Structural Engineering & Statics
where the load goes
Concept

Equilibrium path — where it appears

The whole curve of load against displacement a structure follows, whose maxima are limit points and whose branches are its alternatives.

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

Also named here as stability — the same set of essays touches all of them, so they are one junction rather than several.

050100150200250300350-150-100-50050100150movement of the apex (mm)load (kN)limit point: 133.4 kNit jumps 260 mmas builtat the limitafter it goes

The roof that jumps

Every stability failure in this collection so far has been a bifurcation — a straight thing discovering it can be bent. A shallow frame does something else entirely. It stays perfectly symmetric, deforms steadily, and at some point the load it can carry starts to fall while it is still moving in the direction it was pushed.

stability · snap through stable symmetric — a columnan imperfection is a nuisancecritical89%unstable symmetric — a shellan imperfection is a demolitioncritical77%asymmetric — a frameand it matters which waycritical

A third of what the theory promised

A column with a small crookedness reaches almost its full Euler load. A cylinder with the same relative crookedness reaches a third of its classical one, and the theory is not wrong — what separates them is the slope of the path just past the critical load, which no calculation of the critical load itself can see.

stability · imperfection sensitivity

Named alongside it

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

BifurcationBucklingStabilityGeometric nonlinearityImperfection sensitivityKnockdown factorLimit pointPost bucklingShallow archShell bucklingSnap through

All concepts