14 September 2001

Reader comments received about the WTC Towers collapse:

http:cryptome.org/wtc-collapse.htm

From: DT
To: jya@cryptome.org
Subject: WTC
Date: Thu, 13 Sep 2001 19:21:17 +0000

To add further to the discussion on the WTC collapse...

I am a trained structural engineer who moved to New York in 1999.  I watched the fires and collapse from a pier in NJ opposite the WTC.  I was also amazed when the towers collapsed so vertically, but it seems rational now. A "tube" skyscraper has 50% of its strength on its facade, so it is much more likely to fail in the centre, where it has relatively little steel, and to "pancake" straight down, guided by the strong exterior walls.   A concrete core or even steel core is what is used in most skyscrapers, but has a practical limit of 70-80  stories tall.  These kinds of buildings have almost all of their lateral strength in the core and flimsy exterior walls. 

They might have been more resistant to the fire, but inevitably would also have failed.  However, they would be more likely to topple intact, like a tree.  Horrible as the collapse was, it might have been worse had part of all of the building fallen on the surrounding areas.  Dozens of other buildings might have been affected, along with crowds on the ground.

Date: Thu, 13 Sep 2001 10:39:46 -0500 (CDT)
From: SP
To: <jya@cryptome.org>
Subject: Very Brief Comment

Thanks much for your comments posted on http://cryptome.org

As a non-architect, I would still like to submit an uneducated idea for consideration in the future fireproofing of buildings.

Perhaps the floor could be sloped slightly toward the exterior of the building, away from the centrally enclose fire exits.  Water from fighting fires, and flammable fuels, would then be directed out of the building (much like scuppers on a ship).  The scupper might be little more than a window with a lower sill.  I realize the slope would not be much of a slope, but designing the stairs with a definite lip, or ramp, of 2-3" might help.

From: JD
To: "'jya@cryptome.org'" <jya@cryptome.org>
Subject: WTA Collapse
Date: Thu, 13 Sep 2001 12:52:03 -0700

I'm a fellow Architect from California and enjoyed your assessment of what happened. There are a couple of points that I have comments about.

First, the question of whether they were targetted for their susceptability for structural collapse. While this is possible, I think that their location (free and clear for an air approach - rather than surrounded by other tall buildings) and visibility (both for TV cameras and as a "symbol" of New York) would rate much higher. You could probably create more destruction ramming into a cluster of high rises which would create terrible fire and destruction, but the WTC is a much better Photo Op.

I would also imagine that if collapsing the building were the goal, the planes would have aimed much lower. I don't think that any engineer could easily calculate what the effect of the burning fuel would be or where it would spill, but any engineer would say that crashing into the bottom of the building would be more likely to collapse it than crashing near the top. As long as they are more than a couple dozen floors up, the ability to respond to the fire from the ground is fairly limited. 

This doesn't rule out the possiblity that the structural design was targetted, but both of the reasons above seem to indicate that their were other considerations which may have had a higher priority.

Second. I think that you are correct about the fire being the prime factor in the collapse. If impact or other motion was the cause it would have happened earlier.

Third. I also agree with the assessment that there were no explosives planted in the building. The logical place would not be on the upper floors and the act of carefully placing the explosives where they needed to be to do this sort of destruction would have been noticed.

I think that the collapse was an unplanned effect of this attack, and since it was due to a fire beyond any reasonable expectation there really is no way to write a reasonable building code to protect against it. Even if the building had fully complied with codes, I feel that it would have collapsed in the same way.

From: RN
Date: Thu, 13 Sep 2001 14:22:38 -0400 (EDT)
To: John Young <jya@cryptome.org>
Subject: rebuilding the wtc

> No doubt, there will be calls for restoring them, perhaps even
> bigger, in the name of history, as if what they were was a great
> American dream.

I went to the dentist's office, and found four magazines with the WTC on the cover.  Not because it was news, but because it was part of the great American dream.  It's a symbol of capitalism's success, and it should be rebuilt (in a different configuration) as a symbol of our defiance of anyone who would destroy them:

http://www.filepile.org:8080/f/pictures/rebuilding_the_wtc.jpg

From: KS
To: <jya@cryptome.org>
Subject: WTC
Date: Thu, 13 Sep 2001 19:53:59 -0400

If maybe, and maybe the Trade Center who d be re-build somewhere maybe a good location would be some of the U.S. dessert areas, you do have a lot of desserts? OK?

Instead of going High go low spread it out and build down instead of up.

One observation from a stupid novice?

Date: Thu, 13 Sep 2001 10:05:58 -0400
From: JT
To: jya@cryptome.org
Subject: Trade Center collapse analysis on cryptome.org

I've read with great interest the analyses you posted on cryptome.org and want to thank you for sharing your thoughts.  I have no background in structural or mechanical engineering aside from the very basic courses I was required to take on my way to an elecrital engineering degree.  Nevertheless, my instincts told me that those towers should have withstood the impact of an airliner and the resulting fire; evidently I was wrong, and so I've been very interesting in the informal engineering analysis that's been going on.

I came across this interesting article on the BBC news site:

http://news.bbc.co.uk/hi/english/world/americas/newsid_1540000/1540044.stm

As you might expect from such a publication, it's low on technical details.  Still, I wonder whether you might be able to comment on the article, or find someone qualified to comment, and post the commentary to the cryptome discussion.

To: JT
From: John Young <jya@cryptome.org>

The BBC report on the WTC collapse, along with many other reports by structural engineers, is most informative. The engineers quoted in most of the reports are consistent in their views of the causes of collapse. What remains to be learned is what is known by the engineers and architects who designed the buildings and those who have worked on them since. At the moment they all are saying "no comment" due to national security and law enforcement requests. And what will be learned by detailed forensic analysis to come later. Due to legal liability as well as national security and insurance investigations, it may be some time before we learn the full story -- and that story may be in dispute, if not concealed, for years to come. Concealment of the results of investigations of disasters is often the norm as liable parties engage in prolonged court battles, and in some cases results have been concealed in perpetuity by mutual agreement. A notable architectural instance of this involved the John Hancock Tower in Boston which suffered loss of most of its exterior glass wall, panes popping for a long period of time (for many months guards in huts surveilling the facades) until eventually all had to be replaced. After years of legal battles and settlement the contending parties requested and got a court order to seal the findings.

Unlike transportation crash investigations, in which the National Transportation Safety Board issues reports as soon as possible so corrective actions can be taken to prevent other occurrences, as far as I know there is no similar national body which does performs that public service for building disasters. Celebrated local and insurance investigations, yes, and sometimes FEMA issues snoring assurances, but usually not the kind of meticulous reports by NTSB for every incident. Reports of high-profile disasters are released to the public piecemeal if at all, then quite later, and some of those are misleading, in particular about what could have been done to prevent disaster. It's as though because so many parties were negligent it is better to excuse all of them than to alarm the public. And, as ever, there are venal economic arguments that genuine safety costs more than the public will pay, architecture here mimicking transporation.

From this lack of reporting one might be led erroneously to believe that buildings are less dangerous than planes and trains, and not that real estate interest are more powerful than those of transport, especially in major urban areas like New York City, home of the world's largest number of millionaire and billionaire property moguls and their extensive network of financiers, lawyers, architects, engineers, builders, unions, building officials, suppliers, insurance providers, operating staff, investors and those of us who squat in their sky-high conceits in fear and trembling, head-patted by the world's greatest practitioners of "world class" architectural hype and deception (termed, humorously, "architectural criticism," which never criticizes distasteful building safety -- critics can't read building codes). Read the code of Walter Kirn's recent novel, Up in the Air, in which the main character describes how he came to trust the openly risky world of non-locational airplane travel rather than the hidden risk of architectura infirma."

From: "Craig"
To: <jya@cryptome.org>
Subject: Re: WTC
Date: Fri, 14 Sep 2001 20:52:12 +0930

As a layperson, I found your comments very informative.  Although I am familiar with the WTC only through tv, movies etc it has always been my wish to visit them.

Your comment:

I never heard the Twin Towers referred to as "beloved" as are so many of the globe's architectural landmarks of avarice. Perhaps in death that will happen as with venerated ruins of folly.

They may have been born through folly and avarice but they captured my imagination.  My father is a rigger and he told be stories about some of the feats of engineering performed there. I think at times he wished he could have walked on that steel.

I hope they are rebuilt. They weren't just a symbol to the NYC, U.S but to the world.  They are symbol of what humanity can achieve.  If nothing else, that probably is the true mark of this building, conceived in conceit but a wonder of the world.

I also add my condolences to the citizens of the U.S.

From: I
To: <jya@cryptome.org>
Subject: WTC
Date: Fri, 14 Sep 2001 21:07:05 +0800

This catastrophe is an inditement of U.S. construction standards. The cheap and shoddy methods employed in U.S. construction came home to roost. Thousands of the victims were not killed by the terrorists but by shoddy construction.

A building constructed according to European standards would have been heavily damaged but not collapsed like a card house. What is astonishing that none of the media hounds even questioned why the buildings collapsed instantaneously top to bottom and nothing left.

The attached test of a letter to my architect friends will explain my theory.

My engineering training brings me back to New York I am afraid and as a para architect I will bounce this of you. Remember nobody has raised this point in the media before as it requires "thinking outside the square" and this is new ground and possibly insulting to your profession.

Why have the two (three) towers collapsed like card houses from top to bottom in one hit?

I have lived in the U.S. and watched constructions going up and this is my theory. Yankee towers are totally constructed of steel. Girders are bolted together, floors are concrete slabs poured on corrugated steel sheets. Unlike European/SAand Oz design there is no central core constructed of heavy reinforced concrete. Beams and girders of course receive a thin spray-on concrete coating (which is what caused the dust) but essentially these give in case of fire too as the bolts expand and unlock the friction bond in the joints and presto. Further beams are starting to bend above 900 degrees and lose their strength. My god, fast and cheap triumphed over safety in the U.S. for sure. 

In the World Trade Centre the curtain facade was weight-bearing and fine until it received the ultimate test.

My theory is that on impact the building got sort of whip-lashed and this sheared a percentage of the bolts holding beams and girders together and that put the remaining bolts beyond design stress. Then they gave in too and the entire building collapsed as if not having any inner strenght.

With a central concrete core there would have been heavy losses, but the building would have been intact at least below the impact site.

What further irritates me is the totally ignored safety aspect of skyscrapers and this one applies to Australia too. As if safety means nothing, they get adorned with spires and faux facades to make sure helicopter landings are difficult if not impossible during updraughts caused by fires. This very bad and irresponsible design is STILL GOING ON because spires are soooo pretty and make extra money of course for from jcell phone and TV companies. A triumph of form over function.

The World Trade Centre is deep black mark against the designers and U.S. construction methods in general. What do you think?

G

Date: Fri, 14 Sep 2001 10:15:42 -0400
Subject: WTA/dedicated inspectors
From: N
To: <jya@cryptome.org>

I'm an architect in Providence, RI  and read your comments with interest. Mostly I have done residential construction, so my only experience with structure on this level was in college (RISD '78).

When I saw the collapses (live), they were such clean implosions, matching the best planned demolitions I have ever seen. (Do architects ever miss films of them, or is it just me?) I was sure that previously set explosives must have been involved. On further reflection it occured to me that there's a limit to the impact load from it's upper stories that ANY building can take. If a building had to be able to handle the impact load of the sudden collapse of it's upper stories, wouldn't we be limited to 6 story buildings with very little open interior space? I was only 12 when these buldings were completed, and have no connection to Mr. Yamasaki, I'm not defending him; but it seems to me that between the plane's impact and the resulting fire total collapse was inevitable The exterior skin did the neighboring buildings the great service of containing the collapse. I don't know the potential of sprinkler systems; maybe tall buildings have some future safety improvements there. But if sprinkler systems of that caliber existed now, the Challenger wouldn't have happened, even with it's O-rings.

I would also like to agree with your observations about the quality and dedication of many safety officials. Providence rivals or exceeds NY in it's reputation for corruption, and I'm sure it's often true. For much of my career I was the one elected for code stuff. Like you I was supprised. Not only did most know their stuff and insist that it be conformed to, but also some were patient teachers/interpreters.

From: CB
To: "'jya@cryptome.org'" <jya@cryptome.org>
Subject: Could have been much worse?
Date: Fri, 14 Sep 2001 10:08:55 -0500

I realize the choice of targets was largely political, but they could have done much worse.

Do you think that a plane of that size(or 3 of them) could pierce a dam or weaken it enough to cause it to break?  I do not know much about the geography of the Northeast, but I can tell you that there is a dam 15 miles upstream of Tulsa, Oklahoma that would send a 50 foot wall of water into downtown, wiping out 50 story skyscrapers(okay, we only have one 50 story one) with minutes notice only.  I imagine it would kill 50,000 people quite easily.

Think of the devastation in hitting Hoover dam.  In addidtion to the death from flooding(Vegas? but I have no idea what is downstream), there would be power shortages and prolonged devastation both downstream due to water and up from lack of water(Lake Mead provides alot of water to the region I believe).

Would a plane of that size bounce off Hoover dam and just explode on the side?  A building is not designed to keep a plane from penetrating its core and the fire inside did the real damage, but a dam in a solid concrete. However, Hoover dam is only 45 feet wide at the top and you would however only need to create a crack below the waterline to eventually break the entire structure.  Water would flow through it at tremendous force eroding the dam within hours or even minutes.  Hell you could drive a car bomb right over Hoover dam and weaken it before hand.

I am no expert on dams and I certainly won't win any geograpy contests and I really havn't researched this, but do you think it is possible on SOME dams?

To: CB
From John Young <jya@cryptome.org>

Because aircraft are made of relatively fragile materials compared to massive concrete dams, a crash probably would have little effect. You are right that they are weakest at the top but even at that location they are far stronger than buildings due to the very large hydraulic forces they must contain even at the brim.

To give some support to your theory, Switzerland is the home to several rare thin-shell concrete dams, shaped similar to eggshells to resist hydraulic forces with elegant precisions rather than mass and bulk. An aircraft could indeed fracture one of those. Thin-shell dams are located in several countries including the US.

Earthen dams, which are usually comparatively low, would be vulnerable too. For example, an attack on the levees at New Orleans could be disatrous. Still, even there I think explosives would have to be on board an aircraft to break the levees. Earth absorbs explosive forces quite well -- note the rightly celebrated fox hole.

You may recall instances in war when the military is trying to breach dams and knock-out bridges. It usually takes several direct bomb hits to have an effect. Civil engineering structures, compared to architecture, are greatly superior at withstanding violent attacks of man and nature.

Ships are another matter. Large ships can take out bridges, piers, docks and dams for they are designed to resist similar hydraulic forces and are made of exceptionally strong and heavy materials.

In recent years a new type of hybrid craft has appeared, part airplane, part ship, which initially rests in water but can reach speeds of airplanes well in excess of 100 miles an hour by utilizing lifting design in the craft so that it skims the surface of the water. (The Web has several sites which describe these.)

One of these crafts, some of which are quite large, could have the bulk and speed to breach the brim of a concrete dam, particularly if it was loaded with heavy materials.