Structural Engineering & Statics
where the load goes
Concept

Imperfection sensitivity — where it appears

How much of its theoretical capacity a structure loses to a small initial deviation from its perfect shape. It is decided by the slope of the post-buckling path: a column keeps nearly all of its load and a cylinder keeps a third.

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

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 0.100.323.1610.000%5%10%15%20%25%30%local critical load ÷ global critical load (logarithmic)capacity lost below the weaker single modethe two coincide hereworst: 23% at 0.47at coincidence the loss is 2%

Two ways of buckling at once

A thin-walled column can bow as a whole or ripple in its plates, and each has its own critical load. The received advice is that the worst arrangement is the one where the two are equal. The arithmetic says the opposite — at coincidence the interaction costs two per cent, and the expensive region is where the plates go first.

stability · mode interaction

Named alongside it

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

Post bucklingBifurcationBucklingCold formedCritical loadDirect strength methodEffective widthEigenvalueEquilibrium pathGlobal bucklingKnockdown factorLocal buckling

All concepts