Structural Engineering & Statics
where the load goes
Concept

Fire — where it appears

A design condition in which a structure must keep standing at temperatures that reduce both the strength and the stiffness of its materials. What a fire rating names is a duration in a standard furnace test rather than a temperature, and stiffness usually falls faster than strength.

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

20040060080000.20.40.60.81temperature, °Cfraction of the cold valuestrength runs out at 558°Cstiffness at 500°Cyield stresselastic modulusworking at 60% of cold capacity

The hour that is really a temperature

A fire rating is quoted in minutes and there is no time in the physics anywhere. What decides is a temperature, and the stiffness reaches its limit sixty degrees before the strength does — so the way a member fails can change while it is burning.

materials · fire 3210031610003162100000102030405060age (days, logarithmic)eccentricity including P-delta (mm)settles at 60 mmand this one does notfirst order 20 mmlong-term critical load 29% of the day-one one

The column that fails years later

A concrete column under sustained load goes on straining at constant stress, so its deflection grows — and because the second-order moment is the load times that deflection, the demand grows with it. There is a load below which the two settle and one above which they never do.

stability · creep buckling

Named alongside it

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

BucklingCreepAmplificationCreep bucklingCritical temperatureDivergenceDuration of loadEccentricityEffective modulusElastic modulusImperfectionLoad ratio

All concepts