Concept

No tension — where it appears

The assumption that a material carries compression only, which turns a stress problem into a geometric one. A section obeying it bears only where the resultant produces compression, so its capacity depends on where the resultant lies rather than on how strong the material is.

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

600 kN90 kN·mresultant at e = 150middle thirdbolt carries nothingPartial contactbearing over 300 mm at 10 N/mm² · 50% of 20

Where the structure meets the ground, and when the bolts start working

Push a base plate off its middle third and it lifts off the foundation. The holding-down bolts then carry exactly nothing, and go on carrying nothing until the plate has crushed the concrete underneath it.

connections · base plate
T = 40 kN at 25°no pinnaclee = 0.503 moutside the middle thirdthe line stays in the stone · σ = 351 kPa at the toe

The weight that makes it safer

Every load in this collection makes a structure worse. A pinnacle does not. A masonry pier fails when the line of compression leaves the stonework, and adding weight at the top rotates that line back towards the vertical without adding anything the pier cannot carry — so the stone is not being strengthened, it is being aimed.

structures · buttress
00.10.20.30.40.500.20.40.60.81eccentricity ÷ thicknesscapacity ÷ squash loadthe kern66.7% at the kernno tension only1 − 2e/tslenderness 14.0adds e_a = 17.4 mmEuler is 10×above all of this

It does not buckle, it runs out of width

Every stability failure in this collection is a member that could have carried tension deciding to go sideways instead. Masonry cannot carry tension, and its failure under an eccentric load is not a bifurcation at all — the bearing area simply shrinks until it runs out. The capacity is exactly linear in the eccentricity, Euler's load is ten times anything allowed, and no material property appears until the very end.

stability · wall slenderness

Named alongside it

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

EccentricityBearing stressEquilibriumKernMasonrySelf weightStabilityArchBase plateBearingBucklingButtress

All concepts