[Real Cynic No More]

As a civil engineer with some experience in structural design, I don't agree with this analysis. They didn't have to be hit at a weak point. The columns would not have been designed for the impact. The momentum of the plane (velocity and mass) was so great that if it collapsed enough of the columns at the level it hit or at a lower level, the weight of the structure above is such that once it started falling on the collapsed level, its inertia and weight would have collapsed anything beneath it.

That's one problem I have with these forums, there's too much uninformed speculation out there, and then others repeat this as fact.

[Alberta's Child]

See #8. Fellow civil engineer (the REAL engineers) here, though I avoided structural design problems on my P.E. exam! I would be a better source of information if there was a roadway design issue here.

[Looking for Diogenes]

The momentum of the plane (velocity and mass) was so great that if it collapsed enough of the columns at the level it hit or at a lower level, the weight of the structure above is such that once it started falling on the collapsed level, its inertia and weight would have collapsed anything beneath it. That's one problem I have with these forums, there's too much uninformed speculation out there, and then others repeat this as fact.

I'm no engineer, but the source for the article is Gregory Fenves, a professor of Civil Engineering at the University of California at Berkeley.

The collapse mechanism you suggest does not account for the hour or so that passed between collision and collapse.

[Chemnitz]

I read some expert opinions that make me say "What?!" but I appreciate the wide open forum. There are lots of intelligent comments and eyewitness reports that really help me understand news items.

I am inclined to believe that they aimed the jet at a place where they thought it would do the most damage. Any passenger jet with fuel would do the job, I think, considering the mass times velocity. They wouldn't want to bounce off the top and it would be hard to get down low, I think.

A fireman talked about bombs planted in the building possibly or in the jet. One bystander said a bomb had gone off after the collision. I think they missed no opportunities to make this a major terrorist victory.

[R W Reactionairy]

"That's one problem I have with these forums, there's too much uninformed speculation out there, and then others repeat this as fact."

I liked your analysis until you got to this point. It was Salon's expert who screwed up the analysis (in a way that made me wonder if he has any knowledge of physics or engineering.) You went after a bogus theory the result of which is that those who read your comment learned something. IMO thats one of the strengths os these forums. THANKS. YOU SAID IT BETTER THAN I WOULD HAVE.

[xkaydet65]

For what it's worth in the aftermath of this catastrophe, my Dad worked on the WTC's foundation. He told me 30 years ago that the design was to withstand a direct hit from a 727 travelling at 400 knots. You've got a point about the melting points, but watch the video of the second plane. His target choice wasn't random. It was deliberate. These guys did their homework and left nothing to chance. Only the toughness of the original construction kept them up for as long as they were, enabling thousands to live.

[rumpelstilskin]

hello. it has been suggested to me that besides the plane impact damage, it iz(sic) believed that other explosions may have occurred. do you have an opinion?