Structural Engineering & Statics
where the load goes
Concept

Tilt — where it appears

A rotation of a whole body about a line, as distinct from a deformation within it. A lifted beam's stability is a question about tilt rather than stress, and a building rocking on its foundation converts part of its top displacement into tilt, which racks nothing.

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

1017201710the frame, before it settledsoft ground heresettlement in millimetres, mean 15worst angular distortion 1 in 415 between footings 0 and 1limit 1 in 500 — fails

The settlement that matters is the difference

A building that goes down half a metre uniformly is undamaged and needs a new front step. One that goes down a twentieth as far, unevenly, has cracked. The superstructure can even the difference out — and the only way it can do so is by carrying the difference itself, as a force.

deflection · differential settlement 1015202530354045500510152025beam length (m)factor of safety against rolling1.5, a working factorpast 42 m30 m: 13.3

Hung from above and still unstable

A rigid body hanging from a point above its centre of gravity is a pendulum and cannot fall over. A beam is not rigid, and tilting it puts a component of its own weight sideways — which bows it, which moves its centre of gravity further out. Past a length there is no hook height at which it hangs stably at all, and the length arrives as a fourth power.

stability · lift stability

Named alongside it

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

Angular distortionBeam on springsCentre of gravityDamage criterionDifferential settlementEquilibriumErection stabilityFactor of safetyFoundationImperfectionLateral stiffnessLateral torsional

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