Structural Engineering & Statics
where the load goes
Concept

Concurrency — where it appears

The condition that several forces' lines of action meet at one point, which is what allows a joint to be in equilibrium without carrying a moment. It is a geometric property that has to be built rather than assumed, and a small eccentricity is a moment nobody counted.

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

the loadroller: vertical onlypin: any directionall three lines meet here

Three forces must meet at a point, and a drawing can find it

A body held by exactly three forces has their lines of action concurrent. That is a theorem, it is enough to solve for direction and magnitude, and for a century it was done with a straightedge.

equilibrium · graphic statics the split, at 5.1 mvolume 0.100 × 10⁹ mm³ against 0.204 for a fan from the base3 of 3 members sized by buckling

The tree that strength does not ask for

A branching column carries a roof on many points and reaches the ground on one. Size every member by its stress and the optimum tree turns out to have no trunk at all — the best answer is a fan of straight struts from the base. Put buckling in and the trunk appears, at 57 per cent of the height.

structures · branching structure

Named alongside it

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

FunicularBranching structureBucklingEquilibriumForce polygonForm findingFree bodyFree body diagramFully stressed designGraphic staticsJointLine of action

All concepts