Structural Engineering & Statics
where the load goes
Concept

Ponding — where it appears

The loop in which a flat roof's sag admits water, the water deepens the sag, and the two feed each other until the bay stiffens or fails.

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

00.020.040.060.080.10.120.1400.20.40.60.81sag at the middle of the baywater depth ÷ critical depthλ = 1.00, approached and never reachedreversed construction camber: δ₀ = 0.01

The water that will not run off

A flat roof deflects, the deflection makes room for water, the water deepens the deflection. It is the same equation as a buckling column, with rain in place of the axial load.

deflection · serviceability 1234403020100-10-20-30-40stage in the beam's lifeshape (mm, sag positive)against noneagainst wetagainst deadagainst total

Built to the wrong shape on purpose

A cambered beam is fabricated curved upward so that load bends it down to something like straight. Nothing in the analysis changes, no stress anywhere is altered, and almost every mistake made with it is a bookkeeping mistake about which loads count.

deflection · camber

Named alongside it

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

Deflection limitServiceabilityAmplification factorComposite actionConstruction sequenceCreepCritical loadDeflectionFlexural rigidityImposed deformationLimit statePropping

All concepts