Why did WTC 7 fall? Has a fire ever caused a skyscraper to collapse?

Answer 1

This is a good time to be asking this question, because we are finally starting to get some cold hard evidence, that show us, how those building went down. I present to you some of the most recent non-refutable evidence.

1. We now have eye witness accounts, from people inside of the building, telling of explosions taking place, on different floors, including lower floors, just before the buildings went down. Many of the witnesses, were silenced when the buildings collapsed, but their accounts live on, in just released radio recordings. (I'll try to find them on the Internet for you. I heard the firemens radio conversations, not to long ago.) They went something like this, "What's going on! I'm on the 22nd floor, and I just heard an explosion." "I'm on 72, and I heard one too."

2. Photographs of the buildings, just before it went down, show molten metal flowing out, from the building. Structural steel requires temperatures well beyond burning jet fuel, to melt. Further, the color of the glowing molten metal, is representative of temperatures, again beyond that of burning jet fuel. See source below, for detailed information, reguarding structural steel melting points etc.

3. A chemical analysis of the molten metal, found at the site, shows traces of a chemical called, "Thermate". Thermate charges are used by professional demolition crews, to cut through steel beams, to demolish buildings. Incidentally, the samples were recovered by a member, of the clean up crew, who kept it as a souvenir memento. Most of the scrap metal, including the pools of molten steel, were recovered by FEMA, and discarded. http://portland.indymedia.org/en/2006/06/341238.shtml

4. Thermate traces have also been found, inside the bodies, of those exposed to the gases from the molten debris; people such as firemen and clean up crew members.

I found the following video clips, while conducting research. They do have a bias slant, but they are also very intriguing. Once you see them, you'll never be able to see the 9-ll tragedy the same again: I know I won't.
http://video.google.com/videoplay?docid=1519312457137943386&q=loose+change
http://video.google.com/videoplay?docid=-4258946892514662399&q

Answer 2

WTC 7 fell because it was damaged and set on fire by the collapse of the North Tower. A large piece slid off the top and escaped the "pancake" effect of the rest of the tower. This piece struck WTC 7 across the street. As far as fire causing the fall of a skyscraper, none has ever been exposed to the extremes of heat as the WTC was.

Answer 3

Here you go. Metal building collaspe during fires all the time. As the steel gets hotter and hotter it gets weaker. That's why a black smith can heat a piece of steel then shape it. It is a little know fact that a heavy wooden beam is less likely to fall than a steel truss because the outside of the wood will char and insulate the inside of the wooden beam. A steel truss is made of light steel members which develop strength by the way they are arranged.

How did it fall. There was a very good explaination on the Discovery channel. It goes like this. Number 1 is you had a large plane crash into the building, the plane exploded and the on board fuel started to burn and heat up the steel in the building.

2. The design of the building itself. The columns on the perimeter of the building actuall supported the building. Each floor was attached to this exterior frame. Each floor consisted of bar-joist ( lightweight steel trusses) with metal decking covered with concrete. The entire truss did not have to fail only where the floor connected to perimeter frame.

A single floor falling did not take the building down. The floor imediately above the fire collasped and fell on the floor below it and then the combined load took out the floor below. The ultimate collaspe occured when enough floors came loose from the perimeter columns to allow the columns to collaspe from the weight of the remaining intact building above.

I good way to think of this is that each floor braced the out columns and made them stiffer. If you take a short piece of wire it will support quite a bit of weight but if you make the same diameter wire longer it may not even support it's own weight.

The outer columns buckled like noodles and once the weight of the upper portion of the building hit the lower floors the whole works came down.

I don't think its very amazing when something falls down, its more impressive when it remains standing. It was impressive that the impact of the crash did not knock the buildings over.

Answer 4

WTC 7 lasted for a few minutes (9 I think) longer than its design criteria. This makes it an excellent design. It used no more material than was required. The designer deserves an award for getting the design that close without being able to conduct the actual test first.

Apply enough force or heat to any structure and it will collapse. Looks like a fully fueled large jet is sufficent.

The flaw in the design criteria is that they did not allow enough time to even get those below the fire out.

Answer 5

The WTC were built with an external, weight bearing, steel frame. The steel exo-structure is supposed to be covered with a fire/heat retardant. In the case of the 911 attack, the heat created by the explosion fueled by jet-fuel caused the steel to buckle and therefore weaken the exo-structure.

I believe if the steel beams were adequately coated with flame retardant material, the WTCs would not have collapsed.

Answer 6

I have asked the same questions and got the same answers. No one seems to WANT to find the truth.

Can all these people explain why there was thermite found on some of the steel found at all 3 buildings? Pieces of steel that were not shipped to China, for recycling, before anyone could examine it and really find out what happened the steel.
http://video.google.com/videoplay?docid=-4258946892514662399&q

Also, why did the other World Trade buildings, CLOSER than WTC7 and had more structural damage and fires than WTC7, not collapse ??????

@ LocP - External load bearing steel frame pffft what about the central columns? Watch this and tell me a jet could turn this to dust. http://video.google.com/videoplay?docid=-3135892053682639810&q

Answer 7

according to an architect talking at that time - his theory is like this

the floor which was attacked became weak and starting losing grip on the metal holders / beams / pillars and gave way and fell on the floor below

this this weight of cement and steel was so much that the the immediate bottom floor could not hold on to so much weight and it just collapsed on the floor below

now imagine the floor below has to hold on to weight of slabs of 2 floors above which was just impossible

and that's how the domino effect started and all floors just collapsed one on top of the other and in 20 seconds the whole building collapsed

the way he was explaining - was very convincing

Answer 8

Answer to question 1): An enormous building fell on it, and it was on fire for several hours.

Answer to question 2): If collapse by fire is not a risk, why are buildings protected against it?

Answer 9

The towers fell because of the followings events in succession:

a. The impact.
b. Extreame Heat
c. Melting of the Aluminium girders & frames
d. Accumulation of debris
e. Weight increase lead the remaining building to give up.

Answer 10

no... some buildings have burned for days and not collapse.. watch this video... its biased but its very interesting... and i think most of it is true

http://video.google.com/videoplay?docid=1519312457137943386&q=loose+change

its pretty long...