{"article":{"id":69344,"heading":"Why Did the WTC Towers Collapse?","author":"Saint Huck","created":"2003-07-03 16:04:07","modified":"2003-07-04 08:05:22","last_modified":"Fri, 04 Jul 2003 15:05:22","article":"

Why Did the WTC Towers Collapse?

Immediately after the twin towers of the World Trade Center were struck, it looked as though the buildings might remain standing. While the plane crashes had taken huge chunks out of both towers, the overall structure seemed to be intact, at least to the observers on the ground and the millions of Americans watching the catastrophe on television. But within an hour, World Trade Center 2 had collapsed, followed by World Trade Center 1 only 40 minutes later.

Like all skyscrapers, the World Trade Center was held up by a sturdy metal framework. Steel and aluminum beams were riveted end-to-end to form long vertical columns, which were spaced about 3 feet apart all around the outside of the building. At each floor level, these vertical columns were bound together by many horizontal girder beams. The towers had a similar steel tube framework in the center of the building, which housed the elevators. This tube design left a large area of open space on each floor, with no vertical support columns.

In this giant three-dimensional grid -- called the super structure -- all the weight in each building was transferred directly to the vertical columns. The downward force caused by the weight of the buildings was concentrated into a relatively small area -- the point where the columns rested at the base of the building. At this point, the concentrated force was spread out across the substructure under the building (see How Skyscrapers Work to learn about substructures.)

When the planes hit the two towers, the collisions damaged the structures in two major ways:

They knocked out a large number of vertical columns around the edge of each building and presumably at each building's core.

They ignited the planes' fuel supplies, causing a massive explosion that set each building on fire.

The crash did not take out enough columns to immediately break apart the superstructures; the remaining columns were strong enough to hold up the top portion of each building. But the raging fire heated these standing columns to extremely high temperatures, twisting and weakening them. In the World Trade Center towers, the support structure was designed to withstand a typical building fire for a few hours or more, to give rescue workers time to evacuate the occupants and possibly extinguish the fire. But because of the intensity of the explosions on September 11, and the large amount of fuel feeding the fires, temperatures climbed well above expected levels.

As key structural elements melted, more of the columns buckled. Without adequate column support at the crash site, the top part of each building collapsed onto the lower part of the building.

Essentially, this was like dropping a 20-story building on top of another building. Before the crash, this upper structure exerted a constant downward force -- its weight -- on the superstructure below. Obviously, the lower superstructure was strong enough to support this weight. But when the columns collapsed, the upper part of the building started moving -- the downward force of gravity accelerated it. The momentum of an object, the quantity of its motion, is equal to its mass multiplied by its velocity. So when you increase the velocity of an object with a set mass, you increase its momentum. This increases the total force that the object can exert on another object.

To understand how this works, think of a hammer. Resting in your hand, it doesn't hurt you at all. But if you drop it on your foot, it can do some damage. Similarly, if you swing the hammer forward, you can apply enough force to drive nails.

When the upper structure of each World Trade Center tower fell down, its velocity -- and therefore its momentum -- increased sharply. This greater momentum resulted in an impact force that exceeded the structural integrity of the columns immediately underneath the destroyed area. Those support columns gave way, and the whole mass fell on the floors even farther down. In this way, the force of the falling building structure broke apart the superstructure underneath, crushing the building from the top, one floor at a time.

To put it another way, the potential energy of the building mass, the energy of position it had due to its height and the pull of gravity, was converted into kinetic energy, or energy of motion. This is the same basic principle that professional demolition blasters use to bring down unoccupied buildings.

World Trade Center 2, the second tower hit, actually collapsed before World Trade Center 1. Most likely, this occured because of the planes' relative impact points. The plane that hit World Trade Center 2 crashed lower on the building than the plane that hit World Trade Center 1. Consequently, the strained support columns in World Trade Center 2 had a greater load pressing down on them then the strained columns in World Trade Center 1, so they reached the buckling point more quickly.



http:\/\/www.howstuffworks.com\/sept-eleven7.htm<\/a><\/p>\n","contact":"","link":"","address":"","phone":"","parent_id":0,"mime_type":"text\/plain","summary":"Obviously.","numcomment":20,"fileurl":"\/uploads\/","filesize":null,"article_url":"\/news\/2003\/07\/69344.php"},"attachments":[],"comments":[{"id":69353,"heading":"More from the mountain","article":"More statements of the obvious.","author":"Saint Huck","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 16:33:06","modified":"2003-07-03 16:33:06","fileurl":""},{"id":69358,"heading":"I'm not naive, damn it!","article":"I believe everything that Uncle Sam and Fox News tell me. I also believe in the Tooth Fairy.","author":"Saint Huck","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 16:38:49","modified":"2003-07-03 16:38:49","fileurl":""},{"id":69415,"heading":"Circle","article":" Going back to the same arguments (9\/11, the invasion of Iraq, and so forth) is hardly a waste of time; aside from the fact that many people who often visit this board are very interested in these topics it is also true that people browsing the site are in most cases not likely to go back and read old postings from a week ago; not all of them are familiar with arguments that challenge what the corporate media have to say and the fact that Bush is a bald-faced liar may not be old news to them.","author":"Meyer London","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 19:57:22","modified":"2003-07-03 19:57:22","fileurl":""},{"id":69416,"heading":"Flaws in the Ointment","article":"The above disinfo piece on the top of this thread does not explain the observed phenomena. \r\n\r\nNotable for their abscence:\r\n\r\n1. No explanation for the apparent explosions blowing outward from the buildings below the damaged sections just instants before the collapse began. These are easily visible on Photos and Videos of the towers.\r\n\r\n2. It does not account for the linear fashion in which the buildings collapsed i.e., straight down. In a catastrophic failure the collapse would be non-linear and the building would tend to tip in the direction of the first failures. A straight down collapse would only occur if all four corners collapsed SIMULTANEOUSLY. Not likely to occur in an unassisted collapse.\r\n\r\n3. Seismic Recordings indicate sharp spikes of Seismic activity just prior to the collapse.\r\n\r\n4. Witnesses in the building reported HEARING explosions in the moments before the collapse began.\r\n\r\n5. It does not account for the rate of speed at which the buildings collapsed i.e., at near freefall speed. This would only occur if there was no supporting structure underneath which would slow the fall and result in a slower than freefall rate of collapse. The only way to account for this is if the supporting structure were neutralized i.e., removed. The only known way to do this would be with explosives.\r\n\r\nThe Official Conspiracy Theory as detailed at the head of this Thread is only convincing if you do not take the time to examine what really happened.\r\n\r\n?!! - What Really Happened?","author":"Diogenes","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 20:01:47","modified":"2003-07-03 20:01:47","fileurl":""},{"id":69418,"heading":"Meyer...","article":""Circle" is PsyOps - the intent is to frustrate and demoralize you. Please don't respond to it as you will not be able to engage it in dialog. That is not it's purpose.\r\n\r\n\r\n911 = ?!! = What Really Happened?","author":"Diogenes","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 20:05:45","modified":"2003-07-03 20:05:45","fileurl":""},{"id":69428,"heading":"Refutation","article":""The above disinfo piece on the top of this thread does not explain the observed phenomena. \r\n\r\nNotable for their abscence: \r\n\r\n1. No explanation for the apparent explosions blowing outward from the buildings below the damaged sections just instants before the collapse began. These are easily visible on Photos and Videos of the towers. \r\n\r\nObviously, as the top floors collapsed downward, the huge outward airpressure would "blow out the windows. This is as close to any "observed" explosions you'll get. We've all seen the video. Those outward blasts can be seen all the way down, or at least as low as visibility permits. There is absolutely no evidence of secondary explosions other than this, easily explained, phenomena.\r\n\r\n\r\n\r\n2. It does not account for the linear fashion in which the buildings collapsed i.e., straight down. In a catastrophic failure the collapse would be non-linear and the building would tend to tip in the direction of the first failures. A straight down collapse would only occur if all four corners collapsed SIMULTANEOUSLY. Not likely to occur in an unassisted collapse. \r\n\r\nYou're right to an extant. The four corners did NOT collapse simultaneously. However, given the huge load they SHARED, as one gave way, the others would collapse as close to simultaneously as you can get. The angular displacement in that fraction of a second would be negligable, which, in fact, it turned out to be.\r\n\r\n3. Seismic Recordings indicate sharp spikes of Seismic activity just prior to the collapse. \r\n\r\n\r\nI'm sure I speak for everyone when I say, Please give some credible, verifiable evidence of this. And, bear in nind as you go through your "sources", the size of an explosion, in a skyscraper designed with all manner of shock and sway protection would have to be MASSIVE for a siesmograph reading to note it. Be forewarned.\r\n\r\n\r\n4. Witnesses in the building reported HEARING explosions in the moments before the collapse began. \r\n\r\n\r\nAgain, please list the credible sources backing this up. The sources noting the eyewitnesses who, given all the pandemonium and chaos and DEAFENING ambient noise from screaming and vehicles and THOUSANDS of alarms heard explosions and were able to distinguish those sounds from the sound of the Buildings collapsing almost simultaneously.\r\n\r\n\r\n5. It does not account for the rate of speed at which the buildings collapsed i.e., at near freefall speed. This would only occur if there was no supporting structure underneath which would slow the fall and result in a slower than freefall rate of collapse. The only way to account for this is if the supporting structure were neutralized i.e., removed. The only known way to do this would be with explosives. \r\n\r\nWrong. Even a controlled demo won't make matter, which impedes momentum, vanish. The buldings fell at the rate that they should have. (9.8 m\/sec x sec - the effects of the floors collpsing below them. )Please give some credible evidence as to the rate at which YOU believe that they fell.\r\n\r\nThe Official Conspiracy Theory as detailed at the head of this Thread is only convincing if you do not take the time to examine what really happened. \r\n\r\n\r\nI've yet to read one theory that takes ANY science into account and doesn't rely only on cyber myth.\r\n\r\n\r\n\r\n\r\n\r\n9-11 the day the muslims hit us.\r\n","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 21:58:41","modified":"2003-07-03 21:58:41","fileurl":""},{"id":69438,"heading":"well, we always knew it","article":"\r\nfresca has Alzheimer's or is brain damaged in some fashion.\r\nShe keeps repeating the same thing. Talk about a circle in a rut. She has at least convinced herself. I don't believe\r\nshe has swayed anyone else with the ability to read.\r\nwont stop her though. Arabs, muslims, anyone but the Mossad. Oh yes we BELIEVE you. Sure we do.","author":"Don","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 23:03:01","modified":"2003-07-03 23:03:01","fileurl":""},{"id":69440,"heading":"Don","article":"Feel free to take a break from your childish rantings and take a stab at posting ANY evidence that in any way disproves these facts.\r\n\r\nGo ahead Don. You must be a man of some intelligence. Treat us to a little of it.","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 23:12:06","modified":"2003-07-03 23:12:06","fileurl":""},{"id":69441,"heading":"Sorry fresca","article":"I've read just about all the postings here for about a year\r\nand the huge amounts of diagrams and dissertations from both sides of the debate. Your point of view is simplistic as well as dogmatic. Do you work for the Mossad? You certainly sound like you do. There is no substantive evidence of 'arab' or 'muslim' high jackers. They didn't have an active spy ring or moving company involved in the\r\nevents up to and during Sep. 11\r\nPeddle your piddle elsewhere. It doesn't wash.\r\nOh, and don't try to get me to waste my time convincing you\r\nbecause by your continuous postings, I think you are here\r\nnot to debate but to keep pounding your hate and racist\r\nsuperiority. I'd rather try to teach a pig to fly. \r\nLike you\u2019re always saying; \u2018case closed\u2019.","author":"Don","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 23:29:04","modified":"2013-11-11 00:23:33","fileurl":""},{"id":69442,"heading":"Don","article":"Believe me. I won't ask you to convince me. Your racist gibberish about the Mossad and moving rings is up there with UFO sightings. You're another of the deluded few. You fill the role of someone to ridicule.\r\n\r\nAnd at that, I am an expert. Not that it's much of a challenge.\r\n\r\nI do give you points for dancing around the need to post any evidence for your "theories". But, you can't so I shouldn't be surprised at the obfuscation.\r\n\r\nGo on hating nazi.","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-03 23:36:12","modified":"2003-07-03 23:36:12","fileurl":""},{"id":69448,"heading":"Notice frescaw's first impulse...","article":"...anyone who broaches even potential wrong doing by an Israeli group is immediately branded with the "Racist" "Anti-Semite" slur.\r\n\r\nIt is a great way to silence people and keep them from asking awkward, if you are a Zionazi, questions.\r\n\r\nfrescaw it isn't working as well any more. People are starting to see it for what it is: A cheap shot way of silencing people and defaming their character for merely asking uncomfortable questions or drawing logical conclusions.\r\n\r\nWhy were the Israeli's Dancing?\r\n\r\nWhy were they carrying a large sum of cash in a sock ($4700 to be exact)?\r\n\r\nWhy did the owner of "Urban Moving Systems", the "employer" of the Dancing Israelis, abandon his business and flee to Israel a week later?\r\nHe left a Warehouse full of people's stuff.\r\nHe put his house up for sale - from Israel.\r\n\r\nPerhaps there are innocuous answers?\r\n\r\nPerhaps the Moon is made of Green Cheese?\r\n\r\n911 - What Really Happened?","author":"Diogenes","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 00:08:11","modified":"2003-07-04 00:08:11","fileurl":""},{"id":69477,"heading":"hehehe","article":"First of all, nice dodge of the trouncing I gave you in regards to the refutations of your desperate attempts to disprove the obvious facts about the towers collapse.\r\n\r\nI'll chalk that up as a compliment. Thank you.\r\n\r\n\r\nAnd this gem..\r\n\r\n\r\n"Why were the Israeli's Dancing? "\r\n\r\n\r\nIn as much as you and only a select handful of other racist (notice my use of calling racists, uh, racist) nuts even know what the hell this means, I don't know what I can even possibly say to that.\r\n\r\nBut I do know this. Perhaps some Israeli's were dancing and celebrating.\r\n\r\nI'm sure you and yours were dancing when the arabs attacked us as well. And you all are AMERICAN. So that, at best, that there are scumbags of all nationalities.\r\n\r\nBut look at it this way. You've finally found some Jews you have something in common with and don't need to hate.\r\n\r\nIt's a good thing dio.","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 02:55:24","modified":"2003-07-04 02:55:24","fileurl":""},{"id":69480,"heading":"Banality thy name is...","article":"...frescaw. I am still trying to puzzle out if their was a point in your last post.\r\n\r\nAbout all I could find were the usual distortions of peoples positions when you are unable to offer any substantive response.\r\n\r\nYou know of whom I speak so you can play stupid all you want. However, you are very good at it.\r\n\r\n"A dog has four legs. If you call the tail a leg how many legs does it have?\r\nFour. Calling a Tail a leg doesn't make it a leg" - Abraham Lincoln\r\n\r\nCalling someone a slur because they ask a valid question such as: Why were the "Dancing Israelis Dancing, High Fiving and taking photos of the the fallen WTC Towers" does not make one a Racist. Race has nothing to do with it. National allegiance may. Why were they celebrating the Deaths of 3,000 People?\r\n\r\nWhy did their employer, an Israeli, bolt the country when he learned he was going to be questioned again? Leaving behind a successful business and a Warehouse full of other people's Stored Belongings?\r\n\r\nYou are simply avoiding the issue frescaw.\r\n\r\nOf course it is what I expect. After all it's what you're paid to do.\r\n\r\nP.S. How's the weather in Tel Aviv this morning?\r\n\r\n911 - What Really Happened.","author":"Diogenes","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 03:07:25","modified":"2003-07-04 03:07:25","fileurl":""},{"id":69481,"heading":"Fuck you you whiner","article":""About all I could find were the usual distortions of peoples positions when you are unable to offer any substantive response. "\r\n\r\nI've answered and refuted every one of your silly claims over and over.\r\n\r\nQuit hiding.\r\n\r\nShow all this evidence you claim to have.\r\n\r\n","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 03:09:11","modified":"2003-07-04 03:09:11","fileurl":""},{"id":69483,"heading":"By the way","article":"You continue to ask for comments on subjects which are utterly inverified.\r\n\r\nAll this Israeli shit is just that. It's shit until you back up these myths with some credible evidence. NOT longwinded typings from vanity websites.\r\n\r\nIf there was an Israeli involvemnet then hang 'em.\r\n\r\nBut just because you believe everything that comes down the pike. EVERYTHING except for even the possibility of arab terrorists doesn't compel anyone to respond to you.\r\n\r\nFOR ONCE. JUST FOR ONCE PLEASE post some CREDIBLE news sources coverage of these stories of yours.","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 03:13:05","modified":"2003-07-04 03:13:05","fileurl":""},{"id":69485,"heading":"Blows chunks","article":"-I've answered and refuted every one of your silly claims over and over.-\r\nright; with comments like:\r\n-Fuck you you whiner-","author":"Sheepdog","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 03:15:11","modified":"2003-07-04 03:15:11","fileurl":""},{"id":69490,"heading":"As for your "refutation" of...","article":"...the points I listed: HAR!\r\n\r\n1. I said nothing of Widows. Look at the fucking Photographs.\r\n\r\n2. The building would normally tip in the direction of the failure. The action of a failure on one side would actually reduce the stress on the other side momentarily and then reverse the Vector. The Building would then Shear upward on the opposite side and then collapse.\r\n\r\n3 and 4 are available widely on the net. Try the archives at What Really Happened he has copies of the interviews if memory serves.\r\n\r\n5. What you postulated was a 1 G fall (9.8 MPS\/Sec). A collapsing structure in fact is going to collapse into a resistive mass (unless the support is cut by explosives) and is actually going to collapse at a nonlinear rate of 9.8 MPS\/Sec - R (R being the resistance of the mass, and support structure, below the collapsing superstructure.) As the mass of the collapsing structure increases the rate of collapse will increase but it will always be 9.8 MPS\/Sec - R however as it is nonlinear R will decrease with time. It would be a nontrivial calculation which I am too lazy to do. Do it yourself - you've had Diffeq. You can substitute various values of R but it will always be greater than Zero and always result in a rate of collapse slowed by the mass of the structure (and it's supports) underneath.\r\n\r\nQ.E.D.\r\n\r\n911 - What Really Happened?","author":"Diogenes","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 03:25:23","modified":"2003-07-04 03:25:23","fileurl":""},{"id":69508,"heading":"Again","article":""1. I said nothing of Widows. Look at the fucking Photographs. \r\n\r\n"No explanation for the apparent explosions blowing outward from the buildings "\r\n\r\nThis is what you said. looking at the "fucking" photographs leads to an observation of windows being blown outwards due to greatly increased air pressure resulting from the sudden decrease in the volume of each floor space as the building came down. \r\n\r\n2. The building would normally tip in the direction of the failure. The action of a failure on one side would actually reduce the stress on the other side momentarily and then reverse the Vector. The Building would then Shear upward on the opposite side and then collapse. \r\n\r\nNo. If one corner went the other three would remain holding under a greatly increased load. This would lead to their collapse almost simultaneously. Shear would remain negligable.\r\n\r\n3 and 4 are available widely on the net. Try the archives at What Really Happened he has copies of the interviews if memory serves. \r\n\r\nNothing I can say about a matter of faith without any sources. "Widely available on the net" is dubious at best.\r\n\r\n5. What you postulated was a 1 G fall (9.8 MPS\/Sec). A collapsing structure in fact is going to collapse into a resistive mass (unless the support is cut by explosives) and is actually going to collapse at a nonlinear rate of 9.8 MPS\/Sec - R (R being the resistance of the mass, and support structure, below the collapsing superstructure.) As the mass of the collapsing structure increases the rate of collapse will increase but it will always be 9.8 MPS\/Sec - R however as it is nonlinear R will decrease with time. It would be a nontrivial calculation which I am too lazy to do. Do it yourself - you've had Diffeq. You can substitute various values of R but it will always be greater than Zero and always result in a rate of collapse slowed by the mass of the structure (and it's supports) underneath. \r\n\r\n\r\nI have taken Diffeq and at 4am I'm not going to brush off those cobwebs either. Suffice it to say that I agree with you. The rate of fall would be LESS than freefall. \r\nWhich is exactly what all visual evidence supports. What's the point?\r\nQ.E.D. \r\n\r\n911 - What Really Happened? Muslims hit us.\r\n","author":"fresca","parent_id":69344,"mime_type":"text\/plain","created":"2003-07-04 08:05:31","modified":"2003-07-04 08:05:31","fileurl":""}]}