I need all debunkers I can get!

[Minadin]

Probably microwaves beamed from space. Or maybe explosives placed in the concrete core. It couldn't have been the fire, since that doesn't do anything to steel.

That's right! Steel doesn't burn, so it should be innately fireproof, compared to something like a structural wooden timber. Right?

Oh. Yeah. That's actually wrong. Steel structure is by-and-large more susceptible to failure due to the heat of fires than similar heavy timber construction. We apply various methods to protect it from fires, such as fire-rated insulation, water sprinklers, and the like, to help counteract this shortcoming of the material.

Or, conversely, you might choose to believe that fireproofing systems applied to steel are another conspiracy between the various professionals (architects, engineers, etc) in the construction industry, the contractors, the code officials, the UL, and the fireproofing suppliers to jack up the price of every building everywhere to swindle more money out of our clients. Hey! Maybe that's why all those international (Non-US-based) engineers and architects aren't coming forward to blow the whistle on this 9/11 sham! They're just protecting their bottom line! (Our fees are usually tied into the cost of construction.)

 

[JimBenArm]

(Psst. You do realize my previous post was a jest, right?)

 

[Minadin]

(Yes, I wasn't so much responding to you as continuing your mocking line of thought. It's directed at Heiwa and others who think, like he does, that steel = incombustible = safe. Sorry if my post caused any confusion!)

 

[JimBenArm]

(Very good! Carry on, then!)

 

[DGM]

As I say - most skyscrapers are built according to the same principles as a ... bird cage. Or all of them.

Re fire proofing you generally do not insulate external walls (or columns in same) as they are cooled by the external air.

WTC exterior columns were insulated why do you say they were not?

Can you name other buildings of the same design as the towers like you claim in your paper?

It seams your research abilities are lacking for sure.

BTW Why don't you address the problem of moment forces on the towers?

 

[Myriad]

Here's an example of an error in your paper:

Evidently more than half of the columns were never heated at all. Nevertheless, assuming that more than half of the columns are affected by heat, do these columns actually split or buckle? Why do they not only compress more, while transferring their load carrying capacity to adjacent columns?

(emphasis added)


Are you suggesting that a compressed or buckled column could transfer its load-carrying capacity to adjacent columns? Is this just careless wording, and you meant to say that it would transfer its load to adjacent columns, or did you really mean to say that it would transfer it's load-carrying capacity to adjacent columns?

This is an important question affecting the validity of the remainder of your paper, because your failure to mention increased loads on adjacent columns from the columns buckled and severed by the plane crash suggests that you really did mean to claim that damage to columnns would transfer those columns' load-bearing capacity, as opposed to their load, to adjacent columns. Which would be a patently absurd contention.

You are ignoring a key physical characteristic of the condition of the buildings leading to collapse, and the only rationale you've given for doing so is the silly idea that load-carrying capacity can be transfered from one column to another.

So please, clarify what you really meant in the above quote.

Respectfully,
Myriad

 

[Gravy]

The wall bar is obviously fitted in the wall and cooled by external air and can never be heated very much. That is why the wall perimeter columns were not fire proofed!

Yes, they were, which you'd know if you bothered to learn about the buildings rather than ignorantly ranting about them.

Edit: DGM caught it.

 

[uk_dave]

Has anyone nominated this for a Stundie yet?

I'm just stunned by his unselfconscious arrogance in promoting a complete falsehood as fact.

Heiwa, stick to boats. I note that you at least have the good sense to not mention 9-11 on the homepage of your site. Shame you don't have the sense to educate yourself about the construction of multistorey steel framed structures before attempting to speak about it.

 

[funk de fino]

Probably not, OT of course, but what was the proximate cause of collapse?

Heat from the fire

 

[A W Smith]

Read page 17 of this pdf regarding exterior fireproofing and the reasons for it
http://wtc.nist.gov/NISTNCSTAR1-6A.pdf

 

[A W Smith]

I'm just stunned by his unselfconscious arrogance in promoting a complete falsehood as fact.

Heiwa, stick to boats. I note that you at least have the good sense to not mention 9-11 on the homepage of your site. Shame you don't have the sense to educate yourself about the construction of multistorey steel framed structures before attempting to speak about it.

well his ships are built just like a birdcage right?

 

[Newtons Bit]

Heat from the fire

I would probably say that the load transfer from core columns to exterior columns was more important, but I need to do ze maths.

 

[Gravy]

The stresses in WTC1 wall columns were 22.5% of yield/buckling. In the core they might have been 30% of yield/buckling. Quite obvious from the calculations in my article. Probably less, as the steel was probably better than I assume.

Every skyscraper built in the 60's were built with similar stresses.

Come on, prove the information in the article wrong. Wrong masses? Wrong dimensions of the columns? Errors in the calculations.

Here you go.

NIST NCSTAR 1-6D: Global Structural Analysis of the Response of the World Trade Center Towers to Impact Damage and Fire

You're welcome.

 

[Architect]

But I have - see the link about heated steel in my article, so that's the reason. Why repeat yourself? But you forgot the link to my website http://heiwaco.tripod.com . Very popular and interesting.

With respect, you appear to either misunderstand or willfully misconstrue the point put to you.

You have stated that steel structures are not, in themselves, susceptible to failure during normal fire loading conditions. I have provided you with a series of links which show that this is not, in fact, a tennable position. There is a wealth of fire test data which corroborates heat induced failure at normal fire loadings, and this is reflected in building regulations across the globe.

I therefore put it to you that one of the cornerstones of your argument is a blatant falsehood, and suggest that you either clarify your point or acknowledge your apparent error.

 

[Architect]

Introduction - a bird cage
The structural design of the World Trade Center Twin Towers is very simple as its very lightweight framework is similar to a box shaped bird cage in which human beings are working. Most skyscrapers or office towers in the world are built similarly. None has ever globally collapsed in seconds before or after 911 except WTC 1, 2 and 7.

The bird cage wall bars and their spandrels
The vertical bars of the cage walls correspond to the outer wall steel columns of the Towers and are continuous from bottom to top (albeit 3 wall columns become one at the bottom of the Towers). The cage wall vertical bars are horizontally interconnected at regular levels by spandrels (a word that I cannot find in my Advanced Learner's Dictionary of Current English but probably has Latin origin - spandrilla? - used to support the ceiling of, e.g. the Sistine chapel at the Vatican) that are simple steel brackets. The spandrels act as belts around the bird cage that prevent transverse (outward/inward) deflections of the wall bars. On top of the cage is a roof. Inside the cage are floors fitted bolted to the walls.

Whilst acknowlegiu are simplifying for ease of reference, you make a number of basic errors here. In particular it is important to understand that WTC1 and 2 essentially comprised a composite structure of 4 main elements;

- The external envelope, which provided resistance against wind loads and also carried half the weight of the floors.

- The internal core, which (amongst other things) provided resistance to the overturning moment and carried the remaining weight of the floors.

- The trussed floor girders, which indeed helped restrain the outer facade.

- The roof level girder trusses, which acted to transfer loads betwixt core and envelope.

The important thing here is to understand that the building is dependant upon the integrity of each of these in order to ensure stability, hence the loss of one (beyond certain margins) can - and did - lead to progressive failure.

You also miss a key point regarding the innovative nature of the WTC design, which represented a significant advancement on earlier models due to the additional stability provided by what is sometimes called the "tube within a tube" design, together with what was effectively a continuous external load bearing structure. It is not typical of other tall buildings.

By way of comparison you might want to consider, say, the structure of the Citicorp building (and I've chosen that one on purpose) or older structres by (for example) Mies, which are massively different.

The bird cage analogy is unhelpful for a number of reasons. There is no perceptable dead load, likewise dynamic loads are minimal other than at the base of the cage as there are no intermediate floors. Moreover we could draw a comparison between the relative size of the structural members - cross sectional area will be proportionately excessive in the bird cage scenario.

You know, I can keep going through your paper like this. So can Newton. But you're going to look rather foolish. Do you really want to press ahead with your assinine challenge?

 

[Architect]

Here's another example of where you get it wrong:

To better use the volume of the cage 110 off floors were installed in it at regular intervals. The WTC floors were also very simple. A floors consists of about 4 inch of concrete poured on a thin plate of steel supported by lightweight trusses (beams) bolted to the columns, as you cannot glue concrete floors to the cage walls and core. Thus every wall column also carried a portion of the load of the floors.
The floors can only carry its weight + furniture, decorations and human beings on the floor. If a floor is overloaded for any reason, it will sag and the concrete will fracture in small pieces and the bolted connections to the columns will shear off.

What you mean is that the floors are a composite structure comprising up to 4 inches of reinforced concrete sitting attop permanent steel shuttering, in turn supported by the trussed girders. What you wholly fail to appreciate, presumably because ships don't tend to have such floors, is that the steel shuttering itself acts as reinforcement and hence the pattern of failure will be rather different.

For example excessive load would lead to additional stress on the steel, which is strong in tension, and failure of the concrete (which is strong in compression) will not be the first sympton of failure.

I mean really, do you know anything about building construction?

 

[Newtons Bit]

Here's another example of where you get it wrong:



What you mean is that the floors are a composite structure comprising up to 4 inches of reinforced concrete sitting attop permanent steel shuttering, in turn supported by the trussed girders. What you wholly fail to appreciate, presumably because ships don't tend to have such floors, is that the steel shuttering itself acts as reinforcement and hence the pattern of failure will be rather different.

For example excessive load would lead to additional stress on the steel, which is strong in tension, and failure of the concrete (which is strong in compression) will not be the first sympton of failure.

I mean really, do you know anything about building construction?

Hey, an architect (no pun intended) that actually knows something about composite beam construction! To the lay-people, think of the concrete slab and the floor joist as one combined beam, not two seperate objects acting independantly. You are completly correct, though I have a few things to add.

There is also a pre-composite bending load on the floor trusses as. This is from the load that the wet concrete puts on the truss before the concrete cures and becomes composite with the truss. Right after the concrete cures, there is compression in the top chord of the truss and tension in the bottom chord and no compression in the concrete slab. As load is placed on the now cured slab, the concrete slab goes into compression, the bottom chord of the truss goes further into tension and the top chord of the truss might go into tension or compression (or stay relatively the same) based on how thick the concrete slab is and how far away / how big the bottom chord is.

In the design of composite beams, the strength of the concrete may control, or the strength of the bottom chord of the truss may control. However, the strength of the concrete is typically based upon it's 28-day compressive strength. This strength grows with time (though it does slow down). Concrete that was poured in the 70's with a design strength of 3000 psi might be as high as 5000 psi today. The strength of the truss surely controls.



But that's really a moot point anyways. There's a bunch of other things that will probably fail first. The bearing seat of the truss to the column could shear off, the deck supporting the slab could fail in bending or even shear. Modern engineering practice dictates that the bending failure of the truss should occur first (in other words, the other elements are stronger) so that the failure is elastic, i.e. people can see it and gtfo. However, this practice was created based on problems from the 70's, it's unlikely that the engineers then were practicing it.

In any event, the concrete slab cracking is not going to be the reason why the thing fails. It has a huge reserve capacity, maybe as high as double, then it was originally designed to have.

I can't believe I just wrote all that.

 

[Newtons Bit]

You know, I can keep going through your paper like this. So can Newton. But you're going to look rather foolish. Do you really want to press ahead with your assinine challenge?

I tried, he just ignored me when I found two rather large errors. You seem to be doing just fine on your own though

 

[Architect]

I tried, he just ignored me when I found two rather large errors. You seem to be doing just fine on your own though

I'm thinking of taking it for a living. Erm, just a minute, I do. Ah well.

This is my current favourite of his:

There was therefore plenty redundancy. A plane may crash into the bird cage and nothing happens. A big fire may break out and nothing happens. Why? Because the normal compressive stress in the supporting vertical structure is so low and if any column breaks or buckles, its load is transmitted to adjacent columns via the spandrels and the stress in adjacent columns increase a little. No global collapse is possible under any circumstances.

To state the obvious, there is a dearth of detail as to how the loads transmitted, design capacity of the appropriate members to accept such altered load paths, and thereafter whether the members subsequently carrying the increased vertical load had sufficient capacity.

I mean, it's pretty basic stuff I would expect any competent construction professional to twig.

 

[Heiwa]

Are you suggesting that a compressed or buckled column could transfer its load-carrying capacity to adjacent columns? Is this just careless wording, and you meant to say that it would transfer its load to adjacent columns, or did you really mean to say that it would transfer it's load-carrying capacity to adjacent columns?

This is an important question affecting the validity of the remainder of your paper, because your failure to mention increased loads on adjacent columns from the columns buckled and severed by the plane crash suggests that you really did mean to claim that damage to columnns would transfer those columns' load-bearing capacity, as opposed to their load, to adjacent columns. Which would be a patently absurd contention.

Respectfully,
Myriad

The spandrels connecting the columns transfer compressive load in a broken column to an adjacent column as shear in the spandrel. Example - the original hole in the wall - reason why the wall above does not fall down is simple that the spandrels above keep it in place. It is a simple 2-D strength problem of a vertical grid.

The intact floors above the hole in the wall might also carry some load to the core = pull the wall so it does not fall down. Then we talk 3-D. The vertical grid (the wall above the hole) is connected to horizontal supports, etc.

Easy to analyse with a 3-D beam structural analysis software - takes longer to do long-hand but it is also possible.