The Twin Towers fell because...

[PhilosophyGenius]

Richard- How would you explain the collapse of WTC 7 and the way it feel straigt down in a matter of seconds? How would you explain the fact that Guiliani was warned to move away from the WTC because it was going to collapse before it actually did? (he said that in his own words)

And I hope you stick around this site.

[richard]

First off...This is the internet son, we're all Structural engineers.

That said, I tend to agree with NISTs findings, although I disagree with their conclusion. NIST found several of the steel columns from both towers. The columns in question were all located on floors that had been impacted by the Jets and where the hottest fires had occurred. NIST said that none of the columns tested were have found to have been exposed to anything over 600 or so celsius. NIST also tested many of the floor/truss assemblies. All passed the required fire testing. Which is (If I recall correctly) to be exposed to over 1000 celsius for atleast two hours. The documentary "9/11 Mysteries" has video from the NIST tests you can see for yourself. Secondly, NIST has never once explained what caused both WTC 1 and 2 to completely collapse to the ground. They only attempted to explain what initiated "glabal collapse". Furthermore, I reidderate that NIST has yet to provide a report on bldg. 7 and their current investigation is using controlled demolition through explosive charges as a possible "global collapse" initiater.

FEMA in following the same hypothesis as NIST, said this hypothesis had a "low probability of occurrance".


On a side note: I have spoken to several Cal-Trans engineer's who privately do not believe the official story. Unfortunately in three years of attempts they have refused to go on record and let me bring a tape-recorder. Yes, these are engineers who decide if California freeways are properly fitted for Earthquakes.

I doubt that everyone on this site is a structural engineer, and I don't understand why I should assume everyone is a structural engineer here just because it's the internet. But at least you've read the report, son. The NIST report on WTC 7 has not been published yet, but I have read the preliminary report. I admit that the failure of WTC 7 will be far more difficult to classify.

You say that several Cal- Trans engineers privately do not believe the story. That's fine, if they were to go public with it I'd be happy to read what they have to say. Once again, I have an open mind on the subject. I'm not knowledgable about the subject of military simulations: I prefer to analyze structural aspects rather than chase conspiracy theories. That's what I'm familiar with and that's what I'm interested in. If I came to the conclusion that the Towers may have fallen due to some other circumstance, then I will review other information regarding the conspiracy.

Please point out to me where in the report it says that none of the columns were heated to 600 degrees C. I didn't notice that.

The term "global collapse" means that the whole building fails. The NIST report reviews what initiated the global collapse. "Disproportionate collapse" refers to the whole building's collapse being initiated by the failure of a few critical elements. Such is believed to be the failure of WTC 7. I have no doubt that if demolition is a possible failure for the building, NIST will not neglect to explore that failure mechanism.

The trusses subjected to 1000 degrees C for two hours had their spray on insulation intact, unlike many of the trusses in the Towers after the collapse. The purpose of that test was to determine whether or not the trusses with the insulation on were up to code or not, which they were. As you know, being a structural engineer, there is no possible way that trusses without thermal insulation would be keep their original form if they were subjected to 1000 degrees C for two hours.

[richard]

I guess what you meant by that is that you don't believe I'm a structural engineer. Well, regardless of what you believe, I am a structural engineer, though I'm just starting out. I do have a Master's in Structural Engineering, but I still don't think I'm qualified to diagnose a disaster such as the World Trade Center. I took an earthquake design class in school, but I design in Texas, so we consider wind as a controlling factor instead. Neverless, earthquake engineering have little with the World Trade Center collapse. Earthquake loads are dynamic loads, and cause buildings to oscillate. Earthquake engineering is concerned with the natural period of the building and dampening the oscillations. The WTC Towers did oscillate a little bit, which knocked of some of the insulation, but that's about as much as it has to due with the towers. It might have something to due with the WTC 7 collapse, but I don't know about that yet. Anyway, have a nice day.

[Eckolaker]

I've read many of the papers that say the given explanation of the Towers falling is wrong, because I am intrigued by the growing popularity of this conspiracy theory. I've researched both sides. Every argument I've heard from the conspiracy believers has been either technically incorrect (blatantly), or an oversimplified argument neglecting several important aspects of structural behavior.

I just believe that, because of my knowledge of the structural engineering community, if there was a serious controversy here, I would certainly hear about it from a credible source. I haven't. The few disagreements there have been within the structural engineering community are related to how the stresses were redistributed. Both sides agree that the Towers could not possibly have stood with the heat loads experienced and a large amount of thermal insulation for the steel knocked off. For those of you that don't know, steel loses a very significant amount of strength and stiffness when it reaches high temperatures. Steel also buckles very easily when it has large unrestrained lengths. Steel truss to column connections provide very little (almost negligable) resistance when struck with ridiculously high impact loads, such as the those in the Towers experienced. In fact, the tower falling at a speed close to that of a free-falling object is expected under such loads.

I encourage you all to search for competent sources and observing both sides of the argument, instead of just searching for what you want to hear. That's what I've done and that's how I've come to this conclusion. However, I reiterate that I'm eager to hear a dissenting opinion from an accomplished structural engineer specializing in forensics if there is one.

Uhhh, do you just choose to decide what peices of evidence NIST presented are needed to fit the official story and which ones can be thrown out? How is that NIST could say none of the steel columns reached temps of over 600 celsius, yet you say fires were hot enough to cause steel deformation?

As I can agree that the Floor Truss assemblies were not designed to support the weight of the floors above, but this is what NIST used as the "global collapse" initiater. Plane impacts, fire-proofing removed, hot fires, floor assemblies sagged, top floors crashed down on lower intact floors, and on down, yada yada.

Now, NIST used a Shotgun blast to test how the fireproofing material would react to impacts from high velocity peices of metal. Now, not only did their test not really prove their theory, but it also suggest that both planes would have had to disintegrate into little peices in order for the same effect to be achieved. That said, this test on a hypothesis does not fit the evidence. Evidence of both planes recovered from ground zero after the attacks. In other words, the planes did not turn into "bird shot" after impacting the towers.

Essentially the fireproofing being largely removed is a "Straw man" agrument.

As for the towers falling at an expected free-fall rate without the use of CD, is well, ridiculous. Those were 110-story buildings. If each floor only resisted for 1/20th of a second thats still a huge time gap from virtual free-fall. Secondly, both towers were reduced to dust. Law of conservation of momentum son. You can't have progressive collapse and pulverization. Physics don't allow for it. In order for the towers to collapse at near free-fall speed the impacting floors would literally have to speed up.

Many here will sleep at night with a LIHOP scenario...I know better.

[PhilosophyGenius]

So Richard, what about the wargames and prior knowledge? Does that mean anything to you?

Stick around on this site, it'll be fun.

[Eckolaker]

Please point out to me where in the report it says that none of the columns were heated to 600 degrees C. I didn't notice that.

Well considering its a graphic in the main report, it should be easy to locate. Its actually a over-head floorplan view highlighting the structures. They made several graphics for each floor to not only show heat exposure but damage due to the plane impacts.

The trusses subjected to 1000 degrees C for two hours had their spray on insulation intact, unlike many of the trusses in the Towers after the collapse. The purpose of that test was to determine whether or not the trusses with the insulation on were up to code or not, which they were. As you know, being a structural engineer, there is no possible way that trusses without thermal insulation would be keep their original form if they were subjected to 1000 degrees C for two hours.

Negative, I suggest you view the videos of the tests and review the report. Pretty sure both scenarios were tested. Besides, Structural steel, as you know is given an ASTM rating before fireproofing would be added. Not to mention that a structural engineer would also not consider fireproofing when calculating load bearing under normal conditions, and what building code requires. Fireproofing is only added to decrease a specific columns exposier to fire should on occur in that area.


Furthermore, as you would agree the Floor Trusses only were responsible for bearing the load of that floor and the weight directly connected to its surface area. IE, people, office furniture, etc. Its also largely agreed that the building redistrbuted the load to the remaining intact intact steel box columns and curtain wall members where the planes initially entered the building. Like a pencil penetrating a misquito netting.

[richard]

I feel that I'm one against many here, and though it's fun, I don't have time to respond to all the arguments. First of all, the NIST report in NO WAY says that no column reached a temperature of 600 C. Also, the trusses and columns would fail anyway under much lower temperatures than that considering many of the supports on each floor are removed. The supports of the structure (columns, etc.) were not pulverized. The steel massive steel structure fell and went through the connections below like butter, there's no way those connections could provide 1/20 of a second worth of resistance. Also, NIST concluded that the fire-proofing was knocked off by a debris directly striking it (yes, this does knock of fire-proofing), and slight oscillations due to the airplane impact. NIST left the second element out of its assessment conservatively, because it had little definitive evidence on it. However, NIST does have pictures of trusses not believed to have experienced direct debris impact, but still have the fire coating knocked off.

I'm done for the day, gentlemen, it's been fun. Please, no animosity, I'm as interested as you in the WTC collapse. We just have different opinions. I look forward to more arguments tomorrow, especially if someone can give me information on a credible structural forensics engineer dissenting with the NIST diagnosis.

[Eckolaker]

I guess what you meant by that is that you don't believe I'm a structural engineer. Well, regardless of what you believe, I am a structural engineer, though I'm just starting out. I do have a Master's in Structural Engineering, but I still don't think I'm qualified to diagnose a disaster such as the World Trade Center. I took an earthquake design class in school, but I design in Texas, so we consider wind as a controlling factor instead. Neverless, earthquake engineering have little with the World Trade Center collapse. Earthquake loads are dynamic loads, and cause buildings to oscillate. Earthquake engineering is concerned with the natural period of the building and dampening the oscillations. The WTC Towers did oscillate a little bit, which knocked of some of the insulation, but that's about as much as it has to due with the towers. It might have something to due with the WTC 7 collapse, but I don't know about that yet. Anyway, have a nice day.

Pretty sure its largely accepted by Les Roberton and the likes, that the plane impacts transfer of momentum had little effect on the buidling itself, and the further away from the impact the less likely it would be noticed. Other then the sights and sounds created of course.

[Gold9472]

Richard. Is there a coverup regarding the 9/11 attacks being perpetrated by the U.S. Government?

[PhilosophyGenius]

Please, no animosity, I'm as interested as you in the WTC collapse. We just have different opinions. I look forward to more arguments tomorrow

Cool! Holla back Richard.

It could still be proven without a shadow of a doubt that 9/11 was an inside job with or whithout mentioning the towers.