Structural Engineering & Statics
where the load goes
Concept

Friction — where it appears

3 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
00.511.522.533.544.55050100150200displacement, mmload, kNfriction 137 kNbearing 188 kNslipthe rising branch is drawn, not solved: it is elastic shear of the plates

The joint that carries nothing until it slips

Tighten the bolts hard enough and the plates are clamped together with a force nothing applied. The joint then carries shear by friction, the bolts are in tension and not in shear at all, and the load path has nothing in common with the joint it looks identical to.

connections · slip critical 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.

OverturningSlip resistanceAngle of reposeBearing pressureBolt tensionConnectionEquilibriumFree bodyIndeterminacyLateral pressureLever armLimit state

All concepts