arch 3423 Building Technology II: Building Structures

Term 1 2019-2020

Lecture 5 Form Active: Suspension and Cable Stayed

Four Types of Structures (H. Engel)

• Form Active

• Vector Active

• Section Active

• Surface Active

Four types of cable structures: 1) parallel span systems 2) radial span systems 3) biaxial span systems 4) cable trusses

Form Active Structure (from Engel)

• The shape of a form-active structure is determined by the forces that act on it.

• The natural pressure line or stress trajectory of a form-active structure coincides with the centerline of the profile of the structure.

• Form-active structures develop horizontal thrust forces at their ends.

Tension Support Structures

Span structures (one way) that use tension members to support a roof or floor fall into one of two categories: suspension structures and cable stayed structures

A suspension structure is a hanging tension member, usually curved and flexible, whose shape conforms to the funicular shape corresponding to the magnitude and placement of the loads it supports. For example, a suspension bridge has a flexible cable supporting a uniform horizontal distribution of vertical loads. It’s funicular shape is a parabola.

A cable stayed structure uses straight tension members, usually flexible cables or rods, to support rigid spanning elements such as beams, either at the ends or at points along the beams length. The tension element carries most of the vertical load of the span while the beam acts as a compression member resisting the horizontal pull of the cable. Stayed cable structures generally have straight tension members while suspension structures have curving tension members. The funicular shape of a tension member carrying a concentrated load is a straight line.

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Timeline of Historic Suspension Structures

Cable Suspension Bridge Veranzio 16thC Cable Stayed Bridge

Hall 26 INMOS Microprocessor FactoryExample of a suspension roof structure: roof profile is the Example of a cable stayed roof structure. Cable stays attach to and supportfunicular form of a suspended uniformly loaded structure. long span roof trusses at the third point locations of the span.

Suspension structures

James Findley deck-stiffened suspension bridge Schuylkill, Philadelphia 1808 61m

Suspension bridge structure carryingdead load of the weight of the bridge.Parabolic shape to suspension cable.

Live load on bridge will deform the flexiblesuspension structure at location of load.

A stiff bridge deck structure prevents distortion of the cable by spreadingthe concentrated load over a wider portion ofthe bridge span.

Menai Straits Bridge Thomas Telford 1826 Wales, England (span: 177m)

Approach span of the Menai Straits Bridge Main span of the Menai Straits Bridge

Brooklyn Bridge John Roebling 1883 New York City (span: 486m) George Washington Bridge Othmar Ammann 1931 (span: 1067m)

Golden Gate Bridge Joseph Strauss 1937 San Francisco, CA (span: 1281m)

Cable suspension roof design

One of the earliest examples of cable suspension roof design was a pavilion structure erected for the an exhibitionfair in Novgorod Russia in 1896. The roof design was made of a diagrid cable network supporting a lightweight roofenvelope. The challenge facing designers of suspension roof structures, aside from the complex analysis of thestresses and deflections, was the problem of weight; the suspension roof is a lightweight structure and is susceptibleto wind uplift loads.

Exhibition Hall Vladimir Shukhrov Nizhni Novgorod, Russia 1896

Exhibition Hall E. Beaudouin & M. Lods Paris 1934 (430m)

Municipal Auditorium Lev Zetlin, engr. Utica, NY (USA) 1956 (74 m)

Municipal Auditorium Lev Zetlin, engr. Utica, NY (USA) 1956 (74 m)

Coliseum Matthew Nowicki Raleigh, NC, USA 1953This work by the ingenuous architect/designer Matthew Nowicki uses the double curvature form of the hyperbolic paraboloid to create a self-restraining lightweight suspension roof. Because supporting cables perpendicular to each other are curving either upward or downward, they act in tension to resist both downward gravity forces from the roof weight and upward wind forces. They are attached at their ends to the curving and tilted compression arches that resist the inward tension of the cables and carry the forces to the ground. Their selfweight is supported by the closely spaced columns that doouble as wind columns and envelope structure.

Dulles Airport Terminal Eero Saarinen Washington, DC ca. 1957

Youth Cultural Center Le Corbusier Firminy, France ca.1958

Types of suspension structure supports

Types of suspension structure supports

Types of suspension structure supports

Federal Reserve Bank Gunter Birkirts Minneapolis, MN (USA) 1973

Stayed structures

19th century truss bridges with tension elements: Bollman Truss & Fink Truss

Maracaibo Bridge Riccardo Morandi, engr. Venezuela, SA 1962

Ting Kau Bridge Schlaich Bergermann and Partners Hong Kong 1998

Erasmus Bridge “The Swan” Ben van Berkel Rotterdam, Netherlan 1996

Erasmus Bridge “The Swan” Ben van Berkel Rotterdam, Netherlan 1996

The bridge has four spans – the longest measuring 280m – that carry two footpaths, two cycle paths, tram rails, and two lanesfor road traffic. Thirty-two stays attached to the top of the pylon take the majority of the weight, supported by eight backstays andfive concrete piers. The southernmost span features an 89-metre-long bascule, a section that folds up to allow large ships to pass.

Grand Viaduct Foster + Partners | Michel Virlogeux / Ove Arup Millau, France 2002

Cable stayed roof design

The use of cable stayed structures in architecture has a relatively short history. Prior to the 1950’s there are only afew attempts to support the roof of a building with cable stays (straight tensioned cables as opposed to suspensioncable structures). One of the earliest is the Panorama Hall in Paris in about 1839 by the architect Jacque Hittorf.Several problems had to be solved to make cable stayed structures viable. Foremost was the challenge of theanalysis of these complex pre-tensioned structures. The cable supported tent structures of the Munich SummerOlympic pavilions in 1972 was an important milestone. Today there are many examples of cable stayed roof design.Both cable stayed membrane roofs (such as the Munich Olympic structures) and cable stayed rigid roofs (such as theINMOS factory) are increasingly common.

Panorama Hall Jacques I. Hittorf ca. 1839 Paris (42m)

Panorama Hall Jacques I. Hittorf ca. 1839 Paris (42m)

Panorama Hall Jacques I. Hittorf ca. 1839 Paris (42m)

Alitalia Hangar Riccardo Morandi, engr. Fiumicino, Roma, Italy 1960

Summer Olympics Tent Structures Frei Otto, engr. Munich, Germany1972

Fleetguard Factory Richard Rogers Partnership Quimper, France1981

Case Studies

INMOS Microprocessor Plant Richard Rogers 1982

Renault Distribution Headquarters Foster and Partners 1983

Lowara Factory Administration Building Renzo Piano 1985

Covered Parking Structure ca. 2002Hall 26 Hanover Expo Thomas Herzog 1996

INMOS Microprocessor Factory Richard Rogers Partnership / Anthony Hunt, Engr. Newport, UK ca. 1982

Renault Distribution Center Foster & Partners Swindon, England 1983

Lowara Office Building Renzo Piano Building Workshop nr. Vicenza, Italy 1985

Covered Parking Structure ca. 2002

Hall 26 Hanover Expo-Trade Show Thomas Herzog, arch - Jorg Schlaich, engr Hanover, Germany 1994 - 1996

Competition Brief: 25,000 - 30,000 m2

important criteria: load bearing structure for long spansminimum height roof with high points to enhance natural ventilationdaylight preferred, direct sunlight restricteduse of renewable materials and savings in energy use

Natural light: external sun screening on south façade and rooftriple glazing with light reflecting gridsmirrored soffit

Artificial lighting: lights on sides of glass ducts projected upward and reflected off mirrored ceilinglights on sides of glass ducts projecting downwardsuspended lighting in strip along underside of ceiling

Diagram showing interior air supply, movement and exhaust. Speed of air moving across the roof is increased by venturi effect of air foil on top of each tower. As air rises the sloping form of roof channels heated air to the highest point where it is released to exterior.

View of interior showing underside of roof with wood panel components, sky-lighting and reflective treatment of ceiling. Note the limited penetration of direct daylight on south facing window wall to the right.

View of tie-down cables to prevent roof flutter due to uplift force of wind.Top: Primary structure: suspension elements and towers

Middle: Modification of side structural bays for support of side enclosure

Bottom: Secondary wood panel roof structure spanning between suspension elements at 5.6m o.c.

Horizontal section showing pre-tensioned back to back steel channels. Vertical section showing 80mm x 50mm façade rail.

Transformation diagram of structure span.

1 Conventional frame solution.

2 Suspension structure supported on columns.

3 Buttresses or ‘cantilevered columns’ to resist overturning moment.

4 Use of cable tie-backs. Eliminates bending in vertical mast supports.

5 Use of trussed towers to resist overturning moment.

6 Horizontal framing element to stiffen tower at mid-height.

7 Use of horizontal trusses at ends of suspension element to collect closely spaced suspension members and distribute force horizontally to widely spaced towers.

8 Reverse orientation of towers to facilitate additional spans. Interior ties to prevent uplift and flutter of the roof membrane.

Reference

Structures. 6th ed. D. Schodek and M. Bechthold. Pearson-Prentice Hall, 2008. See Ch. 5: Cables and Arches.

Shaping Structures: Statics. Waclaw Zalewski and Edward Allen. John Wiley, 1998. See Ch. 7 Fanlike Structures

Masted Structures in Architecture. James B. Harris and Kevin Pui-K Li. Butterworth, 1996.