Structural Engineering & Statics
where the load goes
Concept

Overturning — where it appears

3 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
48 kNW = 120 kNmiddle third: ±0.42 mresultant at 1.20 mrestoring 150 kNmoverturning 144 kNmfactor 1.04

Weight is the only thing resisting it

A structure that is strong enough everywhere can still be blown over, and nothing in its material properties has any part in whether it is. The whole answer is a weight and a width — and the failure begins long before anything tips, at the moment one edge stops pressing down.

equilibrium · overturning 15°reaction, leaning 15.0° from the normalthe cone: half-angle arctan μ = 19.3°W = 100demand 25.9 against a capacity of 33.8 — F/μN = 0.77the weight appears nowhere in the cone — only the direction of the reaction is asked about

The force that is whatever it needs to be

Every other force in statics has a value the equations produce. Friction has an inequality instead, so it takes whatever value equilibrium demands and the bound only ever says no — which means a problem with friction in it has a range of answers rather than one.

equilibrium · friction the whole profile185.7 kN/mat 1.90 m0246surcharge20.0 kN/mat 3.00 msoil above water12.0 kN/mat 4.67 msoil at the water table48.0 kN/mat 2.00 m0246submerged soil27.2 kN/mat 1.33 mwater78.5 kN/mat 1.33 mresultant at 1.90 m, which is 0.317 of the height — one third only for a pure trianglethe water term is the largest single one, at 78.5 kN/m of 185.7 kN/m

The load that depends on what carries it

Every other load in this collection is a number the structure is given. Retained soil is not — it pushes with a fraction of its own weight, and the fraction is decided by how far the wall moves. Six millimetres of retreat on a six-metre wall takes a third off the load, and being held still puts it back.

equilibrium · lateral pressure

Named alongside it

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

Bearing pressureFree bodyFrictionAngle of reposeEccentricityEquilibriumFactor of safetyIndeterminacyKernLateral pressureLever armMiddle third

All concepts