Structural Engineering & Statics
where the load goes
Concept

Curvature — where it appears

The rate at which a member's slope changes along it, equal to the bending moment divided by the flexural rigidity. Integrating it once gives a rotation and twice gives a deflection, which is where every deflection calculation comes from.

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

the sectionstrainfreeplanestress-3.98+1.83resultant force 8.3e-14 kN · resultant moment 3.0e-12 kNmno restraint anywhere, and the member is stressed from end to end

The stress nobody restrained

A bridge deck lying loose on its bearings, with nothing holding it anywhere, develops four newtons per square millimetre when the sun comes out. The stress is not caused by restraint. It is caused by plane sections, and it is invisible to every equilibrium check that could be made on the member.

sections · thermal gradient 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

Named alongside it

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

RestraintServiceabilityBearingBridge deckCladdingCompatibilityCrackingDeflectionEigenstressEnd rotationExpansion jointImposed deformation

All concepts