World Trade Center Collapse Theories

[rogerick1970]

So many speculations on how the WTC collasped. But Im just wondering, if they had built the original WTC with a concrete core, would it have had a chance to withstand the attacks?

[Ninjahedge]

It had a concrete core.

The design was a concrete core with a metal exterior shell. One life-saving addition was the "hat" truss on the top that I believe was added (I am not sure) to help increase the stiffness of the building. This acted as a temporary load transver cantelever beam when the perimeter columns were taken out.

Thing is, as the remaining columns got hotter and hotter, their stiffness was compromised and they eventually buckled and failed.

If it was not for the redundant design, however, they would not have stood at all after impact.


As for a 100% concrete structure, I do not think that is 100% possible even now for a building of that height. One MAJOR reason, besides strength of material, would be creep shrinkage of that much concrete over a long term. Having some members with large stresses and others with small over such a long length would promote differential deflection (shortening) over time and cause a problem during the buildings lifetime.

[alonzo-ny]

It had a concrete core.



This is completely incorrect as far as i know, from countless hours research and study and documentaries of the collapse i would say with absolute confidence they did not have concrete cores. It was steel with dry wall. check out some construction images, do you ever see a concrete core?

[wns808]

Alonzo is right about the drywalled core. A window washer and some people trapped in an express elevator in the North Tower on 9/11 were able to break thru the sheetrock w/ his squeege to a bathroom on the 50th floor and escape.

If the core was concrete, that would be a diff. story

[Viktorkrum77]

Just look at the Windsor-Madrid fire, since their concrete core survived, chances are possible. But due to the force it seems doubtful.

[Jasonik]

North Tower Blueprints (http://911research.wtc7.net/wtc/evidence/plans/frames.html)

[alonzo-ny]

If memory serves me right 7wtc and boa are the first buildings in new york to be built with a concrete core. Great link^

[ramvid01]

I always thought that WTC was all steel and no concrete. All the documentaries on it never mentioned concrete, but drywall core (if you can call it that). Supposedly if there had been a concrete core the plane would not have damaged the core as much.

[Jasonik]

Ninjahedge is this you? (http://www.youtube.com/watch?v=KnhuKKl5Fvw)

[alonzo-ny]

I always thought that WTC was all steel and no concrete. All the documentaries on it never mentioned concrete, but drywall core (if you can call it that). Thats why the plane parts

You are right, though the only concrete in the building were on the floorplates.

[Stern]

As for a 100% concrete structure, I do not think that is 100% possible even now for a building of that height. One MAJOR reason, besides strength of material, would be creep shrinkage of that much concrete over a long term. Having some members with large stresses and others with small over such a long length would promote differential deflection (shortening) over time and cause a problem during the buildings lifetime.

Burj Dubai is an all concrete construction.

[ramvid01]

Burj Dubai is an all concrete construction.

To a certain height. Then its a all steel towards the top of the building.

[Stern]

To a certain height. Then its a all steel towards the top of the building.

To my knowledge only the spire will be steel. It doesn't matter though, my point was only that it is not impossible to make a building the height of the WTC an entirely concrete structure. Right now the Burj Dubai is currently at 455 meters to the 413 meters of the former WTC, at this point in its currently it is an all concrete construction. Also the Petronas Towers are a concrete construction, sans the steel spires.

[Vengineer]

I think the only major limitation for concrete construction is the distance in which the concrete must be pumped. They solved this problem on the Burj Dubai by injecting coolants into the concrete to delay its hydration and hardening.

[kliq6]

the col hard to truth is no matter how it was built, nothing at that time nor now is built to withstand the impact of a fully fueled 747 airplane

[Ninjahedge]

This is completely incorrect as far as i know, from countless hours research and study and documentaries of the collapse i would say with absolute confidence they did not have concrete cores. It was steel with dry wall. check out some construction images, do you ever see a concrete core?

Elevator cores are concrete. The suport system was a concrete core and an external steel frame. The plane compromised both when it went through.

http://news.bbc.co.uk/2/hi/americas/1540044.stm

Also, the 9-11 site you referenced to Jason has a LOT of problems with it. Do not even get me started on all the conspiracy theory crap they get into. Also, that is not me in that vid clip.

There is indeed a concrete core, so whoever is telling you otherwise and that the building would not hav ebeen damaged if theer was is lacking some key information.

The building was compromised in a number of ways, one of which being the long span the floor deck was laid out on. There was not much columnar redundancy there. Saving grace was the hat truss which acted as a cantelever support and let the upper storied hang on the core and the columns on the far side from the impact.

Weidlinger Associates, a Manattan based firm specializing in things like this, did the analysis. http://911research.wtc7.net/cache/wtc/official/enr_silverstein1.html

Do a google to find out more if you want.


And Vengineer, the pump time is not the only problem. Differential deflection is a concern, but a lot of companies do not seem to be taking that into account. I am not saying that it is impossible to do what is being done, but that sometimes some things aren't seen until they are actually done and experienced. If Burj has not taken into acocunt the differential deflection between building finish and, say, 5 years after construction, I would not be surprised to see some problems with the fit and finishes on the upper floors after a time....

[Vengineer]

So you're saying that differential deflection is a problem for almost all modern day residential high rises being constructed around the world?

[alonzo-ny]

Look at the images, no concrete on the cores.

http://farm1.static.flickr.com/195/463202979_44e89f91f4_o.jpg

http://farm1.static.flickr.com/197/463202973_f868002fa3_o.jpg

Look at these images for buildings with concrete cores.

http://static.flickr.com/107/301372448_4d9c44a958_b.jpg

http://skyscrapers.cn/forum/attachments/295314016_216581f8a5_o_37eloTNlaIFL.jpg

Not the same, they didnt have concrete cores. The story about the elevator is true. Some people who were trapped in an elevator pried the doors open and smashed through the drywall into a bathroom. Not even the lift shafts were concrete. If you know as much about the trade center as you should to make blunt claims with no proof to back it up you'd know all this. The steel was fire-proofed with a spray on fire-proofing and the core had drywall instead of concrete. This is fact.

The link to 911research proves you wrong. The 1 time the word concrete is used when questioning if alternative fireproofing could have prevented collapse.

"Regarding building materials, Levy says: "Concrete is not foolproof either."

and as much as i hate to admit it but my beloved BBC is wrong.

[Viktorkrum77]

Is the Freedom Tower to have a concrete core, like the last picture above which looks similar in layout?

[alonzo-ny]

Is the Freedom Tower to have a concrete core, like the last picture above which looks similar in layout?

Yes but the FT core will be rectangular not the kind of bow-tie shape of the SWFC.

Could someone explain what differential deflection is?

[Stern]

Is the Freedom Tower to have a concrete core, like the last picture above which looks similar in layout?

The WTC will have a concrete core but it will not look like the above photos. The reason is that there is a peculiar agreement among construction unions in New York that the steel workers must work above the concrete workers working on the core. For this reason the Freedom Tower's construction will look like the construction of One Bryant Park and 7 WTC, both constructions with a concrete core that had a low visibility during construction.

[alonzo-ny]

The WTC will have a concrete core but it will not look like the above photos. The reason is that there is a peculiar agreement among construction unions in New York that the steel workers must work above the concrete workers working on the core. For this reason the Freedom Tower's construction will look like the construction of One Bryant Park and 7 WTC, both constructions with a concrete core that had a low visibility during construction.

Does this have any implications on construction speed at all?

[rogerick1970]

But basically, if another terroist attack happened to the freedom tower, and planes were slammed into the buildings, would the building be albe to withstand. Cause if you think about it, concrete will melyt to because its made with a mixture of sand and water right?

[Viktorkrum77]

But basically, if another terroist attack happened to the freedom tower, and planes were slammed into the buildings, would the building be albe to withstand. Cause if you think about it, concrete will melyt to because its made with a mixture of sand and water right?

To add to his question, what about the Sears Tower?

On a side note, are there any WTC7 construction pictures available?

[Vengineer]

The WTC will have a concrete core but it will not look like the above photos. The reason is that there is a peculiar agreement among construction unions in New York that the steel workers must work above the concrete workers working on the core. For this reason the Freedom Tower's construction will look like the construction of One Bryant Park and 7 WTC, both constructions with a concrete core that had a low visibility during construction.

Is that really why?! I've always wondered why those towers went up like that. Construction unions rule this city.

Perhaps this was also the case for the original WTC?

[Vengineer]

http://algoxy.com/conc/core.html

[rogerick1970]

Is that really why?! I've always wondered why those towers went up like that. Construction unions rule this city.

So learning that 7wtc and BOA was the first buildings in NYC to have A CONCRETE base, that means that the ESB, CB, and Trump Towers are all in danger:(

[Stern]

Does this have any implications on construction speed at all?

Im not sure, the unions are so powerful and only work in their own interests, so I wouldnt be surprised if it does infact slow down the overall construction.

[Ninjahedge]

So you're saying that differential deflection is a problem for almost all modern day residential high rises being constructed around the world?

Generally speaking. Depends on how tall they are and what the difference in stress is.

The problem we saw was with a building whose core was designed mostly for lateral, so the load was much less sustained than the perimeter columns (only a core and one set of perimeter columns). There was only one span in a 55 story building, so the differential added up.

[Ninjahedge]

Is that really why?! I've always wondered why those towers went up like that. Construction unions rule this city.

Perhaps this was also the case for the original WTC?

No, my mistake....

http://www.civil.usyd.edu.au/wtc.shtml

Seems like they deliberately avoided concrete in the core.....

Would it have done better? Maybe, but I think the collapse mechanism might have been different (floor failure rather than columnar failure). But as soon as you start putting in a large concrete core, you also eliminate the need for so much steel at the perimeter, so the project economics would force a design change.

This building may not have fared any better at resisting an airliner collision. I would have to see what fire effects are on concrete and reinforcement....

[Jasonik]

Also, the 9-11 site you referenced to Jason[ik] has a LOT of problems with it.

Are you saying that the more than 100 pages of North Tower Blueprints (http://911research.wtc7.net/wtc/evidence/plans/frames.html) are somehow erroneous? A quick glance at any of them would show anyone with as much knowledge about construction as you purport to have that there is no concrete in the core, just massive steel columns.

http://911research.wtc7.net/wtc/evidence/plans/doc/pac1TowerA/A-A-144_3.png

*****
Would it have done better if the core were made of braided spagetti? Maybe, but I think the collapse mechanism might have been different (floor failure rather than columnar failure). But as soon as you start putting in a large braided spagetti core, you also eliminate the need for so much steak at the perimeter, so the project economics would feed a design change.
*****

The steel core allowed the Towers to respond to wind loads by flexing and swaying utilizing the hat truss to redistribute loads from the tube to the core and vice versa.

http://911research.wtc7.net/wtc/arch/docs/hattruss.jpg

[Vengineer]

http://algoxy.com/conc/core.html

As I've posted earlier, this site's main objective seems to be proving the existence of a steel reinforced concrete core on the WTC towers. They have the project architect quoting a concrete core along with other credible sources. Now I'm really confused. Was there a concrete core or not?

[alonzo-ny]

Original trade center : definitely not
New towers : yes

[Ninjahedge]

Are you saying that the more than 100 pages of North Tower Blueprints (http://911research.wtc7.net/wtc/evidence/plans/frames.html) are somehow erroneous? A quick glance at any of them would show anyone with as much knowledge about construction as you purport to have that there is no concrete in the core, just massive steel columns.

Um...

No, my mistake....

http://www.civil.usyd.edu.au/wtc.shtml

Seems like they deliberately avoided concrete in the core.....

Would it have done better? Maybe, but I think the collapse mechanism might have been different (floor failure rather than columnar failure). But as soon as you start putting in a large concrete core, you also eliminate the need for so much steel at the perimeter, so the project economics would force a design change.

This building may not have fared any better at resisting an airliner collision. I would have to see what fire effects are on concrete and reinforcement....


ST HELL U and read next time. (Acronyms are dirty :rolleyes: )

When someone apologizes for making an error, you do NOT go on and on about it. Now PLEASE do me a favor and retract your insipid condescending remarks and step OFF.

[Jasonik]

I thought you were an expert on the WTC collapse? (http://www.wirednewyork.com/forum/showpost.php?p=159190&postcount=18)

You can't have it both ways. Either you have special knowledge that confers on you some authority on the subject, or you make wild unsubstantiated claims (http://www.wirednewyork.com/forum/showpost.php?p=160355&postcount=2) (in the first reply no less). I'm sorry if you're offending by my inferring the latter, but you leave me little choice.

[Ninjahedge]

I thought you were an expert on the WTC collapse? (http://www.wirednewyork.com/forum/showpost.php?p=159190&postcount=18)

I worked for the company that did the analysis. I am a structural engineer, I have 12 years of experience.

Yes I am an expert you XXXXXXX.

You can't have it both ways. Either you have special knowledge that confers on you some authority on the subject, or you make wild unsubstantiated claims (http://www.wirednewyork.com/forum/showpost.php?p=160355&postcount=2) (in the first reply no less). I'm sorry if you're offending by my inferring the latter, but you leave me little choice.

Wild unsubstantiated claims? You mean like the hat truss you showed in your drawing?

This was meant to bring attention to the fact that I also mentioned the trusses as being a saving grace of the TT structure, not as an accusation of unsubstantial assertions. It was meant to be a disgruntaled statement of agreement, but could be read the wrong way... :(

What's with the animosity? Still crying over Imus? Give me a break. I admitted a mistake about the core, but you gloss right over it and continue to insult me.

Then when it is brought to your attention that I did apologies, you insult me some more instead of apologizing.

What is WRONG with you man? :confused:

[Jasonik]

Wild unsubstantiated claims? You mean like the hat truss you showed in your drawing?

The hat truss schematic whose hotlink has expired can be found on page 11 of the:

Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower (DRAFT)

Found here (The first heading: Full Report (292 pgs.)):

http://wtc.nist.gov/pubs/#draft


Grow a pair.
You've lost all credibility with me.
Remind me to never have you do any of my engineering.

[Ninjahedge]

The hat truss schematic whose hotlink has expired can be found on page 11 of the:

Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower (DRAFT)

Found here (The first heading: Full Report (292 pgs.)):

http://wtc.nist.gov/pubs/#draft


Grow a pair.
You've lost all credibility with me.
Remind me to never have you do any of my engineering.

Like I would want to work with you now.

I was not saying your hat truss was NOT credible, AAMOF, I WAS THE FIRST ONE TO MENTION IT!

GET YOUR ARGUMENTS STRAIT, or do you have a problem with ever admitting you are wrong?

GMAB. I come in, apologize for being incorrect about the concrete core and you PERSIST IN LAMBASTING ME, even misreading things I am posting and using the misreading as some unsubstantiated proof of fallacy when, if you had simply gotten off your holier than thou high horse and READ what I said you would see that I mentioned the hat truss in the very post that I believe you said was full of errors.



As for the 9-11 site you linked to, I read through some of the claims they were making and it seems to be on the conspiracy bandwagon. Pleas pick through it and tell us what you find that may, oh I don't know, disagree with the other things you have posted here in defense of your position.

Pull the arrows out of your side and quit whimpering and maybe you will realize that you were the one who put them there in the first place!

Self inflicted martyrdom is so gauche. :rolleyes:

[Ninjahedge]

Bumping for Veng and some others.


/me leaves.

[rogerick1970]

So was it a concrete core or not?

[User Name]

So was it a concrete core or not?
No, it wasn't.

[Jasonik]

Problems of Disaster Mitigation and Design

Designing tall buildings to withstand this sort of attack seems next to impossible. It would require a much thicker insulation of steel, with blast-resistant protective cover. Replacing the rectangular framed tube by a hardened circular monolithic tube with tiny windows might help to deflect much of the debris and fuel from an impacting aircraft sideways, but regardless of cost, who would want to work in such a building?

The problems appear to be equally severe for concrete columns because concrete heated to such temperatures [800 C] undergoes explosive thermal spalling, thermal fracture and disintegration due to dehydration of hardened cement paste (e.g., Baˇzant and Kaplan 1996). These questions arise not only for buildings supported on many columns but also for the recent designs of tall buildings with a massive monolithic concrete core functioning as a tubular mast. These recent designs use high-strength concrete which, however, is even more susceptible to explosive thermal spalling and thermal fracture than normal concrete. The useof refractory concretes as the structural material invites many open questions (Baˇzant and Kaplan 1996). Special alloys or various refractory ceramic composites may of course function at such temperatures, but the cost would increase astronomically.

Source:
Why Did the World Trade Center Collapse?—Simple Analysis (http://www3.tam.uiuc.edu/news/200109wtc/)
By Zdenˇek P. Baˇzant1, Fellow ASCE, and Yong Zhou

[alonzo-ny]

From the above description it sounds like an all concrete building eg trump chicago would be completely f***** is it was attacked in the same manner, the concrete starts to change properties at 800c less than steel i believe?

[conezone]

Here is a good picture of the core.

http://img233.imageshack.us/img233/2380/twinsbr5.jpg

[rogerick1970]

Here is a good picture of the core.

http://img233.imageshack.us/img233/2380/twinsbr5.jpg


Wow, it looks so fragile. Im suprised on how long these buildings remained up. It was definately an act of God.

[Ninjahedge]

Not really. It was a very economical, but also redundant design due primarily to its hat.

If it wasn't for the hat and the redistribution of loading, they would have gone down as soon as they were hit. It is a term called "progressive failure" where damages to one section of a building compromise a larger area than what is directly supported by those pieces.


Studies are now being performed to prevent things like that, mainly in light of the transfer girder failure and subsequent collapse of the (xx) building in Oklahoma city. The tough thing is, for damage as extensive as this, on a structure this large, it is hard to limit the damage just to the area hit. Even if only half the building above started to collapse, the sheer mass of that much steel and concrete coming down would make for a very unstable structure and might even cause a toppling action rather than the buckling collapse we saw.

As horrible as it was, the pancaking of the towers was a blessing compared to other failure modes. I shudder to think what would have happened if one of them fell over.

[Edward]

... It was definately an act of God.
Which particular god in this instance?

[stache]

A vengeful one?

[rogerick1970]

Which particular god in this instance?

Im talking about my lord and savior jesus christ. I was refering that his grace and mercy saved 10's of thousands of lives that could have parished like the unfortunate ones that did.

[ZippyTheChimp]

Why didn't he just stop the planes?

[rogerick1970]

Why didn't he just stop the planes?


Because unfortunately, he allows some things to happen. For instance, if someone you knew or love found out today that they had cancer, you would be heartbroken, and if you belive in God, you would have resentment towards him. See, we have to understand that sometimes in life, things dont go the way we want them to go, but in the way that God sees fit for things to happen. Unfortunately, God allows some things to happen that may teach us lessons, and make us stronger in the long run. For example, even though 9/11 was a terrible tragedy, it also opened our eyes. It showed America that we were not invinsible, and that we have no earthly control over what happens. It also taught us to live life to the fullest, and never take anyone for granted, because you never know when you might lose them.

Unfortunately, I was numb to the fact, and had to learn the hard way resulting in my family member being killed in the Pentagon. See their is just some things in life that we werent meant to understand. All we have to do is learn from our faults, and strive to be stronger.

[lofter1]

GOD ^^^ as the flakey nonsensical trickster ...

Doesn't score too high on my faith-o-meter :cool:

[lofter1]

For example, even though 9/11 was a terrible tragedy, it also opened our eyes. It showed America that we were not invinsible, and that we have no earthly control over what happens. It also taught us to live life to the fullest ...

I beg to differ ... and you should really speak only for yourself, as you have no idea what I think or what I've learned or what I know.

btw:The events of 9/11 taught me none of those things mention -- some of them I already knew well before the horror show took place -- and some you mention I didn't believe before that day and still don't believe now.

[ZippyTheChimp]

Why didn't he just stop the planes?
Because...
I wasn't really looking for an answer. You have no idea what God thinks, or why he does what he does - like everyone else on earth.

The 19 hijackers thought they knew what God was thinking.

[BPC]

Roger, if you study human history, you will see that as long as some people have been building great cities, other peoples have been destroying them. As long as some men have been building great monuments, other men have been knocking them down. If there is a God, he has always chosen not to intervene. Indeed, nothing about 9/11 was unique, and thus there is no real valuable lesson to be learned from it, except some small ones about locking cockpit doors and such. A hundred years from now, if civilization and history books still exist, the incident will pale in comparison with the incredible carnage of the 20th century that preceded it.

[alonzo-ny]

There is a big difference in the carnage of war and that of a terrorist attack. People are expected to die horribly on a battlefield but not in their office. and also their deaths werent broadcasted to the world. 911 was the most reported incident ever i would guess therefore it wont be forgotten because everyone saw it unlike what i think your referring to in the 20th century. If you think about the Abombs in ww2, that would have been a much more significant if it happened now because instantly everyone in the world would have seen it.

[ZippyTheChimp]

There is a big difference in the carnage of war and that of a terrorist attack. People are expected to die horribly on a battlefield but not in their office.The majority of WWII casualties were non-combatants who did not die on battlefields; unless, of course, you regard the cities they lived in as battlefields.

[alonzo-ny]

I guess i do, I mean it was war in a sense we probably will never really know again but that is the way war was carried out at that time and the citizens were aware of it and therefore it would be shocking when they died. This in my opinion is a much different story from going to another regular day as usual only to have to jump from the 100 floor/ have a 100storey building collapse with you inside/ having debree fall on you/ have your plane hijacked and crashed into a building.

[ZippyTheChimp]

^
Well, Pearl Harbor was very much like 09/11.

If you listen to people talk about it who were alive at that time, they have an emotional attachment that is absent from those of us who know it from history.

We relate to 09/11 in some personal way: directly involved, a witness, or what we were doing when it happened and how we reacted.

At some point in time, we will all be gone, and that connection will be lost. 09/11, like Pearl Harbor, will pass into history. No matter how extensive the media information, it won't be the same for someone who was not yet born when it happened.

[alonzo-ny]

It will be alot easier for some kid in the future to write a essay about but other than that it will just be the the next generations pearl harbor.

[Transic]

Because unfortunately, he allows some things to happen. For instance, if someone you knew or love found out today that they had cancer, you would be heartbroken, and if you belive in God, you would have resentment towards him. See, we have to understand that sometimes in life, things dont go the way we want them to go, but in the way that God sees fit for things to happen. Unfortunately, God allows some things to happen that may teach us lessons, and make us stronger in the long run. For example, even though 9/11 was a terrible tragedy, it also opened our eyes. It showed America that we were not invinsible, and that we have no earthly control over what happens. It also taught us to live life to the fullest, and never take anyone for granted, because you never know when you might lose them.

Unfortunately, I was numb to the fact, and had to learn the hard way resulting in my family member being killed in the Pentagon. See their is just some things in life that we werent meant to understand. All we have to do is learn from our faults, and strive to be stronger.

I think I could get the gist of the situation without having to believe in any particular religion. Thank you very much.

One of the things that really irritated during the immediate aftermath of 9/11 was how certain religious groups tried to take advantage of the confusion. Like those annoying individuals who stood in the general area of WTC while handing out pamphlets and booklets with images of the collapsed Twin Towers and (certain sects) Christian prayers. Nothing like Doomsday to get some people motivated, huh? :rolleyes:

What I felt that day was a sense of violation, of someone intruding into my house and raping me and me feeling powerless to stop it from happening. That an entire nation was in a midst of being violated and so many could not figure what was transpiring. That so many in the nation were ignorant and even dismissant of the existance of a "far enemy", even after incidents like Khobar Towers, Nairobi, Tanzania, Beirut Marine barracks bombing and, yes, WTC 1993. This actually scares me more than the event itself. With the nihilism going on today, it not impossible to imagine that they can win, and Sharia law imposed on all of us. Should that day come, you can forget about having a Supreme Court which defends reproductive rights because there would be NO reproductive rights to defend. Same for civil rights, voting rights, all kinds of other rights many of us consider to be entitled to. Why liberals haven't come around to that fact is the most baffling thing I have found so far. :(

[Stern]

Thread is: World Trade Center Collapse Theories

-Not-

Theories on God

[Transic]

OK, then.

My theory is that Al-Qaeda scoped out the place and knew the ins and outs of the complex. That's how Al Zawahri and Sheik Mohammed devised the plan the destroy them using large jets with a full tank of fuel. They knew that superheated fuel would melt the steel in the Towers, causing them to bend over and finally break. That, in turn, pushed the weight of the sections of the buildings the impact area downward, creating that momentum that we all saw in person. Like Newton's theory, for every action there's an equal and opposite reaction.

Thus, we knew how sophisticated and dangerous they really are. Or so I thought until the appearance of those conspiracy nuts sites.

[alonzo-ny]

this thread hasnt been on topic since the first post

[lofter1]

The wording of the title ("theories") covers a pretty wide area.

Sometimes it's good just to let a thread run wild and see where it goes.

[Stern]

The wording of the title ("theories") covers a pretty wide area.

Sometimes it's good just to let a thread run wild and see where it goes.

I don't think so, the threads already been closed once.

If people want to discuss god I suggest discussing the sure to be contentious topic at Anything Goes or News and Politics.

[lofter1]

It's full of silliness anyway -- so closing it down would be no great loss.

[Stern]

It's full of silliness anyway -- so closing it down would be no great loss.

The topic is not silly. If it was there wouldn't have been a 500 page report on to why the buildings collapsed. Its the childish name calling and the off topic discussions that is silly.

[alonzo-ny]

Pretty obvious thats what he was refering to, he didnt say anything about the topic being silly, you did.

[Stern]

Point is if people stick to the topic, nothing will be silly, nothing will be closed.

Why is everything always made into an issue?

[infoshare]

Why is everything always made into an issue?

Good point!:)

[alonzo-ny]

It is a good point but it became an issue when stern misquoted lofters post and made into something else when it was an innocent comment.

[Stern]

It is a good point but it became an issue when stern misquoted lofters post and made into something else when it was an innocent comment.

I didn't mis-quote lofter. But I dont want to make this an issue, what I really want is for the discussion to get back to topic. I affirmed that the off-topic discussion which this is among is "silly", but because the topic is not, it should remain open. I suggest you re-read my post and that discussion is returned to World Trade Center Collapse Theories.

[alonzo-ny]

Lofter stated the thread was 'full of silliness' not that thread in principle was silly. There is a difference. You then said 'If it was there wouldn't have been a 500 page report on to why the buildings collapsed' even though lofter said nothing of the sort to make you assume he thought it wasnt important.

However re reading your post it seems there is another tone you could have been using which would mean you werent attacking lofters comment but elaborating that it is a worthwhile thread. If this was your intended tone i apologise but it would have been clearer had you not directly quoted lofter which made it seem you were directing your feelings toward his comment.

I think issues like this misunderstanding arise because its hard to tell tone from words and a careless full stop instead of comma can make a big difference and unfortunately this will happen.

[Stern]

Lofter stated the thread was 'full of silliness' not that thread in principle was silly. There is a difference. You then said 'If it was there wouldn't have been a 500 page report on to why the buildings collapsed' even though lofter said nothing of the sort to make you assume he thought it wasnt important.

However re reading your post it seems there is another tone you could have been using which would mean you werent attacking lofters comment but elaborating that it is a worthwhile thread. If this was your intended tone i apologise but it would have been clearer had you not directly quoted lofter which made it seem you were directing your feelings toward his comment.

I think issues like this misunderstanding arise because its hard to tell tone from words and a careless full stop instead of comma can make a big difference and unfortunately this will happen.


It was the latter, my reason was to show why this thread is important and should remain open, just if we could get things back on topic, which seems to be impossible with this particularly doomed thread, again not the topic with is strong, just with all the sillyness.

[alonzo-ny]

On topic, i thought the collapse was a pretty open and shut case now. The force of the aircraft hitting the towers destroyed fireproofing which allowed the intense fire to weaken the steel to the point it could no longer hold the weight of the towers.

The south tower though hit second collapsed first because the impact was lower resulting in more weight bearing down on the damaged floors. The tower collapses when the east facade of columns clearly snap one after the other, there are some close up videos on you tube if you can find them.

The north tower hit higher up and at a more central location stood longer as a result.

What amazes me about the collapse is, with the north tower, when it collapses a massive part of the facade probably only a couple of columns wide and maybe 500ft tall stays freestanding for a good few seconds before falling. Also you can see major parts of the core staying standing before ultimately collapsing.

I disagree withe Ninjas assesment that the hat truss was all that was keeping towers standing as i think the structure created a corbal effect when the impact hole was created and the weight was redistributed around the hole. The same was as when you remove a lintle from a brick window this would happen.

http://farm1.static.flickr.com/217/476438132_ae14b371b0_o.jpg

The dotted line where the lintle was and you can see how a hole is created where bricks are no longer structural and how the load is redistributed. I seen documentries about the WTC where engineers (perhaps leslie robertson but dont quote me) agree with this theory.

also there is a good view of the south towers collapse in this video the you dont normally seem to see. You can really hear the forces at work systematically gaining momentum destroying the tower.

http://www.youtube.com/watch?v=oLsdc6A68y0

Fast forward to 04:30

You will see its pt 8 of a series, its a decent docu i guess.

[injcsince81]

What amazes me about the collapse is, with the north tower, when it collapses a massive part of the facade probably only a couple of columns wide and maybe 500ft tall stays freestanding for a good few seconds before falling. Also you can see major parts of the core staying standing before ultimately collapsing.



I saw and took a picture of that standing part of the facade from Jersey City.

After a few seconds it was gone.

[alonzo-ny]

It amazed me how something so tall and unstable could stay upright at all

[Ninjahedge]

OK, then.

My theory is that Al-Qaeda scoped out the place and knew the ins and outs of the complex. That's how Al Zawahri and Sheik Mohammed devised the plan the destroy them using large jets with a full tank of fuel. They knew that superheated fuel would melt the steel in the Towers, causing them to bend over and finally break. That, in turn, pushed the weight of the sections of the buildings the impact area downward, creating that momentum that we all saw in person. Like Newton's theory, for every action there's an equal and opposite reaction.

Thus, we knew how sophisticated and dangerous they really are. Or so I thought until the appearance of those conspiracy nuts sites.

Trans, I seriously do not believe the terrorists knew that they would be able to take teh building down in the way it came down. They just knew that ramming a large plane full of fuel into teh side of teh building would be more damaging, and definitely easier to accomplish, than any other action.

It was a trump card that was played and they were undoubtedly surprised, and quite pleased at its final result.

Its subsequent reaction was something they nkew would be coming, but did not look forward to, although it has ironically helped their cause due to the lack of proper focus on our end.


But back to OT. It is hard to say what would have prevented something liek this from happening. You do not design a building to withstand a tornado, you do not design it to withstand an airplan impact. You just try to make sure you have ways of getting people to safety if either of those happen.

We were lucky that thes buildings were as annoyingly redundant, while still being EXTREMELY cost effective.

It was never designed for that, but sometimes designs work in more ways than were originally intended.

[Ninjahedge]

On topic, i thought the collapse was a pretty open and shut case now. The force of the aircraft hitting the towers destroyed fireproofing which allowed the intense fire to weaken the steel to the point it could no longer hold the weight of the towers.

The south tower though hit second collapsed first because the impact was lower resulting in more weight bearing down on the damaged floors. The tower collapses when the east facade of columns clearly snap one after the other, there are some close up videos on you tube if you can find them.

Actually, the problem was ven more simple. The second hit went first because it clipped teh core columns on teh front corner. If you look at the animations of the impacts that were shown earlier, you can see teh direction of the impact and debris.

That being the case, theer was nothing available to redistribute the load, so it was more prone to collapse. My former company did an extensive study on this and presented it to all of us in a series of lectures. Quite interesting, and I think the matter is no longer deemed "top secret" so you may be able to find it....

The north tower hit higher up and at a more central location stood longer as a result.

Partially correct. The height did matter, but the impact site mattered more. I believe one of teh engines took out the columns I mentioned in the second strike, but most of the columns in the core of the first were still intact.

What amazes me about the collapse is, with the north tower, when it collapses a massive part of the facade probably only a couple of columns wide and maybe 500ft tall stays freestanding for a good few seconds before falling. Also you can see major parts of the core staying standing before ultimately collapsing.

This was probably shearing action with the long span trusses not being especially suited to impact shear load.

I disagree withe Ninjas assesment that the hat truss was all that was keeping towers standing as i think the structure created a corbal effect when the impact hole was created and the weight was redistributed around the hole. The same was as when you remove a lintle from a brick window this would happen.

Except that there were not many horizontal transfers around the hole. The beams around the perimeter were not moment connections, tehy were only shear connection being held together by them, and the slab itself. There was very little, albeit some, corbel action.

The building was designed to be as light as possible. Between the long span joists, and the all-steel core, it was made to be as light as possible so it could reach teh design height with the materials available at the time.

also there is a good view of the south towers collapse in this video the you dont normally seem to see. You can really hear the forces at work systematically gaining momentum destroying the tower.

http://www.youtube.com/watch?v=oLsdc6A68y0

Fast forward to 04:30

You will see its pt 8 of a series, its a decent docu i guess.

I will have to take a look.

The most facinating thing I thought I saw was the superposition of a high-def finite element model of the progressive collapse overlaid on the actual video.

It was kind of freaky to watch. You could feel the steel bending as you saw it.....

[alonzo-ny]

The most facinating thing I thought I saw was the superposition of a high-def finite element model of the progressive collapse overlaid on the actual video.

It was kind of freaky to watch. You could feel the steel bending as you saw it.....

Anywhere we can see this video? The most horrifying thing about the video i posted is the sound. u dont hear it so close like that in most videos, like someone is ripping it apart.

[Ninjahedge]

Anywhere we can see this video? The most horrifying thing about the video i posted is the sound. u dont hear it so close like that in most videos, like someone is ripping it apart.

the first set shows them kind of small.

I have searched teh company website, but they do not seem to have it up. They never really had the knack of giving people what they wanted to see (besides, with something like that, bandwidth would go through the roof!!!)

It showed it kind of crunple-dent, then all start falling at the same time. It only showed the first few seconds of the collapse, but using a finite element modeler to match the collapse means that, most likely, most of the design assumptions that were made match the actual physical capacities and behavior of the structure.

(IOW, if they had this connected to that too rigidly, it did not collapse the same way, etc etc).

I will keep looking, and maybe even ask them if they have it available yet....

[alonzo-ny]

You can see the corner crumple in this vid. FF to 2:20

[rogerick1970]

When I made that comment, I had no intensions on forcing my beliefs on others, or offending anyone. Now unfortunately, everyone in this worlsd isnt going to believe the same, but that staement is what I believe. However, I do believe that I have the right to voice my opinions as being a citizen of America. But I do want to say if this statement offended anyone, I apologize.


Back on Topic: So if the Freedom Tower was hit with a plane, how much longer would it be able to withstand compared to the originals? Obviously it would be longer since it is a concrete core.

[alonzo-ny]

not sure, i think it would have a chance of staying up, depending on alot of variables.

Thing is it gets thinner further up. You could says it more vulnerable higher up but it also therefore has less weight pushing down on the damaged area.

The real question is, the originals with concrete core and the external columns within concrete. What would have happened then. I think they would have remained standing with almost everyone getting out bar thoses killed in impact, but this kind of structure would have been majorly over engineered.

[rogerick1970]

not sure, i think it would have a chance of staying up, depending on alot of variables.

Thing is it gets thinner further up. You could says it more vulnerable higher up but it also therefore has less weight pushing down on the damaged area.

The real question is, the originals with concrete core and the external columns within concrete. What would have happened then. I think they would have remained standing with almost everyone getting out bar thoses killed in impact, but this kind of structure would have been majorly over engineered.

Well unfortunately, whoever designed the original towers never thought it had a chance of being attacked by a 737 jet full of fuel. So hopefully, the same mistake wont happen again since the FT has a concrete core.

[User Name]

Well unfortunately, whoever designed the original towers never thought it had a chance of being attacked by a 737 jet full of fuel.
I don't know that it's possible to design a usable building to survive a fueled heavy jet being piloted into it. Even if it were, could it withstand 2 or more impacts? I'm sure someone would take the new design and any boastful statements made about its survivability as a challenge to be proven wrong.

So hopefully, the same mistake won't happen again since the FT has a concrete core.

We'll have to see.

[alonzo-ny]

The easiest way to keep a building standing an aircraft attack is to have stronger, locked cockpit doors or prevent the terrorists getting on the plane in the first place.

No terrorist will ever try to hijack a plane like that again because every passenger will be aware of impending doom and will attack the terrorists ala flight 93. It was a really big trump card and they played it.

[cfrobel]

Well unfortunately, whoever designed the original towers never thought it had a chance of being attacked by a 737 jet full of fuel. So hopefully, the same mistake wont happen again since the FT has a concrete core.

They said it could survive the impact from a jet travelling around landing speed in the case that it was lost in poor weather conditions, not ones travelling 500-600 mph.

[Ninjahedge]

The easiest way to keep a building standing an aircraft attack is to have stronger, locked cockpit doors or prevent the terrorists getting on the plane in the first place.

YES!

No terrorist will ever try to hijack a plane like that again because every passenger will be aware of impending doom and will attack the terrorists ala flight 93. It was a really big trump card and they played it.

Before it was thought that if your plane was hijacked, you just sit and be quiet and it will land in an airfield and then someone will try to rescue you.

But now that this trump card has been played, people will not sit tight on the plane. Hell, one of the planes that was hijacked in 2001 had its passengers get up and try to do something! the chances of that now are 100%.

[Ninjahedge]

They said it could survive the impact from a jet travelling around landing speed in the case that it was lost in poor weather conditions, not ones travelling 500-600 mph.


It did.

It stayed up for quite a while.

Could you please show who said this and what were the parameters? I doubt anyone said it would withstand a jet as big as the 747, and especially not one full with fuel.

(Also, I believe the jets hit at 200-300 MPH. 600 MPH at altitude is nearing mach 1...)

[alonzo-ny]

My understanding is that the scenario engineers anticipated was a slow moving 707 (biggest plane at the time) about to land which is lost in the fog.

Do you think if the planes were empty of fuel would the towers have stood?

[cfrobel]

It did.

It stayed up for quite a while.

Could you please show who said this and what were the parameters? I doubt anyone said it would withstand a jet as big as the 747, and especially not one full with fuel.

(Also, I believe the jets hit at 200-300 MPH. 600 MPH at altitude is nearing mach 1...)

The speed of sound is 769 mph so 600 is still far off of mach 1... Well I found the speeds which were a bit lower then I thought (found on page xlii in the Executive Summary of the NIST report):

AA 11 = 443 +-30
UAL 175 = 542 +-24

And actually the NIST provides an answer regarding design specs accounting for the impact of a 707 (I did read somewhere else about being able to take the impact from a slow flying 707 but no idea on the accuracy of that):

"The capability to conduct rigorous simulations of the aircraft impact, the growth and spread of the ensuing fires, and the effects of fires on the structure is a recent development. Since the approach to structural modeling was developed for the NIST WTC investigation, the technical capability available to the PANYNJ and its consultants and contactors to perform such analyses in the 1960s would have been quite limited in comparison to the capabilities brought to bear in the NIST investigation."

http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm

[rogerick1970]

Will the other towers also have a concrete core?

And isnt their some kind of test that can determine just how much a tower can withstand?

[Ninjahedge]

The speed of sound is 769 mph so 600 is still far off of mach 1... Well I found the speeds which were a bit lower then I thought (found on page xlii in the Executive Summary of the NIST report):

AA 11 = 443 +-30
UAL 175 = 542 +-24

And actually the NIST provides an answer regarding design specs accounting for the impact of a 707 (I did read somewhere else about being able to take the impact from a slow flying 707 but no idea on the accuracy of that):

"The capability to conduct rigorous simulations of the aircraft impact, the growth and spread of the ensuing fires, and the effects of fires on the structure is a recent development. Since the approach to structural modeling was developed for the NIST WTC investigation, the technical capability available to the PANYNJ and its consultants and contactors to perform such analyses in the 1960s would have been quite limited in comparison to the capabilities brought to bear in the NIST investigation."

http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm

Speed of sound changes with air density, so at sea level the SOS is faster than at XX altitude. Even temperature and humidity play a role!

Anyway, when planes are flying that low that close to NYC, even if they are by mistake, they are usually not at cruising speed. They have just taken off or are about to land, so it does not make much sense to design for a full-speed fully-laden impact.

I will have to confirm this, but I also believe a 707 is much smaller than a 747, and I have heard speculations about many buildings being designed for various plane impacts, but word around the engineering community is that most were not really designed for any major impact.

Most of the stories start off legitimate, such as designing for a cessna or other small personal craft, but then as it gets passed on, the "cessna" becomes a "plane". The "Plane" becomes a jet, and people start to speculate on what Jet. Then someone "hears" that a 747 could huit the Empire State Building, and you get the final culmination of rampant public speculation. A rumor that is hard to find any real data on.

I will have to read teh full NIST link you provided though. Thanks for reffing it!

[Ninjahedge]

PS, where were the speeds listed?

I do not dout you in your reference, but they still sound awfully fast!!!!!

[pianoman11686]

The planes that hit weren't 747's. They were 767's, if I remember correctly.

[Ninjahedge]

The planes that hit weren't 747's. They were 767's, if I remember correctly.

Oops.

I just knew they were BIG!!!!

Bigger than any other strike in the past, and definitely not designed for.

[alonzo-ny]

The buildings were designed to survive a slow moving 707 impact, the 707 being the largest aircraft at the time. Ive seen this on numerous documentries and coming out of leslie robertson's mouth.

[Bob]

The B767 is capable of takeoff weights of 300,000 lbs or more, making it a "heavy" aircraft by FAA standards. It is larger than a vintage B707. FWIW.

[kz1000ps]

There's a video on Youtube that was taped from a news station helicopter that was flying over Jersey somewhere. It shows a zoomed-out shot of downtown with no plane in sight, meaning if you can calculate roughly how far it was the Towers to the edge of the screen, you can figure out how fast the plane was going for yourself.

This clip shows Tower 2 getting hit (8 minutes in), so please be prepared. The helicopter footage starts at 7:38

http://www.youtube.com/watch?v=6YOu2Qy0A0s

[cfrobel]

PS, where were the speeds listed?

I do not dout you in your reference, but they still sound awfully fast!!!!!

I only went through the executive summary of the NIST report and found the table of the speeds on page xlii. I am sure more indepth information regarding the speeds and how they calculated the estimates within the document.

Yes the speeds were extremely fast for that altitude, a 767 cruising speed at 35,000 feet is 530 mph (Mach .80). Also at a speed of 564 mph at about 1000 feet you are barely operating within the operational capabilities of the 767 which maxes out at 567 mph.

Regarding the speed of sound, sound travels 761 mph at sea level in static conditions, so if they had throttled it as hard as they could at the end, no way they could have kept that jet at that speed for an extended period of time at that altitude and not lost control, they could have achieved 550+ and still been 200+ mph off breaking the sound barrier.

[jc84144]

Well this may seem a bit random... but Bin Larden graduated from university with a degree in civil engineering so with some knoladge of the complex, he probably could of known the fate of the buildings. Also with the popular increase of the internet in the years leading upto the attack, it probably would of been even easyer to get infomation on the complex. Also the 1993 bombers expected to destroy the towers (but where sold the wrong explosives) so im guessing they did on 9/11 as well.

[rogerick1970]

Well this may seem a bit random... but Bin Larden graduated from university with a degree in civil engineering so with some knoladge of the complex, he probably could of known the fate of the buildings. Also with the popular increase of the internet in the years leading upto the attack, it probably would of been even easyer to get infomation on the complex. Also the 1993 bombers expected to destroy the towers (but where sold the wrong explosives) so im guessing they did on 9/11 as well.

I agree, Bin Laden definately knew what he was doing and planned 9/11 for years strategically for years since 1993 was a failure. 9/11/2001, he wanted to make sure those buildings were down.


But why the WTC? I mean the Sears Tower is the tallest in the U.S., so doesnt that have a more potent statement:confused:

[jc84144]

I agree, Bin Laden definately knew what he was doing and planned 9/11 for years strategically for years since 1993 was a failure. 9/11/2001, he wanted to make sure those buildings were down.


But why the WTC? I mean the Sears Tower is the tallest in the U.S., so doesnt that have a more potent statement:confused:

But the World Trade Center is more of a "icon" of Americas wealth and power. Its also more famous then the Sears tower, and it's in a more famous city, New York which is also a icon of power and wealth.

(Also the WTC design was said to offend bin larden, becuase of the "fork" design at the base, was simular to some muslim icon (or somthing like that) )

And of course, this way he got to take down 2 towers, instead of 1.

[jc84144]

--

[rogerick1970]

I just hope the same thing doesnt happen to the new WTC Complex. This process has taken so long :(

[jc84144]

--

[rogerick1970]

Well im pretty sure there wont be anymore attacks using passenger planes, as its a lot harder now, and even if they do, passengers wont follow orders.. (flight hostesses are even trained since 9/11 to NOT keep passengers calm in a hijacking (i think thats a nice was to tell them to take action))

Think the main problem they have will be from explosives, but these will be with minamal damage and deaths (becuase there going to be very carfull was goes into that building, so the device would have to be small enough to get through security).

So im pretty conferdent it wont happen again.

I hope no. How long will it be till the core of the FT starts to rise? Because everytime I think about 9/11 the faster I want this building to go up.

[jc84144]

--

[kz1000ps]

How long will it be till the core of the FT starts to rise?

You're hilarious. That question has been answered 300 times in the FT thread and yet you never seem to listen to it.

[alonzo-ny]

ive noticed rogerick on skycrapercity alot, posting the exact same stuff over and over. ive no problem with rogerick but posting these questions over and over is useless and spams up a thread. fortunately here at wired it doesnt fly.

[rogerick1970]

ive noticed rogerick on skycrapercity alot, posting the exact same stuff over and over. ive no problem with rogerick but posting these questions over and over is useless and spams up a thread. fortunately here at wired it doesnt fly.


:mad: