Structural Engineering & Statics
where the load goes
Concept

Plate buckling — where it appears

Out-of-plane rippling of a thin panel in compression or shear, at a stress proportional to the square of thickness over width.

Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.

1002003004005006007000200400600plate width (mm)slender beyond 370 mmyieldcritical stress — inverse square in the widthwhat the plate actually delivers, over its full width

The plate that ripples, and the width that is left

A wide thin plate in compression buckles at a stress that has nothing to do with the strength of the material. It then goes on carrying load — the middle drops out, and the edges work harder.

stability · plate buckling stiffeners at 1000 mmthe band at 22.5°the truss it has becomestiffener in compression,web in tensionbuckles at 383 kN · carries 696 kN · a stocky web would reach 953 kNσ in the band 252 N/mm² over 541 mm

The panel that carries more after it has failed

Everywhere else in this field a critical load is where the argument ends. A thin web is the exception — it buckles visibly, in waves anybody can see, and then goes on to carry nearly twice as much again by turning itself into a truss nobody drew.

stability · tension field flat: I = 6750 mm⁴folded: I = 67.50×10⁶ mm⁴300gain 10000× = (100)²limited by buckling of the leg: the leg goes at 27 N/mm²

Folded until it spans

A flat sheet has a second moment of area of B·t³/12 and will not span anything. Folded, the same material has B·t·h²/12, and the gain is exactly the fold depth over the thickness, squared — a ratio with no material in it and no width in it.

structures · folded plate

Named alongside it

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

EfficiencyLocal bucklingPlate slendernessPost bucklingStiffnessCritical loadEffective widthForm findingLoad pathOne way spanningOptimisationSecond moment of area

All concepts