Structural Engineering & Statics
where the load goes
Concept

Cladding — where it appears

The envelope hung on a structure, which carries wind to the frame and is racked by whatever the frame does. It is the component most often damaged by movement, and its tolerance is a movement rather than a stress.

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

012345678-0.03-0.02-0.0100.010.020.03along the span (m)deflection, each scaled to the same mid-span drop3.20 · a uniform load3.00 · a load at mid-span2.99 · a triangular load3.60 · a load on half the spanθ = C · δ/L, and the same δ gives 1.21× the rotation across these

The angle nobody limits

Every serviceability rule in this collection limits a displacement. What a bearing, a joint and a cladding gap actually have to accommodate is an angle — and the angle is locked to the displacement by a coefficient that contains no material, no section and no span.

deflection · end rotation 050100150200250300350400020406080100120sideways movement (mm)height (m)bendingracking366 mmroof drift 1 in 328 · worst storey 1 in 296

Two motions with one name

A tall building's sway is two movements added. A frame racks like a stack of parallelograms, worst at the bottom; a cantilever bends about its base, worst at the top. The total at roof level says nothing about which storey is worst, and on this building it is neither.

deflection · drift components

Named alongside it

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

ServiceabilityStiffnessBearingBending stiffnessCantilever actionCompatibilityCurvatureDeflected shapeDeflectionDriftEnd rotationExpansion joint

All concepts