Originally posted by baumusc
1) There was a loss of momentum in all three collapses. No collapse happened at free fall speed, to suggest it did is just being disingenuous.
2) When supporting trusses were taken out by the plane impact and subsequent explosions the remaining trusses took on the weight that the others were meant to support. That means that the safety factor designed into the building was compromised greatly. Add to that fire and heat to the remaining trusses and the fact that steel loses 10% of its strength at 450 C (840 F), 40% at 550 C (1022 F) and at temperatures above 800 C ( 1475 F), it loses 90% of its strength, you can see that even a 40% weakening of the remaining trusses could cause a collapse.
3) The damage to the exterior and core trusses was quite extensive as shown in this computer animation. Damage occurred on core trusses spanning 6 floors.
http://www.youtube.com/watch?v=cddIgb1nGJ8
4) The simple answer is it did provide resistance which can be seen in the collapse videos. When you basically chop the top off of a building and then drop the top on the remaining structure the walls of that structure are going to want to blow outwards which is exactly what happened with the WTC 1 and 2 collapses. To say that the remaining structure offered no resistance is simply incorrect. When you watch any collapse video you can see columns far outpacing the collapse of the building. Not only are the columns falling faster than the building but they are also falling faster than the debris cloud which is also falling faster than the building. This proves the buildings fell well below free fall speed. Free fall collapse with no resistance would have taken slightly more than 9 seconds. The WTC 1 building took 12.8 seconds to collapse and the WTC 2 building took 11.6 seconds to collapse. Both collapses occurred in a different manner and both were slower than free fall.
5) Like I said in #4 the collapses of both WTC 1 and 2 showed different properties and both took different time periods to collapse.
6) In WTC 7 there were three main trusses that supported the building. Firefighters reported that one of the main trusses was heavily damaged from the skyscraper that fell on it.
7) The collapse of WTC 7 didn't happen at free fall speed. It took 8 seconds from when the penthouse collapsed for the rest of the exterior to start collapsing. Structural engineers suspect that when one of the main trusses failed due to structural damage and unchecked fires that the floor structures began to collapse. This led to the penthouse collapse along with the majority of the rest of the interior. Then after 8 seconds of interior collapse the exterior shell of the building collapsed.
http://www.youtube.com/watch?v=_kSq663m0G8
8) Already answered above.
9) It wasn't. Conservation of energy is actually ignored by you since you seem to suggest that 7,500 gallons of the 10,000 in the planes when they hit simply vaporized in a ball of flame that didn't cause any real damage. That is a lot of energy just disappearing according to you. Personally I believe a lot of that energy went into damaging the structure around it.
10) I don't see how F=ma was ignored. You are going to have to be more specific.
1) Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.cfm That's 2.25 seconds worth of free fall Baum.... Lying doesn't make you correct
2) I have discussed thermodynamics here. Ambient temperature does not mean that the steel had been heated to that temperature. The steel started out at room temperature. It was being heated, but there is no way that it could have been heated to those temperatures ion that amount of time. Visualize putting a roast in a 400 f oven. It takes time to heat that roast to 165 f because of the rate of heat transfer. It is not a situation you understand, quite obviously. Go put a ham in the oven.... wait 4 hours... check the internal temperature. Now I am not saying that steel is the same as ham in the realm of thermal conductivity, but since you obviously understand nothing about thermal conductivity and rates of heat transfer, it is an example I figure you can relate to. Steel is ok at heat transfer. In order to weaken the steel, it must be heated to a temperature, not exposed to heat. Based on the thickness of the steel in the WTC towers, it would have taken significantly more time to be heated to a temperature that would cause weakening.
http://www.physicsclassroom.com/class/thermalP/u18l1f.cfm http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html3)It's not my first time watching the purdue simulation. I watch with amazement as a piece of aluminum completely severs every steel beam in it's path. even after it has used up the energy to sever one column, it has enough energy to destroy another. Amazing, isn't it!
4)n other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was
unable to stop or even to slow the falling mass. http://www.nist.gov/el/disasterstudies/wtc/faqs_wtctowers.cfm5)But the mechanism of collapse was the same. Sagging this and buckling that with fires being in perfect locations and fireproofing removed in that fire location, which magically transferred heat into a material quicker than can be calculated... cool
6)Where is you source for this firefighter comment? I could tell you that firefighters said anything I feel like!
Firefighters said that a genie appeared and said bin laden wished for the building to collapse7)back to 1
Originally posted by
Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall) http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.cfm
That's 2.25 seconds worth of free fall Baum.... Lying doesn't make you correct8)Not really... you made unobserved claims. There are no "core trusses" there are floor trusses. What I am asking is, where was the damage on the 50th floor... 40th floor etc. You claim that the entire structure was damaged. You do realize that the planes had a finite amount of energy, right? That energy had to be used to sever columns, remove fireproofing and exit the building. Where did the extra energy come from?
9)you mean that fireball that left through the building? The one that was observed leaving the building? That is the one that damaged the 40th floor? The fireball that you claim went through 90,000 cubic feet of elevator shaft straight down, while there was still 20,000 cubic feet of elevator shaft above? If we actually add together all of the elevators on the impact floor, it is well over 2 million cubic feet of elevator shaft, yet it went down to the lobby, and had enough energy left to blow marble slabs off the wall, and destroy the windows? You don't see the size of this set of buildings as important at all?
10) Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased. You claim that the mass of the falling top portion increased as it collapsed, thus the fall should have slowed or reduced it's acceleration, yet the observed is almost zero acceleration. It should have been an observable decrease in velocity, not constant!
Then there is newton's third law. The top portion had the same force exerted on it that the in tact portion had. Observable destruction of the bottom portion would indicate destruction of the top portion as well. I think you see the top portion as a solid abject that had a constant crushing effect. If your assertion of damage building wide was correct, the top of the building would also have been structurally compromised, which would have caused it to essentially disintegrate, like the rest of the building diod, leaving nothing behind for the crushing of the bottom portion. You can't claim that the bottom of the building had all of this extensive weakening and structural damage, while the top portion was a massive anvil.
