This June,the British Constructional Steelwork Association is hosting two FireEngineering Seminars, and a likely topic for discussion is how the temperatureprofile of steel beams can affect the temperature at which they fail.
Generallyspeaking, steel beams fail – that is, stop acting elastically and begindeforming plastically – at around 550 degrees Celsius.
But industrywiki site SteelConstruction.info, which is co-maintained by the BCSA, notes howthe temperature profile of the beam changes this when it is used to support aconcrete slab above.
Thetemperature profile refers to differences in heat between different surfaces ofa beam – in this case, between its exposed lower surface, and the upper surfaceon which a concrete slab rests.
In thisstructure, the upper surface of the steel beam may only be at 360 degreesCelsius, with the lower surface at 620C.
At fullload, this is the temperature at which the beam will fail; but at anywherebetween 550C and 620C, when ordinarily you might expect it to collapse, thecooler portion of the beam is able to withstand the load without the hottestpart breaking.
This is justone example of how structural steel can withstand heat, helping to ensure thatstructures and inhabitants alike survive any fires that break out.