For the twin Towers of the world trade center to collapse on itself in such a short space of time. After all,the heat was only at the top
2007-12-20 17:00:36 · 4 answers · asked by ? 4 in Science & Mathematics ➔ Engineering
The heat wasn't at the top, it was where the planes hit and the fuel caught on fire, which were down the building somewhat.
Two things combined.
First off, the contractor used so-called "spray-on" insulation instead of a wrapped insulation on the columns. The force of the impact actually knocked off parts of the insulation esp. at the side clips, thus making it much easier for local melting. Secondly, the effective length of a column is doubled if side supports are present. When the clips melted the columns were effectively put under twice the load they were supposed to hold and the floors just pancaked down on top of each other.
2007-12-21 05:29:54 · answer #1 · answered by Hate the liars and the Lies 7 · 1⤊ 0⤋
Heat does reduce the strength of steel, Since the temperature was around 1500 degrees the steel would have become so soft that it would ve been compromised. To your second question, floors on the tower was like a stack of cards one on top of other. when those top floors collapsed naturally the rest had to come down as you have removed the steel from those floors (all floors above the impact) but not their weight
2007-12-21 01:22:46 · answer #2 · answered by Anonymous · 1⤊ 0⤋
The steel supports were built to take a vertical, relatively stable load. When the upper floors slammed into the lower ones, the load wasn't stable. When the upper floors collapsed inward, the load wasn't vertical.
If you're careful, you can stand on top of an empty soda can - as long as the load is vertical. If you shift your weight or dent the can, it will collapse immediately. Same kind of thing.
2007-12-21 01:40:28 · answer #3 · answered by Tom V 6 · 1⤊ 0⤋
The heat softened the steel holding up the top floors. Once they started to collapse, the inertia of the falling top floors crushed all the floors below one after another after another. Let's say the top 10 floors dropped at one time. Buildings are not usually designed to withstand having another building dropped on top of it.
2007-12-21 01:07:26 · answer #4 · answered by Gary H 7 · 2⤊ 0⤋