What temperature does steel lose strength?
At about 550° C (1,000° F) steel is at 50% strength and at about 800° C (1472° F) structural steel loses 90% of its strength. The properties of steel vary widely, depending on its alloying elements. What temperature does jet fuel reach in open air? 287.5 °C (549.5 °F). Already you should be seeing a problem that jet fuel can’t heat steel hot enough to lose 50% of its strength, and this is before the heat conductivity of steel in a structure is factored in. And this is before we observe that the buildings were over-designed by at least a factor of 2 and that NIST said the jet fuel burned off in the first few minutes (assuming of course that it was a commercial jet). The next two problems are that: “(1) modern office contents, including furniture, computers, floor and wall coverings and curtains are not a rich source of fuel and generally incorporate fire-retardant materials and (2) modern office contents are spread out through a large volume of space as well, creating a diffuse, lower-i