Structural Engineering & Statics
where the load goes
Concept

Geometric nonlinearity — where it appears

Behaviour in which the equilibrium equations must be written on the deformed shape, so that stiffness depends on how far the structure has moved.

Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.

050100150200250300350-150-100-50050100150movement of the apex (mm)load (kN)limit point: 133.4 kNit jumps 260 mmas builtat the limitafter it goes

The roof that jumps

Every stability failure in this collection so far has been a bifurcation — a straight thing discovering it can be bent. A shallow frame does something else entirely. It stays perfectly symmetric, deforms steadily, and at some point the load it can carry starts to fall while it is still moving in the direction it was pushed.

stability · snap through the cable alonekink of 0.0083 radwith the stiffening girderthe cable takes 83% of the load; the girder spreads it over 183 mμ = L√(H/EI) = 4.93

The deck is not there to carry the load

A cable takes the shape of whatever is on it, which is exactly the problem — under a point load its shape is a kink, and a kink is not a road. The stiffening girder exists to spread the load until what reaches the cable is something the cable's own shape is right for.

structures · stiffening girder

Named alongside it

The objects these essays reach for when they reach for this one.

BifurcationBucklingCatenaryCharacteristic lengthDeflectionElastic foundationEquilibrium pathForm findingFunicularHorizontal thrustLimit pointLoad sharing

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