[Forte Runningrock]

Floors can't collapse inside the outer building structure because it's all one and the same!! Each floor of a high rise building is essentually all one piece supported by pilars, stack one on top of the other. Some pillars are lessor supporting pillars that don't run through several levels, others are main supports which run through several levels to which the slab is attached to.

[Sender]

Whether the airliners alone caused the collapse or whether it was helped along by explosives, I think the obvious result proves that a high-rise structure can collapse upon itself. If you watch the videos, the failure happened up high, around where the planes hit. The buildings failed from the top down, all the way to the ground.

Even if you postulate the existence of explosives, I don't think al Qaeda managed to hide explosives in each and every floor of the WTC, nor could they sequence the explosions to make it appear that the buildings fell down from their own weight. Whatever happened to start the failure, it continued on its own due to...gravity.

[Calpernia]

Sorry, I don't understand anything about construction to follow what you said. The floors did come down into the lobby though.

[supercat]

Floors can't collapse inside the outer building structure because it's all one and the same!! Each floor of a high rise building is essentually all one piece supported by pilars, stack one on top of the other.

Some buildings are constructed such that every 10-12' of exterior wall is supported by the floor below which is in turn supported by the wall below that, etc. The WTC was not constructed in such fashion. The walls themselves were pretty solid, and the floor trusses were fastened to them. The wall columns did rely upon the floor trusses to provide lateral stability, but the gravitational loads of the wall columns did not rest upon the floor trusses. Indeed, for a building of that height, putting the weight of the upper floors on the lower floors would have been absurd.