How did the twin towers collaps on 9/11 ?
Why the Twin Towers Collapsed Paula Hawkins When two Boeing 767s crashed into the Twin Towers, Tower One took 103 minutes to fall while Tower Two only lasted for 53 minutes. There is no simple answer to the question of why the Twin Towers collapsed. Engineers, academics and demolition experts have not found agreement on the subject. Charles Clifton, structural engineer at the New Zealand Heavy Engineering Research Association, believes ‘the impact damage, not the severity of the fire was the principal cause of the ultimate collapse’. This view is shared by Gregory Fenves, professor of civil engineering at the University of California. However, Eduardo Kausel, professor of civil and environmental engineering at Massachusetts Institute of Technology (MIT), believes that fire was primarily responsible. So does Robert McNamara, president of the US structural engineering firm, McNamara and Salvia. But Oral Buyukozturk, another professor of civil and environmental engineering at MIT and Mark
They were bombs, all right – twin engine commercial aircraft carrying over 100 tons of jet fuel (kerosene) and travelling at over 500 knots (if they had been airborne at that altitude and speed much longer, the wing struts would have failed and torn off the wings). The impact delivered 5 billion joules of kinatic energy – the equivelent of a 2000 lb bomb. While the damage this caused to the framework was considerable, what was worse was that the shock wave blasted away most or all of the fire insulation. That left the 80 tons of Jet-A spread across the entire floor burning at 500-1500 degrees F. While this wasn’t hot enough to actually melt (as in convert to liquid) the steel support trusses holding up the 4-inch concrete floor slabs, it WAS more than enough to weaken them structurally to the point where, after an hour or two of such heat, their structural strength dropped below that needed to hold the slabs, and it fell the 15 feet or so to hit the next slab, already weakened by the s
