What REALLY happened on 9/11??

Question

I want some real structural engineers to answer this question. Over 40% of Americans believe that the Twin Towers were brought down by explosives. That's a big number. Are all those Americans nuts? On the morning of 9/11/01 my colleague was on the phone with her husband, a structural engineer. He said that he didn't think the Towers would come down, BUT, he did describe a scenario by which they might come down. He was wrong about them not falling, but was dead on about the manner by which they would fall. Isn't it possible that the fire really did bring down the towers? I'm not ready to accept that my government ACTIVELY murdered 3,000 people that morning (though I've already accepted that they might have done so PASSIVELY).

Just structural engineers. No conspiracy wackos.

I'm not a conspiracy nut. I want to believe that the fires brought down the towers. I would simply like a STRUCTURAL ENGINEER to explain it to me. Feel free to use big words. I'm plenty smart...

Answer 1

The steel supports are covered with insulation to protect them during a "normal" fire - this insulation, as well as some of the structural integrity of the joints and beams themselves, were obviously destroyed or severely damaged when the first plane bashed through nearly the entire width of the building.

Valid fact: Structural grade steel loses approximately 50% of its strength at 1100 degrees F.

I would have been more surprised had the thirty or so floors above the impact area not hammered down on this weakened structure and continued to demolish the lower building structure. The difference between instantaneous impact and static weight is apparent every time you hammer a nail into a piece of lumber. Try pushing the nail in with just the weight of the hammer, or several hammers for that matter.

Answer 2

Firstly to set up and demolish a building that size with explosives would take considerable engineering input - involving many people. Very hard to keep secret between that many people, not to mention getting into the building and setting it all up without anybody there noticing.

Yes, the building was destroyed by fire as far I am concerned. When the design engineer for the building appears on Foxtel openly crying that the building he designed collpased and killed so many that good enough for me.

Anyway, from all accounts and articles i've read and seen the fire rating to the structural columns was either damaged in the initial impact or poorly applied (the code has since been changed in the US) and this allowed the fire to directly attack and weaken the columns. Also, the flooring system employed visco-elastic dampers (flexible) couplings at their supports as a passive means of controlling building vibrations or acclerations under wind and seismic loading. Humans are susceptible to vibrations. The fire also damaged the supports which lead to the collapse of the floors. The weight of the building above falling down onto the lower level caused the remaining building to collpase.

Of course this is only my opinion based on information I have seen.

Answer 3

Maybe it's the phase of the moon or something, but this week we've had too many questions that are virtual carbon copies of yours. Despite the doubts of 40% of the public, the facts remain unchanged. You know exactly what they are and I'm sick and tired of repeating them. Nothing's changed except the press is now whipping up the conspiracy wackos.

The kerosene fires did bring both towers down and not one reputable engineer who's examined the freely available data has argued otherwise. I'm reminded of the "controversy" about evolution. The ignorant whip-up a firestorm of pseudo-doubt and use it to maliciously discredit expert opinion. Sound familiar?

Answer 4

it was the fire that brought down the towers. they were actually able to withstand the jet crashes, but the massive amount of fuel that was on board each jet ignited and caused the supports for the trusses to fail. it was a progressive failure, since the floors above fell and overloaded the other supports.