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Prof. Wolfgang Schueller

This presentation will introduce the new generation of structures that has developed primarily during the 1950s to about

1990. It is emphasized that structure is architecture and not just plugged into architectural space. I will concentrate on the

experience of building structures from a visual point of view primarily, as seen through the eyes of a design engineer and

architect, rather than a detailed discussion of structural behavior, refinement of structural performance, or efficient

construction methods. In other words, this lecture will celebrate the joy of structures as architecture and engineering art.

The cases are shown in the context of education as unique solutions, which demonstrate the complexity and creative mind of

designers and express the infinite richness of architectural form.

I like to briefly remind you of the basic position of the structural engineer which often is perceived by architects as a very

narrow one. The structural engineer is responsible for safety, to him the building is a body that is alive, its bones and

muscles are activated by external and internal forces. As it reacts, it deforms and suggests the pain it must endure at

points of stress concentration. The arrangement of space, which defines members and their spans, becomes most important in

controlling the force flow to the foundations and reducing stress concentrations to a minimum. In other words, engineers

visualize buildings in an animated state moving back and forth as can be convincingly expressed by computers through

virtual modeling.

In contrast architects must respond in the design of buildings to the broader issues of the environmental context, be it cultural

or physical. I must emphasize that the theme of my presentation is not addressing the difference between structural engineers

and architects is, but that structure does not only provide support but also can be architecture.

A. Introduction: S T R U C T U R E I S A R C H I T E C T U R E

First I like to remind you that the development of modern building support structures has its origin in the inventive spirit

of structural engineering and the rapid progress in the engineering sciences during the 19th

century, as reflected by:

The enormous volume of the iron-glass structure system of the Crystal Palace in London (1851, Joseph

Paxton), constructed in the short period of only six months.

The longest span of 480m (almost 1600 ft) of the Brooklyn Bridge in New York (1883, John and

Washington Roebling),

The unbelievable height of the 300 m Eifel Tower (nearly 1000 ft) in Paris (1889, Gustave Eifel)

This world of engineering was absorbed into architecture by the early modernists at the beginning of this century. They were

concerned with the articulation of the functional spirit: form follows function, and the honest expression of building

construction by freeing the hidden structure from its imprisonment of the wall, by exposing it.

The full integration of the spirit of structural engineering into architecture happened during the 1950s and early 1960s or so,

i.e. Structure is Architecture. One group of architects even went so far to claim, Architecture is Structure. It was the work

of the pioneer design engineers Maillart, Torroja and Nervi that had a strong impact on the new generation of architectural

designers of the 1950s such as Eero Saarinen, Kenzo Tange, Marcel Breuer, and many others.

The DEVELOPMENT of a NEW LANGUAGE OF STRUCTURES in

ARCHITECTURE

during the second half of the 20th century

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The expression of structures during this era of the 1960s took many directions ranging from the minimal and functional forms

of Mies van der Rohe, Philip Johnson, SOM (Bruce Graham/ Fazlur Khan, Myron Goldsmith), and possibly I.M. Pei, to the

more sculptural forms of Paul Rudolph, Marcel Breuer, Kisho Kurokawa, and B. Goldberg.

Also, during this period, the experimentation with structures, as started by the design engineers of the 19th century, continued

by adding the integration of complex geometry and bionics (i.e. by studying and copying natural systems), especially as

related to minimum weight and surface structures which was brought to a high level of sophistication by Frei Otto,

LeRicolais, Buckminster Fuller, Felix Candela, Heinz Isler, and many others. The space frames, cable structures, prestressed

membranes, and pneumatics skins of the Expos in Montreal (1967) and Osaka (1970) convincingly represent this world of

structural experimentation.

The experimentation with structures is also reflected by the constructivist art of modernism and was first articulated

particularly by the dreams of designers such as by the pioneers Antoine Pevsner and Naum Gabo at the early part of this

century in Russia, and later by Alexander Calder's kinetic art and Kenneth Snelson's tensegrity sculptures.

The early position of architecture as structure is very much reflected by,

Villa Savoye, 1929, Poissy-sur-Seine, France, Le Corbusier; the new aesthetics of modernism is expressed by:

(1) the pilotis or ground-level supporting columns, (2) the flat roof used as living space, (3) the free plan made

possible by elimination of bearing walls, (4) the freely designed facade unrestrained by load-bearing

considerations consisting of thin skin and windows

The early position of architecture as structure is very much reflected by, the drawing of Mies van der Rohe's

52-story, 212-m IBM Tower in Chicago (1973) celebrates the frame and the geometrical order of the grid

the building organization is controlled by the geometry of the 9 x 12 m bays (30 x 40 ft); the mathematical

regularity of the frame layout almost subdues the expression of its structural action. This regular frame layout is

typical for many buildings today because of its simplicity of construction.

This expression of minimal geometry, however, is surely not dated as expressed by the rational, neo-

classicistic Fuji Television Headquarters in Tokyo (1996) , designed by Kenzo Tange more recently. Here

office and media towers are connected by 100 m long sky corridors providing urban spaces and elements such

as small plazas, promenades, staircases, bridges, and terraces at various levels. The mega-framework consists

of Vierendeel steel columns and beams with reinforced concrete that support a 32-m titan covered globe

containing a restaurant.

B. T H E B I R T H O F U N I Q U E S T R U C T U R E S: a period of transition

During the late 1960s and early 1970s or so, architects understood the spirit of the engineering discipline and began to

separate themselves from the predominance of structural engineering thinking. They had matured and developed the

necessary courage to invent their own structures by superimposing upon them other ideas and meanings such as the effect of

context, symbolism, possibly fragmentation in geometry and material. In other words, during this period, also sophisticated

individual structures occurred in response to particular situations quite in contrast to the catalogued structure systems as

identified by numerous types of line diagrams and rules of thumb.

The 22-story, 100-m high, BMW Building in Munich, Germany (1972, Karl Schwanzer) consists of four suspended

cylinders. Here, four central prestressed suspended huge concrete hangers are supported by a post-tensioned

bracket cross at the top that cantilever from the concrete core. Secondary perimeter columns are carried in tension

or compression by story-high radial cantilevers at the mechanical floor level. Cast aluminum cladding is used as

skin.

C. A N E W G E N E R A T I O N O F S T R U C T U R E S: the beginning

C. A N E W G E N E R A T I O N O F S T R U C T U R E S: the beginning

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It was during the time of post-modernism of the late 1970s and early 1980s when the progress of new structural thinking

went unnoticed by most architects in the USA and particularly in architectural education where architectural theory began to

flourish. The potential of those new structures as space makers were not studied; the structures remained hidden and solely

used to do their job as support. In contrast, in Europe the experimentation with structures continued by often brutally

exposing structures and expressing them in a rather animated fashion.

An early example of this new type of structure in the USA is the 59-story, 279-m, 46 m square (152 ft) Citicorp

Building, New York (1977, Stubbins), where the powerful expression of structure unfortunately is hidden behind

the post-modern skin. The renowned structural engineer LeMessurier introduced a new way of thinking about the

building body and structures with his spatial 8-story series of chevron braced stacks which act as 3-dimensional

units. This new breed of megastructure looks so simple but is so complex in behavior. Here, the core acts as an

interior vertical beam with respect to wind within the stacks.

In contrast in Europe, Richard Rogers, in his love for technology exposes in the Lloyd's of London (1978 - 86) the

functioning of the building body by introducing a much freer and exuberantly decorative treatment of the structure

recalling the 1960s plug-in cities of Archigram. In the typical Rogers kit-of-parts fashion, he broke the monotony of

the classic frame and expressed, a piece of machinery with flexible kits, moving parts, a network of ductwork and a

mechanically ventilated cavity faade (i.e. 3 layers of glass). He freely manipulated the form of the concrete skeleton

structure by stepping it at various floor levels and surrounding the braced perimeter concrete frame by six

structurally independent satellite service towers with permanent maintenance cranes located on top of them, while

the internal perimeter columns carry the elaborate 240-ft (about 73 m) high central atrium structure crowned by a

barrel vault.

Naturally, it all started with the 6-story Pompidou Center in Paris (1977) by Piano and Rogers, which introduces a

new generation of structures by exposing its functional layers of structure assembly, stairs, corridors, escalators and

air ducts. Its tension-braced hinged assembly structure is quite opposite in spirit to the conventional rigid

monolithic construction. The basic structure consists of parallel 2.4 m (8-ft) deep Warren truss beams that span c.

45 m (147 ft) across the building to rest on small cantilever beams called gerberettes, which are cast-steel beams

pin connected to interior water-filled cast steel tubular columns and tied down by exterior vertical tension rods. For

the first time cast steel was used to articulate the joints.

University Clinc (Klinikum), Aachen, Germany, 1981, Weber + Brand

D. T H E N E W L A N G U A G E O f S T R U C T U R E S

A new language of structures may be characterized by the breakdown of the building into smaller assemblies, by complex

shapes and geometries, by fractured forms (e.g. fractal mathematics), by hinged assemblies, multi-layered construction, forms

in tension and compression, i.e. buildings have muscles, mixed and hybrid structures, cast metals, lightweight composite

materials, complex spatial geometries, and so on. There is even an indication that certain passive structures may be replaced

eventually by active structures with their own intelligence. We are already quite familiar with smart materials and energy

dissipation systems.

In the following discussion of cases, structures may take three positions, more or less:

The complex hidden structure derived from intricate geometries and not from the nature of the support structure as

convincingly demonstrated in the Guggenheim Museum in Bilbao, Spain, by Frank Gehry (1997). For typical

complex buildings computers find the layout of structures within given boundaries.

The structure as the primary idea of architecture, but not necessarily derived from traditional engineering thinking

of optimization or tectonic expression, but other intentions: architects invent structures - subjectivity and creativity

are introduced in spite of the limits imposed by the rules and physical laws of engineering.

The dialogue (or play) of architecture with structure, or symbolism with tectonics, on a more local scale, possibly as

a leitmotif: architecture as structure detail.

I will present some of those characteristics by addressing:

1) the large scale of the high-rise building

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2) then the smaller and more human scale of lower buildings

3) the effect of the building section, or the columns as space makers

4) achieving the long span through arches and the corresponding effect on space

5) glass-skin structures

6) the final conclusion

D.1 THE LARGE SCALE: highrise buildings

I will proceed first by showing several high-rise buildings that are broken up, hollowed out, lifted up, subdivided into

smaller buildings, placed on top of each other, or by using mega-structures. An early example of this free manipulation

of material space is,

The 21-story bridge-like concrete structure of the Hypobank in Munich, Germany (1981, Walter and Bea Betz),

where the structural concept demonstrates another kind of a new generation of structures. Its shape reminds one of

the metabolist architecture of the 1960s in Japan although somewhat softened by less articulation of tectonics and

through the use of the skin and the lightness of the triangular prisms. Here, four cylindrical towers with a story high

platform at the 11th service level (that consists of three rigidly connected prestressed box-like girders) form an

irregular spatial rigid megaframe. This structure supports 15 stories above and the hanging 6 stories below.

The 43-story, c. 200-m high, Hongkong Bank in Hong Kong (1985, Foster/Arup) is an ikon of the 1980s - it is a

celebration of technology and architecture of science as well of function as art. It expresses the performance of the

building and the movement of people. The stacked bridge-like structure allows opening up of the central space with

vertically stacked atria and diagonal escalator bridges by placing structural towers with elevators and mechanical

modules along the sides of the building. This approach is quite opposite to the central core idea of conventional

high-rise buildings. The support structure is clearly expressed by the clusters of eight towers forming four parallel

megaframes. A megaframe consists of two towers connected by cantilever suspension trusses supporting the

vertical hangers which, in turn, carry the floor beams. Obviously, it was not the intention for the structure to

articulate structural efficiency.

Hiroshi Hara, the architect of the Umeda Sky City, Osaka (1993) called the building with the urban roof and

floating gardens, city in the air. The building expresses postmodern sensibilities, challenging the unity of form by

articulating diversity. The 40-story, 173 m high double-tower (54 m apart) is connected by a huge 2-story 54-m

span roof bridge structure with a large circular sky window. This square platform- bridge (150 m above the

ground) provides urban space and gardens in the air. The human scale is reinforced by a pair of almost floating

escalators, free-standing transparent elevator shafts and staircases, as well as a 6-m wide steel sky bridge that links

the buildings at the 22 level. Although the building required advanced structural engineering especially in

earthquake country, Hara did not express the effort of the support structure; he softened structural engineering by

the finish of reflective glass, polished aluminum plates, undulating surfaces, etc.

The 19-story City Gate in Duesseldorf , Germany (1998, H. Petzinka + Fink Arch./Ove Arup preliminary design of

structure) consists of 80 m towers with the top three floors connected. The space between forms a 58 m (184 ft) tall

atrium with suspended glass curtain facades enclosing the enormous volume. The twisted composition of the

rhombus-like arched building adds a daring futuristic image to the city skyline. Exposed are the two triangular

trussed framed core towers, which clearly give lateral support to the building. These mega-columns are

connected to form three portal frames that is a Z-like bracing system in plan view; they seem to tie the vertical

open atrium space visually together. The support of the mega columns is suggested to the outside through the

transparent glass skin. The steel pipes of the trussed frames are filled with concrete. Not only the futuristic space

atmosphere (which includes air bridges at various levels), but also the highly energy efficient design must be

recognized.

The Commerzbank in Frankfurt, Germany, (1997, Norman Foster/Arup) is with nearly 300 m height the tallest

office building in Europe. It is the world's first ecological (green) high-rise tower, energy efficient and user

friendly. In other words, the goal was an environmentally friendly architecture that is living in harmony with

nature and the integration of innovative concepts of energy conservation. Four-story gardens spiral around the

gently curved triangular plan with a central atrium serving as a natural ventilation chimney. In other words, fresh

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air penetrates the central vertical atrium through the winter gardens to provide natural ventilation. The building

structure consists of the vertical cores at each of the corners of the triangular plan linked and braced along the

perimeter by staggered 8-story Vierendeel frames, which in turn, bridge the 4-story open garden spaces at various

levels that are connected to the central atrium shaft. The steel /concrete structure acts as a perforated tube

providing the necessary lateral and torsional stability.

In contrast, the monumental Tokyo City Hall (1991) by Kenzo Tange is designed in the postmodern style reminding

us of French cathedrals composed with computer chips. The double-tower structure, a 48-story, 243-m high

building consists of 6.4-m supercolumns (i.e. shafts) forming a megaframe. The supercolumn is made up of four

1.02-m steel box columns linked by K-braces. The megacolumns are interconnected by 1-story deep belt trusses at

the 9th, 33rd, and 44th floors. Column-free space is allowed between the super- columns using two-way beam grids

In contrast, the 18-story, 87-m high N.V. Nederlandse Gasunie in Groningen, 1994, Alberts and Van Huut bv, is

more organically shaped. It seems to be the skin, which is constantly in movement under the change of sun and

weather. The slender tall building (1:6.69) consists of load bearing concrete walls anchored front to back by two

nearly 0.5 m thick (20-in.) diaphragm cross walls. The central foyer is spanned by a 3-story, 2-legged A-frame

which carries the central column around which the concrete stair case seems to be suspended and spirals upward

thereby articulating the dynamics of space. This complicated, 3-dimensional structure forms the central vertical

backbone of the building body. The 60-m glass wall in front appears almost like a waterfall; it is carried by an

enormous steel space frame.

D.2 THE HUMAN SCALE: lowrise buildings

The next group of buildings represents smaller scale structures articulating similar concepts as before, such as:

expressing the assembly character together with lateral bracing, or freedom of form giving from traditional construction

possibly resulting in irrational organization of materials and spaces

The Kandel apartment building, Heidenheim, Germany, 1997, Hoefler Arch., appears like several buildings on top

of each other, each one with its own support structure. In other words, the building mass is broken up into different

structures. Notice the red column running diagonally all the way up to the roof relaxing the hierarchy of the support

structure.

The Information Box is a temporary structure at the Potsdamer Platz in Berlin, Germany, 1995, Schneider +

Schumacher; it looks like a container sitting on a forest of columns. The container floats high above the ground

and sits on the inclined exposed steel columns suggesting the building support. The window areas indicate large

open inside spaces.

The dramatic building massing of the Hamburg Ferry and Cruise Ship Terminal (1994, William Alsop/ Ove Arup)

reminds one of shipbuilding construction. The upper building portion and the balcony at the building end are

supported by inclined pylons and tie rods reminiscent of the cranes and derricks along the quay side.

Frank O. Gehry's, three building complex (one is clad in metal, one in plaster, one in brick), Neuer Zollhof (1998)

in Duesseldorf, Germany, looks like an unstable collage. The walls of the center building have a surface whose

shape is much like that of folds of hanging fabric, where the undulating wall is clad in polished stainless steel. It is

an example of how computers are required to deal with the complexity of form in designing and building a

structure. The architect used Catia to model the distorted and twisted faade walls with window boxes sticking out,

which are identical for all three buildings. In contrast to Gehry's Guggenheim Museum in Bilbao where the complex

surfaces were formed by skeletons, which were skinned, in the Neuer Zollhof they were solid concrete walls for the

middle portion of the building group (but for the 13-story tower concrete frame construction with fill-in masonry

walls was used). The walls were constructed from prefab panels (i.e. first Styroform molds, then steel reinforcing

and finally concrete) all different from each other using Computer Aided Manufacturing (CAM). In other words, the

construction of the houses was approached similar to the production of car bodies or airplane wings.

In the Saibu Gas Museum (1989) in Fukuoka, Japan, by Shoei Yoh, 4 floors are suspended from column shafts from

within the building to liberate the ground floor from columns. The design with its central trees articulates an almost

poetic expression of industrial technology.

The School of Architecture at Lyons, France (1989, Jourda and Perraudin) incorporates a variety of structural

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forms and materials including arches, trabeation, cross-vaulting bearing walls, glass skins, and fabric membranes.

The idea of the architecture is derived from the education of architects. It introduces a vocabulary of materials,

details, and construction systems. The building consists of a massive concrete base, an open 2nd floor studio space

covered with a timber framed vaulted structure (i.e. inclined radiating glulam timber struts rising to the roof), a

central spine covered with a light-weight glass structure and cable trusses, and along the outside a fabric membrane

to provide shade. At the junction of the glulam wood members castings are used to articulate the joining between

beams and columns.

Nick Grimshaw clearly expresses the structure of the Sainsbury Supermarket Camden Town, London (1988). The

main parallel 40-m span frames consist of slightly arched roof trusses suspended from tapered cantilever steel

girders, where the flat profiles preclude the benefit from arch action. These girders form the long interior arms of

asymmetrical double cantilever beams supported on concrete-filled stunchions, while the short arms project

outside beyond the wall cladding where the arches are tied down by back-stays that consist of four 50 mm vertical

tension rods.

In contrast, the main structure for the Wilkhahn Factory, Bad Muender, Germany, 1992, by Thomas Herzog Arch.,

is parallel to the faade (i.e. longitudinal); the building integrates function, construction, ecological concern and

architecture. The 5.4 m wide (18 ft) tower structures that contain the offices and service zones, are centered at 30 m

(98 ft) and give support to the long spans of the cable-supported beams (24.6 m/81 ft). The formal configuration

of the cables (1.5 m deep) convincingly reflects the moment flow of continuous beams under gravity load action.

The diagonal bracing of the towers seems to give lateral support to the post-beam timber structure to resist wind

with a minimum effort.

Of exact opposite character is the Vitra Museum, Weil am Rhein, Germany, 1989, where Frank Gehry articulates

complex building bodies and irrational arrangement of shapes together with distorted geometry and construction

cause an exciting space interaction.

In the Palais du Cinema in Paris (1994) Frank Gehry expresses the explosive nature of form and complex

geometry, he articulates volumes that seem to tumble out. The inside of the building is as resolved and eroded as the

outside (inverse of the outside) almost like medieval urban spaces. The intersection of stairs, corridors, openings,

intersecting planes, cause a very dynamic explosive inside space. The complex geometry requires complex

hidden structures.

The Hysolar Institute at the University of Stuttgart, Germany (1988, G. Behnish and Frank Stepper) reflects the

spirit of deconstruction, it looks like a picture puzzle of a building - it is a playful open style of building with

modern light materials. It reflects a play of irregular spaces like a collage using oblique angles causing the structure

to look for order. The building consists of two rows of prefabricated stacked metal containers arranged in some

haphazard twisted fashion, together with a structural framework enclosed with sun collectors. The interior space is

open at the ends and covered by a sloped roof structure. The bent linear element gives the illusion of an arch with

unimportant almost ugly anchorage to the ground.

D.3 THE COLUMN AS SPACE MAKER

The next group of slides addresses the column as space makers, or demonstrates the effect of the

section as a controlling design determinant rather than solely considering the dogma of the

plan. Column types include slender and stocky ones, compression and tensile columns, straight and inclined or branched

columns, but they all are space makers.

The Netherlands Architectural Institute in Rotterdam (1993, Jo Coenen) is clearly divided into several sections.

The concrete skeleton dominates the image supplemented by steel and glass. The main glazed structure appears to

be suspended, and allows the concrete load-bearing structure behind to be seen. The high, free-standing support

pillars and the wide-cantilevered roof appear more in a symbolic manner rather as support systems.

Art Museum, Wolfsburg, Germany, 1993, Peter Schweger Arch.: the building floats into space. The building is

laid out on an approximately 8.10 x 8.10 m (27 x 27 ft) grid and is further subdivided into 1.35 m square bays. The

plaza seems to reach/move into the building - the building is naturally grown allowing the interaction of building

and urban space, where the diagonal access ramps/stairs forming the connecting element (i.e. entrance at building

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corner). The interaction of the building is especially articulated by the thin cantilevering roof at 19 m (62 ft) height

carried by the slender columns. The building gives a feeling of openness and and permeability. The logic of

construction, transparency, lightness, quality of detail all transmit a sense of clarity (i.e. no deliberate confusion as

in some of the other cases).

Axel Schultes, the architect for the City Museum, Bonn, Germany (1992) calls the building the house of light. The

curved flat roof sits on a forest of irregularly arranged columns. The grouped columns seem almost to generate a

human quality in articulating space rather than supporting the roof, the columns seem to penetrate through the roof.

The 300-m long oval-shaped Grand Palais, Lille (1995, Rem Koolhaas/ Ove Arup for structures), is divided into

concert hall, conference center, and exhibition halls. Koolhaas uses exposed concrete surfaces and a great deal of

plywood and plastic to reduce the costs. The combination of unusual materials and unexpected angles seem to

reflect an anti-poetic mood (a punk-like aesthetics) and redundancy of structure. The structure takes the place

of language and reflects only the illusion of support (e.g. arch vs. columns, and hanging columns or tension ties to

reduce bending moment at center span). Notice the stairs as an important architectural element.

For the multi-bay structure of the shopping center near Nantes, France (1988, Rogers/Rice) 94-ft (29 m) high

tubular masts, spaced at 47 ft (14 m), support the roof framework in a spatial fashion from above without

penetration of the roof. Only certain combinations of the 3-dimensional network of rods and struts are activated

under various load actions. Under wind uplift, the tensile rod-strut system forms an inverted V-shaped truss.

An example of the early period is the Patscenter in Princeton, USA (1984, Rogers/Rice).The building consists of

parallel planar guyed structures along the central spine consisting of c.9 m wide portal frames set 11 m on center

that support on top c.15-m high A-frames which consist of inclined pipe columns connected to a large ring plate

from which are suspended steel rods to other ring plates on each side of the spine. Inverted truss action is required

for wind uplift where the central hangers act in compression, hence had to be tubes.

The immense, c.153-m span roof of the beautiful Lufthansa Hangar at the Munich Airport, Guenter Buechl + Fred

Angerer Arch., 1992, is supported by the diagonal cables suspended from the c.56-m tall concrete pylons

The Renault Center, Swindon, U.K. (1983) by Norman Foster and Ove Arup is a spatially guyed structure. Truss-

like portal frames are placed along the 24 x 24-m (79-x79-ft) square bays, but also along the diagonal directions.

Rods are suspended from the top of the 16-m (53-ft) high tubular steel masts in the orthogonal and diagonal

directions to support the tapered portal beams at their quarter points. In the center portion the sloped beams are

cable-supported from below. The cable configuration follows the moment diagram of a multi-bay portal

frame with hinged basis under uniform gravity loading by efficiently resolving the moment into compressive

and tensile forces. The slender tubular columns are laterally braced with four prestressed rods that are connected to

their sloped beams thereby providing a moment connection.

Whereas before, the cables supported a rigid cylindrical roof structure, in the Schlumberger Research Center,

Cambridge, UK (1985, Hopkins/Hunt) it is a spatial domelike undulating tensile fabric membrane. The ship like

masts and rigging as well as its high level technology and detailing reminds one of Roger's earlier work. The central

portion of the building is subdivided by four parallel exposed portal steel frames into three bays, each 24 x 18 m (79

x 59 ft) in size. It consists of horizontal 24-m (79-ft) open triangulated truss girders and nearly 8-ft (c.2.5 m) wide

vertical trusses which support two pairs of upper and lower booms. The two inclined upper tubular masts are

supported by tie rods, which are braced by lower masts (struts). Cables are suspended from the masts to give

support to two parallel ridge cables at certain pick-up points. The translucent Teflon coated fiberglass membrane is

clamped and stretched between ridge cables and steel work.

Quite different in spirit are the slender and minimal abstract planar, tree-like c.30-m (100-ft) high masts for the

Horst Korber Sports Center in Berlin, Germany (1990, Christoph Langhof) with their five branches linked by

cables from which the light cable roof trusses are hung but only on one side (i.e. asymmetry). The symmetrical

abstract forms of the masts are completely opposite in expression from the tectonic shapes of most of the other

examples which have been shown, they don't seem to give support.

The huge steel trees of the Stuttgart Airport Terminal, Stuttgart, Germany (1991, von Gerkan & Marg) with their

spatial strut work of slender branches give a continuous arched support to the roof structure thereby eliminating the

separation between column and slab. The tree columns put tension on the roof plate and compression in the

branches; they are spaced on a grid of about 21 x 32 m (70 x 106 ft).

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D.4 THE TECTONICS OF CONSTRUCTION

The tectonic organic world of structural resistance has become quite fashionable especially with the architect/engineer

Santiago Calatrava. He is fascinated with how the structure works and how the loads are carried to the ground which he

demonstrates by articulating its tactile quality and the organic nature of the skeleton comprised of sculptural, bony-shaped

elements asymmetrically arranged. He is concerned with the logic of material and the beauty of the section, he emphasizes the

dynamics of structure by making the potential movement of forces visible. He achieves that by expressing the unbalance of

forces.

The supporting cantilever frames of the glazed canopy structure of the Stadelhofen Station, Zurich, Switzerland

(1990, Santiago Calatrava) capture movement. The columns seem to be just caught in time by the vertical struts. In

other words, it seems as if the cantilevers are on the verge of rotating by articulating the hinge like tubular beam and

by letting the slanted columns be just caught on time by the vertical struts. They are surely influenced by

biological forms where the steel profile of the tapering members suggests a tectonic presence, frozen suspension

and almost organic joints. The sword-like steel plates of the cantilever beams carry the glass roof and are welded to

a continuous 12 cm (5 in.) dia. steel tube that acts as a beam and torsion ring to transfer the loads to the inclined,

branching Y-columns of triangular cross-section which, in turn, are stabilized by vertical hinged pendulum

columns. The 2-legged composite columns are spaced at almost 6 m (20 ft).

The Public Library in Munster, Germany (1993, Bolles + Wilson) is divided into two sections connected by a

bridge. The asymmetrical, inverse A-frame not only carries the sculptured roof structure but also provides a

vigorous energy and dynamics to the urban space.

The grandstand of the Charlety Stadium at the Cite Universitaire in Paris (1994, Henri and Bruno Gaudin) is

brought alive by its organic and tectonic presence. From the highly articulated slanted concrete buttress piers is

cantilevered the stayed steel canopy on top and the upper seating below. The play between tension and

compression, between force resolution at the joints and stress concentrations in the members is forcefully

articulated. From the inclined, 50-m high corner light masts at the lower level a conical Teflon membrane is

suspended to give lateral protection to the grandstand.

D.5 SPANNING SPACES WITH ARCHES

This collage type visual study introduces the next theme that of the structure as span, in this case achieved through the

arch; it attempts to articulate the spirit of the support structure resisting lateral thrust, in other words the tectonics of

construction.

This collage type visual study introduces the next theme that of the structure as span, in this case achieved through

the arch; it attempts to articulate the spirit of the support structure resisting lateral thrust, in other words the

tectonics of construction.

The lateral thrust

The curved roof of the Kansai Air Terminal (1994) by Renzo Piano (and Peter Rice for structures) spreads over an

artificial island like a glider. The irregular roof curve consisting of arcs of different radii, is shaped by the

aerodynamics of the large-scale air jets ventilating the whole space, that is the regulation of air movement.

The three-dimensional, triangular truss-arches span 83 m and have a total length of 150 m each is supported by

inclining columns and by vertical columns at the curb; the arches seem barely connected the building.

The column supports at the Novotel Belfort, Belfort, France (1994, Bouchez), almost seem human and express how

effortless the arch action is transferred down to the ground.

The visually dominant arches of the new Leipzig Fair, Leipzig, Germany, 1996, (van Gerkan+Marg Arch, Ian

Ritchie Arch. for glazing, Polonyi Struct. Eng.), make a strong statement and remind one of the glass and iron

architecture of the 19th

century (e.g. Crystal Palace, Galerie des Machines in Paris, 1889). The hall is about 243 m

long, has a clear span of 80 m (262 ft), and 30 m (98 ft) up to the vertex. The primary system consists of the

trussed triangular arches that contain a service walkway, and where the top chords span across the adjacent

service roads. The sole purpose of the arches is to give lateral support to the tubular steel grid vault through its steel

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outriggers. The depth of the arches varies from 4 m at the crown to 10 m at the ground. The steel grid vault is

formed by 3.125 x 3.125 m (appr.10 x 10 ft) cells, from which is suspended by frog fingers the glass vault beneath.

The glass panes are approximately 3.1 x 1.5 m and are joined with silicone. It is the largest suspended glass shell in

existence today.

Oguni Glass Station, Kumamoto Pref., 1993, Shoi Yoh Arch., is a small gas and service station covered with a

unique glass canopy suspended from arched concrete frames. The thin glass membrane of glass plates with an

inlayed layer of perforated aluminum sheet comes alive with sparkling brilliance when the sun shines through it.

The 100-m span tied arch Japan Bridge in Paris (199 , Kisho Kurokawa) consists of the two main inward leaning

tubular steel arches, the walkway of triangular precast concrete panels covered by a curved glass enclosure, and the

support of the arched spatial cable-strut network. The walkway and glass enclosure are suspended from the

arches. The lateral arch thrust is taken by the cable-strut network at the base. Torsion due to lateral loads is

efficiently resisted by the triangular cross-section of the bridge (i.e. torsion box).

Kempinski Hotel, Munich, Germany, 1997, H. Jahn/Schlaich: the elegance and lightness of the the 40-m (135-ft)

span glass and steel lattice roof is articulated through the transparency of roof skin and the almost non-existence of

the diagonal arches which are cable- supported by a single post at their intersection at center span. This new

technology features construction with its own aesthetics reflecting a play between artistic, architectural

mathematical, and engineering worlds. The depth of the box arches is reduced by the central compression strut

(flying column) carried by the suspended tension rods. The arches, in turn, are supported by tubular trusses on each

side, which separate the roof from the buildings.

The Munich Airport Business Center, Munich, Germany, 1997, Helmut Jahn Arch.: also is an open public atrium

as transition between building blocks or walled boundaries to form a square which is covered by 6 arch-supported

membrane leaves. In other words, a transparent roof is carried by spatial triangular column frames. Here a minimum

of structure gives a strong identity to space.

The Satolas Airport TGV Train Station, Lyons, France (1995, Santiago Calatrava) consists of the big entrance hall

and the long naves. The 40-m high (131-ft), 100-m wide, 120-m long entrance hall appears like a huge sculpture

reminding us of a bird or butterfly that has a triangular plan with asymmetrical cantilevers. Here, the central spine is

a 90-m (295-ft) span 3-dimensional arched torsion ring steel truss with a variable triangular cross-section where

the two tubular bottom chord arches are anchored in immense single-fluted concrete thrust blocks or buttresses (one

in front and two at the buildings rear) that look like animated. Steel ribs laterally brace the huge curtain wall box

columns, which also carry most of the cantilever wing weight. The columns, in turn, rest on massive concrete arches

on each side, which carry most of the building weight. The bird consist of 1300 tons of steel resting on the two

concrete arches. The heavy closely set black steel members seem over structured because of the density of the

layout. The oversized members obscure the relationship between the structure of the roof and the support of the

glazing.

The long naves over the 3-bay track level are covered by 53-m (174-ft) wide lamella vaults of slender ribs on a c.

9-m (30-ft) structural bay. Each of the three vault segments rests on the apex of two triangular concrete supports

(i.e. the side walls are rows of multi-faceted V- shaped concrete columns). The middle tracks are for through trains

that move over 300 km/h requiring careful calculations of shock waves. The thrust of the vault at the middle

segment is released by the box at the core, i.e. the triangular supports at the middle part of the vault are tied together

at lower level creating an enclosed box tunnel at the core of the station.

The lattice like barrel vaults can also be visualized as diagonally intersecting two-way arches, or almost like a

triangular folded plate membrane with a maximum of material removed, leaving only folds. The roof panels are

either glazed (clear), opaque (concrete panels) or left open, creating defused light and mystical spatial qualities. The

wings are clad in reflected aluminum. The long naves represent a spectacular vaulted space, airy, translucent, with

an effortless organic fluidity and lightness.

How opposite in spirit is the delicate roof structure of the Lille Euro Station, Lille, France (1994, Jean-Marie

Duthilleul/ Peter Rice) consists of two asymmetrical transverse slender tubular steel arches (27 cm or 10.75-in dia.,

set at about 12 m or 40 ft on center) braced against buckling by deceitfully disorganized ties and rods; this graceful

and light structure, in harmony with the intimate space, was not supposed to look right. A series of slender tubes are

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supported on arches which, in turn, carry the approximately 1.8-m or 6-ft deep longitudinal cable trusses that

support the undulating metal roof. The support structure allowed the gently curved roof almost to float or to free it

from its support, emphasizing the quality of light.

D.6 GLASS STRUCTURES

The next topic addresses briefly glass-skin structures, or glass as a structural material, where many of them are tension

supported. Here the tensile glazing support structure becomes part of the glass skin; the traditional nonstructural members of

glass and sash become structural. Special, non-conventional details are used as based on forging, casting, and machining

steel. The glass weight is transferred across star-shaped (e.g. H-,or X-shaped) castings to vertical tension rods or each panel

is hung directly from the next panel above. Vertical or horizontal cable-truss systems give lateral support to the glass wall.

The glass panels are glued together with silicone which makes them quite rigid so that racking movement is allowed in the

sliding of the bolt connections to the star-shaped castings. Some typical examples are:

Shopping Center Dalian, China

The development of suspended glass skins has been significantly influenced by the glass walls for the three

monumental greenhouses equivalent to a 10-story building that are attached to the south side of the Museum of

Science and Technology, Parc de la Villette, Paris (1986, Fainsilber/Rice). The tower like structures are about 32

m wide by 32 m high and 15 m deep. They capture and store heat for the museum. The glass wall is subdivided

into 16 approximately 8-m square (27-ft) modules, which form the basis for the primary stainless steel tubular

frame which is laterally supported against wind by cable trusses. Each of the 8-m (27-ft) square modules consists of

sixteen 2-m square glass sheets laterally supported by a secondary system of horizontal cable beams (tension

mullions), which are stabilized by the glass. The glass panels are suspended from the main frame. They are attached

to each other with clear silicone sealant and are joined at the corners by a molded steel fixing that allows movement

and reduces stress concentrations. The glass weight is transferred in tension from the lower to the upper panels and

is hung from the main frame beam by prestressed spring devices that act as shock absorbers and allow

readjustment in case of unusual loading.

The composition and materials of the massive skeletal support structure for the glass houses in the Parc Andr-

Citron, Paris (1992, Patrick Berger/ Peter Rice) remind one of the past in contrast to the language of the minimal

glass walls. The 15-m high portal frames are cladded in wood and stone (spaced at 15 m) and are connected by

edge beams at the roof level. The glass walls seem to be independent of the internal support structure and are

suspended from the top edge beam by spring connections as in the Museum of Science, La Villette. The connections

act as solid support under normal loads but as shock absorbers under shock (over) loads to prevent accidental

damage to the glass. The glass walls are laterally supported by the primary vertical cable trusses adjacent to the

steel columns (which also provide the connection to the building skeleton) and the secondary horizontal lens-

shaped cable beams with a central spine compression member that resists the tension in the cables. Vertical cables

resist the buckling of the horizontal trusses vertically.

An extraordinary complex spatial steel framework supports the glass skin of the 22-m (71-ft) high, 35 x 35 m (115

x 115 ft) Pyramid at the Louvre in Paris (1989, I.M. Pei/ Roger Nicolet). Here, stainless steel bowstring trusses

form a two-way diagrid structure on each plane of the structure. In other words, sixteen crossed beams of different

lengths are placed parallel to the diagonal edges. By extending the truss struts, the aluminum mullion frame is

supported. To prevent the outward thrust of the pyramid and to stabilize and stiffen the shape, the four faces are tied

together by 16 horizontal counter cables (i.e. belts) in a third layer thereby bracing and stressing the diamond-shape

network. In their search for visual lightness the designers developed a difficult layout of structure, which reflects a

celebration of structural complexity and still achieving the goal of transparency and an almost immaterial lightness

with its thin member fabric.

D.7 NEW DIMENSIONS OF STRUCTURES

In the conclusion, unique examples are shown, where the architecture masterfully interweaves structures and technology

with spatial qualities.

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With the elliptical glass atrium hall of the Tokyo International Forum, (1997), Rafael Vinoly together with the

structural engineer Kunio Watanabe express true structural originality. The unique 208-m long roof structure that is

about 31.7 m wide, resembles an exposed ship hall or prehistoric structure which floats 60 m above the ground

and together with the suspended lightweight ramps and bridges reflects an almost medieval cathedral like

impression. The parabolic spatial roof arch structure with its 42-m cantilevers is supported on only

two monumental conical concrete-filled steel pipe columns spaced at 124 m. The columns taper from a maximum

width of 4.5 m at roughly 2/3 of their height to 1.3 m at their bases and capitals, and they are tied at the 4th and 7th

floors into the structure for reasons of lateral stability.

The main span of the roof structure which is about of 12-m depth at mid-span, consists of a pair of 1.2-m tubular

inclined steel arches that span 124 m between the columns and curve up in half-arches in the cantilever portion.

A series of 16 tension rods inversely curved to the compression arches complete the beam action. The layout of

the compression arches and tension rods that follow directly the bending moment diagram under gravity load action

of a beam with double cantilevers, are separated by 56 curved steel arch-ribs which also support the roof beams.

The glass walls are supported laterally by 2.6-m deep free-standing vertical cable trusses which also act as tie-

downs for the spatial roof truss.

As impressive, possibly more heroic is the TGV Station, Paris-Roissy (1994, Paul Andreu/ Peter Rice). Here, the

roof is freed (separated) from the structural support, it seems to float above the walls - they never touch. It consists

of parallel crescent-shaped transverse trusses (48 m or 156-ft span, 4 to 7 m or 13 to 23 ft deep) of triangular

cross-section. The two 36 cm or 14-in. dia. bottom chords form an arched ladder where the members merge at the

ends (i.e. lens-shape) and are connected by the diagonal ties and slender vertical tubular web members to the

horizontal solid rods of the top chord which are prestressed to keep them in tension. The trusses are hanging at the

top chords near the center-span from asymmetrical tree columns on concrete pylons in the longitudinal direction.

The truss ends are pulled down by prestressed vertical tension rods to control truss movement. The concrete pylons

are located between the trusses so that the bottom chords seem unsupported. A further confusion is caused by the

heavy suspended arch and the thin horizontal tie, which should be the other way around according to conventional

thinking, but the truss is not simply supported at the ends as the form suggests. The main trusses support

longitudinal triangular steel trusses which, in turn, carry the orthogonal steel grillage with glass panels. The glass

wall is laterally supported by vertical tubular cantilever masts with cantilever arms and are spaced at 4.75 m; the

glass panels are hung from the cantilever arms. The masts are as much as 17 m high and are braced by pretensioned

cables against twisting. The building column grid is offset from the trusses and vertical tension rods to avoid the

impression that the roof is hanging or the masts carry the roof.

I like to conclude my presentation with La Grande Arche, Paris (1989, Johan Otto von Sprechelsen/ Peter Rice for the

canopy) where the architecture masterfully interweaves the spontaneity of the moment and technology as reflected by the

tensile roof and elevator tower, with the symbolism of the giant arch, a modern version of the Arc de Triomph.

La Grande Arche is a giant nearly 110 m hollow cube. The 35-story side buildings are bridged by 3-story frame

beams at the top. The primary structure of each of the about 18-m wide side buildings consists of four post-

tensioned concrete mega-frames tied together every seven floors and stabilized by diagonal walls at the corners

thereby forming nearly 21 meter squares in elevation. The frames and walls rest on neoprene cushions, the only

movement joints, on top of huge caissons.

The floating, tensile textile membrane over the base reflects the lightness and spontaneity of the cloud and contrasts

the perfect geometry of the giant cube thereby introducing a human scale besides providing shelter and improving

wind conditions. The complex cloud structure consists of diagonally cross-braced parallel lens-shaped cable

beams prestressed against free-form edge cables. The translucent fabric membrane is stressed against the underside

of the cable beams and also supported by small flying struts at the center of the meshes. The composite prestressed

structure is suspended from the walls of the cube. The free-standing nearly 92-m (300-ft) high cable-braced steel

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lattice elevator tower is anchored laterally to the building with horizontal guyed columns.

The architecture clearly demonstrates that there can be harmony between the preservation of the past and the inventions

of the present, and that they do not necessarily represent opposite positions.