Structural Engineering & Statics
where the load goes
Generator

The fire-curve generator

Rendered here at the parameters it defaults to, with every essay that calls it — which is the same list as the blast radius of changing it.
The hour that is really a temperatureThe retention factors for carbon steel against temperature: the yield stress and the elastic modulus. The modulus falls away first — at 500°C the steel has kept 78% of its strength and 60% of its stiffness — so a member's failure mode can change during a fire. A member working at 60% of its cold capacity runs out of strength at 558°C, and out of the stiffness for the same ratio at 500°C, 58 degrees earlier. There is nothing about time in any of it: a fire rating is a temperature the member must not reach, converted into the minutes a particular fire takes to get it there.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

1 essay calls fire-curve. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

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 Materials

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.

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