I posted some of this in another thread already but am adding to it here. Material science and structural mechanics are a lot more complicated than you may think.
Steel loses its strength fast at those kinds of temperatures- whatever temperature it ended up being- I do believe it said 50% or so in that article. Engineers calculate with a material safety factor, which and depending on certain things, is sometimes up to 50%. Now this alone may not have been enough. Load calculations are also done with a safety factor, however the fact that at least the sides where the impact took place a number of supporting structures would have been ruined would have caused more loading on other supporting structures and, thus causing them to fail. Did you know, in fact, that wood does better in a fire? Interesting little fact, but wood burns on the outside and builds itself an insulation layer that causes the rest of it to take longer to burn. Ever notice a campfire.
Furthermore, failures and stuff often come down to what would seem as small details. Like how the beam were jointed or water maybe getting into the wrong place, or pouring concrete in wrong conditions, etc. Engineers, like said, calculate with safety factors to cover for such things. Once in a while, unforeseen things come up. It was said that the buildings were built to withstand what happened to them... that doesn't mean they can't fall down. How often have Boeings flown into the side of a building? How can anyone actually calculate something like that with surety. It can't be done, and in this case, all safety factors were over-stepped. It happened before (ie Titanic) and it'll happen again.
Aside from that, at least from what I saw in the actual videos of the buildings collapsing, it is pretty clearly seen that the buildings fail at the point where the planes hit them, and then causing the upper part to fall onto the lower.
I think it is good to question, but as far as that Loose Change video goes, the physics and structural failures of these buildings goes are his worst arguement. Things can't just be compared like that, especially by people who seem to have no idea about the science behind it.
This goes for the Pentagon too. I'd have a harder time trying to make sense of a hole that was the same size as the jet as what the hole really was. Ever seen that Myth Busters where they shoot those crazy fucking guns right into water? For the biggest one (not a gun fan, so I don't know the name, but trust me it was huge) made a splash in the water so big that the water splashed up to a 30 ft or so roof. The bullet basically shattered within two feet of water. Use this as a comparison. Maybe then you will get an answer about why there was shockwaves after the plane hit, and why it basically disentegrated. In the video he compares this crash to others, where in the others there is always lots of the plane left. He is comparing planes that crash at like most a 30 degree angle to the impact plane to one that crashed at 90. I mean... Even if a plane were to crash at basically a 90 degree angle to the ground, it wouldn't look like what happened to the Pentagon one. Think about a bullet again as an anology, and what happens when you shoot it into the ground.
This guy is a filmaker, not a physisct, scientist or engineer, so take him for just that.
