To: Raymond Duray who wrote (15276 ) 1/14/2005 3:13:47 AM From: Michelino Read Replies (1) | Respond to Edgar anticipates your arguments. As he points out heat and temperature are two different things, in fact his theory can account for lower temperatures than I've read elsewhere:It is known that structural steel begins to soften around 425°C and loses about half of its strength at 650°C.4 This is why steel is stress relieved in this temperature range. But even a 50% loss of strength is still insufficient, by itself, to explain the WTC collapse. It was noted above that the wind load controlled the design allowables. The WTC, on this low-wind day, was likely not stressed more than a third of the design allowable, which is roughly one-fifth of the yield strength of the steel. Even with its strength halved, the steel could still support two to three times the stresses imposed by a 650°C fire. tms.org
