how did the twin towers fall?

i was just wondering. if the planes hit the top of the towers, how did they colapse? it seeems that it would just burn and break off the top, instead of toppling down to the ground. it seems that they would have been built stronger than that.? just a question, if someone could answer that would be great.
thanks

im out
-mindtrip02

Dear mindtrip02,

if someone could answer that, that would be not great at all because, errm, maybe 90% of all posts in this subforum would be obsolete :-)

Rumor has it the fire weakened the steel beams so much that they couldn't support the weight of the top anymore. When they finally gave in, gravity just sort of pulled the top through the lower part of the building.

Others believe that pre-planted explosives brought the towers down.

Choose your truth ;-)

[edit on 12-10-2006 by Akareyon]

Yeah, most of the posts on this forum are geared around that question.

It depends on who you ask. "Pancake theory" seems popular, but is no longer supported by the investigative government agencies (ie NIST), which have slowly backed away from it in the past few years.

A pancake collapse is something that happens to concrete structures with weak connections to the vertical support columns.



It is not known to happen with solidly-welded steel skyscrapers. Again, the main investigative body for the collapses for the government is also backing away from this theory (at least partially, they still think in terms of it from problem to problem as they see fit, ie how the collapses managed to keep going without slowing down). Most/all mechanism-specific problems pointed out with the collapses revolve around this theory.


Rather than a relatively neat, floor-by-floor collapse as seen above (which, again, only occur in certain types of concrete structures), we saw this:



Not even much of anything in the footprints.



The vast majority of the masses of both Towers were ejected outwards during their collapses, much or most of it without so much as bending or twisting at the edges, which one would expect from a "natural" collapse, ie from torsion.



Above is a 22-ton section of (unbent) perimeter columns ejected laterally about 600 feet from WTC1 onto the Winter Garden building.


Should they have toppled over? For WTC2, I think so. For WTC1, there weren't even enough floors falling for that to happen. It would have just stopped, end of story. That's assuming they should have began collapsing to begin with, which is also highly debated, because hydrocarbon fires have not been known to cause serious damage to steel skyscrapers, especially within only a time span of less than 2 hours.

There's a lot more information scattered around the forums here. Depending on which threads you drop in on, you may find a lot of good, relevant information, or you might find a bunch of trivial crap. Websites like Scholars for 9/11 Truth present more accessible information, or 9/11 Research.

[edit on 12-10-2006 by bsbray11]

The towers collapsed after standing for longer than the top structural engineers in the world expected them to.

The temperatures of 800 degrees were sufficient to significantly weaken the steel at the WTC. That combined with the weight of the tower and the sheer fact that there was a 767 jet rammed into each tower lead to a collapse.

Once one floor collapsed it would fall onto the floor below it. Then the next floor would have the force of 2 floors falling on it and then the next floor would have to force of 3 floors and so on until all floors have collapsed.

If you watch the recently released video of 9/11 by a woman living near the WTC's you'll see the core of the towers remains standing far longer than the rest of the building. Prime evidence of a pancake collapse.

On the way down the air inside each floor was shot out various places of the buildings as one floor falling on another floor caused the air to compress. Thus witnesses feeling a rush of air come down the stairs when the towers began to fall.

Various reports have been done by structural engineers on this topic. Independant, and government related.

Dear doctorfungi:

You’ve addressed the mother of all questions. Should we believe the “experts”? Experts say this and experts say that. Since the dawn of time, throughout the ages, “experts” have postulated all kind of “nonsense”. And it’s no different nowadays. Keep in mind you can find a “Nobel laureate” to support practically ANY position.

This is why it’s so important that we do our own research and try to form our own opinions. A healthy skeptical attitude will serve one well in life no matter what. Whether while visiting a doctor or a car mechanic. As I have previously suggested in some of my posts, all of us can see how common materials such as steel and concrete behave under stress. We can all conduct our own little “backyard experiments” to see what happens when these two substances are exposed to fire or free-falls. It’s perfectly reasonable and scientific to do this. Don’t let sages of the day keep you from researching an independent perspective of the 9-11 events.

Greetings,
The Wizard In The Woods

Originally posted by doctorfungi
Once one floor collapsed it would fall onto the floor below it. Then the next floor would have the force of 2 floors falling on it and then the next floor would have to force of 3 floors and so on until all floors have collapsed.

This is NONSENSE. It DID NOT HAPPEN THAT WAY. Ok?

Read over this: www.studyof911.com...

It will show you that the vast majority of the debris did NOT fall straight down onto the next floor, then the next, next, etc., but was EJECTED out of the footprint.

I don't care what your opinion is, but what you have suggested there is demonstrably false. The mass is not multiplying when a huge fraction of it is being chucked overboard.

If you watch the recently released video of 9/11 by a woman living near the WTC's you'll see the core of the towers remains standing far longer than the rest of the building. Prime evidence of a pancake collapse.

Well maybe you should call up NIST and let them know!

NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel “trusses” integrated with a concrete slab; see diagram below).

wtc.nist.gov...


Welded steel buildings do not pancake. I posted an image of a pancake collapse above. Licensed professional structural engineer Charles Pegelow was interviewed by James Fetzer, and Pegelow said pancake collapses only occur in certain types of concrete structures when the connections to the supporting columns are very weak.

Btw, structural engineers also came out after 9/11 saying the fires must have melted the columns. Many of them said this, prominent SE's, professors at universities. For the most part, they're stupid here, because they don't study building collapses. They don't even study the effects of fire upon steel. That's a metallurgist. And after the collapses started? Mechanical engineer, physicist, anyone that studies dynamic loads, but not a structural engineer, who only deals with statics.

Various reports have been done by structural engineers on this topic. Independant, and government related.

The only independent "reports" (many of them just ordinary web pages, ie Eager's) have been debunked even by the government by now, because no one can get their story straight.

Just face facts man. There is no consensus on how they fell.

It is not common knowledge. It is not well-established. Literature, even from people subscribing to the "official account", is contradictory. Pancake collapses, no pancakes, trusses, "zippers", and all sorts of hogwash that doesn't have a handle. The most thorough report of them all, the NIST Report, doesn't even describe a specific global collapse mechanism. You have nothing. Your expert opinions are vague and/or non-existant, or contradictory.

[edit on 14-10-2006 by bsbray11]

I am not sure, But I heard Bigfoot, Elvis, 2Pac and Biggie Smalls were seen leaving the scene wearing jackets that said "Mossad". They got in a car driven by Dracula and escaped the Osama Bin LAdens family...


Sorry, had to post that. There is no true reason, and more that likely there will never be. There is no precedent for what has happened, and it cannot be compared to any other accidents due to the rare design of the buildings and the size.

The more I investigate this, the more I think that it was the initial construction and design that led to the collapse. There are 100's of threads in this forum, I would advise you to take a look and read. BSBray and HowardRoark have very good input in many of the posts.

The towers were not designed to take the impact of a jet that size at that speed. It is truly a miracle that they were not sheared in half on impact. A smaller building would have. In 93 they(terrorists) placed the trcuk in the correct spot to topple one tower into another. Luckily, this did not happen.

The interior of the building started to collapse, and it 'pulled' the exterior columns in, and the towers at that point could not hold themselves, and the collapse initiated.

www.pbs.org...

www.pbs.org...

Also watch the 9/11 conspiracy one. Good information.

Check out some of the articles on here, they are very informative. Do not be afraid to keep your beliefs either on the collapse. It was not explosives, implosions or the MOssad/CIA, it was Al Qeada and they caught us with our pants down, around our ankles...

Originally posted by Akareyon
Dear mindtrip02,


Rumor has it the fire weakened the steel beams so much that they couldn't support the weight of the top anymore. When they finally gave in, gravity just sort of pulled the top through the lower part of the building.

Others believe that pre-planted explosives brought the towers down.

[edit on 12-10-2006 by Akareyon]

I think it was most likely explosions, because there was explosions at the bottom floor right as the first plane hit the tower. So it's possible, some possibly living people snuck into the building and set explosives in there, and just stayed in NYC to make sure it all went well. That's what I think happened. It also explains building #7.

Originally posted by doctorfungi
The towers collapsed after standing for longer than the top structural engineers in the world expected them to.

The temperatures of 800 degrees were sufficient to significantly weaken the steel at the WTC. That combined with the weight of the tower and the sheer fact that there was a 767 jet rammed into each tower lead to a collapse.

Once one floor collapsed it would fall onto the floor below it. Then the next floor would have the force of 2 floors falling on it and then the next floor would have to force of 3 floors and so on until all floors have collapsed.

If you watch the recently released video of 9/11 by a woman living near the WTC's you'll see the core of the towers remains standing far longer than the rest of the building. Prime evidence of a pancake collapse.

On the way down the air inside each floor was shot out various places of the buildings as one floor falling on another floor caused the air to compress. Thus witnesses feeling a rush of air come down the stairs when the towers began to fall.

Various reports have been done by structural engineers on this topic. Independant, and government related.

this is all quite correct,
but don't confuse or put a mental image in your mind that the 'pancake collapse' was like a stack of 45 records (old tech vinyl) dropping down one upon another,
in some uniform & precise manner!

the designers, engineers, were attempting to fashion a type of 'unitized' construction, where the central core, floors & exterior walls were all an integrated system which supported each other, & the 'desired' result would be that the stress forces, sway & elasticity would all be distributed primarilary between three (3) floors/levels at the same time....avoiding any 'universal collapse' scenario !!!

But the 'weakest link' (of this unitized, self-supporting redundancy) was the long span of the floor trusses, & the truss connections with the perimeter 'columns' (what we would call metal outside walls)

when these 'weakest links' failed because of the fires caused by commercial passenger jets, laden with fuel deliberately 'kamakizied' into the towers, it was only a matter of time until gravity took over.

as someone noted, large sections of exterior wall (columns) remained together,
to my mind that evidence suggests that the floor truss connections with the exterior wall (columns) were sheared off as the outer edges of the floor slabs pancaked downward....catapulting the lightweight concrete & the floor trusses, outward from the core columns that were welded to the floor trusses in the 'unitized' construction/fabrication model. & viola! the witnessed blowout of atomized concrete & the twisted or severed metal in the debris pile in the 'footprint' area, along with large sections of bolted & welded together exterior wall sections

one of these days i'll make a video representation of the process

welcome -mindtrip02

If it pancaked, it would be stacked like pancakes. However, you made some good points Studio. I'm going to call you that for now on. Anyway, I think whomever was able to put explosives in all 3 of those buildings(WTC, #5, and #7) and cause the fire and the second explosives clearly knew this. The goverment may have found out shortly after the attacks. But I think they distorted a limited amount of it, to keep the public from hurting people.

Originally posted by esdad71
It is truly a miracle that they were not sheared in half on impact.

Why does it seem like you're the only person in the world to think this, and most others are pretty familiar with the actual impact damages by now, and how little damage they actually did?

WTC fell because of explosions and possiblity high temptatures burning the building. It's debatable about building 7, some people think fire, some think explosions.

Just from my own perspective I don't agree with the pancake theory, why make a skyscraper that can't handle the weight above it? thats just my own opinion when looking at the situation straight away. Bsbray pretty much summed it up.