New York City activist

December 7, 2007

Engineers were surprised by the WTC collapses

Unfortunately I can’t locate the source for this right now, but I recently came across a claim, by some official-story defender, to the effect that “as soon as the planes hit the Twin Towers, every engineer in the world expected them to collapse.” Whoever made that claim, it is definitely false. Even the better-informed “debunkers” would not agree with it.

Some quotes showing that many engineers were surprised

Even the latest Bazant paper, Collapse of the World Trade Center Towers: What Did and Did Not Cause It? (PDF) by Bazant, Le, Greening, and Benson, June 22, 2007, admits:

Whereas the collapse of the World Trace Center (WTC) Towers on 9/11/2001 set a record of mass murder in the [sic] U.S. history, to structural engineers it came as the greatest surprise since the collapse of the Tacoma Narrows Bridge in 1940. Immediately after the aircraft impact, the structure behaved as expected, but not after the fire.

This from a paper by Zdenek Bazant, whose progressive-collapse hypothesis is one of the foundations of the official story. One of the co-authors is Frank Greening, a well-known “debunker.”

Let’s look now at Behind the Collapse, an interview with Tom Bearden, David Childs, and Jonathan Barnett, on the PBS site, May 1, 2002. Tom Bearden is quoted as saying:

Until the Twin Towers of New York’s World Trade Center disintegrated, no modern steel skyscraper had ever collapsed.

In fact, the entire architectural and engineering communities were stunned.

David Childs, a prominent New York architect who is working on the redevelopment of Ground Zero, is quoted as saying:

Well, I was shocked when they fell down, quite frankly. I was standing at the window when I saw this young man who works with me with this… this look of horror on his face, a very young man, and he said, “Will they fall down?” I said, “Absolutely not.”

And in fact, these kinds of designs have performed extraordinarily well over history. In fact, until this occurrence, no building had fallen down because of fire. There have been major fires, and a couple of floors had fallen down or whatever, but the steel structure is a very efficient and safe structure, particularly this kind of core design.

(By “no building” here, he must mean “no modern steel-frame skyscraper.” Plenty of other kinds of buildings have fallen down due to fire.)

In the Wikipedia article on the Collapse of the World Trade Center, the section on the History of investigations begins as follows:

The collapse of the World Trade Center came as a surprise to engineers. “Before 9/11,” wrote the New Civil Engineer, “it had been genuinely inconceivable that structures of such magnitude could succumb to this fate.”[33] While the initial damage from the airplanes was severe, it was localized to a few floors of each tower. The challenge for engineers was to explain how local damage could result in the complete progressive collapse of three of the biggest buildings in the world.[22] Interviewed by the BBC in October 2001, the British architect Bob Halvorson correctly predicted that there would be “a debate about whether or not the World Trade Center Towers should have collapsed in the way that they did.” The autopsy would involve careful analysis of the plans of the WTC, its construction, eye witness testimony, video of the collapses, and examination of the wreckage. Emphasizing the difficulty of the task, Halvorson said that the collapses were “well beyond realistic experience.”[34]

The footnotes are as follows:

22. Bažant, Zdeněk P.; Mathieu Verdure (March 2007). “Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions” (PDF). J. Engrg. Mech. 133 (3): pp. 308-319, doi:10.1061/(ASCE)0733-9399(2007)133:3(308). Retrieved on 2007-08-22.

33. Oliver, Anthony (June 30, 2005). Lasting lessons of WTC. New Civil Engineer. Retrieved on 2006-07-28.

34. Whitehouse, David (2001). WTC collapse forces skyscraper rethink. BBC News. Retrieved on 2006-07-28.

What this does and does not mean

The above quotes do not, in and of themselves, prove that the WTC buildings could not have collapsed as per the official story.

Science is full of surprises. There have been surprises in the opposite direction, too, where buildings that were expected to collapse did not collapse. Examples include the Broadgate fire and the Cardington experiments, as discussed in Susan Lamont’s Ph.D. thesis (a copy of which appeared on the Nerdcities/Guardian site, mirrored on Jim Hoffman’s site).

Furthermore, it seems to me that there is a big methodological problem with the whole field of structural engineering. In one of the comments after my post about Fire temperatures and steel temperatures, an official-story defender who is apparently also a structural engineer wrote:

This is engineering not science. 99% of the time, all you ever have is preliminary measurements plus calculations. Half the buildings you’ve ever been in were never tested at all, they were simply designed to a code or spec and put together. The other half may have had some testing of assemblies. In either case nobody ever tested the final building to see if it performed exactly as designed.

To which I replied:

What you’re describing here is not a difference between “engineering” and science, but rather a difference between structural engineering and not just science, but also most other kinds of engineering. If structural engineering had the same methodology as most other kinds of engineering (e.g. electronic engineering), then complete prototypes would be built and thoroughly tested, not for every single building, but at least for every type of building, and for every building of a new and unusual design. Obviously this would be quite expensive.

Anyhow, to me this implies that the whole field of structural engineering should be thought of as being pervaded by a huge degree of uncertainty. Thus, to the extent that buildings are “over-engineered,” the point would be an attempt to compensate for that uncertainty. Do you agree?

In the language of software engineers, many buildings, however “over-engineered,” should nevertheless be thought of as beta versions, with no 100% guarantee that they don’t have possibly-catastrophic bugs.

So, we have no 100% assurance that the WTC buildings could not have collapsed without hitherto-unacknowledged extra help.

Nevertheless, by the same token, I would also argue that too many people, including engineers, have been too quick to accept Bazant’s hypothesis as an established scientific fact.

Only recently have structural engineering scientists begun to study, in any great depth, the admittedly complicated question of how and under what circumstances progressive collapse can occur. (See, for example, The science of how buildings fall down by Colin Nickerson, Boston Globe, December 3, 2007.) So, the appropriate attitude on this question is to wait and see.

In the meantime, there are some strange things about the way that the WTC buildings collapsed, especially WTC 7, that should make us at least a little bit suspicious.

And there are plenty of other strange things that happened on 9/11 that are worthy of investigation too.

P.S., 12/9/2007: More and more, I am beginning to get the feeling that the whole field of structural engineering may be rather underdeveloped as a scientific discipline, compared to other kinds of engineering, due to an infrequency of bona-fide scientific experiments. If the admittedly not very many sources I’ve seen on this matter so far are correct, then there just hasn’t been enough funding available for very many experiments involving a variety of full-scale prototype buildings to see what it would really take to make different kinds of buildings collapse. If that’s true, then that in itself would be a good reason to regard even leading structural engineers like Bazant as far from infallible.

P.S., 12/10/2007: I just now found this thread in the JREF forum which begins with a paper that is said to debunk Gordon Ross’s attempt to debunk Bazant. I haven’t yet looked at the paper itself, but I noticed something else very interesting. Another post in the same thread, by the same person (“Newtons Bit”), ends with with this quote: “Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance.” James E Amrhein.

P.S., 2/28/2008: My remarks above about about the field of structural engineering may be mis-stated. For the further development of my thoughts along these lines, see the section Structural engineers and arguments from authority, including P.S.’s, in my post Common a priori objections by “debunkers,” including arguments from authority and the “someone would have talked” and “too many people” arguments, and see also the comments below that post.



  1. One analogy that has sometimes occurred to me is that if you were to make a particular structure collapse, say a bridge, by, say, removing a bunch of its key bolt connections and then lighting it on fire in the middle of the night, and then asking structural engineers to determine why it failed, what would they say? Imagine if they only had a few sections of the bridge to examine and none of those sections were where the bolts were? They would never determine that “some bolts must have been removed.” They might be inconclusive, but to me, this is sort of a simple analogy to why structural engineers are not the answer to everything about a collapse, especially a unique one in the history of structural failures — they are not forensic scientists and they will likely try to fill in the blank with the tools they have, just like Western MDs do (poorly at times), i.e., the most likely component to have failed probably did, due to ‘fire weakening’. Determine the most likely component, then spread the effect via a hand-waving theory like “progressive collapse.” End of story.

    Comment by reader21 — December 8, 2007 @ 1:56 am | Reply

  2. (This comment is an edited pingback.)

    Pingback by Demolition of WTC: Let’s not overstate the case, please « New York City activist — December 9, 2007 @ 3:05 am | Reply

  3. newtonsbit makes the following mistakes in his critique of Ross.

    1. He says he is using a rotation of 30 degrees in each of the three hinges but uses Pi/12 to represent them. Pi/12 is 15 degrees. He also suggests that 30 degrees is conservative and that the columns will fracture at 8-12 degress rotation. On the contrary, there is photographical evidence of wide flange shapes bent at > 45 degrees.

    2. He is using a stiffness C that is too high because he doesn’t include all floors. I have calculated the elastic wave propagation and it should reach the ground during the time the first impact is still in the elastic mode.

    3. His argument that Ross includes plastic deformation energy twice due to the inelastic collision is incorrect because the upper floor of the lower block is restrained for some period of time. The collision cannot modelled as a simple inelastic collision until the supports fail and the floor is free to move.

    4. He is using 1.0 for the effective length factor (K) which is for conservative design. Both horizontal members and the concrete diaphram reduce this (0.65-0.70 suggested by Tony Szamboti).

    All of the above mistakes are in favor of collapse continuation.

    On the other hand, he also has an assumption in favor of collapse arrest. This is not a mistake but rather an assumption based on missing information at the time. He uses estimated values for column cross-sectional areas that are roughly 30% to large.

    Comment by gregoryurich — January 31, 2008 @ 11:14 am | Reply

  4. To Gregory Urich:

    Thank you very much for your comment here. I will have to look at this matter in more detail later.

    To other readers: Gregory Urich’s comment is a response to my link to this thread in the JREF forum which begins with a paper that is said to debunk Gordon Ross’s attempt to debunk Bazant. I personally have not yet studied either paper in enough detail to comment.

    Comment by Diane — January 31, 2008 @ 7:44 pm | Reply

  5. Well I dont think Ive seen anything on seismic activity, so I guess Ill post it here. Please take a good look at “LaBTop’s” thesis here..

    And read through this thread and the one he links..

    His reply to R.Mackey here(see first post) here..

    Lot of reading but I think you’ll find it interesting.
    He’d be happy to answer your questions over there.

    Comment by ldressler — February 24, 2008 @ 3:36 am | Reply

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