Originally posted by Professor: Even if the steel did not melt, the effects of prolonged elevated temperatures caused it to expand, soften, sag, bend, and creep. The intense heat also affected the concrete floor, which, no longer adequately supported by the structure in place before the impact, began to crack, spall, and break up, compromising the synergistic action of the parts of the structure.......... Charles Clifton, a New Zealand structural engineer, argued that the fire was not the principal cause of the collapse. He believed that it was the damaged core rather thn the exterior tube columns that succumbed first to the enormous load from above. Once the core support was lost on the impacted floors, there was no stopping the progressive collapse, which was largely channeled by the structural tube to occur in a vertical direction.[/i] --------------------------
So what you are saying is in a nutshell, the experts consider that it is perfectly natural to assume that the plane/tower event caused the collapse, but they're not actually sure how it happened.
Care to answer this question.
How did the FBI know to go and see Huffman aviation less than 4 hours after the attack?
A lucky guess, or failure yet again in the intelligence gathering , Coincidence Theory anyone?
What I am saying, in a nutshell (as good a term as any to describe it! ), is that the experts are not sure exactly how the collapse happened, but they've offered a number of likely mechanisms to explain the collapse, alone or in combination, based on the crashes and fires. None of these sober-minded engineering scientists has suggested otherwise. It's not like anyone has done systematic research into how skyscrapers collapse when hit by jumbo jets loaded with fuel.
I am certainly NOT defending the US intelligence gathering effort, which clearly screwed up. I have no idea how the FBI was led to Huffman aviation school that trained the hijackers. I was addressing the question of the WTC collapse.
Posts: 1991 | Location: U.S. | Registered: 06-03-02
There are numerous pieces of evidence which indicate demolition. It is remiss of the investigators to decide that demolition should not be considered as a possible cause of the collapses.
Collapse studies have been done from a computer modelling standpoint where the amounts of fuel, amount of original damage etc have been entered. Only when these figures are at the very high end of the damage/fuel variables will the buildings collapse. It would be quite simple for someone to put this on a website, so we can see how all three towers "theoretically fell down". This has not yet happened , I will not hold my breath.
Whilst looking for backup for the above I found this picture.
Since this is evidence of something, can anyone tell me what exactly it is evidence of(I am referring to the large blak puffs of smoke eminating from quite a distance below the flling tops). I think I know, but I'd like someone who believes the Coincidence Theory to explain it. The page the picture is from is very interesting if you would care to look at the page itself.
Also I would like everyone to consider this statement:-
It is highly unlikely that jet fuel was present to generate such explosions especially on lower floors, and long after the planes hit the buildings. Dr. Shyam Sunder, Lead Investigator for NIST stated: "The jet fuel probably burned out in less than 10 minutes.”
So consider the size of the pieces of girder used in the WTC and imagine that you had just one of them. Then take the office furniture flooring carpeting , pot plants and electical equipment from 50 offices. Now set fire to the office furniture et all. How long do you think it would take to heat it to 800 degrees centigrade?(Most of the easily combustible components will have burned within 10 minutes) Then consider that there are 47 columns in the central core, all the time remembering that these are extremely strong since it is the central core which is the main load bearing structure.
These are questions which I have no answers to but unless you are aware of the questions, then you can not have considered the alternatives.
Posts: 31 | Location: Ancient Rome | Registered: 03-02-06
It kind of addresses what happened the instant of collapse. The pancake theory is moot since it does not consider the central column. If the floors pancake down on each other then what happens to the central core. I can see how the floors could fall down on each other, and leave the core standing, but not how the core was disintegrated without some deviation from it's own footprint. Presumably someone could explain this to me.
Posts: 31 | Location: Ancient Rome | Registered: 03-02-06
I'm not sure what else to tell you. You seem quite determined to listen to conspiracy theorists while ignoring the work of qualified experts or while digesting the work of qualified experts in a dishonest manner.
1. If you have studied engineering in the least bit, it would be very simple to determine why the buildings fell straight down. A free body diagram looks at the forces acting on a body in space. In this case we would be looking at the top of the building above the area of structural failure caused by the failed fire-proofing and intense heat. The area above that failure had significant mass. The lateral loads were insignificant comparitively. I don't have exact numbers but let's just guess... the weight of one of the building floors is 4500 tons. It's about 200 feet square so each square foot has a vertical arrow down of 22.5 tons. There is just about no lateral load that can overshadow that downward pull of gravity... it gets zero'd out effectively. So the buildings fell in on themselves in a nearly straight downward manner. Not at all surprising unless you know nothing of structural dynamics.
The reason you imagine that the steel core would be left standing is because you are not understanding the behavior of a steel structure nor the way steel fails and how a building floor is tied together. I'm sorry but the only way I can explain how I think you are failing to understand this is because you think steel has ultimate strength and doesn't fail... it does fail when the load bearing on it exceeds it's failure strength. It buckles and allows the load above to gain dynamic force as well as the static loading.
2. As the article points out. Controlled demolition takes weeks of examination in the field and then demolition teams will cut through 90% of critical beams and columns where they place the explosives. It is not something that you can sneak around and do. It is ludicrous to me that people are saying this is an option. If you've ever studied how demolition teams work, you would know that it just isn't an option.
3. If you look at figure 5 in the last article I posted, you will see the way the long span open web steel joists are tied to the perimeter columns. If you visualize this connection as a small steel plate with a few bolts holding up thousands of pounds of structure, perhaps you will better understand how failure happened. Specifically how failed floors would simply sheer away from their supports. You might also gain a better understanding of how it is that the floors would pancake and fall on each other. The center steel columns would be no contest against the dynamic force of this effect. To demonstrate - take a 5 pound weight and balance it on your head. Now take that 5 pound weight and have someone drop it on your head from 10 feet. We are talking about 45,000 tons so imagine the difference if you can still think after the experiment.
4. The core that you mention in one of your posts was covered with drywall and spray on fireproofing. There is no reputable expert on engineering that doesn't understand that this was a critical part of the failure. The drywall and spray insulation were blown apart during the impact. This allowed the exposed steel to be directly effected by the heat of the fire. Initially people believed that the steel melted, but that is not exactly how it works. Steel loses strength with heat. It then will reach failure at a much lower weight than designed. The column system was designed to be redundant, BUT it was designed for adjacent redundancy meaning that if one column failed the two adjacent would take that load. The problem with the fire on the floor was that the fire caused simultaneous loss of strength on the column core of the building. This meant that the 45,000 tons of the building above was no longer being supported on a column core that could hold it. So it collapsed.
5. As one of the articles mentions, Building #7's collapse isn't well explained because there really wasn't much interest in it at the immediate time when the adjacent 2 411 meter high buildings had fallen in the same area. I believe that the article I posted gives several possible explanations but the most plausible is that the structure of the building was severely undermined when 1,000,000 tons of building had fallen right next to it generating enough force to register on the seismic level.
6. I really don't understand your comment about the seismic effect of the collapse. It is no mystery that 1 million tons of falling building at a rate of 200 m/sec would register. This is especially simple to understand when you know that the foundation of a tall structure reaches into the crust of the earth at a significant depth (think of a tree). Because the members of a building are connected and therefore deeply embedded caissons and piers would shake as the connected structure fell, the fall of the buildings would make deliver a good shake to the island of Manhattan.
Your picture didn't link correctly. I have no idea why black smoke would be a mystery. When things burn carbon comes off. Light your sofa on fire to see this effect.
When considering temperatures of fires it is important to understand flash points. While Dr. Sunder may have stated what you quoted, there is no argument in the rest of his findings that the fire didn't cause the steel to weaken. I find no one that makes that claim and I feel that your understanding of steel structurally is too weak for you to understand. Steel has bearing capacities. The steel designed for the WTC was designed to hold the weight above with some redundancy. With prolonged exposure to fire it loses that strength that is needed. Even if the fire didn't reach 800 degrees centigrade, the lack of fire proofing would have exposed the steel to its deadly enemy. Those of us that are qualified to build buildings or design buildings understand this. Steel and heat do not mix which is why no one should fly airplanes laden with jet fuel into a building.
I believe that you are trying to understand the tragedy, but I also feel you are highly motivated to not believe the experts in favor of conspiracy theories. It has gotten to the point of foolishness now. Could you please read what I've posted and stop your hunt with the conspiracy sites and focus on what highly respected academics in the field of Structural Engineering are writing? It makes no sense to use the research of one chemical engineer to debunk all the work that structural engineers are doing and citing comments out of context as you have is very intellectually dishonest.
I am quite sure that Dr. Sunder would be quite aggravated to be used in an argument that controlled explosives were used in a situation that he's publish some 10,000 pages discussing. His conclusions agree with the information I've posted here.
This message has been edited. Last edited by: aminator2002,
Posts: 3056 | Location: USA | Registered: 06-04-02
By the way, I've reviewed the site that you linked to in your last post.
Here is the only quote of someone that is thinking clearly about the physics involved:
"(The “open air” floor design of the towers was an undeniable contributing factor in the propagation of the transfered energy of collapse. But you don’t want to do the math because you damn well know the collapse of those 20 floors above was beyond the load limits of individual floor trusses. The flaw in the tower’s design was THEY WERE NOT DESIGNED to be abused in this fashion. They are not AIRCRAFT RUNWAYS. But there are a lot of folks out there like you who still hold onto the MYTH that these towers were designed to take the forces of horizontal impact, uncontrolled fire without benefit of a fire suppression system, shattered insulation coatings on floor trusses and momentum of sequential collapse of 20 floors.) "
The calculations that the engineers on that site are not the right ones. You have to use steel design limit formulas to understand this. They seem determined to say that if the horizontal impact was resisted by the steel then the force of the collapsed floor dynamic load could be resisted by the same steel. They also argue that because the columns were three story high that they would not fail from one floor... total nonsense.
Also, the idiots on that site claim that somehow structural engineers were kept from examining the site. One of my best friends is a PE and spent weeks there on the site starting a couple days after the collapse. He had access to all relevant design and construction documents. Many of his colleagues were there as well, but then he works for one of the highly reputable firm that was hired to do the examination. The claim that structural engineers were kept out of the area or denied access is crazy. The site was very dangerous... I have pictures of it and the people that went there were trained to work safely and they also had the obligation to make sure the collapsed structure was safe for those poor souls that had to search and rescue and remove the debris. The assertion that the site was cleaned up fast to avoid examination is also ludricrous. It was cleaned up fast because it was a massive pile of wreckage impeding the operation of New York City subways, motorways and business.
I can't believe some of the nonsense on that site and more over that it's posted by people that claim to have academic backgrounds. Read the reports I've posted please and realize that the formulas being used by the people posting on that website are not right because they do not consider the design strengths correctly.
I mean for pete's sake they state that they don't have access to the design documents... how can they claim to be able to put together calculations of any sort of credibility?
Posts: 3056 | Location: USA | Registered: 06-04-02
I will reiterate what I said earlier. On September 11, 2001, while watching the events unfold, our Chief Engineer predicted the fall exactly as it happened several minutes later. And this guy is no dummy; he co-authors the more recent editions of a standard handbook issued to nearly every engineering student in America. You can have all the fun you want with conspiracy theories.
Posts: 7903 | Location: in the backwoods of North Carolina | Registered: 06-07-02
Originally posted by Sarai: I would like to see the sources for the "evidence" on that site, Fourbrick. For example, these two:
(2) The tape of interviews of air traffic controllers on-duty on 9/11 was intentionally destroyed by crushing the cassette by hand, cutting the tape into little pieces, and then dropping the pieces in different trash cans around the building
(3) Investigators for the Congressional Joint Inquiry discovered that an FBI informant had hosted and rented a room to two hijackers in 2000 and that, when the Inquiry sought to interview the informant, the FBI refused outright, and then hid him in an unknown location, and that a high-level FBI official stated these blocking maneuvers were undertaken under orders from the White House
Just because a website says something happened doesn't mean it is true.
You state that"just because a website says something happened doesn't mean it is true".
Do you apply this same rule to everything you read in your favorite newspaper... your favorite book ... or hear from your favorite tv newscaster... or radio station talk show host???
Or do you only apply this scrutiny to those with whom you disagree ???
), is that the experts are not sure exactly how the collapse happened, but they've offered a number of likely mechanisms to explain the collapse, alone or in combination, based on the crashes and fires. None of these sober-minded engineering scientists has suggested otherwise. It's not like anyone has done systematic research into how skyscrapers collapse when hit by jumbo jets loaded with fuel.
