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大家知道,结构钢在425℃左右开始变化;温度升高到650℃,其强度约降低一半。但是即使是损失了50％的强度,仅此而论,也不足以说明世界中心大厦坍塌的原因。前面已经读到,大厦是按照抵抗风力来进行许用设计的。事发当时的风力比较弱,大厦受力不会超过允许值的1/3,只相当于结构钢屈服强度的1/5左右。即使由于大火,温度升高到650℃,强度降低了一半,仍能经得住当时2～3倍的风力作用。 大火引起的另外一个问题是钢结构件发生变形。大火的温度在各
As we all know, structural steel begins to change at about 425 ℃; the temperature rises to 650 ℃, its strength is reduced by about half. However, even at a loss of 50% of the intensity, this is not enough to explain the collapse of the world center building. As I have read earlier, the building is designed to allow for wind resistance. The incident was relatively weak wind, the building will not exceed the allowable value of 1/3, equivalent to only about 1/5 of the yield strength of structural steel. Even with a large fire, the temperature was increased to 650 ° C and the strength was reduced by half, still able to withstand the 2 to 3 times the wind at that time. Another problem caused by the fire is the deformation of steel structures. The temperature of the fire in each