Talk:Collapse of the World Trade Center/Archive 17

"Total progressive collapse" section is (still) wrong
This section consists entirely of an out of context simplified model by Professor Zdenek Bazant. The columns did not buckle at every story as claimed in this section. Otherwise the multistory exterior wall debris and large transient core remnant would not have existed. The real collapse progression mechanism was floor beam/truss failure. This has been acknowledged by multiple sources for a long time. This error feeds conspiracy theories. Please replace the whole section. 69.94.46.44 (talk) 11:00, 5 January 2022 (UTC)
 * You may be confusing WTC 1 and 2 with WTC 7. In any case, the preceding section addresses the issue of the floor truss structure (the WTC 1/2 floors were composite trusses, not beam-framed) pulling on vertical elements or becoming disconnected and providing no bracing.  Acroterion   (talk)   13:40, 5 January 2022 (UTC)
 * Actually, the anon may have a point. There's a new paper co-authored by Uwe Starossek (who is already cited heavily in the section) that says explicitly that the Twin Tower collapses were not a series of column failures: "the crush-down in the WTC Twin Towers was (floor-plate-failure)-driven, and that the columns (of the intact lower section), much stronger than the governing floor plates, never had a say in the matter." Since I wrote much of this section back in the day, I feel some responsibility for it and will try to fix it over the next few days. Fortunately, the new paper is published under a Creative Commons license. So we can use some of the illustrations to explain the idea directly.--Thomas B (talk) 15:55, 5 January 2022 (UTC)
 * Thanks. I'm wary of WP picking out one structural element as a definitive causation, but we should certainly discuss the most recent analysis - and illustrations are even better. The mention of "floor beam" got my attention, since there were few such elements in the WTC towers.  Acroterion   (talk)   01:35, 6 January 2022 (UTC)

Big relief to see the improvement, but it is still not enough. The section is still mostly just the old one with a few terms swapped. The result is the presence of unwanted things like "crush down" "too block" etc, and overall vague communication. The point being made is very simple: the fire induced column failure lead to the whole building above falling on the floor beams and trusses below, which were not designed to hold it. So the debris crashed to the basement, peeling the walls and separating the core columns in the process.

I suggest taking guidance from NIST WTC Tower FAQ question 18. --Comment by anon 69.94.46.44, moved Jan 8.


 * (I hope you don't mind I moved your comment in line with the usual threading procedure.) The "crush down"/"crush up" language is in the new Lalkovski and Starossek paper, which is definitely WP:RS. And what you describe is what the article says. If you want to suggest (or make) specific improvements, go ahead.--Thomas B (talk) 16:47, 8 January 2022 (UTC)


 * Just learned to use this page.


 * I recommend deleting the first paragraph save for the last sentence. It was only needed to explain progressive column failure, and since that is gone, the presence of this content is potentially misleading


 * The reference to column misalignment should probably be less explicit. Meaning the current text should be replaced with "When the columns failed, the mass of the building above fell onto the beams and trusses of the floors below, which were not designed to hold it."


 * I would still argue for the removal of all Bazant terminology, for brevity and clarity. So the last two paragraphs should be replaced with "The rubble crashed to the basement, tearing away all the truss framed office areas and much of the core beams, peeling the walls and leaving core columns without bracing. Walls landed up to 150 meters (500 feet) away, heavily damaging nearby buildings, and large remnants of the core (40 stories in the South Tower and 60 in the North Tower) were visible up to 25 seconds after collapse initiation." 69.94.46.44 (talk) 13:17, 9 January 2022 (UTC)

Semi-protected edit request on 10 January 2022
Replace text of section "Total collapse progression" with



When the columns failed, the mass of the building above fell onto the beams and trusses of the floors below, which were not designed to hold it.("NISTFAQ") As a result, the rubble crashed to the basement, tearing away floor trusses and core beams, peeling the walls and leaving core columns without bracing.("FEMAch2","LalkovskiStarossek")

Suggest phone of freefalling wall sections

The first fragments of the North Tower landed 11 seconds after collapse initiation, and the South Tower, after 9 seconds. ("NISTFAQ") Wall segments consisting of one or more 3 story tall prefabricated panels landed up to 150 meters (500 feet) away ("FEMAch2"), damaging nearby buildings. Large remnants of the core (40 stories in the South Tower and 60 in the North Tower) stood up to 25 seconds after collapse initiation before collapsing. ("NISTFAQ") suggested photo of WTC1 exposed core

Consequently remove last paragraph of intro of section "collapse".[User:Anon4z58u770|Anon4z58u770]] (talk) 05:30, 10 January 2022 (UTC)


 * Red information icon with gradient background.svg Not done: please provide reliable sources that support the change you want to be made.Kpddg  (talk)  06:35, 10 January 2022 (UTC)

How about now? Anon4z58u770 (talk) 07:29, 10 January 2022 (UTC)


 * Oppose. The edit you're proposing would remove a lot information based on recent sources and leave only bare bones based on older sources. You'd have to explain how what is there now is wrong, and then either provide better sources or a better reading of the existing sources.--Thomas B (talk) 16:27, 10 January 2022 (UTC)

I apologize for the delay in providing a full explanation. The purpose of this edit is to rephrase the existing information for brevity and clarity. This will replace redundant, overly technical or potentially misleading phrasing in a section errors in or misunderstandings of which has caused much confusion and conspiracy theories.

The new sources are omitted because information they provide is already available from older, more relevant ones such as NIST  — Preceding unsigned comment added by Anon4z58u770 (talk • contribs) 17:51, 10 January 2022 (UTC)
 * Like I say, you'll have to explain which sentences are misleading and redundant.--Thomas B (talk) 18:31, 10 January 2022 (UTC)

Here follows the detailed criticism of the existing content.

The third paragraph of the intro to parent section "collapse" and possibly the second describe collapse progression and therefore belong in subsection "total collapse progression".

Subsection "total collapse progression" starts with a discussion of potential energy and dynamic loads. This was needed to explain the original progressive column buckling model but is now of marginal relevance.

The text speaks explicitly of column misalignment. But this is better replaced with a reference for mass landing in places it doesn't belong, meaning the floor beams and trusses.

The section emphasizes intactness of the falling top floors of the building, by speaking of a "top block" destroying the stories below. But this is missing the point, which is that mass was landing where it didn't belong.

The use of technical terms such as "crush down" to describe the simple phenomenon of rubble crashing down to the basement is completely unnecessary and in fact harmful.

And lastly, many of these more technical aspects +Bock's, crush downs and crush ups) are simply quirks in the one dimensional models used by various authors, and do not necessarily represent real building behaviour. We do not want criticism of these models to become a criticism of progressive collapse as the failure mode of the Towers. Anon4z58u770 (talk) 19:11, 10 January 2022 (UTC)


 * You seem quite critical of the Bažant and Zhou (2002) explanation, which Lalkovski and Starossek (2022) describe as "currently widely accepted among engineering professionals" . They have some criticisms too, but these are already part of the article now, at least as I understand them. What published criticism of Bažant et al. are you basing your suggestions on? Remember that Wikipedia articles must be based on WP:reliable sources, not the WP:truth as you see it.--Thomas B (talk) 08:57, 11 January 2022 (UTC)

How about if I take back that last paragraph criticizing Bazant and Zhou? Anon4z58u770 (talk) 13:01, 11 January 2022 (UTC)


 * It's not about your opinion of them (or mine). On what basis (on the basis of what published sources) do you propose we remove the "top block" crush down/crush up model? It seems to be the received view in the literature (from Bazant & Zhou 2002 to Lalkovski & Starossek 2022).--Thomas B (talk) 16:26, 11 January 2022 (UTC)

I have disabled the request. I would like suggestions on improvements before rr enabling Anon4z58u770 (talk) 03:12, 12 January 2022 (UTC)
 * I suggest you start a section here on the talk page about one of the things you'd like to see changed. Some of the things you're suggesting don't seem right to me. But if we take them one at a time then it'll be easier to assess.

Which ones are wrong? Anon4z58u770 (talk) 03:07, 13 January 2022 (UTC)
 * That's not how it works. Propose some particular edits and provide sources to support them. Otherwise your suggestions can't be considered.--Thomas B (talk) 05:49, 13 January 2022 (UTC)

Semi-protected edit request on 13 January 2022
This is s request for edits to section "Collapse".

Request move third paragraph of intro, During each collapse. .." and append it to subsection "Total progressive collapse" The content of this paragraph is more on topic in this location. Anon4z58u770 (talk) 10:17, 13 January 2022 (UTC)
 * Red information icon with gradient background.svg Not done: The paragraph is much more general than the section on the mechanism of progressive collapse. It belongs in the intro.--Thomas B (talk) 10:34, 13 January 2022 (UTC)

Semi-protected edit request on 13 January 2022
I think it would be useful to add these relevant photographs to section ', Collapse"

East wall of South Tower bowing from NIST NCSTAR 1-5A figure E-14

East wall of South Tower buckling figure 29 in https://ukdiss.com/examples/world-trade-center-failure-mechanisms.php

Sagging and disconnected floors in South Tower NCSTAR 1-5A fig 9-73, 6D fig E-12

North Tower core remnant https://www.reddit.com/r/911TruthWiki/comments/3rbeid/core_structure_remnant_of_world_trade_center_1/ Anon4z58u770 (talk) 12:21, 13 January 2022 (UTC)
 * Red information icon with gradient background.svg Not done: There is no indication any of those images has a compatible license. ScottishFinnishRadish (talk) 12:35, 13 January 2022 (UTC)

Semi-protected edit request on 13 January 2022 (2)
Section "total progressive collapse" says:

"Structural systems respond very differently to static and dynamic loads and, while the towers were designed to support enormous weight under normal conditions, they provided little resistance to the moving mass of the section above the damaged floors. In both cases, the collapses began with the drop of the upper section through the height of at least one story (roughly three meters or ten feet), yet a fall of only half a meter (about 20 inches) would have released the necessary energy to begin an unstoppable collapse.[32) As the columns failed they came out of vertical allignment and the upper section impacted the floor plate (not the columns) of the first intact story beneath it.[28]"

Request replacement of the above with this more clear explanation from a more authoritative source.

"There was more than enough gravitational load to cause the collapse of the floors below the level of collapse initiation in both WTC towers. The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case). Since the number of floors above the approximate floor of collapse initiation exceeded six in each WTC tower (12 floors in WTC 1 and 29 floors in WTC 2), the floors below the level of collapse initiation were unable to resist the suddenly applied gravitational load from the upper floors of the buildings." Anon4z58u770 (talk) 15:18, 13 January 2022 (UTC)
 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. ScottishFinnishRadish (talk) 15:40, 13 January 2022 (UTC)

Semi-protected edit request on 13 January 2022 (3)
Section "Total progressive collapse" says

"As the columns failed they came out of vertical allignment[sic] and the upper section impacted the floor plate (not the columns) of the first intact story beneath it.[28"

This strikes me as a needlessly emphatic way to point out the obvious. Any sensible reader would figure out that an uncontrolled fall of 12 feet would cause a misalignment of at least a few inches, and the column slices would most likely miss one another.

Another, though not as important issue is the unusual term "floor plate". Wider audiences would be better served by terms such as "horizontal beams and floor trusses". Anon4z58u770 (talk) 15:30, 13 January 2022 (UTC)
 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. ScottishFinnishRadish (talk) 15:44, 13 January 2022 (UTC)
 * I've wikilinked the word floor plate. Wikipedia articles are written to provide comprehensive coverage of topics, and I believe this detail helps achieve that. –– FormalDude  talk  17:59, 13 January 2022 (UTC)

Copyright of NIST images
Are diagrams/renders/photos in the NIST WTC reports permitted to be hosted on this site? Anon4z58u770 (talk) 16:01, 15 January 2022 (UTC)
 * In general, documents created & published by government employees are public domain. Are there specific image files you're concerned about? &mdash;  The Hand That Feeds You :Bite 19:31, 16 January 2022 (UTC)

I wanted to know if the NIST figures were the reason for rejection this https://en.wikipedia.org/wiki/Talk:Collapse_of_the_World_Trade_Center#Semi-protected_edit_request_on_13_January_2022_2 Anon4z58u770 (talk) 19:44, 16 January 2022 (UTC)
 * That was rejected because you didn't show that those images were sourced to a compatible license or were public domain. And since this was a question about your previous request, you probably should've just asked there instead of starting another section. &mdash;  The Hand That Feeds You :Bite 20:51, 16 January 2022 (UTC)

Misleading WTC7 GIF
The Gif of WTC7 collapse is misleading, as it in its the collapse of the east penthouse Abdullah Ali 4z5 (talk) 07:34, 2 October 2022 (UTC)

Fixed Abdullah Ali 4z5 (talk) 17:04, 2 October 2022 (UTC)

Commons files used on this page or its Wikidata item have been nominated for deletion
The following Wikimedia Commons files used on this page or its Wikidata item have been nominated for deletion: Participate in the deletion discussions at the nomination pages linked above. —Community Tech bot (talk) 05:22, 9 October 2022 (UTC)
 * WTC1bowing1.jpg (discussion)
 * WTC2bowing1.jpg (discussion)
 * WTC7 collapse camera 3.gif (discussion)

Time-to-collapse explanation
The present explanation based on an NYTimes article is wrong. It is also un the wring section. It should be in the section "collapse initiation". I will replace it with the explanation from the NIST report shortly. Abdullah Ali 4z5 (talk) 01:49, 18 December 2022 (UTC)

I have added the correct explanation in the correct section, but I am unwilling to remove the obsolete one until someone confirms I can Abdullah Ali 4z5 (talk) 05:20, 18 December 2022 (UTC)

How is it wrong? The two explanations can coexist. Hmm1994 (talk) 20:00, 19 March 2023 (UTC)

Getting rid of "crush down/crush up" sequence
in section "Collapse of the Towers" we read

"This continued until the upper block reached the ground and the crush-up phase began. Here, it was the columns that buckled one story at a time, now starting from the bottom. As each story failed, the remaining block fell through the height of the story, onto the next one, which it also crushed, until the roof finally hit the ground."

This is unimportant and moreover verifiably false. The videos show the exterior walls of the top block in freefall around the tower. This is clearly visible in the north and west sides of the North Tower, and the west side of the South Tower.

And that does not change the overall mechanism of collapse, which is the overloading of floor connections.

' Abdullah Ali 4z5 (talk) 03:48, 13 June 2023 (UTC)


 * Source? Watching a video of the collapse doesn’t count.  Acroterion   (talk)   04:01, 13 June 2023 (UTC)
 * I find it odd that what
 * anyone can see with our own eyes requires a peer reviewed study to verify.
 * T
 * There are none, but here is an anonymous analysis of the footage
 * https://web.archive.org/web/20200704225610/http://www.sharpprintinginc.com/911/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=287&MMN_position=621:621
 * I doubt these qualify as Wikipedia sources though.
 * There are links at the bottom of each page linking to four pages when ch describe the motion of individual walls Abdullah Ali 4z5 (talk) 07:46, 13 June 2023 (UTC)

Copyright of NYPD photos
I found some aerial photos by the NYPD that would be very useful here. But I don't know what the NYPD copyright policy is Abdullah Ali 4z5 (talk) 13:18, 28 July 2023 (UTC)
 * In general, the works of state and local governments are copyrighted, or assumed to be, unless they've explicitly released them under a public domain or Wikipedia-compatible license. Only works by federal employees created in the course of their duties are assumed to be public domain.  Acroterion   (talk)   16:35, 28 July 2023 (UTC)

Semi-protected edit request on 11 September 2023
Lig i8y (talk) 16:38, 11 September 2023 (UTC) there is something i want to add about the history. This is a tragic event of the US history. I would like to put some other imporant stuff.
 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. Troutfarm27  (Talk) 16:39, 11 September 2023 (UTC)

Is BLAZE-SHIELD D necessary?
Is this paragraph about the specific fire-proofing necessary?
 * According to NIST NCSTAR report, in 1969, BLAZE-SHIELD D fireproofing was used, a mixture of cement and asbestos fibers. When its use was discontinued, the spraying proceeded with one of three different sprayed fire-resistive material (SFRM) insulation: BLAZE-SHIELD DC/F, BLAZE-SHIELD II, or vermiculite plaster, which was coated on the trusses, perimeter columns, spandrels, and one or more surfaces of the core columns.

I would like to just remove it. Thomas B (talk) 20:13, 7 November 2023 (UTC)
 * I don't think that the brand name is needed either, but the composition is important in view of the health issues faced by survivors and workers. Acroterion   (talk)   23:37, 7 November 2023 (UTC)
 * Good point. The article already mentions asbestos and I'll reduce the rest to "vermiculite plaster". Thomas B (talk) 07:05, 8 November 2023 (UTC)
 * Depending on the source of vermiculite, that could contain asbestos too, albeit inadvertently. However, I haven't seen any sources that characterize the vermiculite additive, so that wording should be fine.  Acroterion   (talk)   12:15, 8 November 2023 (UTC)

Evactuation Questions
When was WT7 evacuated? I assume that the two big towers were evacuated immediately after impact. I'm not sure if they evacuated both towers after the first impact, or if the evacuation of the south tower didn't begin until it was hit. But I have no idea at all about WT7, since it wasn't hit. Did they evacuate it immediately on impact? Or did the evacuation begin when it got hit with the debris that started the fires? The article is silent on this question. The section on the collapse of WT7 says that "Some firefighters entered 7 World Trade Center to search the building." It says nothing about anybody else that may have been there. It also says that "…the sprinkler system required manual initiation of the electrical fire pumps." This information would be more useful if I knew if there were still people there to do this. And did the fire fighters turn those pumps on? Also, the article has a section called "Emergency response and evacuation," but it never discusses evacuation. I would like to see answers to these questions in the article. MiguelMunoz (talk) 00:15, 26 November 2023 (UTC)