Structural Engineering & Statics
where the load goes
Concept

End rotation — where it appears

The angle a member's axis makes with its original direction at a support. It is fixed by the deflection and the shape of the load rather than by the material or the span, and it is what a bearing, an expansion joint or a cladding gap has to accommodate.

Named by 2 essays across 2 fields — 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 4 per unit lengthshear20.4moment51.8 at x = 5.10the moment peaks exactly where the shear passes through zero

The support that is not a point

A reaction is drawn as a single arrow because the equilibrium equations only need its total. Underneath the arrow is a bearing of some width, delivering a pressure over that width, and almost everything a designer would like to know about the region near a support is a consequence of the width the arrow does not have.

internal-forces · support width

Named alongside it

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

BearingCompatibilityBending momentCladdingContinuityCurvatureDeflectionDistributed loadExpansion jointFree bodyImposed deformationJoint stiffness

All concepts