Bridges

domes

stresses: hoops (circular around), meridian (longways around) mostly in compression but some tension in lower hoops

Framed Tube

Four Walls subjected to wind: when separated, the 2 walls bending about their weak axis offer minimal resistance, but when joined act as a tubular structure, the weak walls forced to participate in resisting wind Khan

German vs. Spanish Tradition of Vaulted Form

German: rigid adherence to mathematics, classical shapes( domes, barrels) Spanish: more playful, courage to be creative, classical and non classical shapes (hyperboloid, hyper)

Pedestrian Bridges

Jörg Schlaich: should be more fun, make people feel alive inclined masts, assymmetry, deck curvature, motion

Heinz Isler

"natural" forms (pneumatic-- inflated membrane and hanging-- pure compression) creating curved shell on square plan (prestressed beams on perimeter) expensive, custom made wooden arches are reused many times influenced by candela

World Trade Center 4, Richard Garlock, NYC

(in right corner)

Reinforced Concrete

Concrete with steel in it. Steel is extremely ductile and excellent in tension place reinforcement where there is tension (the bottom) Used by Robert Maillart

Gothic Cathedral

Pointed arches flying buttresses Ribbed vault ceiling Viollet le Duc restored many cathedrals (structure generates form) dematerializing walls (light) expression of verticality height

Robert Maillart

Same teacher as amman salginatobel, schwandbach, tavanasa reinforced concrete

Creep

Studied by Eugene Freyssinet for years load a concrete column with load p and you have instant shortening. hold load p constant and over time, continues to shorten denied by science

Deflection Theory

The heavier the span weight (ql), the greater the cable tension the greater the cable tension, the stiffer the span the stiffer the span, the less need for deck trusses (elegance of thin deck)

First to use ideals of structural art to critique bridges (ex: Bonar Bridge improved construction principles, external appearance, save material) Bridges became more advanced with time

Thomas Telford

Pierre Lardy

Well educated in science and engineering Christian Menn and Heinz Isler where his students

ferrocement

alternating layers of aggregates and fine steel mesh no wood forms needed can make 1.5 in thick and have large strains with no cracks

Precasting

cast concrete in a reusable mold or "form" when concrete hardens, element is lifted into place

Prestressed Concrete

concrete is compressed before applying load overtime concrete shortens due to creep, "regular" steel cannot stretch enough before failing high strength steel can stretch further to overcome shortening caused by creep compressive stresses induced by high strength steel prior to loading will balance out the tensile stresses

Deck Stiffened Arch

deck and arch deflect together and parapet is a means of stiffening

Self-anchored

deck resist horizontal reactions in compression temporary deck support required during erection

Back-anchored

end blocks resist horizontal reactions no temporary deck support required during erection

Cable-stayed bridges

fan: radiate from a single point, tension gets bigger in longer cables harp: parallel cables, all tension equal cables in tension, deck in compression

barrels

flow of forces -long (beam like) -short (arch like)

buckling

major consideration in steel structures steel is very strong therefore does;t need a lot of material for strength, but buckling can occur taller buildings have more buckling