles, except in heavily loaded areas, where grid shell by ensuring that the nodes with usually they were welded. six members did not appear to be distinct, single elements. Because of the shell’s double curvature, each of the members at the prismatically shaped nodes meet at different angles in three dimensions. These nodes were manufactured using 5-axis milling machines and bolted to the

F

067

G

SINGAPORE (SG)

MOTORWAY BRIDGE IN SUNDSVALL

070

ISARSTEG NORD BRIDGE IN FREISING

082

QUEENSFERRY CROSSING NEAR EDINBURGH

088

PEDESTRIAN BRIDGE IN BE’ER SHEVA

098

KIENLESBERG BRIDGE IN ULM

106

069

SINGAPORE (SG)

Architects K R A M Group / Rundquist ­Arkitekter, Stockholm (SE)

Structural engineer ISC Consulting Engineers, Copenhagen (DK) Centerlöf & Holmberg, Malmö (SE)

Motorway Bridge in Sundsvall

070

071

1.420.000 ~+39.080

+19.617

~+32.580 -14.500 88.000 113.000 126.500 141.000 156.500 170.000 1 2 3 4 5 6

2

156.500

8

7

141.000

9

8

126.500 113.000 88.000 10 11 12

9

10

11

12

21/3 20.0 00

21/2 32.0 00

21/1 19.0 00

0

92.50

20/9

0

00

00

A = 125 0.0 B = 200 0 0.00 20/851.5 00

20/695.000

20/525.000

01.00

88.0

00.0

7.500

20/22

20/1

19/9

19/9

1

3

2

+3 +28.044 +28.044+28.044 +23.305+23.305 +23.305

+1

+14.470 +14.470+14.470

+19.617 +19.617+19.617 +11.850 +11.850+11.850 +5.000 +5.000 +5.000

+36.468 +36.468 +28.044 +28.044 +23.305 +23.305

+14.470

+2.800

-0.840 -0.840 MW MW

-0.840 MW

+18.930 +18.930

+19.860 +19.860

+18.930

+19.860 +19.860 +19.860

sections -0.840 -0.840-0.840 scale 1:1500 MW MW MW MW = mean water level

-0.840 -0.840 MW MW

-0.840 MW

10 +33.542 +33.542 +33.542

072

+38.698 +33.542 +33.542

+33.542

+19.860

+17.530 +17.530

+17.530

+11.850

site plan scale  1:40 000 +38.698 +38.698 +38.698

30

9 +38.698 +38.698

+36.468

-0.840 -0.840 -0.840 MW MW MW

+28.044

+23.305 +14.470 +14.470

+2.800 +2.800 +2.800

6

5

+11.850 +11.850 elevation, top view of +2.800 +2.800 +5.000 0 +5.000 structure scale  1:10 000

840 W

20/368.000

1

7

6

5

4

3

7

8

+24.589

+17.530 +17.530 +17.530

-0.840 -0.840-0.840 MW MW MW

Motorway Bridge

-0.840 -0.840 MW MW

11

+30.069 +30.069 +30.069 +17.740 +17.740 +17.740

-0.840 -0.840-0.840 MW MW MW

-0.840 MW

-0.840 -0.840 MW MW

-0.840 MW

12

+26.966 +26.966 +26.966 +24.589 +24.589 +24.589 +14.140 +14.140 +14.140 +0.800+0.800 +0.800

+4.50+4.50 +4.50

The new motorway bridge gently curves across the bay along Sweden‘s eastern coast, roughly 400 km north of Stockholm. It is part of the expansion project for the E4 European road, closing a gap between Stockholm and the Finnish border. The decades-old goal was to improve capacity, security and environmental sustainability of the road section in ­order to relieve pressure on the Sundsvall city centre. In 1995 an important step was taken by initiating an open competition that was won by the project group KRAM and its proposal “Dubbelkrum”. In 2009, following an EU-wide prequalification, the client commissioned a group of contractors and engineers with the turnkey delivery of the entire bridge project. The design relates to the city as well as the surrounding hilly landscape. Despite its tremendous dimensions and a length of 1420 m the bridge doesn‘t seem to dominate its surrounding. Instead, similar to a dialogue with the environment, it defines the bay as a new urban space. Reminiscent of a delicate uninterrupted line it connects the coastal a ­ reas and describes a curve both from above and in profile. Three elements characterise the overall composition: massive, faceted concrete piers rise above the water. Above them a disaggregated structure comprised of steel tubes unfolds. With seeming ease it carries the wing-shaped bridge deck. Pier shape, steel tube structure as well as span change incrementally. The span decreases from 170 m in the centre field to 88 m along the border fields. Its slope declines towards the bridge heads while the pier dimensions are reduced proportionally. All steel components were manufactured in southern Germany, pre-assembled in Szczecin in P ­ oland and then transported to Sweden for ­completion. Based on sophisticated logistics, a European steel project was created on an i­mpressive scale. Andreas Gabriel

073

Sundsvall (SE)

A

B

40° 40°

C

3m

3m

A

1,5 m

L/3

H/3

L 18°

7m

H/3

L 18°

3/8

L/3

2/3

H

H/3

A

45°

H

1/3

D

L/3

H/3

7°

1,25 m

5/8

3°

+0.0 MW-0,81 m

074

MOTORWAY BRIDGE

+0,0

E

4.271

30.154

4.860

7.893

4.111

3.852 2.568 1.284

8.176

7.000

3.810

6.000

1

6.000

3.810

855

7.000

300

2

4

~44.384° ~46.543°

4750

12 500

~45.111° ~45.816°

.7

12

50

≈

8

8

≈

50



4

3



.7

4750

+18.630 +17.030

Pier 4

F

+0.000

A top view, bottom deck, section 5 scale 1:1500

For the in-shop assembly with welding robots, the sections of the box girder were divided into seven sections of 16 to 24 m in length.

075

SUNDSVALL (SE)

B horizontal section of profile detail and elevation, abutment scale 1:750

C, D elevation, section (architect’s drawing) scale 1:750

E sections, scale 1:250 1 10 mm steel sheet metal 2 14 mm steel sheet metal 3 Ø 1727/ 25,4 mm steel tube 4 hydraulic press to prestress bracing

F bearing, substructure section, isometric illustration

Text Kjeld Thomsen, ISC Consulting Engineers, Copenhagen (DK)

G

Organic soil

Sand fill Sand Rock

H

I

315

a

375 14

157.5 157.5

55 123

R40

R145 b

150

R25

315 375 14

157.5 157.5

55 123

R20

R145 J

G foundation situation of the bay scale 1:1500

H F-E-M analysis of steel tube connections

076

MOTORWAY BRIDGE

I bracing detail views a original b optimised form

J completed element at the workshop in Sengenthal

150

R25

STRUCTURE Steel sheet coffer dams serve as foundations. The bridge piers are poured in concrete on top of them. Further above, the raised and continuously welded structural steel hollow section features tapered edges that reduce wind loads and increase the structure‘s aero­dynamic stability. The bridge possesses a very complex geometry. Each one of the 364 interior bulkheads placed at 4 m intervals is different. In general, they are designed as truss frames with tube sections as bars. Two interior sheet metal flanges set apart at 8.5 to 13.4 m serve to distribute load concentrations and enable load transmission into the bearings. The orthotropic deck consists of 14 mm thick sheet metal. It is stiffened by 6 to 8 mm thick trapezoidal sheet metal flanges. In order to prevent warping, the side and bottom sheet metal elements are stiffened similarly. The bridge deck is elevated by welded steel tubes with diameters of 1219 to 1930 mm. Bracings between vertical elements transmit horizontal loads into the piers. The skewed steel tube bra­ cing is pre-stressed in order to assure the dead load is transferred to the permanent structural system, hereby reducing the bending moments in the main girder due to dead load of the main girder. The abutments can absorb loads of up to

077

Sundsvall (SE)

38 NM (along pier 6 and 7). All steel components consist of steel of the S 355 type in normalized and killed quality. All connections were analysed by use of the finite element method in order to determine on accumulated peak loads for fatigue analysis. The bridge rests upon spherical bearings on top of the piers. Only pier 6 features a fixed support. From here, the bridge can expand and contract in both directions. ­Expansion joints along both bridge heads can absorb deformations in length of up to +/- 480 or 580 mm.

Text Stephan Lüttger, Max Bögl Group, Sengenthal (DE)

K

L

M

N

O

P

Q

078

R

MOTORWAY BRIDGE

K bridge section, isometric illustration

L segment components, ready for transport (max 6 × 6 × 24 m)

M semi-automatic in-shop production at the headquarters of the Max Bögl Group

N–P transport and assembly with dedicated equipment

Q transport route

R assembly phases

PRODUCTION Due to a tight overall schedule and the harsh winter climate of central Sweden, during which the bay becomes impassable, the steel superstructure had to be erected within the 2013 summer period. This was only possible with a sophisticated logistics concept and serial prefabrication of construction components of up to 38 m in width, 160 m in length and a weight of up to 2500 t. For this purpose an assembly line was set up that was automated as far as possible and equipped with newly developed production machinery. The steel hollow section, divided into three cells and elevated on top of ten concrete piers, was subdivided into eleven large components. Their width ranges from

27 to 38 m and their height from 3.3 to 6.5 m (Fig. K). For production purposes they were ­further subdivided into seven segments ranging from 16 to 24 m in length. Each is comprised of two border elements, two interior volume ­elements and two to six panel elements (Fig. L). In a weekly rhythm all elements were manufactured for each of the 64 segments, including an average of 16 orthotropic plates for each of them.

TRANSPORT AND ASSEMBLY Company-owned heavy duty transport delivered the elements weighing up to 100 t to the Main-Danube Canal. Here, they were loaded onto 45 barges and transported to Rotterdam, where they were transferred onto 45 coastal freighters. Two ships with the elements for the end sections and the construction components for elevating the deck (pier slabs and struts) were transported directly to Sundsvall. The elements of the other sections were first brought to the company-owned pre-assembly site in Szscecin. After pre-assembly, each section was loaded onto two 210 m long skidways. Every 2.5 weeks a pontoon barge transported the sections to the assembly site. The equipment for lifting the 2500 t sections to a height of 40 m was developed and erected during the course of the project. Derrick cranes with two strand jacks with 650 t capacity were attached to the assembled components. In ­addition, a lifting portal with two 650 t strand jacks set on top of a pontoon was in position. The portal featured an additional cantilever that was used to lift the pier slabs weighing up to 160 t on top of the next available concrete pier, where they were initially mounted as cantilever beams. Bridge components were then raised from the pontoon by the derrick crane and the lifting portal. They were swivelled sideways and lifted at an angle in order to avoid collisions. After turning them into p ­ osition they were connected via temporary fittings. In addition, the pier slab was fixed along its upper end. In order to avoid distortions the fixed connection at the pier needed to be disconnected. While the pontoon barge returned to 079

Sundsvall (SE)

Szscecin, the welding and metalwork began ­between components and the pier slab connection, followed by lifting the four struts into position. They measure up to 35 m in length with a tube diameter of up to 2 m and a weight of up to 54 t. Before welding the bearings they were prestressed via interior ­hydraulic presses. Most sections were assembled by late summer. Due to heavy swell along the travel route the assembly of the final components had to be postponed until early 2014. The bay had already frozen over. An icebreaker cleared the area, and the final section was raised and connected.

080

Motorway Bridge

081

Sundsvall (SE)

Architects J2M Architekten, Munich (DE)

Structural engineer Bergmeister Ingenieure, Munich (DE) Oliver Englhardt, &structures, Munich (DE) B&C Associati, Como (IT)

Isarsteg Nord Bridge in Freising

082

083

A

B

C

C bending moment diagram My max My = 8120 kNm; min My = -13 564 kNm

A site plan scale 1:2000

B shear force diagram VZ max VZ = 2072 kN; min VZ = -1063 kN

084

Isarsteg Nord Bridge

The town of Freising has grown much larger over the years; mainly on the right bank of the Isar, the side of the river opposite the town centre. With completion of the Isarsteg Nord Bridge, that area of town now has a much better link to the centre. In 2013, the local council issued a Europe-wide tender for the design of the combined pedestrian and cyclist bridge under the VOF procedure. The winning design by Christoph Mayr, Oliver Englhardt and Josef Taferner a ­ ppealed to the town council mainly because it interfered to the minimum extent with the natural environment along the Isar and its form integrated subtly into the riverside ­landscape. The 160 m long, 58 m main span bridge ­connects three footpaths and cycle routes and has two sets of stairs and two ramps. The forked form of the bridge is based on a tree branch. The likeness is not limited to the rust-brown colour of the weather-­resistant steel, but also its structural concept. The structural and functional features are combined in the new bridge; the pathways, ramps and stairs also act as spanning and supporting members. The main “bough” and its smaller “branches” are made from the same materials, designed on the same structural engineering principle and connected to one another at the forks by a moment connection. The main path kinks slightly at these points to slow down bridge users in an informal, natural way. Jakob Schoof

085

Freising (DE)

Text Oliver Englhardt, &structures, Munich (DE) Christoph Mayr, J2M Architekten, Munich (DE) Matthias Gander, Bergmeister Ingenieure, Munich (DE)

D

E t = 15 mm

3000

50

50 125

1300 1000

4 4

2%

350

2%

30

5 6 7

1230

8

180

150 ≈ 15 mm

50

3

t = 25 mm

1250

80

2

1005 150 1200

t = 15 mm

t = 15 mm

t = 15 mm

Querschott t = 15 mm

1

t = 15 mm

150 ≈ 15 mm

t = 15 mm

Querschott t = 10 mm

3700

t = 10 mm 150 ≈ 15 mm

80 65

Steife in Kiellinie 200 ≈ 20 mm

t = 25 mm

t = 30 mm 500 ≈ 20 mm

t = 15 mm 150 ≈ 15 mm

t = 25 m m

150 ≈ 15 mm

Betonsockel

G

30  10/15

7 12/10 712/10

2 12/15 212 je Kopfbolzen auf Querschnitt 40  12

liegend verlegt 7 16/15 3012/10

7 12/10

2016/15

11 16/15 11 16/15

je Ankerkopf 2 16

je Ankerkopf 2 16

10  16/15

8 16/15

316

je Ankerkopf 2 16

40  12 lg = 1.78 m 17 60

12

15

30 10 lg = 2.00 m 30 70 1.00 6  20

20 12 lg = 1.60 m 1.00

20

liegend zu verlegen lg = 6.20 m 7 16 3.00 30 14/10

26

3 10

lg = 3.00 m 3.00

17

20 16

60

F

je Ankerkopf 2 16

steel profile 3 4 mm sintered wire mesh anthracite, 40 mm mesh 4 65/15 mm preoxidised steel flat 5 5 mm stainless steel rope

D sectional view of pier (deck plate omitted)

E detailed section of bridge deck / pathway surface scale 1:50 1 fi 50/50/4 mm preoxidised steel section 2 125/80 mm beech handrail screwed onto

086

ISARSTEG NORD BRIDGE

6 pathway 150 –180 mm reinforced concrete slab, brush-finished surface 7 Ø 20 mm shear studs 8 15 – 30 mm preoxidised steel plate

F reinforcement drawing for north-west abutment scale 1:50

G cross-sections of hollow box beam (selection) scale 1:100

A JOINTLESS WHOLE The design of the Isarsteg Nord bridge not only harmonises the bridge with its surroundings; it applies the same integral approach to the structural and functional concepts. The bridge is designed as a moment-resisting frame whose components − superstructure, piers, foundations and abutments − are connected to one ­another without bearings or movement joints. The construction principle for the superstructure, stairways and supports is always the same: a wedge-shaped torsionally stiff steel hollow box with a varying cross-section. The superstructure has a constant depth of 1.20 m. Transverse bulkheads welded into the hollow box at approximately 3 m centres act as transverse beams in the bridge deck. Two intermediate supports, each comprising a pier and a stairway on opposite sides of the deck, transfer the loads into the foundations. The whole steel structure is welded to be air and watertight. The 3 m wide bridge deck consists of a 15 cm thick reinforced concrete slab (concrete class C35/45). The brushed-finish slab acts ­compositely with the deck plate (tmax = 25 mm), distributes concentrated loads and provides the running surface. The integral form of construction allows the foundations and abutments to be much smaller than usual. The Isar bridge is founded at depth on 250 mm diameter bored piles, which are designed as raking tension or compression piles ­according to the resultant bearing forces from the main load cases. Only the eastern ramp has a spread foundation because it meets and penetrates the ground gradually at a shallow angle. The bridge was precambered to allow for the deflection due to self-weight. Under maximum applied (live) load, the bridge deflects 72 mm (equivalent to l/780). Investigations of the bridge’s dynamic behaviour found the first natural mode to be a vertical sinusoidal vibration with a natural frequency of 1.33 Hz and a modal mass of 65 t. A vibration damper ensures user comfort.

087

Freising (DE)

The number of different materials was consciously reduced and selected according to ecological principles. The steel structure is ­fabricated from weldable weather-resistant structural steel grade S355 J2G2W. This steel develops a strong, dense oxide layer and therefore requires no further corrosion protection. A conventional coating would need to be completely replaced every 30−40 years, involving complex and expensive anti-pollution measures in these very natural surroundings. Chromate-reduced cement containing no ­additives that might adversely affect groundwater was used in the foundations. The abutments and pile caps were buried well below ground to protect them against corrosion. The use of imported fill was avoided by ensuring all four ends of the bridge were termi­nated at the existing level of the riverside or bank paths.

Design engineering Jacobs Arup Joint Venture, Edinburgh (GB)

Structural engineer Forth Crossing Design Joint Venture: Leonhardt, Andrä und P ­ artner, Beratende Ingenieure VBI AG, Stuttgart (DE) Ramboll Group A/S, ­Copenhagen  (DK) Ramboll UK Limited, Southampton (GB) Sweco UK, Leeds (GB)

Queensferry Crossing near Edinburgh

088

089

64 m 80 m 90 m 87 m 87 m 87 m 87 m 104 m

223 m

650 m 202.267 OD

A elevation scale  1:10 000

090

queensferry crossing

650 m 210.717 OD

Opened in September 2017, the Queensbury Crossing road bridge spans the Firth of Forth and connects Edinburgh with northern Scotland. It replaces an overloaded suspension bridge constructed in 1964, which will in future carry only buses, bikes and pedes­trians. Together with the world-famous red cantilever railway bridge from 1890, they form a unique ensemble of bridge structures from three centuries. The decision to adopt an cable-stayed bridge was based on economy, f­unctional requirements and topographical ­circumstances: a rock projecting out of the w ­ ater offered a potential support in the ­middle of the firth. Because the engineers – not least out of aesthetic considerations – were seeking a symmetrical overall solution, they eventually settled on 2× 650 m main spans, which also provided the required openings for shipping. This determined the position of the two outer towers and the approach viaduct on the southern side. With a total length of 2.64 km, the structure is the longest three-tower, cable-stayed bridge in the world. Burkhard Franke

650 m

223 m

104 m 101,5 m

202.267 OD

091

edinburgh (GB)

N1

N2 ST

NA

NT

CT

N1

N2

NA.1

N1.1

NA

Text Martin Romberg, Leonhardt, Andrä und Partner, Stuttgart (DE) NA.1

N2.1

N1.1

N2.1

NA.2 NA.3

NA.2 NA.3

ST.2 N1.2

N2.2

N1.2

N2.2

NA.4

NA.4

B

C

D

51 MN

51 MN

51 MN

E SA S8

S7

S6

S5

S4

S3

S2

S1

ST

NT

CT

ST.2

0,66 %*

B system, middle tower

C system, outer tower

D system, anchorage pier

092

QUEENSFERRY CROSSING

E static system, plan and elevation

N1

OVERALL CONCEPT OF THE STRUCTURE A characteristic feature of the structure is the two diamond-patterned areas of the bridge elevation where opposing triangular fans of cables overlap. This detail provided the ­answer to a ­fundamental problem for multi-span inclined ­cable-stayed bridges: with ­single- or two-tower bridges, the towers are tied back by anchor cables, usually to stiff, land-side secondary spans. With three towers, this option for stabilisation is not available for the middle tower. Pos-

sible solutions included a very stiff deck, very stiff towers or various forms of cable arrangements. With the Queensferry Crossing, the ­stiffness of the whole system is increased by overlapping the inclined stays in the centre of the two main spans.

BEARING SUPPORT CONCEPT The middle tower is monolithically connected to the superstructure and carries all the loads arising from the carriageway in this area (Fig. B). The outer towers, on the other hand, are separated from the superstructure by a 70 cm gap, to avoid strains imposed by t­emperature changes. The superstructure is supported exclusively by the cables, while horizontal forces from wind are transmitted through vertical orientated bearings into the towers (Fig. C). Because of these sliding bearings, ­torsion in the superstructure arising from e ­ ccentric traffic loads or wind is ­resisted by the inner bridge piers S1 and N1. To combat uplift forces here, the bridge superstructure is tied down onto these V-shaped piers

093

edinburgh (GB)

with a prestressing force of 2× 51 MN (Fig. D). ­Expansion joints are provided at the two abutments only, with the result that the movement at the southern abutment, which is 1,560 m from the fixed point at the middle tower, amounts to 2,270 mm.

F

G 9200

8000 5600

1200

6600

1300

950

1500

1200

1300

3300

7000

3300

5200

1500

950 5176

3922

3922

H

1624

4900

5653

2547

2547

5653

4900

1624

5176

39800

I

J

F horizontal sections of tower at 120 m and 180 m height G cantilever start

094

QUEENSFERRY CROSSING

H section superstructure scale 1:250 I anchorage box of tower

J detail superstructure scale 1:50

CONSTRUCTION While the middle tower was founded on rock ­protruding out of the water, up to 30 m diameter caissons were required for the outer towers and the first anchorage pier on the southern ­approach viaduct. The towers themselves were constructed using internal and external climbing forms in 54 lifts of up to 4 m in height. The inner climbing form was replaced by steel hollow boxes in the area of the cable anchorages. The maximum 16.20 m long steel elements for the superstructure were prefabricated in China and brought to Scotland by sea. The concrete for the top slab supporting the carriageway came from a mixing plant specially set up for the project in the nearby port of Rosyth. An over 80 m tall floating crane installed the first four segments of the superstructure and a temporary working platform along with the two traveller cranes eventually required for the cantilever superstructure construction at each of the three towers. After the concrete deck slab of the starter segments were constructed in situ as a special case, they were attached to the first cables and lifted by the working platform. This was followed by the c ­ yclic process of constructing the cantilever superstructure: the superstructure segments were positioned on pontoons, then lifted ­using the traveller cranes to the installation level, aligned, fixed in place with bolted interlocking plates, welded and then the

cables ­attached. Before stressing the cables the concrete stitches between the segments were cast. The traveller crane then moved forwards to the new front edge of the superstructure to lift the next segment. Just before the final segment filled the gap in the main span, the middle tower had 322 m of superstructure cantilevering to either side, making it the world’s largest structure of this kind. Wind load calculations were very important at this stage of construction. Because the natural frequency periods of the middle tower in the computer model were calculated as greater than 11 s, resonant oscillations and deformations at the end of the superstructure of 0.9 m horizontally and 2.0 m vertically had to be taken into account. Inclined tie-down cables were installed between the superstructure and the foundation to reduce the bending moment in the tower in this condition. The ends of the cantilevering superstructure were brought to the correct level and alignment before the final segment could be installed. The strands of the cables still to be installed at that stage provided the r­ equired 700 t ballast. The last closure segment was put in place in February 2017; the bridge was opened by the Queen on 4 September 2017.

CONSTRUCTION ELEMENTS The superstructure in the length supported by cables is a three-cell composite cross-­ section composed of a 30 m wide steel box beam and 5 m projecting concrete slabs on either side. Four longitudinal webs form the ­central spine, which carries transverse frames at 4.05 m centres. The cables from the middle tower are anchored to the inner side of the two inner webs; the cables from the two outer towers are attached to their outer sides. This offset arrangement allows the cables to be overlapped. The concrete slab at carriageway level is prestressed transversely to prevent cracking due to the centralised cable anchorages and the reduction in torsional stiffness this would otherwise produce. The 202 m and 210 m high towers have an u ­ pwardly tapering reinforced concrete crosssection with a maximum wall thickness of 2.40 m. The cables are anchored by steel h ­ ollow 095

edinburgh (GB)

boxes with shear studs cast compositely into the concrete in the upper part of the towers (Fig. F). A total of 288 inclined cables each ­consist of bundled seven-wire parallel strands. The fewest number of strands in any cable is 45. This is the shortest cable on the middle tower. In contrast, the shortest cables on the two ­outer towers carry the largest loads and are therefore the “thickest” cables with 109 strands. In some cases the loads on the towers, ­cables and superstructure were much greater during construction than after the bridge was complete.

096

queensferry crossing

097

edinburgh (GB)

Architects Bar Orian Architects, Tel Aviv (IL)

Structural engineer Rokach & Ashkenazi Consulting Engineers, Tel Aviv (IL)

Pedestrian Bridge in Be’er Sheva

098

099

415 350 447 515 563 580 563 515 447 369 350 420 380 538 653 415350350369447 515 563 580 563 515 447 369350350415420380380 425538 653 350 369 350 415 380 425 16198 16198

A

754 754

825 825

850 850

825 825

754 754

653 538 425380 380420 653 538 425380 380420

3 3 2 2 1 1

4 4

3 3

5 5

B A elevation scale 1:1250

B plan scale 1:1250

100

Pedestrian Bridge

1 university access 2 access to technology park 3 elevator 4 escalator 5 station

At the heavily used northern railway station of the important desert city of Be’er Sheva in southern Israel, the completion of a 200 m long footbridge provided an important urban infrastructure link. The impressive steel bridge completes a quick pedestrian connection between Ben Gurion University, the station and the new Gav-Yam Negev Technology Park. Moreover, the bridge fulfils all the criteria for a new urban landmark and underlines the image of Be’er Sheva as a well-planned centre for commuters journeying to work from the country’s central region. While the slightly skewed alignment arises from the structure’s urban situation, the ­asymmetric division of the bridge into two u ­ nequal length segments of 70 m and 100 m is in response to the uneven disposition of the tracks below. Both bridge segments are structurally similar, lenticular space trusses and a centrally positioned walkway. The segments have different cross-sections because of their unequal spans, but care was taken to minimise the effect of this on the striking overall impression created by the bridge’s continuously curving contours. Amlis Botsch

101

Be’er sheva (IL)

Text Devan Levin, Rokach & Ashkenazi Consulting Engineers, Tel Aviv (IL) Nir Ovadya, Bar Orian Architects, Tel Aviv (IL)

C

D

C tie-back at bridge walkway end

D static scheme and deflection diagram

102

PEDESTRIAN BRIDGE

EMBLEMATIC STEEL STRUCTURE A system of laterally inclined planar trusses surrounds the walkway of the Be’er Sheva bridge. The trusses of the two unequal-length main spans are not of constant height, varying from 0.6 m at the ends to 7.5 m and 11 m at mid-span respectively. Because of their characteristic ­appearance, these types of structures are called

lenticular trusses. They are very efficient for simply supported girders of this size. Despite the great structurally effective depth at midspan, where the maximum bending moment occurs, they nevertheless possess a visually ­appealing height-length ratio.

STRUCTURAL SYSTEM FOR STATIC EFFECTS The Be’er Sheva bridge is defined by three static systems, corresponding with the three main loading axes. In the vertical direction, the total load is composed of self-weight and live load in a system comprising two independent single-span space trusses resting on hinged bearings. In spite of the continuous truss cords over the middle pier, the spans themselves can be considered as independent because the small cross-section at the pier is flexible in terms of its bending resistance, while the great structural effective depth at mid-span provides much higher bending s­ tiffness. Therefore the support moment and rotational deformation of the middle pier are reduced to a minimum and can be dis­regarded. The largest loads in the longitudinal direction are caused by thermal ­expansion of the bridge. Therefore a statically-­

103

Be’er sheva (IL)

determinate system was selected so that these deformations do not cause additional imposed stresses. Both spans are supported at the bridge ends on steel pinned bearings at the base of the end supports designed to allow ­longitudinal movement. The middle pier is built into its foundation to provide the necessary longitudinal stiffness. Transverse forces from the wind, seismic loads and horizontal live loads are carried by the whole bridge acting as a continuous girder on three separate hinged bearings.

DYNAMIC EFFECTS Long-span steel bridges tend to have a low natural frequency and can easily resonate in response to the footfall frequency of the crossing pedestrians. During the design ­process, the dynamic load behaviour was e ­ xtensively analysed in cooperation with Professor Izhak Sheinman at Technion, the Israel Institute of Technology in Haifa. To reduce the cost of using vibration dampers, the bridge deck was additionally fixed to the supports

2

(1

05

)

30

-6

0(

80

)

1

of the northern escalator. A friction bearing was designed for this task. This bearing resists the ­relatively small dynamic forces but behaves as a sliding bearing to allow slow thermal expansion movements.

-8 5

4

55

3

118

5

30

(-4

15

0)

30

40

5)

104

7

25

(-6 55

61

E

60

6

3

Pedestrian Bridge

5

8

F

2

9 5

4

3

1 10

6

5

11

7

3

8

PRODUCTION AND CONSTRUCTION The varying geometry of the complex space truss, with different cross-sections and distances between the main chords, the changing lengths and connection angles of the cross beams preclude any kind of standardised element. However, the early design of a 3D model allowed the form-finding process to be optimised based on the structural engineering calculations and later permitted paperless, smooth working with the steelwork contractor. The individual components were prefabricated in the factory and preassembled close to the erection site into five segments. After constructing the

E detail typical cross­ section scale 1:50

F detailed section middle pier bearing scale 1:50

105

Be’er sheva (IL)

1 2 3 4

truss chord, welded truss web HEA 200 tensile rod IPE 160

5 6 7 8

middle pier and the two end supports, the ­smaller 230 tonne then the larger 430 tonne segment of the bridge were lifted into position and welded together. This overnight operation interrupted rail traffic for less than 24 hours. ­Following the primary structural elements, the bridge finishings were added, elevators, escalators, walkway lighting, landscaping, etc. The bridge was officially opened in January 2016.

plated beam bamboo deck surface IPE 200 HEA 440

  9 HEA 700 10 middle pier, steel, ­concrete-filled 11 HEA 450

Architects Knight Architects, High Wycombe (GB)

Structural engineer Krebs+Kiefer Ingenieure, Karlsruhe (DE)

Kienlesberg Bridge in Ulm

106

107

70

60

50

elevation, general ­arrangement scale 1:1500

108

Kienlesberg Bridge

40

30

20

10

The city of Ulm has developed a 9 km long tram line to connect the city centre with the “Science City”, a research and education complex in the north-east, founded 30 years ago. The central link in the line is a major new bridge, installed just in the vicinity of the main station. Following a 2012 design competition won by engineers Krebs+Kiefer in a consortium with Knight Architects, the client, Stadtwerke Ulm, initiated the bridge project in an extraordinarily complex construction context: the new bridge had to carry a pedestrian and cycle lane, alongside the two tram tracks over a busy rail intersection run by Deutsche Bahn. In addition, the tram line runs very close to the Albabstieg Tunnel portal currently under construction as part of the Stuttgart–Ulm line. An interdisciplinary cooperation between G ­ erman engineers and British architects has resulted in a bridge which exemplifies how traffic planning, geometric and constructional complaints, as well as the close relationship to the historic Neutor Bridge dating from 1907, can lead to a structure in which construction and design complement each other coherently. Roland Pawlitschko

109

ULM (DE)

Text Jan Akkermann, Krebs+Kiefer Ingenieure, Karlsruhe (DE) Bartlomiej Halaczek, Knight Architects, High Wycombe (GB)

A

B

a

b

c

1500

6000

300 700

4150

4150

4150

4150

800

800

800

2.5 % +4.472400

800 607

700 800

800

800

800

800 607

2400

1750

var. 1750 –1850

var. 1750 –1850

1750

1750

2400 2.5 % +2.47 1700

700

2400

2.5 %

2.5 % +2.47 700

2.5 %

1700 2.5 %

var. 17502.5 –1850 %

var. 1750 2.5 %–1850

1700

700

2.5 % 2450 1450

595 800

1700

1750

2450

800

2.5 % 2.5 %

2.5 %

2.5 %

2000

700

4150

4150

700

5800

2000

700

4150

4150

700

300

300

airtight welded hollowbox girder

B flow of forces on the asymmetric section

900

900

900

300

900

GOK

Kienlesberg Bridge

GOK

300

900

900

1500

300

900

900

300

C cross-section at pier ­supports, scale 1:100

110

2.5 %

5800

airtight welded hollowbox girder

A bending moment diagram for constant girder height (a) for undulating girders (b) as well as idealised structural system (c)

2.5 %

1450

595 800

300 700

center of track

C

6000

center of bridge

1500

center of track

2.5 % +4.47

CONDITIONS AND RESTRAINTS: GEOMETRY AND SITE The horizontal and vertical alignment of the 270 m long crossing were heavily determined by the situation on the ground. The south-east end of the line follows the Neutor Bridge embankment, then curves 30° to the west to make a straight crossing approximately 70 m further down the line. Existing railway tracks made an equidistant or symmetrical placement of supporting piers impossible. The site constraints ­involved an elevated railway track at the low eastern end of the bridge. The clearance envelope here, which is close to the bridge’s soffit,

eventually defined the bridge’s slope as well as its soffit appearance. The pedestrian deck is ­located on the south side of the bridge – facing the historic centre with the famous Minster – which added to the complexity as the cross-­ section would be highly asymmetric (Fig. B).

STRUCTURAL DESIGN: FORM FOLLOWS FUNCTION Early in the design stage it became clear that the bridge had to be longitudinally launched, which ruled out a structure below deck. Instead an asymmetric trough was c ­ hosen, defined by two continuous, longitu­dinal beams which frame the tram envelope. A pedestrian deck is attached to the southern beam as a free cantilever. The main beams undulate in their depth, crudely following the natural bending moment curve of a longitudinal beam. This not only increases transparency, but also creates a visual reference to the Neutor Bridge located just next to the new crossing. Increased spans at the bridge centre and the additional load of the

111

ULM (DE)

4– 6 m wide pedestrian deck resulted in the two main girders of the southern beam having to be significantly deeper. In order to increase transparency, these two girders have been dissolved into two arched trusses which became the focal points of the design (Figs. B, C).

112

Kienlesberg Bridge

113

ULM (DE)

D

E

F

pp. 112–113 Longitudinal displacement with launching nose (red) at grid line 50; ­historic Neutor Bridge in the background

D bridge fitting out with surfacing, overhead contact wires, track construction, guardrails and lighting

E fabrication of main girder consisting of airtight, welded steel hollow box sections

114

Kienlesberg Bridge

F stacked towers at the steel tube bridge piers before lowering

CONSTRUCTION: EVERYTHING HAS ITS PURPOSE The bridge starts at an embankment right at the eastern abutment of the Neutor Bridge. The concrete structure serving as the abutment of the new bridge crosses a service road, therefore it forms a rigid concrete frame counting as span one. From the abutment, the main bridge, a five-span orthotropic steel plate deck is supported on two hollow, airtight welded longitudinal girders. The entire struc-

ture is semi-integral: it sits on four pairs of slender tubular steel columns which are welded to the superstructure and firmly bolted to the pile caps of the foundation providing a rigid, moment transmitting connection in each case (Fig. F).

CONSTRUCTION: PRECISION IN A TIGHT CORNER Assembly took place near the first span on a platform over the railway tracks. The prefabricated superstructure segments were delivered on site, welded into larger sections – including a launching nose – and launched in eleven ­incremental steps. Due to limited vertical space the entire superstructure was assembled 3.5 m above its final position (Fig. pp. 112–113). ­After the launching was complete, the steel bridge was supported on stacked steel billets (Fig. F).

By sequences of lifting the bridge, ­reducing the height of the stack of steel billets and then lowering the bridge, it was possible to arrive at the design levels to allow the bridge superstructure to be finally welded to the tubular pier heads.

AN INTERDISCIPLINARY APPROACH The requirements and restrictions on the ­Kienlesberg Bridge and the need for it to fit in with the urban context all contributed to the specialness of the final structure. Close by and to the west there was the Neutor Bridge, to which the design made explicit reference

115

ULM (DE)

from the very beginning. Architects and engineers worked closely together during the whole design to optimise the structure and the architectural concept of the geometry.

INTESA SANPAOLO HIGH-RISE BLOCK IN TURIN

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MORPHEUS HOTEL IN MACAU

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EXPERIMENTA SCIENCE CENTER IN HEILBRONN

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OODI CENTRAL LIBRARY IN HELSINKI

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ARENA OFFICE BUILDING IN HERZOGENAURACH

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Architects Renzo Piano Building Workshop Genua (IT) / Paris (FR) / New York (US) Studio Inarco, Turin (IT) (Consulting Architects)

Structural engineer Expedition Engineering, London (GB) Studio Ossola, Turin (IT) Studio Tecnico Majowiecki, Bologna (IT) FHECOR Ingenieros ­Consultores, Madrid (ES)

Intesa Sanpaolo H ­ igh-Rise Block in Turin

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At 166 metres, the tower is a distinctive feature in the Turin cityscape in which its height is surpassed only just by the tip of the historic “Mole Antonelliana”, the national film museum. Its brilliant white load-bearing structure – tapering columns connected by diagonal and horizontal ties – appears to shimmer as the ­defining design element through the glazed double facade. Through the close linking with the surrounding public open space, the new seat of one of Italy’s biggest banks becomes part of the daily lives of the city’s inhabitants, promising more than an extravagant expression of the monetary strength of the banking industry: designed specifically with sustain­ability in mind and since awarded the LEED Platinum certificate, the striking structure ­rises from the centre of the newly designed Nicola Grosa Park and sits on a basement of parking garages and utility services rooms, a restaurant and a children’s nursery with 6 an internal courtyard. Slightly inset and with seats for more than 350, a multifunctional auditorium that can be used for public presentations and exhibitions floats above the ground floor area. Twenty-seven 5 7 office floors with north-facing meeting and training rooms extend above this level. A reinforced concrete circulation core to the north end of the floor plate and external steel columns allow open, flexible office 6

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section scale 1:1500

 1 reception   2 circulation core  3 courtyard  4 café   5 meeting room

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Intesa Sanpaolo High-Rise Block

floor layouts oriented to the west and east with plenty of natural light entering the spaces through a slender-framed double facade. The integrated photovoltaic arrays on the southern facade provide a significant contribution to the power required to operate the building – and is only one component of the comprehensive energy strategy, with night cooling and natural ventilation through the ­facade, and the use of ground and rain water. A glazed stair cantilevers from the south elevation and contains climbing plants like a ­conservatory. It filters sunlight and provides a direct connection between the office floors. The tower is topped by a roof pavilion, inspired by the great glasshouses of the 19th century and can be accessed by the general public. This multi-storey roof garden with a restaurant and exhibition area offers a unique view of the Turin Alpine panorama. Andreas Ordon

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Text  Julia Ratcliffe, Expedition Engineering, London (GB)

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STRUCTURAL DESIGN The tower design was conceived in 2006 by Renzo Piano Building Workshop and Expedition Engineering in response to an invited international competition. A fundamental principle of the winning scheme was to lift the main volume of the tower above the ground to ­create a connection between the main street – Corso Inghilterra – and the adjacent public park. This feature was a major influence on the development of the tower’s primary load-bearing frame and stability system. On the basis of this concept, the design team developed a hierarchy of structural elements and detailing. This is legible

from the massive megacolumns to the filigree of the roof-top glasshouse. Each element was carefully developed and tested against aesthetic and functional criteria with the close collaboration of all the designers to ensure the details could be realised to the highest technical standards. The exposed steelwork framing was formed from steel plate for consistency of architectural language throughout the building and to assist with development of complementary connection detailing.

DESIGN AND REINFORCEMENT The east and west elevations feature a braced exoskeleton with three megacolumns spaced 16.5 m apart on each side. The six 175 m high columns ­taper from 2800 × 1970 mm at the second basement ­level, where they are supported on the reinforced concrete substructure, to 700 × 600 mm at the top of the tower. In 2007, the engineers used a forerunner of the Grasshopper software package for the parametric design to a ­ rrive at the geometry of the columns based on single curvature plates. Horizontal bracing struts between the megacolumns at every fourth storey support the outer skin of the double facade. The structure has to withstand lateral wind forces, seismic effects and permanent overturning moments from the ­cantilevering conference rooms on its northern side. It was originally envisaged that the central ­circulation core would also be steel to simplify procurement and construction sequencing. An increase in steel prices during the design period was a prime driver in the decision to change to a reinforced concrete core. This change had the added benefit of i­ncreasing the lateral and torsional stiffness and damping, which led to a reduction in the perceptible accelerations due to lateral wind forces. This meant that there was no longer a need for provision to be made for a high-level tuned mass vibration damper with its associated high cost and space requirements. A major challenge of this comparatively late change was developing models to calculate long-term differential shrinkage and creep of the core relative to the surrounding braced steel structure, and designing modified connection 123

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­ etails and a construction sequence to accomd modate these movements. The office floor slabs are constructed from high-quality exposed prestressed, precast concrete channel units with an insitu concrete topping slab to form 230 mm deep internal voids. The slabs are supported by steel beams between the columns at each floor. Air is naturally drawn through these voids from the east to west elevations through the stack effect of the double-skin facade to take advantage of night cooling in the summer months. The soffits are exposed and detailed for integration with lighting and suspended radiant panels using energy from ground source heat pumps.

TRANSFER TRUSS CONSTRUCTION A 2,350 tonne trussed girder construction spanning in two directions was required to transfer the loads from the internal columns supporting the 27 office floors above the auditorium. This structure spans up to 30 m between the six megacolumns and the core. The 6.5 m deep trussed girders consist of rectangular sections fabricated from high-strength steel plates (up to 120 mm thick) and are located within the equipment room level at the 6th floor. On the south facade, the truss is increased to 20 m deep and contained within the rear wall of the auditorium. Assembled at ground floor level, the truss was lifted using a strand jack system, which was installed on the already completed parts of the megacolumns, and then welded into position in 2012. For the design of the trusses, which transfer the loads from the internal columns of the office floors to the core and megacolumns, the

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engineers worked closely with the construction contractors, steel fabricators and welding specialists to develop connection details including using castings at the intersection of the trusses. The engineering designers used the Rhino software package from the outset as a 3D sketching tool to communicate the structural principles and develop key details with the design team. Geometry exported from these models formed the basis for the first analysis simulations. They were subsequently used in the detailed design and in the global analysis models. Then a series of finite element models of critical elements and connections were used to assess their behaviour. This allowed load concentrations to be identified and located, which was particularly relevant to the transfer truss connections.

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INTESA SANPAOLO HIGH-RISE BLOCK

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THE “SERRA”, CROWNING THE TOWER A naturally ventilated glass roof pavilion offers a public all-season garden with a view over the city and beyond to the Alps. The Serra crowns the tower and reaches 15 m into the air over three levels from a 30 × 30 m square base floor plan. It is constructed from slender welded steel columns and beams. Inspired by Paxton’s 19th century Crystal Palace, it was conceived from the start as an interplay of delicately proportioned components on a regular 1.5 m planning module. The design developed as a system-­ built structure made out of standard components and connection details. The slenderness of the elements was a significant aesthetic criterion: the perimeter columns are no more than 150 mm in depth. Horizontal rod bracing in the walkways and the roof laterally restrain the wall elements, transferring wind and megacolumn ­restraint forces into the supporting base structure through diagonally crossed prestressed high-strength steel rods on the perimeter ele­ vations. The requirements for detailing the paired-plate members were consistently applied to achieve clarity and simplicity using slim

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cross-sections, which required precise and ­meticulous structural engineering analysis. The saw-tooth roof profile allows diffuse north light to enter and is used for ventilation. The roof trusses are integrated into the roof profile and the compact size of the diagonal members ­maximises the indirect daylight. Rainwater is ­collected from the roof and used to water the plants within.

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Architects Zaha Hadid Architects, London (GB) Leigh & Orange, Hong Kong (CN) CAA C ­ ity P ­ lanning & Engineering Consultants, Macau (CN)

Structural engineer Buro Happold Engineering, London (GB)

Morpheus H ­ otel in Macau

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The Morpheus Hotel in Macau, China, is part of the City of Dreams high-rise premier leisure and entertainment complex. In addition to 770 hotel rooms over 40 storeys, it also has r­ etail outlets, bars, restaurants, exhibition and conference rooms as well as a casino and a roof terrace with a large open-air swimming pool. The building is designed as a 160 m high vertical extrusion on a rectangular footprint. The architects integrated a total of three voids into this block similar to the traditional Chinese carved jade, which makes the long, cuboid volume – together with an offset external steel structure, the exoskeleton – an unmistakable and extraordinary building sculpture. In terms of its construction, the hotel consists of two opposing reinforced concrete cores that are linked to one another in the lower and upper storeys as well as

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externally with the ­aluminium panel-clad exoskeleton. This form of construction allows load-bearing walls and columns to be largely dispensed with for the hotel rooms in the area around the core of the building. The central atrium above the entrance hall ­extends upwards between the two cores for almost the whole height of the hotel (Fig. E). Guests can gain the best impression of the space by travelling in one of the twelve glass elevators. From there, the elevator passengers can gaze in wonder at the amorphous transitions between the three voids, look into the hotel’s sculpturesque interiors and experience spectacular panoramic views of the city. Roland Pawlitschko

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Text Wolf Mangelsdorf and Tim Kelly, Buro Happold Engineering, London (GB)

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D diagram of exoskeleton member sizing

E view from the entrance hall upwards into the atrium

EXTERNAL LOAD-BEARING STRUCTURE The characteristic exoskeleton structure, which works in conjunction with two reinforced concrete cores to form the main l­oad-bearing system of the Morpheus Hotel, fulfils an important dual function: it provides the main vertical and horizontal load-bearing elements and ­defines the architecture. Zaha Hadid Architects and the Buro Happold team of facade and structural engineering d ­ esigners cooperated ­intensively to develop this structure. Key considerations during the design ­included the best ways of constructing this form of building, its structural performance

and the opportunities for rationalising the glass ­facade. The architects also wished to avoid the use of visible horizontal ties in the exoskeleton. The Client stipulated that the load-bearing structure should be offset from the facade.

SINGLY CURVED STEELWORK COMPONENTS The designers developed a geometrical solution that allowed the use of only singly curved structural members in the doubly curved central area of the building. This simplified not only the fabrication and erection of the steelwork components but also the detailing at the nodes where members with different geometries meet. The exoskeleton members consist of ­fabricated, hot rolled square hollow sections varying between 700 × 700 × 70 mm (S460) at the base to 350 × 350 × 19 mm (S355) at the top of the building. Steel hollow section stubs pass through the facade to connect the exoskeleton to the floor plates. The latter are formed from hot rolled universal beams acting compositely with a 190 mm thick reinforced concrete slab cast on a profiled metal deck. The beams are positioned on hotel room ­partition lines to maximise the floor-to-ceiling height within the rooms.

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The structure at the two restaurant floors in the central section of the building (levels 21 and 30) consists of a series of trusses spanning 36 m between the two reinforced concrete cores. A similar series of trusses is p ­ rovided at level 39. These work together with the exoskeleton to support the sky pool and hotel suites above the upper void in the central section.

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CONSTRUCTION SEQUENCE Parts of the site contained partially constructed foundations from an earlier planned ­development. The existing piles, which were 2.4 m in diameter and socketed into rock s­ trata up to 35 m below ground level, and the existing 3 m thick pile caps had to be modified and additional 2.8 m diameter piles installed. The concrete cores were constructed ahead of the steel exoskeleton using a jumpform shutter. While the atrium zone and the hotel tower wings could be constructed in a simple bottom-up manner, the central section had to follow a defined and structurally verified construction sequence. This involved a tem­ porary tower that occupied the whole space between the cores. The trusses at levels 21, 30 and 40 in the central section were erected in parallel with the

exoskeleton. The construction sequence was verified using a series of digital models for 30 intermediate construction stages to calculate the magnitude of the locked-in stresses, which were then combined with the in-service design forces for the design of the members and connections. The predicted movements of the building during construction were calculated by Buro Happold and provided to the contractor and fabricator, together with the required structural geometrical presets to counteract predicted elastic and in­ elastic shortening of the structure.

SEAMLESS DIGITAL PROCESSES The structural analysis and design of the structure were carried out in a project-specific, ­fully computerised and seamlessly integrated workflow developed in collaboration by Zaha Hadid Architects and Buro Happold. Rhino /Grasshopper was used for form-finding, Robot / Midas for the structural analysis model and Revit for the drawing production. Connection construction

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Architects  Sauerbruch Hutton, Berlin (DE)

Structural engineer schlaich bergermann ­partner, Stuttgart (DE)

Experimenta Science Center in Heilbronn

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The Experimenta Science Center opened in 2009 in a former warehouse by the River Neckar in Heilbronn, Germany. The objective was to make the natural sciences and technology ­accessible to all the senses for visitors of any age. The popularity of this “world of learning and experience” led to a design competition for an extension being held in 2013. The winning design was by architects Sauerbruch Hutton. With a floor area of about 18,000 m2, it was conceived as a spatial spiral that twists upwards around a central atrium, taking the visitor through a variety of rooms offering selective views of the city and the surrounding vineyards. After passing through the foyer, visitors enter the thematic worlds and studios arranged on each floor via the spiral (Figs. A, B). The studios are located centrally within the 4atrium as glass-enclosed spaces and together form stacked, completely glazed volumes. The flat-roofed, lower part of the new building ­contains a ground-floor restaurant and a two-storey ­science dome comprised of a planetarium and experi4 mental theatre, which is accessible from the lower level. 7 6 7 6

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The new five-storey e ­ xperimenta building is defined structurally by ceiling-height trusses, which are connected through the concrete floor plates to a reinforced concrete core. The triangular facade elements with printed and opaque glass surfaces serve to highlight the structure behind the facade. The visually striking building is composed of casually stacked volumes. The new structure is already a new signature landmark in Heilbronn. It opened in 2019 for the start of the National Garden Show and draws around 250,000 visitors annually. Roland Pawlitschko

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Text Michael Werwigk, schlaich bergermann partner, Stuttgart (DE)

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SCOPE OF WORK The five storeys of the geometrically challenging building have similar, pentagonal floor layouts and are stacked like boxes offset to one another. They each consist of an exhibition area, or “theme world”, and a circulation area serving as a link between storeys as part of a spatial spiral of rooms connecting all floors.

The structural engineering objective was to devise an efficient and effective load-bearing structure for these two main functional elements, which are arranged around a central, vertical circulation core and atrium area.

STRUCTURAL CONCEPT One critical aspect of the flow of forces is that most of the vertical load is transferred between floors at locations through columns where the floors intersect each other. These columns were optimised to be located such that vertical force could be transferred across multiple storeys without lateral deviations (Fig. C). The load-carrying capacity and stiffness of the main trusses were verified early in the design. This allowed the spiral of rooms to be free of intermediate supports, with the exception of the continuous main columns. Furthermore, the main trusses are suspended by tensile elements only, which allowed the facades to be ­entirely transparent with large glazed panels. This aspect of the design had a positive effect on the cost-efficiency and constructability of the steelwork and chimed with the design concept by a ­ llowing panoramic views from the spatial spiral to the countryside. Composite decks with cross-beams at 3 m centres and span lengths up to 15 m are ­arranged around the atrium area and span from the reinforced concrete core and inner trusses to the external walls. This allows the exhibition areas to be free of intermediate supports. The building core transmits vertical loads and offers space for vertical circulation while also providing horizontal stiffness. In the area of the ground floor slab, the composite steel-concrete sup-

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porting structure changes to water-impervious reinforced and prestressed concrete, where the special exhibition areas and technical equipment rooms are located below the water table. Loads are transmitted from there by the locally reinforced and elastically supported slab on grade into the foundation soils. Tensile anchors resist uplift forces.

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Because of the complex geometry of the struc- In addition to the facilitation of structural design ture, it was designed using a 3D model that and the verification of the overall building model, ­parametrically idealised, analysed, materialised, the comprehensive modelling of the structure optimised and finally integrated the ­details into also allowed the analysis of the dynamic behavBIM. All the main elements were ­included in the iour using natural frequency and activated mass 3D model. All elements were visualised for deci- calculations. This showed that the building would not be excited by internal or external oscillatsion-making, checked for collisions, and their data prepared three-dimensionally for manufac- ing loads. This was important for many reasons, including the vibration-sensitive astronomical turing, and then converted for two-dimensional observatory on the roof. design documentation. The complete structure – i.e. in situ-­ concrete basement boxes and composite steel-concrete members – was transferred from the 3D overall model into an FE model with all the structural components and eccentricities (Fig. E). This a ­ ccurate stiffness model was then used to analyse the global stability of the building (e.g. ­uplift, foundations) and to design all the local members that play a part in the overall system. 400 400 400 400 400 The cross-sections were determined by ß ß ß the ­deflection of the large glass facades and ß ß the modularisation members by ß ß ß ß of particular ß ß ß ß ß ß ­mplementing uniform plate thicknesses, rather 400 400 400 than by their ultimate load-bearing ­capacities. 400 400

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DESIGN AND ANALYSIS

Obergurt Fachwerk 2.OG, auskragend

Anschlusslasche, mittig Weiterführung Mantelprofil in Abstimmung mit (Fachwerk 2.OG) Fassadenbefestigung / Fassadenplanung Kreuzsteife t=20 Anschlusslasche, mittig (Fachwerk 2.OG)

Anschlusslasche, mittig (Fachwerk 2.OG)

(Fachwerk 2.OG) Diagonale Fachwerk 2.OG

Kreuzsteife t=20

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1 steel-concrete composite column 2 bottom chord 3 top chord 4 diagonal 5 truss column

H truss joint, deck above 2nd floor, with vertical step and diagonals axonometric section scale 1:50

I truss joint, deck above 1st floor, with vertical step (diagonals not shown) axonometric section, scale 1:50

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J composite beam arrangement

1 top chord 2 reinforced concrete core 3 bottom chord 4 composite beams 5 edge beams

K reinforcement plan L erection sequence

CONSTRUCTION AND DETAILS The design of the joints and connection details was largely influenced by the complex geometry, structural safety and constructability. Transport difficulties precluded pre­ fabrication of complete truss walls. A modular system was developed by detailing the connections so that chords, columns, diagonals and beams could be prefabricated and then erected on site quickly and precisely, to a global accu­ racy of ± 20 mm, accommodating all erection tolerances and free of imposed stresses. In principle, all the loads on horizontal surfaces were picked up as line loads by the edge chords and from there transferred into vertical members, i.e. the structural inner cores of the main columns. This basic joint detail (Fig. H, I) was varied depending on the applied loads, geometry and member cross-sections to create 28 different standard detail groups. The connections of the V-truss diagonals to the chords were moment-transmitting bolted joints (Fig. F), while the chord/column connections were non-moment transmitting bolted plate joints. In a few special cases, the highly loaded diagonals connected to the columns at steep angles and had to be site-welded. The height of the cantilevered wall trusses was based on the height of the upper and lower chords of the main trusses. However, the need to incorporate thermal insulation and waterproofing systems while maintaining an apparent

constant height at the corners required the cantilevering truss walls to be reduced in height by stepping the chords appropriately. The concrete encasement or fire pro­ tection cladding of the columns and beams ­satisfies F 90 requirements. The decks were constructed using in situ concrete on stay-inplace, compositely acting profiled steel formwork panels and d ­ esigned to behave as thermally activated components. Because all the horizontal forces are transmitted by diaphragm action of the deck into the stiffening core, the reinforcement and composite beams were oriented orthogonally to the core (Figs. J, K).

ERECTION SEQUENCE The main reinforced concrete core was constructed first using climbing formwork. The components required for the subsequent connection of the deck beams were cast into the core concrete. Threaded bar couplers and ­rebend connections provided continuity into the deck concrete. The storey-high composite steel construction was assembled from the individual components on site as follows (Fig. L): the diagonals were erected first, then the chords and the edge beams. Then the cross-beams could be installed and the Holorib profiled metal deck placed upon them. Next the layers of reinforcement and thermally activated concrete system pipework were fixed in place and the deck slabs concreted. Decks were cast in alternate halves 147

heilbronn (de)

to allow ongoing erection of the steelwork and concrete operations. Temporary supports, scaffolds and bracing provided lateral and vertical restraint to the trusses during construction as work progressed, until the concrete had achieved the required strength. Erection tolerances and global accuracy were maintained through the use of special filler plate connections and reaming of bolt holes.

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Experimenta Science Center

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Architects ALA Architects, Helsinki (FI)

Structural engineer  Ramboll Finland, Espoo (FI)

Oodi Central Library in Helsinki

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site plan scale 1:10,000 sections scale 1:1,000 floor plans scale 1:1500

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entrance foyer multipurpose hall restaurant cinema group rooms /studios

7 stepped seating 8 child / family zone 9 library

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OODI CENTRAL LIBRARY

7

Helsinki’s new central library lies in the heart of the city, between the parliament building, Töölönlahti bay and the main railway station. The straight rear elevation of the building follows the railway line, which passes quite closely behind it. The sculptural frontage opens o ­ nto Kansalaistori Square. A glazed roof storey with an attractive, undulating ­window wall forms the top of the building. The facade facing the square is clad in spruce boards and twists along its length to create a curved entrance area, seemingly drawn down into the interior of the library. The timber surface, tilted almost to the horizontal, becomes the ceiling of the foyer behind the curving line of the glass facade. A restaurant, cinema and multipurpose hall are intended to entice more of the passing public to enter. Visitors ascend a double spiral staircase set into the glass ­facade or an escalator in the rear part of the building to reach the upper floors. In contrast to the column-free foyer, the whole of the s­ torey above is defined by the building’s structural elements. The size of the rather small, ­enclosed rooms determines their type of use. A curving, stepped sitting area has the timber-clad profiles of the load-bearing structure ­informally superimposed upon it and forms the internal face of the curved facade. The reading room, another space glazed on both sides under an organically curved, white, cloudlike ceiling is found on the more orthogonally laid out roof storey. Circular skylights transition gently into the ceiling surface and contribute to the calm, bright atmosphere of this space, a welcome place of withdrawal from the commercial bustle of the city. A balcony terrace, cantilevering far beyond the western side of the reading room, offers views onto the busy city and creates an inviting, weather-protected forecourt at the edge of the square. Burkhard Franke

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Text Simon de Neumann, Ramboll Finland, Espoo (FI)

A

+14.08 +13.73

+16.100

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A elevation and plan view of the arches scale 1:666

B The two arches in the context of the overall structure: the front arch is 1.6 m wide. The height

C The special box-slab structures at the arch ends with the attachment points for the tendons

D The arches are each supported by five steel truss towers during erection

varies between 1.6 m and 2.4 m. The rear arch has a cross-section 1.2 m wide and a height of between 1.4 m and 1.8 m.

STRUCTURE FOR A COMPLEX SHAPE The new building for the Oodi Library resulted from an international competition, which was won by ALA Architects in 2013. The main characteristics of the design are the open, column-­ free foyer with a curved ceiling and the balcony terrace with the large cantilever towards the west. The structure behaves as a bridge spanning over a future tunnel planned to run directly under the building. The task for the engineers from Ramboll charged with the structural design in 2014 proved to be complex: the space available for the load-bearing structure was quite tight due to the architectural requirements placed on the room-defining surfaces. The structural depth available for the bridge construction at the vertex over the foyer was hardly more than two metres, while the end supports were ­restricted to two relatively small areas. Loads from the upper storeys had to be transferred into the main structural members from over more than two-thirds of the depth of the building. In addition, the balcony, which projects up to almost 14 m beyond the west facade, creates a highly asymmetrical loading pattern. In response to D

155

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these requirements, the engineers devised a system of two outwardly tilted arches with a span of 109 m (Fig. B). The 12.5° tilt of the front arch reduces the ­balcony cantilever, while that of the rear arch at 22.5° minimises the transverse deck span distances. There remained enough room in between them for the feature suspended spiral staircase that defines the foyer. The longitudinal profile of the arches deviates slightly from the ideal line; their cross-sections result from the axial forces and bending moments arising from the imposed loads. Thus the depth of the hollow box profiles varies over their length, with the more heavily loaded front arch also being wider (Fig. A). In order to resist the considerable horizontal forces from the arches, their bases are tied together by 17 tendons designed for a total tensile force of 115 MN and cast into the ground floor slab. The arches and tendons terminate in special box-slab structures made from welded steel plates, which transfer the vertical forces into the foundations (Fig. C).

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Oodi Central Library

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BALANCED SYSTEM The asymmetric system consists of two vertically tilted arches, which take all the vertical loads but have a natural tendency to overturn outwards. For this reason, the arches are connected by 4.50 m deep truss girders at 6 m centres and tied back to the cores in the back of the building, which in turn are tied down to rock. The truss chords support the floor slabs on both upper storeys. Tendons cast into these slabs connect the arches to three reinforced concrete cores in the part of the building to the rear and to two further cores at the building ends. On the outside of the front arch, the truss girders continue as welded I-beam cantilevers and support the balcony. The balcony projects up to 13.50 m in front of the west facade and therefore 17 m in front of the vertex of the arch. In this area specifically, the cantilevers are only 2 m deep and transfer considerable tension and compression forces into the truss girder chords.

The steel construction of the irregularly undulating roof surface forms an independent structure of welded I beams and steel hollow profile columns supported by the arches and truss girders. Bracing is provided at the ends and in the rear area of the building by diagonals. Because some columns are omitted in the area of the arch vertices, the span of the roof girders varies between 12 m and 24 m, and their height also varies accordingly. Pin-jointed, single-span beams mean the roof structure is relatively flexible in order to avoid imposed strains in the roof surface caused by vertical movements of the arch construction.

E

E overall structure of arches with tendons, building cores, truss girders, cantilevers and roof structure

F truss girders before the erection of the cantilever

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G section showing the structural principle

H suspended spiral staircase

I timber-clad diagonals of the steelwork trusses in the second floor

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Dachkonstruktion/ roof structure

Gelenk/ pinned connection pinned connection Zug/ tension tension force Druck/ compression compression force

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tendons in floor slabcantilever balcony

vorderer Bogen/ front arch

hinterer Bogen/

concrete core rear arch

Bodenplatte EG/ ground floor slab

cantilever balcony rear arch

front arch

STB- Konstruktion/ concrete support of arches

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concrete support of arches

helsinki (FI)

I

CONSTRUCTION PROCESS The deformation of the arches and cantilever in relation to the building size is relatively high from a structural design point of view. The vertical deflection of the arches under self-weight and live load is up to 80 mm, while that of the balcony front edge can be as much as 200 mm. So that these components conform with the design geometry when the building is completed, they were designed and manufactured to

6650

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L cantilever during erection

J section through truss girder and cantilever scale 1:100

K axonometric illustration showing the arches, truss girders and cantilevers

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OODI CENTRAL LIBRARY

7100

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16002400 16002400

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have an appropriate precamber. The arches each comprise six 18 m long segments. Each segment was lifted into position by crane and welded on site. In order to be able to continue steelwork erection while the arches were being constructed, temporary steel truss towers with reinforced foundations were erected under the five butt joints of each arch.

flat 16 mm

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MINIMISING RISK THROUGH SIMPLIFICATION The whole structural design process was ­defined by tight cost and time budgets and a mandatory architectural form. The complex arch construction, which was the first of its type, equated to over 40 % of the 2,400 t of steelwork erected and represented not only a considerable part of the material costs but also a challenge for the local construction ­contractors – and therefore a risk factor that could attract a corresponding contract price surcharge. As much simplification as possible became the strategy for the design and fabrication of the arch structures and for the selection of all other components of the whole structure. Therefore, proven components and methods were used, such as orthogonal reinforced concrete cores in the rear part of the building, deck support systems out of ordinary commercially 161

helsinki (FI)

available WQ system steel beams and prestressed concrete hollow-core deck slabs. The trusses connecting the arches run in a flat plane. The hollow box sections of the arches consist of 60 mm thick, flat S355 steel plates, while the flange plates of the front arch are 100 mm thick. The load capacity of the arch is defined exclusively by the size and thickness of the steel plates: plate stiffeners were largely omitted on the grounds of cost. The simplicity of the arch profile in general is in contrast to the complicated individual connections of the truss girders in detail. A digital BIM planning model simplified the design of these connection points, no two of which are the same.

Architects  Behnisch Architekten, S ­ tuttgart (DE)

Structural engineer Werner Sobek, Stuttgart (DE)

Arena Office Building in Herzogenaurach

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163

With two landmark buildings, the Adidas Group has, for the time being, concluded c ­ onstruction on its campus on a former US military base in Herzogenaurach, Germany. Together with an artificial lake, the staff restaurant by Cobe and the adminstration building by Behnisch Architects form the new entrance to the campus as well as a discreet barrier b ­ etween its internal and public areas. The Arena houses some 2100 workplaces as well as the visitor reception and a cafeteria. According to Stefan Behnisch, the idea of a flexible workspace distributed across three floors was based on an analysis of the company’s i­nternal processes. The client also wished for the building to stand out as a clear architectural symbol. This led to the design of a 143 × 118 m cuboid resting on 67 inclined supports. Six inner courtyards bring natural light into the deep upper floors, which seem to hover above the campus landscape. The aluminium brise soleil that covers the building’s four sides looks like a delicate mesh from a distance, but reveals its true dimensions close-up: each of its diamond-shaped openings is about 8 m

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1 4 5 4 “Laces” office building 5 brand centre 6 “Halftime” staff ­restaurant 7 “Arena” office building

location plan of Adidas Campus scale 1:25,000 floor plans scale 1:1500

1 “Spikes” office building (former barracks) 2 fitness centre  /nursery school 3 multi-storey car park

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Arena Office Building

7 6 3

long. In addition to its function as a shading system, which was tested in thermodynamic simulations, the brise soleil mediates between the building scale and the human scale. The ground floor, with the reception, cafeteria and presentation areas, resembles a concrete hill with green embankments and seems more like part of the campus landscape than part of the building. The only elements connecting to the office levels are two concrete access cores and the atrium penetrating all levels, where a sculptural staircase held by steel truss girders leads up from the entrance level to the lowest office level. Two smaller open staircases on ­either side of the main atrium connect the office floors with each other. Jakob Schoof

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Text Angelika Schmid and Roland Bechmann, Werner Sobek, Stuttgart (DE) Norbert ­Sauerborn, Stahl + Verbundbau, Dreieich (DE)

A

B overall section scale 1:1000

A The three upper floors rest on a total of 67 composite steel-concrete

i­nclined columns. The ­columns provide most of the building’s horizontal stiffness.

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Arena Office Building

C schematic drawing of the structural system

FLOATING CUBE AND GREEN HILL The impression of a raised cube above a green landscaped hill, which the architects sought to create for the Adidas Arena, is achieved with a composition of two completely separate structural parts. The ground floor storey is a reinforced concrete structure with a roof planted in some areas and capable of supporting foot traffic. The elevated three-storey main body of the building with office floors, on the other hand, is

a steel hybrid ­construction. The inclined composite steel c ­ olumns supporting the main body penetrate the ground floor ceiling slab without being structurally connected to it.

FLEXIBLE FRAME CONSTRUCTION The load-bearing structure of the office storeys was intended to highlight the lightness of the ­elevated part of the building. The client also called for the layout of the office interior to be open plan without partitioning elements. Other objectives were to optimally integrate the building services equipment and minimise the consumption of steel. To provide as flexible a floor layout as possible, the above-ground storeys are Vierendeel trusses with their verticals in an 8.10 m grid. The three-storey steel structure rests on a total of 67 inclined columns and cantilevers outwards up to 11.5 m beyond the column heads. The ­inclined columns carry most of the vertical and horizontal loads. In contrast, the central reinforced concrete core adds little to the horizontal B

aa

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Druck/Compression Druck/Compression Druck/Compression compression

167

Zug/Tension Zug/Tension Zug/Tension tension

herzogenaurach (de) Gelenk Gelenk Gelenk

stiffness of the building. Only one side of the core is connected horizontally to the floor slabs, while the other side provides only vertical support to the steel structure. Nine vertical openings pass through the Vierendeel construction. They act as light wells; some also provide space for stairs between the floors. The openings contribute significantly to the natural illumination and vertical transparency inside the building.

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1 Ø 813 mm hollow steel-concrete composite columns, narrowing at the ends to Ø 663 mm

2 steel I beam h = 1550 mm 3 HEA 700 steel beam 4 600/600 mm steel box column

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MATERIAL EFFICIENCY AS A DESIGN OBJECTIVE To minimise the number of columns required, the designers investigated many alternatives with different column layouts and grid dimensions using a comprehensive finite element model. As far as the structural design was concerned, the determinant parameters were the maximum permissible deformation along the facade and a minimum of steel in the beams. The main supporting level of the structure of the three-storey cuboid is the grillage of beams underneath the first upper floor, which is also the main service cavity. The floor slab itself is connected to the bottom of the 1.55 m deep main beams, which are welded from plates 35 to 70 mm thick, so that the beams extend 1.19 m above the floor slab (Figs. D, G). 700 mm diameter web openings and top flanges lowered by 415 mm over the middle part of the span allow services pipes and ducts to be routed horizontally. In the top three storeys, the load-bearing structure comprises HEA 700 and HEA 500 sections, which are haunched at the 600 × 600 mm and 300 × 300 mm box columns. Pairs of secondary beams at 2.70 m centres span between the main beams. These secondary beams carry

the 15 cm thick composite floor slab. A tightly meshed grid of pipes cast into the slabs forming the ceilings to the upper storeys allow them to serve as thermally activated components. The beam-to-beam connections were designed to require very few site welds. The deep main beams were generally delivered in two-span segments, which weigh up to 44 t. Their haunched ends were welded onto the columns in the fabrication works. The end-plate connections between the individual beam segments were made on site with prestressed bolts (Fig. D). The joints were detailed for ease of ­installation and form full moment connections. Shim plates accommodate the longitudinal tolerances at the end plate joints.

FIRE PROTECTION WITHOUT CLADDING Although the service cavity and the underside of the floor slab are fitted with a sprinkler system, the steel components have a fire resistance requirement of R90. For the most part, this is achieved with a two-component reactive fire protection system and a top coating. Fire-­ protection cladding or a spray-on, fire-­resistant plaster provides the same fire rating in concealed areas. The secondary beams ­require no fire protection coating, which was justified here using a Cardington design approach for the first time in Germany. The floor slabs within each

E The steel structure is ­exposed in most areas of the office floors.

D view into the main beam level under the 1st floor

The composite steel-­ concrete slabs are supported by ­profiled sheets welded to the I beam webs.

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8.10 × 8.10 m bay were d ­ esigned as a tension membrane inside a peripheral compression ring. The main beams and the slab reinforcement were designed to have adequate load-carrying capacity in the event of a fire and to keep bending deflections below specified limits.

F The design team used pre-deformed finite element models to verify the stability of the haunched beams. A

number of cross-section combinations and forms of buckling were considered in order to cover all situations for each of the 30 beam types.

G section through steel structure (part) scale 1:250

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HIGHLY LOADED: INCLINED COMPOSITE COLUMNS The 15 m long columns carrying the elevated superstructure are arranged in ten groups of four and nine groups of three in a V converging towards their foot (Fig. C). The column bases ­consist of precast reinforced concrete units. These units were set accurately on their foundations, which consist of groups of bored piles, and cast into the 50 cm thick base slab. Highstrength concrete, 150 mm thick steel plates and heavy reinforcement concentrated below the column bases transmit the vertical and horizontal forces into the foundation. At the column heads, thick, stiffened, welded steel plates transfer the loads from the

main beam intersection points (Figs. I, J). The columns were fabricated about 50 mm too short to allow for dimensional tolerances and various deformations of the steelwork grid during construction. These were accommodated after installation by the insertion of shim plates. In addition to the shims, deformable washers compensate for rotations at the bearings. The washers deform under load and therefore transmit ­only normal forces from the office floors to the columns but no eccentricity moments.

PREASSEMBLY AT GROUND LEVEL The steelwork for the elevated storeys was mainly assembled at ground level on around two hundred 2 m high temporary supports and then lifted to a height of 12.5 m on hydraulic jacks (Figs. H, L). The circumstances of the site meant that this method of erection offered several advantages compared to conventional installation at the final height. First of all, the steelwork for the lowest structural level makes up one-third of the total tonnage and involves many site welds. The assembly of all this steelwork was much more efficiently done at ground level than at a height of 12.5 m. In a ­ ddition, the reinforced concrete slab at ground-floor level allowed access for concreting to proceed without interrupting operations on the levels above. A large scaffold would have been required for assembly at 12.5 m height and this would have made work on the ­inclined columns at the same time more or less impossible.

J section through a column head scale 1:30 1 base plate of the cast-in plate 2 connection plate

H preassembly of the upper storeys on 2 m high ­temporary supports

I installation of an inclined column showing the ­column head before ­cladding

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The preassembly of the Vierendeel frame was done in six segments connected only at the end of the assembly into a large single unit. Shrinkage of the concrete slabs and temperature movements of the steel structure would thus only act relatively late on a large, complete structure. The steelwork preassembled at ground level included the main beams of the two lower storeys, the box columns between them and parts of the columns and beams of the two upper storeys. The profiled sheet, reinforcement and concrete were placed in the lowest of the four ceiling slabs before the structure was jacked up.

3 spacer plate 4 shim plates 5 load-distribution plate 6 shim plates as required 7 deformable washer 8 grouted joint

  9 end plate 10 column head plate 11 shear peg 12 temporary clamp (column foot: construction similar but no shim plates)

HOW DO YOU LIFT 12,500 TONNES? In preparation for the lift, the steelwork contractors positioned a total of 76 lifting supports with hydraulic jacks near the inclined column bases on top of the piled foundations (Fig. L). The superstructure weighing 12,500 t at this time was then lifted in 50 cm steps a total of 10.5 m. It took 95 hours to reach the final height. The Vierendeel structure was braced against the main reinforced concrete core of the building during the lift. Two temporary support towers were erected in the light wells and several temporary bracings were used in the structure itself. The lifting supports were tied with diagonal steel cables to the ground to prevent the supports from overturning. The 67 inclined precast columns were installed in their V arrangements after the lift.

K

L

M

M deformation analysis of the lobby staircase on the finite element model for a vibration frequency of 4.6 Hz (1st natural frequency)

K The column heads were welded from below to the underside of the main beams in the factory.

L 76 hydraulic jacks lift the superstructure more than 10 m into the air in less than a week.

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Then the hydraulic jacks were depressurised in a controlled operation and the weight of the structure placed upon the V columns. Only after the structure had been lowered into place could work on the construction of the reinforced concrete ground floor begin. While this was going on, the steelwork for the upper storeys was completed, the profiled sheets were put into position and the remaining three floor slabs were concreted.

THE LOBBY STAIRCASE AS A CENTRAL MEETING PLACE The main staircase in the lobby connects the semi-public entrance area with the working floors on the storeys above. It takes the user up the 13.5 m height difference and spans from the main landing a horizontal distance of about 15 m to the exit from the stairs on the first floor. In order to ensure the staircase construction could be column free, it has two intermediate landings that cantilever up to 4.6 m out from the main reinforced concrete core. In addition, parts of the handrail over these components act as a truss. A particular aspect addressed in the design was the susceptibility of the staircase to vibrations. Excitement of the staircase caused by footfall was possible in principle because of the long spans. Detailed calculations were 173

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necessary to verify the usability of this part of the structure (Fig. M). The analysis showed a first natural frequency of 4.6 Hz. According to relevant literature, footfall traffic does not present a risk of susceptibility to vibrations on a structure with a natural frequency in this range. However, to be on the safe side, the design provided for a possible later installation of tuned-mass dampers. Early use of the staircase confirmed that there was no tendency to vibrate, even when used by large numbers of people.

OBSERVATION TOWER IN BRIGHTON

176

LAUSWARD POWER PLANT IN DÜSSELDORF

184

MEIXI URBAN HELIX IN CHANGSHA

194

VESSEL IN NEW YORK

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THE SHED CULTURAL CENTRE IN NEW YORK

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HERZOGENAURACH (DE)

Architects Marks Barfield Architects, London (GB)

Structural engineer Jacobs UK, Manchester (GB)

Observation Tower in Brighton

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On the line of Brighton’s old West Pier, which burned down in 2003, leaving only a charred steel skeleton to brave the wind and weather, a new symbolic structure opened under the name “British Airways i360” in the southern English coastal city in August 2016: a 162-m-high tower with a diameter of only 3.9 m on which a continuously glazed observation pod moves up and down. The idea for this “vertical pier” between Regency Square and the shingle beach goes back to architects and entrepreneurs David Marks and Julia Barfield, who also conceived the London Eye’s giant wheel at the end of the 1990s and cooperated closely with engineers Jacobs on both projects. The observation pod, which is fitted out with a bar and has an external diameter of about 18 m, travels at a speed of 0.4 m/s and carries up to 200 people to a halt at a height of 138 m. An energy

a

6 5

7 2 4

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5 office 6 exhibition 7 kitchen 8 café

floor plan scale 1:800 section visitor centre scale 1:250

1 tower 2 pod 3 shop 4 event area

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Observation Tower

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8

recovery system ensures that almost half the energy required to ascend the tower is recovered on descent. Not least because of the streamlined pod, the efficient damping system with “sloshing liquid dampers” and the metal cladding to r­ educe horizontal wind forces, visitors can e ­ njoy a safe and com­ fortable ride, even in strong winds. The ascent in the observation pod begins on the roof terrace of the visitor centre, which is situated on the beach promenade and has a lower floor at beach level.  Roland Pawlitschko

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brighton (gb)

Text  John Roberts, Jacobs UK, Manchester (GB)

A SLENDER TOWER MADE FROM 17 STEEL CANS The tower comprises 17 sections (known as “cans” by the team), which are typically either 6 m long (the lower and thicker-walled cans) or 12 m long (the upper and thinner-walled cans). An early design decision was taken by the engineer in consultation with the contractor that the tower would be erected by an unusual “topdown” method, whereby the top section of the tower (erected with a crane at ground level) would be progressively jacked up to allow insertion of the next can down to be carried out close to ground level (and always at the same location). This had significant benefits in terms of erection safety and the achieved accuracy, but brought with it the need for extensive temporary works, ­including a purpose-designed jacking frame that provided lateral stability to the upper sections of the tower as well as verti180

Observation Tower

cal load capacity during each jacking cycle. The cans were fully fitted out with all internal and external parts in the fabricator’s workshop in Rotterdam and then delivered directly to site by a single barge, which landed on the beach immediately adjacent to the works to avoid any need for road transport or double handling. The tower erection was carried out in a very short period of just ten weeks from the day of the beach landing. The achieved verticality was ­extremely impressive: a deviation significantly less than 1/1500 of the height.

FOUNDATIONS The tower foundations are deceptively simple – a square reinforced concrete pad base 24 m × 24 m × 3 m thick. The ground conditions are also relatively simple to describe – about 6 m of beach shingle (coarse gravel with large rounded stones) overlying a stable chalk rock. The physical requirements for a basement below the beach level floor of the visitor centre allowed a “floating” (balanced) foundation to be used. The net effective bearing pressure at the foundation level 6.5 m below ground level is reduced from the pre-construction situation, because while 7200 tonnes of overburden materials were removed during the excavation, only 4150 tonnes of concrete and 1200 tonnes of tower, pod and counterweight have been put back. Therefore, the net effective pressure at foundation level has decreased. The foundations are designed to deal with the maximum wind overturning moment from the worst predicted 50-year storm. The principal foundation issue related to the construction period. The foundation level is well below the tidal water table (the water level follows the tide level on the adjoining beach with a time lag of 2 hours 15 minutes) and both the shingle and the chalk are porous materials, so

A

A first, second and third vibration modes

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BRIGHTON (GB)

there was no possibility of using a “cut-off” wall to isolate the excavation from the water. Therefore, the water table had to be temporarily lowered during construction using a deep well-point dewatering technique, which remained active until the concrete base was cast and cured. The holding-down bolt assembly for the tower had to be placed with great precision due to the number of M85 holding-down bolts, which had little scope for tolerance in movement during the installation of can 1.

B

C movement

wind B manufacture of tower top sloshing liquid damper

movement

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OBSERVATION TOWER

C vortex shedding across the direction of wind flow

SLOSHING LIQUID DAMPERS The tower is very slender, with a height-to-width ratio of over 40:1. As a consequence, it has a very low first mode natural frequency of 0.19 Hz and even the second and third mode natural ­frequencies are low in structural terms at 1.9 Hz and 4.36 Hz respectively. All three frequencies are therefore damped using a total of 76 sloshing liquid dampers ­installed at three locations inside the tower. They are most effective at the point of maximum movement and hence the first mode dampers are at the top; the second mode dampers are at both the top and the double curvature “bulge” position; and the third mode dampers are at the lower triple curvature “bulge” position. Each damper comprises an annular, sealed stainless steel box with internal baffle plates and they are all fitted tightly against the inner wall face of the tower structure. Slosh-

ing liquid dampers are very unusual and were selected here because there was simply not enough physical space to install conventional mass-spring dampers – but they also have a wide band response so they are par­ticularly ­effective here, where the natural f­requency of the tower varies slightly, depending on the position of the pod and the passenger load.

PERFORATED CLADDING While the cladding provides the aesthetic function of concealing from view the tower can joints, the balancing cables (which connect the pod to the counterweight inside the tower) and the electrical busbar system, it ­also has a significant technical function in minimising the possibility of vortex shedding-induced motion of the tower during windy weather. The problem of vortex shedding is, of course, well known to structural engineers; when the vortex shedding frequency at a particular wind speed matches one of the natural frequencies of the tower, ­dynamic amplification can occur and cause large movements or structural damage. The cladding is perforated with a selected voids ratio of approximately 40 %, which ­allows the wind to flow through the surface to an annular void between the tower and the rear

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cladding face. This secondary flow can also flow back out again in zones of l­ower wind pressure. This action interferes with the smooth flow around the perimeter that normally generates vortex shedding, and therefore prevents the vortex shedding “locking on” to the natural ­frequency.

Architects kadawittfeldarchitektur, Aachen (DE)

Structural engineer Bollinger+Grohmann, Frankfurt am Main (DE)

Lausward Power Plant in Düsseldorf

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2 1 1 District heating extraction 2 Turbine hall

sections “City Window” floor plan whole power plant scale 1:1500

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Lausward Power Plant

3 Boiler house 4 “City Window”

Stadtwerke Düsseldorf, the city’s public utility company, operates a modern, highly efficient power plant on its Lausward site, which is surrounded on three sides by the Rhine and lies directly adjacent to existing power plant units. The architectural theme for the new build r­ esulted from a facade design competition held by the city: a series of tall frames form the visible envelope of the whole plant and bring them together to create the overall form. Groups of similarly sized elements make the power plant components beneath legible, while special frames add excitement and rhythm to the elevation. The most prominent and largest element is a stack enclosure, which is glazed on two sides and carries a ­visitor platform at 40 metres above ground. This “City Window” is turned 15° relative to the power plant and therefore provides an ­inner-city vista. The steel-frame structure and thermal envelope of the halls comply with the normal standards applied to power plant construction. Only the outer skin was adapted by the architect and constructed from silver-coloured coated steel structural liner trays. The recessed joints consist of black perforated sheet metal plates with a white refracting surface, which is illuminated from the sides at night by fluorescent tubes. The light-coloured frame with dark joints reverses its look at night and turns into a symbolic light sculpture of vertical bands of light.  Burkhard Franke

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Text Burkhard Franke, Munich (DE)

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A axonometric structure with reinforced concrete core, visitor platforms and “Stator”

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“CITY WINDOW” STRUCTURAL CONCEPT The size and the two glazed main facades of the 60-m-high and 38-m-wide “City Window” ensure it is the most structurally challenging element of the power plant envelope. Buildings that were viewed by the operator as not essential for the functioning of the plant had to be detached from the boiler house and stack. For this reason, a 40-m-high opening was cut in the facade facing the power plant, which is connected to

the boiler house by movement joints only. In ­addition to ten smoke extraction openings, the roof surface has a circular hole for the stack but makes no direct contact with it.

STIFFENING The inside of the rectangular cuboid is mostly empty, with no structural elements providing paths for transferring loads into the foundations. The two glazed main facades also contribute no stiffness to the structure. A northern stairwell core provides north-south stiffening alone, The cross-braced roof and an adjacent full-height steel-frame structure stiffen the main structure torsionally and in the east-west direction.

A 3D structural analysis using the response spectrum method showed that wind was the critical load for the stiffening system in both main axes, but all structural connections were designed to resist earthquake loads.

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VERTICAL LOAD TRANSMISSION All vertical loads are carried by the steel columns and the reinforced concrete core. The structural members above the opening in the facade facing the power plant transfer

their loads through a truss into the flanking columns – with the building corner stiffened by a narrow trussed girder.

“STATOR” A solid wall in front of the glass facade takes up the direction of the power plant again and forms its architectural termination. This component is internally stiffened by cross-bracing. However, the facade columns are relatively flexible in the transverse direction and cannot transfer force

onto the main building body. The “stator” therefore contributes hardly anything to the stiffening system, but influences the building’s dynamic structural behaviour.

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8 240/120 mm welded steel spreader beam HEA 240 steel facade 509  40 60 beam

REINFORCED CONCRETE CORE /  IN-BUILT COM­PONENTS The stairwell core was slip-formed in reinforced concrete. The reinforcement gradually reduces with height. Pockets were left for the prefabricated staircases and landings to be subsequently lifted into place in the stairwell. Connection fittings were precisely cast into the core during the slip-forming process to ­allow connection to the steel facade. This required particular care because the 25-cm-thick wall panels of the core towards the top have only a limited capacity to accom­modate bending moments. After installation, braces and bolts are welded onto connection plates cast into the integrated building components to carry the loads from the beams. The facade beams continue at a distance of approximately 60 cm from the narrow core sides and are each supported at two points on the wall. The beams do not transfer the com-

Vertical section of facade scale 1:20

1 “Stator” facade: facade 30 mm liner; tray system steel sheet t = 1 mm b ­ evelled; 30 mm subconstruction thermally separate; vapour control

192

Lausward Power Plant

membrane; facade system panel; bevelled steel plate with 200 mm mineral wool thermal insulation; IPE 260 mm steel beam

pressive and tensile forces and horizontal forces directly but are bolted to a spreader beam. Each end of the spreader beam has steel plates to transfer compression forces and is held in place by a hook plate. The i­ntermediate spreader beam minimises the ­lever arm in the transfer of the load into the concrete and provides the means of making adjustments during steelwork erection.

2 “City Window” facade: 2× 10 mm laminated safety glass, screenprinted; steel tube in post and beam construction; facade beam: HEA

 40 mm steel profile; 2 ­facade post: HEB 450 mm steel profile

2

1

193

DÜSSELDORF (DE)

Architects KSP Jürgen Engel Architekten, Frankfurt (DE) / Peking (CN)

Structural engineer Weiske + Partner, Stuttgart (DE)

Meixi Urban Helix in Changsha

194

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site plan scale 1:7500

axonometric illustration of the town planning axis, Meixi

section, plan layouts scale 1:1500

196

MEIXI URBAN HELIX

1 longer access bridge 2 information centre and café 3 internal “amphitheatre”

a

A conical, 30-metre-high double helix forms the new landmark of Meixi International New City. This new city development area in Changsha, a metropolis home to seven million people in Hunan, China, offers space for an ecologically pioneering project with districts for residential and business, research and science, and art and culture on an area of 38 km2 around the artificial Meixi Lake. The Meixi ­Urban Helix stands in a highly visible position on a rectangular island at the end of a planned but yet to be realised town planning axis. Visitors can reach the open structure across two bridges, the longer of which connects directly to the external spiral at a height of 10 metres. From here, a six-metre-wide walkway ramp winds around the outside of steel columns a ­ rranged in a crown-like supporting structure, which increases in radius with height to achieve a diameter of 88 metres at its ­highest point. The walkway then transitions smoothly into an internal downward spiral and emerges onto a public plaza after a total developed walkway length of about one kilometre. Housed in a reinforced concrete podium are a café, exhibition space and an information centre. The central internal area resembles an amphitheatre and provides a suitable enclosed setting for all kinds of events. The sole practical function of the sculptural pedestrian walkway is to offer its users a place to stroll and enjoy all-round views onto the lake and across one of the fastest-growing metropolitan areas in the world. Burkhard Franke

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changsha (cn)

Text Ulrich Breuninger, Weiske + Partner, Stuttgart (DE)

A

11.25° 11.25° 11.25° 11.25°

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walkway

walkway

column

column

A geometry comprising circular segments and top section of the walkway

B column crown on a circular foundation

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MEIXI URBAN HELIX

degree of structural utilisation of columns for various connection types and walkway loadings (high loadings in red):

walkway column

C pinned at columns fixed at walkway

D fixed at columns pinned at walkway

E fixed at columns fixed at walkway > final selection

SETTING THE ARCHITECTURAL OBJECTIVES Intensive cooperation between architects and structural engineers, including the German and Chinese design teams in the later design stages, defined the character of this project, which was realised in only five years. The architects developed a shape for the viewing platform in an international competition in 2013. This structure was intended to impress not by its height but rather by an extensive, continuous spiral move-

ment with a diameter that increases with height. The outer walkway of this elegant shape climbs, the inner descends into the structure. In the early stages of design, it was decided that the spiral walkway should be the dominating feature of the exterior of the sculpture, the columns should retreat into the background as much as possible.

STRUCTURAL ENGINEERING CONCEPT

F

From the beginning, the structural engineers considered the spiral as a tube with high bending and torsional stiffnesses. It is supported at its edge at regular intervals on a crown of columns. The columns are loaded only in the direction of their axis so that they can be designed to be as slender as possible. In the competition entry, the regular edge support of the walkway was from two separate series of columns: one for the inner and one for the outer walkway. As the design progressed, the columns were amalgamated into a single series, so that the effects of the eccentricity of the loads from the spirals would largely cancel one another out.

F section scale 1:333

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CHANGSHA (CN)

Geometrically, a circle divided into 32 segments is superimposed on the helix in plan. The columns are positioned at a rotational incremental spacing of 11.25° (Fig. A). The structural depth of the columns in the plane of the crown radius decreases with height, which allows them to carry the cumulative vertical loads efficiently and produce a built-in support effect at their base. A ring beam foundation on large-diameter bored piles carries the vertical loads (Fig. B). The bending moment of the columns is shortcircuited in the ring beam foundation. Horizontal forces from the inclined columns also prestress the ring beam. So the piles only have to bear the vertical load of the columns. The structure is stiffened in the tangential direction by a system of delicately proportioned steel rod bracing between the columns. Their very shallow inclination reduces the horizontal stiffness of the structure and therefore the reaction forces in response to earthquake loading. The stiffness of the connection between the columns and the walkway is particularly important for the overall structural system. Therefore, the structural engineers investigated the effects of pinned and fixed variants for the connection (Figs. C – E). The lowest column loading and therefore the smallest dimensions arose from having a stiff, fixed connection at the column and at the walkway edge.

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section forces diagram (envelopes):

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H vertical and horizontal section of the column connection scale 1:100

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MEIXI URBAN HELIX

I bending moment My

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K torsional moment Mt

STRUCTURAL STEELWORK DESIGN Apart from the base and foundations, the Meixi Urban Helix was designed completely in steel. In the People’s Republic of China, this form of construction presents a challenge to structural engineers, because there are no national standards for special structures designed in steel. There is also a requirement for an external expert commission to check and approve all of the design. For this reason, a local partner office became involved. The walkway and columns are constructed out of welded hollow box sections. Plate projections at the welds were avoided in order to reduce the risk of corrosion at the inner edges and to give the structure its clean lines. The sections of walkway between each pair of columns consist of two segments (Fig. G). The hollow boxes are triangular in cross-section 203

CHANGSHA (CN)

and stiffened by bulkheads and internal welded T-sections. The structural advantages of this triangular shape meant that 15 mm thick plate was adequate for the external skin. A subconstruction supports the timber walking surface and the seats shaped to follow the curve of the spiral. The narrow sides of the columns, which are fabricated from 20 mm thick plate, have a face width of 300 mm. The walkway/column connection detail was designed to be as simple as possible. It consists of an extension of the walkway bulkhead plate at the support point. This plate forms a fixed connection into the hollow box of the column. The 30 mm diameter steel rod bracing between the columns is scarcely visible, except from close up, and therefore does not adversely affect the structure’s clarity of expression.

Architects Heatherwick Studio, London (GB)

Structural engineer AKT II, London (GB) Thornton Tomasetti, New York (US)

Vessel in New York

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Looking like a gigantic inverted beehive, “Vessel” occupies the central public open space in Hudson Yards on the west side of Manhattan. At a height of 46 m, the viewing platform is high enough to give visitors a view over the now partially built-over Long Island Rail Road depot towards the Hudson River. On the other hand, the project is tiny in relation to the skyscrapers with heights of up to 400 m surrounding it. At an estimated total cost of US$25 billion and comprising around a dozen residential and ­office towers, luxury shops and restaurants, a huge arts and cultural centre and access to the High Line Park to the south, Hudson Yards is one of the largest real estate projects in the USA. Against this background, the spectacular publicly accessible sculpture designed by Heatherwick Studio in London was intended to be, among other things, part of the marketing strategy for this newly created district and – in view of its considerable construction cost – could only be financed in this way. In urban planning terms, the Vessel is a landmark in the middle of a square and enhances the public space as an attractive assembly, event and exhibition venue.

location plan scale 1:5000

section, plan view, ground level layout plan scale 1:750

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vessel

From a distance, the perforated structure a ­ ppears initially to consist of multiple kinked horizontal bands that resolve themselves into multi-layered staircases in an arrangement of considerable complexity as the viewer gets closer. Visitors to the staircase sculpture ascend a few steps on a circular base, which ­elegantly conceals the complex foundations, before entering the centre of the structure through openings between the five support points. Those who do not wish to use the l­aboriously designed inclined elevator climb radial staircases to the first intermediate platforms on the outside of the structure. From here s­ ingle flight staircases lead alternately on the inside and outside of the sculpture via 16 intermediate levels up to the five highest platforms. Because the diameter of the sculpture increases with height, the top staircase landings are also the longest. With this sculpture, it is not a matter of climbing to the highest point to gain the best possible view but finding a f­avourite position on its circumference to enjoy not only the view of the surroundings but also onto the astounding geometry of the structure comprising 160 staircases. Burkhard Franke

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Text Albert Williamson-Taylor, Alessandro Margnelli and Edoardo Tibuzzi, AKT II, London (GB)

A

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A basic geometry: diamond grid

B two-layer mantle of stairs and landings

C optimising the structure

D moving the stairs apart creates room for the load-bearing structure

E axonometric illustration of the complete structure

F deformation diagram

G tuned mass damper inside a structural module

H section through the structure scale 1:500

208

VESSEL

GEOMETRY AND FORM In that boundary zone between architecture, art and research, the complex structure of the Vessel translates a parametrically developed ­geometry into a buildable physical structure. The appearance of the barrel-like volume is based on a diamond grid pattern with the ­longitudinal axes of the diamonds running horizontally. This grid forms the basis of a similarly shaped network of staircases and landings (Fig. A). An inner and an outer layer of hori­ zontally linked staircases create a mantle of space in which people can walk in any direction (Fig. B). During the course of the design, the

stairs were moved apart from one another (Fig. D) to create room between them for the actual load-bearing structure: a diagrid shell with honeycombed, six-sided openings from the inside and outside of which the staircases are suspended. In the parametrised 3D model, this three-layer envelope is then transferred to the rotationally symmetrical, downwards-­tapering basic form of the design, whereby the honeycombs become smaller towards the bottom and larger towards the top (Fig. E).

STRUCTURAL CONCEPT

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new york (us)

this is mainly a function of the structure’s geometry. Following analyses of various usage scenarios, the designers opted for the installation of tuned mass dampers (TMD) inside the monocoque structure (Fig. G). They attenuate the movement of the structure’s components with the help of an inertial mass and thus limit the amplitude of the vibrations.

22,850 22,850 H +59,130 +59,130 +55,926 +55,926 +52,722 +52,722 +49,518 +49,518 +46,314 +46,314 +43,288 +43,288

+37,236 +37,236 +34,566 +34,566 +31,540 +31,540 +29,048 +29,048 +26,022 +26,022 +23,708 +23,708 +20,860 +20,860 +18,546 +18,546 +16,410 +16,410

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The diagrid shell carries all the vertical and ­horizontal loads. The welded steel plate struc­ tural members are designed as a monocoque to maximise the efficiency of the six-sided cross-­ section. They can be identified from outside the structure by their black, painted finish. The staircases themselves cantilever radially from this structural layer in both directions and are clad with shiny copper-nickel alloy plates. Attached to the main structure, the staircases increase the stiffness of the shell. This creates a three-part load-bearing cross-section, which takes a more symmetrical form with increasing height (Fig. H). The plate thicknesses increase from 8 mm in the more lightly loaded upper areas to 80 mm near the highly loaded base of the structure. The inclined elevator guide rails are both the geometric seam of the diagrid shell and its structural spine. Therefore, the largest deformations due to static loads occur on the side of the structure opposite the elevator (Fig. F). The crucial factor in the design of the load-bearing system is, however, not self-weight, service or wind load but the dynamic behaviour of a structure that acts like a large spring. Consequently, the main issue in the design was the comfort and safety of the users and not the structural stability of the sculpture. An upper limit to acceleration was introduced to ensure that a feeling of discomfort or even panic does not occur among what could be a group of people rhythmically bouncing whilst attending a concert. Increasing the mass or the stiffness of the structure would have no significant effect on its vibrational behaviour as

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I detailed section of landing at level 15 scale 1:50 FFL = finished floor level TOS = top of steel construction

J typical module butt joint with connection plates scale 1:50

K axonometric illustration of a prefabricated “dog bone” module

L stress diagram at the module butt joint taken from the finite element model

axonometric “dog bone” module:

M top steel plate of monocoque with assembly openings

N inner structure with stiffening plates

O bottom steel plate of monocoque with assembly openings and side cladding

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FABRICATION AND ERECTION To make it possible to fabricate the apparently monolithic structure of the Vessel, it was broken down into 80 similar modules. Each module consists of a middle part with a platform and four half-length staircases branching off it that were later to be butt jointed with their ­respective neighbours. These modules were a double-Y shape, which was nicknamed the “dog bone” (Fig. K). The connections were made with splice plates (Fig. J). Assembly openings allowed access to the bolts from the inside (Figs.  I / M / N / O) and were later sealed with welded or bolted plates.

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The position of the building site directly on the Hudson River allowed supplies to be delivered by ship, including the large modules, which had typical dimensions of 15 × 7 m. All elements were prefabricated in Monfalcone, Italy, and ­arrived prefitted with drainage pipes, electrical cabling and oscillation dampers. Trial connections of the modules took place before transport so as to ensure the high ­accuracy of fit demanded of the connection plates. The components were lifted into position on site by crane and put together like a giant 3D jigsaw puzzle.

Architects Diller Scofidio + Renfro, New York (US) Rockwell Group, New York (US) (Collaborating Architects)

Structural engineer Thornton Tomasetti, New York (US)

The Shed Cultural Centre in New York

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The Shed art and cultural centre opened in the new upmarket Hudson Yards quarter on the west side of Manhattan in April 2019. One of the project’s special features in view of the surrounding luxury real estate is its explicit affordability to all people of the city. Also worthy of note is the building itself. The Shed consists of an eight-storey new build with a steel load-bearing structure physically linked with the neighbouring high-rise also designed by Diller Scofidio + Renfro and Rockwell Group. The new build has exhibition and event areas, galleries, a theatre with rehearsal rooms, a creative laboratory and a rolling shell. The area immediately to the east of the building is the 1860 m2 plaza – an open-air space for concerts, events and performances, which can be completely enveloped by the rolling shell moving on six bogie wheel assemblies powered by 12 electric motors.

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2 a 1 The McCourt 2 gallery 3 foyer 4 rolling shell 5 plaza 6 theatre 7 stage technical area

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4 a

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Inside this shell with 9 m high lifting doors, the plaza becomes a visually, acoustically and thermally isolated space for up to 3000 people (The McCourt) that doubles the floor area of the new build and can be completely darkened. Large, openable facade areas on the east side of the new build allow direct linking of the two spaces – for example by spectator stands partially in the building and partially under the shell. When no events are being held, the ­inverted U-shaped shell in steel and clad with 148 fritted, air-filled ETFE cushions rolls back to nestle around the roof and sides of the new build. Roland Pawlitschko

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Text Scott Lomax, Thornton Tomasetti, New York (US)

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A sketch showing the general structural behaviour of the rolling shell

1 main wall verticals and diagonals form a diagrid 2 transverse section acts as portal frame

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B behaviour of the structure under vertical loads (red: compression, blue: tension)

C behaviour of the structure under wind load (red: compression, blue: tension)

ONE BUILDING, TWO INDEPENDENT STRUCTURES The Shed consists of two completely independent volumes: a fixed steel-braced building and a telescoping outer shell that rolls 35 m out over the adjoining plaza (Fig. A). The 35 m high fixed building has three double-­height galleries and an upper single-­ height floor with skylights. The 30 m clear spans in the galleries are created by 1.6 m deep castellated beams running north-south, with 5 m end cantilevers extending to the north and south facades. The fixed building is a three-sided box stiffened by two elevator cores and diagonally braced frames on the north, south and west sides. The glazed east facade is free of stiffening elements and can be completely opened on the lower two storeys. Glass cable net facades ensure maximum transparency for the north and south sides.

The rolling shell is also designed as a box with three sides: the west side has no structural ­elements, while the walls of the other three sides consist of an exposed steel diagrid. Transverse trusses support the roof and connect the north and south walls. Under the roof is a thea­ trical deck containing the stage equipment (Figs. B, C). The facades and roof are clad with fritted ETFE cushions.

CUSTOMISED STEEL SECTIONS FOR THE ROLLING SHELL The north and south walls of the rolling shell consist of primary and secondary diagonal steel elements. The vertical elements have a constant trapezoidal cross-section over the straight segment and change to tapered sections in the rounded segment at the transition to the roof surface. The diagonals have a tapered cross-­ section with a maximum width at the nodes, which reduces to a minimum section in the middle. As the sections taper, two of the plates are warped in shape. Sections for this part of the structure were ­designed and built up out of individual plates not only to meet the strength and stiffness requirements but also to be visually appealing. They were designed to be thick enough not to require internal longitudinal struts, which would otherwise increase the risk of deformation and telegraphing of welds or internal diaphragms, but thin enough to allow practical fabrication of the warped sections. Steel-framed, 9 m high doors with glass panels make up the lower parts of the north and east facades of the rolling shell and lift vertically to create an open-air event environment. The

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doors are hoisted using a simple cable and winch system, with the winches housed in the theatrical deck area. While the operating system is simple in concept, space limitations led to challenges in routing the cables, deflector sheaves and locating the winches.

DRIVE SYSTEMS AND BOGIES Several systems for moving the shell were investigated. Ultimately a rack-and-pinion drive system with two sleds on the roof of the stationary building was selected. One of the two sleds has an extension boom (Fig. D), which is supported on the roof of the stationary building only in the case of extreme horizontal loads to mobilise the bracing effect of the otherwise structurally independent building. The structure is supported on 6 bogie wheel assemblies with 1.8 m diameter, 250 mm wide wheels rolling on MRS 221 rails at plaza level (Fig. E). Four of these bogies consist of two wheels each and the two most heavily loaded bogies at the eastern end have four wheels. The bogies ride along a pair of rails spaced 1 m apart which form a 83 m long runway. The loads are equally shared over the pair of wheels on each bogie by a gimbal joint. The sled drives are connected via a reaction arm and sliding bearing system to the trusses in the roof of the shell, thus releasing five ­degrees of freedom while allowing only longitudinal forces to be transmitted in the direction of

motion. This linkage mechanism is necessary in order to allow relative movements between the stationary and moving structures in all directions other than in the longitudinal direction of motion. Each sled is powered by six 15 HP electric motors, which drive the pinions through a planetary gear reducer. The dynamic control system and variable speed motors backed up with ­hydraulic reaction blocks control the end stops of the shell, resulting in smooth acceleration and deceleration. It takes five minutes to open or close the 4000 t structure.

PARAMETRIC GEOMETRY MODEL The structural analysis used finite element models. The diagrid form went through several early development cycles and models had to be updated quickly to respond to design changes. A parametric geometry model allowed this. Communications platforms developed by Thornton Tomasetti such as Konstru with scripts

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specially developed for use within Grasshopper meant the designers could perform updates to the analysis models without having to rebuild them on each occasion.

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E exploded drawing of a bogie with two wheels

F conically tapering cladding on the internal sides of the vertical structural elements containing the ventilation ducts

G the wheels of the movement system run on crane rails

H fabrication of a steel node in the factory

I distribution of stress within a structural node of the rolling shell

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J schematic vertical section through a steel node

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K horizontal section through vertical structural element scale 1:50

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ETFE cushion primary construction lifting gate cladding for ventilation ducts

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AUTHORS

226

IMAGE CREDITS

228

PROJECT PARTICIPANTS

229

IMPRINT

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AUTHORS JAN AKKERMANN Jan Akkermann is managing partner at Krebs+Kiefer ­Ingenieure and was involved in the structural design of the Kienlesberg Bridge from the time of the competition.

design at the AKT II consultancy in London and was­ jointly responsible for the construction of the Vessel in THORSTEN HELBIG Thorsten Helbig is managing New York. partner at Knippers Helbig and was jointly responsible CHRISTOPH MAYR Christoph Mayr is an archiwith Boris Peter for the ROLAND BECHMANN tect. His consultancy J2M structural engineering Roland Bechmann is chairArchitekten working with design of the Technology man and partner of the engineers from Bergmeister Center in Chicago. Werner Sobek engineering Ingenieure and &structures OLIVER ENGLHARDT consultancy, which was won the competition for TIM KELLY ­responsible for the structu- Oliver Englhardt is a civil the Isarsteg Nord Bridge in Tim Kelly is a structural engineer. He and his conral engineering design of Freising. design engineer at Buro the Arena office building in sultancy &structures were Happold and was the proresponsible for the structu- ject manager for the consHerzogenaurach. SIMON DE NEUMANN ral engineering design for Simon de Neumann is truction of the Morpheus the Isarsteg Nord Bridge in Hotel. AMLIS BOTSCH an engineer specialising Amlis Botsch studied archi- Freising. in structural steelwork at tecture and worked at the Ramboll in Espoo. He manaDEVAN LEVIN Institute of Building Structu- BURKHARD FRANKE ged the design and consDevan Levin works as a Burkhard Franke is a freeres and Structural Design truction of the steel structucivil engineer at Rokach & lance architect, editor and (ITKE) with Professor Jan re for the Oodi Library. Ashkenazi Engineers and Knippers. He was a freelan- photographer. He is a frewas project manager for ce editor at Detail between quent author of articles for BAS VAN OOIJEN the structural engineering Detail and structure – pub­ design of the Be’er Sheva 2016 and 2019. Bas van Ooijen is a structulished by Detail. ral engineer and was the Bridge. ULRICH BREUNINGER project manager at Grontmij ANDREAS GABRIEL Ulrich Breuninger is mana(now Sweco Netherlands) SCOTT LOMAX Andreas Gabriel, who is ging partner at Weiske + responsible for the structuScott Lomax is a structuPartner structural engineers, an architect with extensive ral engineering design of ral engineer and a senior lectures on composite steel practice experience, was the Central Station in The principal for the engineeconstruction at the Techno- an editor at Detail up to the ring consultancy Thornton Hague. year 2018, where he was logy University of Applied Tomasetti, which was re­involved with the concepSciences Stuttgart (HFT) sponsible for the structural ANDREAS ORDON Andreas Ordon is an tion and implementation and is a certification engiengineering, facade and neer for construction in the of themed pub­lications, ­kinetic design of The Shed. ­architect and works for fields of concrete and steel ­specialist books and new He is also an assistant pro- ­Stollenwerk Architekten. structures. He was respon- journal profiles. From 2014 to 2017, he fessor at the Pratt Institute sible in Germany for the was a freelance editor for and a member of the advistructural engineering MATTHIAS GANDER the maga­zine structure – sory council of the Urban design of the Meixi Urban Matthias Gander is a civil Assembly School of Design published by Detail. engineer. He and his conHelix. and Construction in New sultancy Bergmeister Inge- York. NIR OVADYA nieure were responsible ED CLARK Nir Ovadya was an architect Ed Clark is a director at for the detailed design for with Bar Orian Architects WOLF MANGELSDORF Arup and heads a multi-­ the Isarsteg Nord Bridge in Wolf Mangelsdorf is a and project manager for the disciplinary department for Freising. ­structural engineer at Buro Be‘er Sheva Bridge. Happold and was the project building design in London. partner for the construction ROLAND PAWLITSCHKO In the Coal Drops Yard pro- BARTLOMIEJ ­HALACZEK ject, he led the design team Bartlomiej Halaczek is a civil of the Morpheus Hotel. Roland Pawlitschko is from the concept developengineer and architect and an ­architect as well as an ment stage up to complewas responsible as an asso- ALESSANDRO MARGNELLI author, architecture critic Alessandro Margnelli is tion. ciate at Knight Architects and translator. He has been for the architectural design ­director of engineering and working as a freelance 226

CRISTOBAL CORREA Cristobal Correa is a director at Buro Happold Engineering in New York and was responsible for the structural engineering aspects of the Jewel Changi Airport project. He is also professor for structural ­engineering at the Pratt ­Institute in New York.

APPENDIX

of the Kienlesberg Bridge in Ulm.

editor with the Detail editorial team since 2007. BORIS PETER Boris Peter is managing partner at Knippers Helbig and was jointly responsible with Thorsten Helbig for the structural engineering design of the Technology Center in Chicago. JULIA RATCLIFFE Julia Ratcliffe is a structural engineer and the founder of scale consulting ltd. She was formerly a Director of Expedition Engineering in London and was responsible for leading the structural engineering design team for the Intesa-Sanpaolo tower in Turin. JOHN ROBERTS John Roberts is a structural engineer and director of operations at Jacobs UK in Manchester. He was the chief engineer for the design and construction of the Observation Tower in Brighton. MARTIN ROMBERG Martin Romberg is Corporate Officer and Group ­Manager in the International Bridge Department at Leonhardt, Andrä und Partner in Stuttgart. On the Queensferry Crossing project, his main responsibility was the geometry and installation of the cable and superstructure. KLAAS DE RYCKE Klaas De Rycke is managing director of Bollinger+ Grohmann Sarl in Paris and Brussels and also on the board of Bollinger+ Grohmann Holding AG. He supervised the Quai de la Moselle Sports Hall project in Calais during the competition and design phase. 227

NORBERT SAUERBORN Norbert Sauerborn is co-­ partner and manager of the engineering office at Stahl + Verbundbau in Dreieich, which was involved in the construction of the Arena office building in Herzogenaurach.

management board at schlaich bergermann partner, was the project manager responsible for struc­ tural engineering design and the construction of the Experimenta Science Center from the time of the competition.

ANGELIKA SCHMID Angelika Schmid is an authorised signatory for the Werner Sobek engineering consultancy in Stuttgart and was the project manager for the Arena office building in Herzogenaurach.

ALBERT WILLIAMSON-­ TAYLOR Albert Williamson-Taylor is director of engineering and design at the AKT II consultancy in London and was ­jointly responsible for the construction of the Vessel in New York.

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 building. He also edited the maga­zine structure – pub­ lished by detail. KJELD THOMSEN As managing director of ISC, Kjeld Thomsen was ­responsible for the structural engineering design of the steel superstructure on the Sundsvall motorway bridge. EDOARDO TIBUZZI Edoardo Tibuzzi is director of engineering and design at the AKT II consultancy in London and was jointly responsible for the construction of the Vessel in New York. AGNES WEILANDT Agnes Weilandt is a structural engineer and, as a partner at Bollinger+Grohmann, is responsible for many French projects. MICHAEL WERWIGK Michael Werwigk, who is a member of the extended

AUTHORS

IMAGE CREDITS ROOFS

BRIDGES

BUILDINGS

SPECIAL STRUCTURES

MATMUT ATLANTIQUE STADIUM IN BORDEAUX Page 11, 14 right: Cabinet Jaillet-Rouby Page 12, 18: Iwan Baan Page 13: Iwan Baan /  Herzog & de Meuron Page 14 left, 17 left and centre, 19: Herzog & de Meuron Page 17 right: James Sanders / Herzog & de Meuron

MOTORWAY BRIDGE IN SUNDSVALL Page 71, 78 top, bottom left and centre: Max Bögl Group Page 73, 74: Kasper Dudzik Page 76, 77: ISC Consulting Engineers Page 78 bottom right, 80/81: Torbjörn Bergkvist

INTESA-SANPAOLO HIGHRISE BLOCK IN TURIN Page 119, 124 top right, 125: Michel Denancé Page 121, 122, 126, 127: Enrico Cano 124 top left: Chris Wise / Expedition Engineering Page 124 bottom left: Raphael Petit Page 124 bottom right: Renzo Piano Building Workshop

OBSERVATION TOWER IN BRIGHTON Page 177: Jacobs UK Page 178–182: British Airways i360

CENTRAL RAILWAY STATION IN THE HAGUE Page 21, 24/25, 29: Jannes Linders Page 23, 26: Bart van Hoek

ISARSTEG NORD BRIDGE IN FREISING Page 83, 87 left and centre: J2M Architekten Page 84: Oliver Jaist Page 85, 87 right: Bruno Klomfar

MORPHEUS HOTEL IN MACAU Page 129: Bartosz Kolonko Page 130: Paulo dos Sousa QUEENSFERRY CROSSING Page 131, 134/135: Ivan NEAR EDINBURGH Dupont TECHNOLOGY CENTER Page 89, 94: lukas.kohler@ Page 132: Virgile Simon IN CHICAGO lap-consult.com Bertrand Page 31: McShane Con­ Page 90, 91: Transport Page 136: Zaha Hadid struction, Rosemont (USA) Scotland Architects Page 32–39: Simon Menges Page 92 left, 93, 96/97: PA Images EXPERIMENTA SCIENCE QUAI DE LA MOSELLE Page 92 right: bastian. CENTER IN HEILBRONN SPORTS HALL IN CALAIS [email protected] Page 139, 145 top: Page 41, 47 bottom: faceB Spannverbund Page 43: Maxime Delvaux Page 141, 144, 148/149: PEDESTRIAN BRIDGE Page 44, 47 top: Delphine Jan Bitter IN BE’ER SHEVA Lermite Page 145 bottom: schlaich Page 99, 104: Nir Ovadya Page 47 centre: Jonathan Page 100–103: Amit Geron bergermann partner Alexandre KIENLESBERG BRIDGE OODI CENTRAL LIBRARY COAL DROPS YARD IN ULM IN HELSINKI IN LONDON Page 107, 114 top left and Page 151, 153, 155, 156/157, Page 49, 54 left, 55 right, bottom: Krebs + Kiefer / 159 centre and bottom, 161: 57: John Sturrock /Argent Ilp Knight Architects Tuomas Uusheimo Page 50, 54 right, 55 left: Page 108, 112/113, 114 top Page 154, 159 top: Ramboll John Sturrock right: Wilfried Dechau Page 51: Luke Hayes Page 109: P. Blaha ARENA OFFICE BUILDING Page 55 centre: Arup IN HERZOGENAURACH Page 56: Hufton + Crow Page 163, 168 left, 170, 172: Marc Pfeiffer JEWEL AT CHANGI Page 165, 166, 168 right, AIRPORT IN SINGAPORE 173: David Matthiessen Page 59, 64/65, 66: Jewel Changi Airport Devt. Page 60, 63, 67: Safdie Architects Page 61: Darren Soh

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LAUSWARD POWER PLANT IN DÜSSELDORF Page 185, 190, 191: Bollinger+Grohmann Page 186 top, 187, 188, 192, 193: Jens Kirchner Page 186 bottom: Siemens MEIXI URBAN HELIX IN CHANGSHA Page 195, 198, 203: KSP Jürgen Engel Architekten Page 197, 199–202: Marcus Bredt VESSEL IN NEW YORK Page 205: Cimolai Page 207, 213: Michael Moran for Related Oxford Page 210/211: Getty Images THE SHED CULTURAL CENTRE IN NEW YORK Page 215, 218, 221 centre, 222/223: Iwan Baan, courtesy of The Shed Page 217: Wade Zimmerman Page 221 left: Brett Beyer Page 221 right: Thornton Tomasetti

COVER IMAGE MEIXI URBAN HELIX IN CHANGSHA KSP Jürgen Engel Architekten Unless specified otherwise, all drawings have been supplied by the architects and engineers mentioned in the project texts.

PROJECT PARTICIPANTS ROOFS

BRIDGES

MATMUT ATLANTIQUE STADIUM IN BORDEAUX Architects: Herzog & de Meuron, Basel (CH) Structural engineers: Cabinet Jaillet-Rouby, Orléans (FR) Structures Ile de France, Montrouge (FR) Clients: ADIM Sud-Ouest (Vinci Construction), Mérignac (FR) CPI SOMIFA (Fayat Group), Floirac (FR) Landscape architects: Michel Desvigne Paysagiste, Paris (FR) Main contractor: SOGEA Sud Ouest Hydraulique, Pessac (FR) Castel & Fromaget, Fleurance (FR) GTM Bâtiment Aquitaine, Mérignac (FR) GTM TP GC, Mérignac (FR) Razel-Bec, Orsay (FR) SEG-Fayat, Floirac (FR) CENTRAL RAILWAY STATION IN THE HAGUE Architects: Benthem Crouwel Architects, Amsterdam (NL) Structural engineers: Sweco Nederland, De Bilt (NL) (formerly Grontmij, De Bilt (NL)) Clients: ProRail, Gemeente Den Haag, VROM and Nederlandse Spoorwegen, The Hague (NL) Contractors: Strukton, Maarssen (NL)

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TECHNOLOGY CENTER IN CHICAGO Architects: Barkow Leibinger, Berlin (DE) Structural and facade engineers: Knippers Helbig, New York (US) / Berlin (D) Client: Trumpf Inc, Farmington (US) QUAI DE LA MOSELLE SPORTS HALL IN CALAIS Architects: Bureau faceB, Lille (FR) Structural engineers: Bollinger+Grohmann, Paris (FR) Client: Ville de Calais (FR) Steelwork: BC Metalnord, Téteghem (FR) Groupe Demathieu Bard, Montigny-lès-Metz (FR) COAL DROPS YARD IN LONDON Architects: Heatherwick Studio, London (GB) Detailed design: BAM Design, London (GB) Structural engineers: Arup, London (GB) Client: Argent Group, London (GB) Main contractor: BAM Construction, London (GB) Steelwork: Severfield, Thirsk (GB)

PROJECT PARTICIPANTS

JEWEL AT CHANGI AIRPORT IN SINGAPORE Architects: Safdie Architects, Singapore (SG) Roof structural engineers: Buro Happold Engineering, New York (US) Roof structural engineering and detailed design: RSP Architects Planners & Engineers, Singapore (SG) Client: CapitaMalls Asia Limited and Changi Airport Group, Singapore (SG) Roof structure: Mero-TSK, Würzburg (DE) ETFE cushions: Vector Foiltec, Bremen (DE)

MOTORWAY BRIDGE IN SUNDSVALL Architects: KRAM Group, Stockholm (SE) / Rundquist Arkitekter, Stockholm (SE) Competition: KHR Arkitekter, Copenhagen (DK), Møller & Grønborg, Copenhagen (DK), Rundquist ARchitekter, Stockholm (SE) Detailed design: Rundquist ARchitekter, Stockholm (SE) Structural steelwork design: ISC Consulting Engineers, Copenhagen (DK) Structural concrete design: Centerlöf & Holmberg, Malmö (SE) Client: Trafikverket (Swedish Transport Administration), Sundsvall (SE) Fabrication and erection of steel structure: Max Bögl, Neumarkt Sengenthal (DE) Hydraulic engineering: Strabag / Josef Möbius, Västerås (SE) ISARSTEG NORD BRIDGE IN FREISING Architects: J2M Architekten, Munich (DE) Structural engineers: Bergmeister Ingenieure, Munich (DE) Oliver Englhardt, &structures, Munich (DE) B&C Associati, Como (IT) Client: City of Freising (DE)

BRIDGES (continued) QUEENSFERRY CROSSING NEAR EDINBURGH Design engineering: Jacobs Arup Joint Venture, Edinburgh (GB) Final design: Forth Crossing Design Joint Venture: Leonhardt, Andrä und Partner, Beratende Ingenieure VBI AG, Stuttgart (DE) Ramboll Group A/S, Copenhagen (DK) Ramboll UK Limited, Southampton (GB) Sweco UK, Leeds (GB) Construction: Forth Crossing Bridge Constructors: Hochtief Solutions, Essen (DE) American Bridge International, Coraopolis (US) Dragados, London (GB) Morrison Construction, Edinburgh (GB) Independent design check: URS, Aecom, London (GB) Client: Transport Scotland, Glasgow (GB)

BUILDINGS KIENLESBERG BRIDGE IN ULM Project and structural engineers: Krebs+Kiefer Ingenieure, Karlsruhe (DE) Architectural design: Knight Architects, High Wycombe (GB) Client: SWU Stadtwerke Ulm /­ Neu-Ulm (DE) Erection and detailed design: Klähne Beratende Ingenieure, Berlin (DE) Construction: SEH Engineering, Hanover (DE) Geiger & Schüle Bau, Ulm (DE) Inspection engineer: Dr.-Ing. B.-F. Bornscheuer, Stuttgart (DE)

PEDESTRIAN BRIDGE IN BE’ER SHEVA Architects: Bar Orian Architects, Tel Aviv (IL) Project team: Gidi Bar Orian, Nir Ovadya (project manager), Liat Kraus, Ofri Broza Structural engineers: Rokach & Ashkenazi Consulting Engineers, Tel Aviv (IL) Client: Be’er Sheva Municipality (IL) Landscape designers: Eitan Eden Architects, Tel Aviv (IL) Main contractor: Shura, Caesarea (IL) Steelwork: Adi 2000, Netanya (IL) 230

APPENDIX

INTESA-SANPAOLO HIGHRISE BLOCK IN TURIN Architects: Renzo Piano Building Workshop, Genoa (IT), Paris (FR), New York (US) Studio Inarco (Consulting architects), Turin (IT) Structural engineers: Expedition Engineering, London (GB) Studio Ossola, Turin (IT) Studio Tecnico Majowiecki, Bologna (IT) FHECOR Ingenieros Consultores, Madrid (ES) Client: Intesa Sanpaolo Facade engineers: RFR, Paris (FR) Landscape designers: Atelier Corajoud, Paris (FR) Studio Giorgetta, Milan (IT) Interior architects: Michele De Lucchi, Milan (IT) Pier Luigi Copat Architectures, Paris (FR) Contractors: Rizzani de Eccher, Pozzuolo del Friuli (IT) MORPHEUS HOTEL IN MACAU Zaha Hadid Architects, London (GB) Leigh & Orange (Executive Architect), Hong Kong (CN) CAA City Planning & Engineering Consultants (Local Architects), Macau (CN) Structural engineers: Buro Happold Engineering, London (GB) Client: Melco Resorts & Entertainment, Hong Kong (CN)

EXPERIMENTA SCIENCE CENTER IN HEILBRONN Architects: Sauerbruch Hutton, Berlin (DE) Structural engineers: schlaich bergermann partner, Stuttgart (DE) Client: Schwarz Real Estate, Neckarsulm (DE) Projektsteuerung: Drees & Sommer GmbH, Stuttgart (DE) General Construction Management: Drees & Sommer GmbH, Stuttgart (DE) Steelwork: spannverbund, Waldems-Esch (DE) OODI CENTRAL LIBRARY IN HELSINKI Architects: ALA Architects, Helsinki (FI) Structural engineers: Ramboll Finland, Espoo (FI) Project management: Ramboll CM, Espoo (FI) Client: City of Helsinki (FI) Contractors: YIT, Helsinki (FI) E.M. Pekkinen, Espoo (FI)

SPECIAL STRUCTURES ARENA OFFICE BUILDING IN HERZOGENAURACH Architects: Behnisch Architekten, Stuttgart (DE) Structural engineers: Werner Sobek, Stuttgart (DE) Client: adidas, Herzogenaurach (DE) Landscape architects: LOLA Landscape Architects, Rotterdam (NL) Facade engineers: KuB Fassadentechnik, Schwarzach (AT) Main contractor: Züblin, Stuttgart (DE) Steelwork: ARGE WoS Steelwork: Züblin Stahlbau, Hosena (DE) stahl + verbundbau, Dreieich (DE) Fire safety engineers: Endreß Ingenieurgesellschaft, Ludwigshafen (DE)

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OBSERVATION TOWER IN BRIGHTON Architects: Marks Barfield Architects, London (GB) Structural engineers: Jacobs UK, Manchester (GB) Client: Brighton i360 Ltd, Brighton (GB) Vibration engineering consultant: Prof Max Irvine, Sydney (AU) Observation pod consultant: Nic Bailey Design, Dartmouth (GB) Main contractor: Hollandia Infra, Krimpen aan den IJssel (NL) Observation pod, drive & control: Pomagalski, Voreppe (FR) LAUSWARD POWER PLANT IN DÜSSELDORF Architects: kadawittfeldarchitektur, Aachen (DE) Structural engineers: Bollinger+Grohmann, Frankfurt am Main (DE) Client: Stadtwerke Düsseldorf (DE) Lighting engineers: Andres Lichtplanung, Hamburg (DE) Structural steelwork and metal facades: Züblin Stahlbau, Hosena (DE) Building services and main contractor: Siemens, Erlangen (DE)

PROJECT PARTICIPANTS

MEIXI URBAN HELIX IN CHANGSHA Architects: KSP Jürgen Engel Architekten, Frankfurt (DE) / Beijing (CN) Structural engineers: Weiske + Partner, Stuttgart (DE) Client: Stadt Changsha (CN) VESSEL IN NEW YORK Architects: Heatherwick Studio, London (GB) Construction architects: Kohn Pedersen Fox, New York (US) Structural engineers: AKT II, London (GB) Engineer of record: Thornton Tomasetti, New York (US) Client: Related, Oxford Properties Group, New York (US) Landscape designers: Nelson Byrd Woltz, New York (US) Steelwork: Cimolai, Porcia (IT) THE SHED CULTURAL CENTRE IN NEW YORK Architects: Diller Scofidio + Renfro, New York (US) Partner architects: Rockwell Group, New York (US) Structural, movement system and facade engineers: Thornton Tomasetti, New York (US) Client: The Shed, New York (US) Drive system consultant: Hardesty & Hanover, New York (US) ETFE cushions: Vector Foiltec, Bremen (DE)

IMPRINT EDITOR Jakob Schoof

DESIGN strobo B M (Matthias Friederich, Julian von Klier, Monnier Ostermair)

EDITORIAL TEAM Roland Pawlitschko, Lena Stiller

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

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APPENDIX

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. 

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No other construction material can match steel’s suitability for bridging long spans and realising unusual building geometries. “Slender. High. Long – Steel Structures” documents outstanding buildings and engineering structures in steel. This includes not only bridges, sports facilities, factories and exhibition halls but also administration and cultural buildings, such as the Oodi Central Library in Helsinki, the Adidas Arena in Herzogenaurach and the large-scale, accessible sculpture, Vessel, in New York. In extensive text and detailed drawings, the engineers involved in their design explain the concepts of the steel structures and the solutions they found for realising them.

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