New(?) 911 bad science

[Donnie B.]

If memory serves, the towers both collapsed at a fairly constant speed. That is, once the progressive failure began, each subsequent floor failed at more or less the same interval after the last.

If that's true, it suggests a couple things to me. First, it puts the "free fall" argument to bed. A free-falling object accelerates, it doesn't fall at a steady speed -- unless it's at terminal velocity, but I don't think that applies to the WTC towers case.

Second, and this is somewhat more speculative, it suggests that the towers were almost strong enough to resist the progressive failure altogether. Had this not been true, the collapse would have accelerated. (Imagine dropping a heavy book from just above a house of cards -- you wouldn't notice much difference from a free-fall case.)

Now, I have no numbers to back this up, but I'm going to guesstimate that the north tower's strength was within an order of magnitude of that which would have been needed to stop the collapse near the top. The south tower, maybe not so close, since there was much more mass above the failure point.

Imagine how that might have gone: the top section falls maybe four floors' distance, and then stops. It sits precariously balanced atop the remaining tower. The fires are nearly extinguished, snuffed out as if trampled by a giant's foot. Daring rescuers evacuate survivors from the upper floors via helicopter. And then... the world's biggest controlled demolition job to remove those unattached upper floors.



Okay, structural engineers, tell me how wrong I am...

[Metricyard]

Imagine how that might have gone: the top section falls maybe four floors' distance, and then stops. It sits precariously balanced atop the remaining tower. The fires are nearly extinguished, snuffed out as if trampled by a giant's foot. Daring rescuers evacuate survivors from the upper floors via helicopter. And then... the world's biggest controlled demolition job to remove those unattached upper floors.



Okay, structural engineers, tell me how wrong I am...

I'm willing to wager that if the towers didn't collapse, the CT'ers would be claiming conspiracy because it should have collapsed.

[Gillianren]

Again, I was never really surprised that the collapse continued once it started, or terribly surprised that the collapse followed the damage. (My timeline for the morning is different than most given my late wake-up time and time zone; I didn't see any of it until after it happened.) While I'm not an engineer, that was a lot of damage, and--because I grew up and still live in earthquake country--I'm perfectly aware of pancaking. Heck, the dorms I lived in during my final two years of college are designed to pancake in a severe-enough earthquake rather than knock into each other and cause even greater damage.

So here's my question, I suppose. If it's "common sense" that's important, here, why is my common sense response invalid?

[Dave J]

The collapse did "appear" rather neat, or as neat as the collapse of a 100+ story building can be.
Much has been made of the collapse time. Show me a video, beginning to end, that shows that the roof parts of a tower hit the streets at (almost) the same time as a dropped hammer.
There is so much dust and debris, I cannot see how such an "estimate" can be made. It is a guess at best. Once the top of the towers fall into the debris cloud, anything after that is supposition. I can only see that a lot of the collapsing energy is being taken by the material at the collapse point at any given moment, and it is being expended basically outwards. Meanwhile, the "undamaged" parts of the upper portions continue down. We cannot ascertain at what point the roof hits the ground, or the top of the pile below.
I haven't seen a video that shows physical evidence, start to finish, of a visable top part hitting the ground.

[twinstead]

So here's my question, I suppose. If it's "common sense" that's important, here, why is my common sense response invalid?

Well, duh, only common sense that supports a conspiracy is valid.

Where have you been?

[PhantomWolf]

I have to admit I haven't read the paper in question, but something I have noted is that most CT's only pay attention to the supporting columns. But the thing is, most of the collapsing material didn't fall onto the supporting columns, it fell onto the floor area. That means that the area of support that would have had to stop the collapse wasn't the core colums, or the perimeter columns, it was the brackets that held the trusses to the spandels, and something tells me they weren't designed to hold up the amount of rubble falling onto the floor areas. As those brackets failed, the floors would have fallen onto the next floor, and without the floors supporting them, the columns were done regardless.

Now I'm not an engineer either, nor do I play one on TV, but this does seem common sense to me, so am I totally wrong, or not?

[Donnie B.]

There are some videos of the collapse that make the sequence you described quite obvious. In some views, long vertical columns (exterior, I think, but can't be sure) can be seen standing independently for a short time after the floors collapsed. Eventually, of course, the slender columns buckled and fell.

[JayUtah]

Yes, the perimeter and/or core walls were observed in some cases to linger above the collapse front, supporting the contention that a significant amount of energy was spent on the relatively insubstantial flooring. But the flooring was an integral part of the overall structural system. How can "insubstantial" flooring be crucial? Because bracing requires comparatively little strength itself, but it conveys considerable axial strength to the principal member.

Unbraced columns are subject to a number of failure modes that Ross doesn't seem to consider.

[Chainsaw1]

I have to admit I haven't read the paper in question, but something I have noted is that most CT's only pay attention to the supporting columns. But the thing is, most of the collapsing material didn't fall onto the supporting columns, it fell onto the floor area. That means that the area of support that would have had to stop the collapse wasn't the core colums, or the perimeter columns, it was the brackets that held the trusses to the spandels, and something tells me they weren't designed to hold up the amount of rubble falling onto the floor areas. As those brackets failed, the floors would have fallen onto the next floor, and without the floors supporting them, the columns were done regardless.

Now I'm not an engineer either, nor do I play one on TV, but this does seem common sense to me, so am I totally wrong, or not?

I kinda think that is what Edgar's, MIT, and Greening, said Dr. Jones actually concludes that it was impossible for it to have occurred that way though.
The problem is that a lot of the CTers an the like do not understand the structure.
The structure of the Twin Towers was designed to transfer load, it was tack welded and bolted together because bolting the structure allows for more motion and flexibility than a solid welded structure would be capable of.
Bolting also allows for easy replacement of parts that might wear over time, these buildings were never designed to be static, and I believe that some of the central core bracing had been replaced do to wear over time.
This building was designed to move and with movement comes wear unavoidable. The constant construction and Inspection that the CTers point to was only standard maintenance for a non static building, nothing more.
The building was designed so that if a 707 struck the building the outer wall would not cause the building to fall the load would be transfered to the central column structure, but that requires the floor beams to remain intact, keeping the core stiff. Failure of the floor trusses allows the central column to fail, you can even see it in the videos if you look at the first moments of the collapse note the strain on the undamaged outer wall.
If you look for the Fulcrum points you will see it, it is simple leverage.

[andyschlei]

I'm willing to wager that if the towers didn't collapse, the CT'ers would be claiming conspiracy because it should have collapsed.

A bet you would win!

[JayUtah]

The problem is that a lot of the CTers an the like do not understand the structure.

Nor do they understand that they don't understand the structure.

The core columns were tack-welded probably for a variety of reasons. Here's where we have to sit back and think about whether the tack-welding really might have made a difference.

But the WTC core columns were segments stacked one atop the other, as a child (and the Egyptians and Greeks) stacked blocks. Columns bear best in axial compression, and segmented columns rely on keeping the segments lined up. That's what the bracing was supposed to do, whether it was the bracing inside the core or the bracing achieved by the floor trusses. The perimeter columns were more securely attached top to bottom because they had to bear in tension as well.

Imagine taking the roof off the WTC and pouring a massive bucketload of debris down on top of it. A small portion of the debris will strike columns axially. The vast majority of the debris will strike horizontal members: perimeter spandrels, floor trusses, and core I-beams. These are relatively easy to fail because they bear the impact as beams. But these members also do double-duty in horizontal axial compression and tension as bracing members. You only have to knock one end of a brace loose for it to stop acting as a brace.

So as your debris wipes out floors and other horizontal pieces, more and more of your columns (perimeter and core) are left unbraced. The susceptibility to failure increases with the square of the effective column length, so the columns will eventually fail under self-loading.

But all it takes is a sideways knock from a piece falling near a column to push it enough out of alignment to fall. This is especially true with the tack-welded core columns. They would be somewhat equivalent to a set of unsharpened pencils stacked end-to-end vertically. As long as you can brace them and keep them in balance at regular intervals, you'll be fine. Remove enough of that bracing and the core column will collapse.

[Chainsaw1]

The tack welds on the buildings, were mostly an OSHA regulation until the bolts could be torqued properly. The tack welds probably did not provide sufficient support to the core, as the bolting structure was designed to allow for some movement. The tack welds would have eventually broken on their own, as the building moved according to what I read at the time of the buildings construction it was expected they would. Their were some welds and reinforcing plates to arrest some harmful movement to the structure, however these were done only in a few critical areas.
I remember a lot from the engineering mags that I read in High school, and the Stories articles and engineers that I have talked to on this since before the World Trade Centers construction.
I have followed it from first construction, though its destruction, it is sad that such a bright monument to human engineering, is now a pile of dust, the only thing sadder is the loss of life and the waste of life!

[PhantomWolf]

You know, the more I learn about these buildings the less I'm surprised they fell, and the more I'm baffled to the CT's appearently deliberate blindness to why it happened.

[johnp]

The tack welds on the buildings, were mostly an OSHA regulation until the bolts could be torqued properly. The tack welds probably did not provide sufficient support to the core, as the bolting structure was designed to allow for some movement. The tack welds would have eventually broken on their own, as the building moved according to what I read at the time of the buildings construction it was expected they would. Their were some welds and reinforcing plates to arrest some harmful movement to the structure, however these were done only in a few critical areas.

the bolts and welding seem to have resisted well at least in that image

http://911research.wtc7.net/wtc/arch/docs/image5.jpg
more details


Also of interest why the 9/11 Commission Report as well as the Fema report

claim(?) ... the towers' cores were "hollow steel shaft[s]:"

Demonstration that towers core were not a hollow steel shaft
http://911research.wtc7.net/wtc/arch/core.html

[Vermonter]

I think that there needs to be a certain blindness in order for it to work.

Otherwise intelligent people can and sometimes will become rabid CT'ers once they get a notion in their head and refuse to see otherwise. Several of my coworkers are like that. I try to explain what I've learned, and they play a political card, or handwave it away. When confronted with evidence of the plane hitting the Pentagon, "the government can do anything" was the response.

When my dad first saw the FOX special on the Moon Hoax, he had some serious doubts on Apollo. After he and I did some looking up and research, he found that the FOX special was full of hooey. The important thing is that CT'ers do not believe they can be proven wrong, I think. There's no flexibility or a chance for them to even look at the evidence. If it conflicts with their preconceived notion of how something happened, it gets waved away as irrelevant.

[JayUtah]

Demonstration that towers core were not a hollow steel shaft...

I would accept "hollow steel shaft" as a description of a box column.

[Vermonter]

the bolts and welding seem to have resisted well at least in that image

http://911research.wtc7.net/wtc/arch/docs/image5.jpg
more details


Also of interest why the 9/11 Commission Report as well as the Fema report

claim(?) ... the towers' cores were "hollow steel shaft[s]:"

Demonstration that towers core were not a hollow steel shaft
http://911research.wtc7.net/wtc/arch/core.html

Apparently 911Research doesn't like hotlinking images. Regardless...

I looked at the pic and the other link. They look pretty dang hollow to me. They don't resemble any solid rectangular device I've seen.

Look at the picture closely. The steel that is running from left to right behind the worker looks like a steel rectangular column. Looking at the link, they show a diagram of such a column. The image of the WTC being constructed is too small and grainy to show what's really going on there.

I wonder why 911 Research is arguing what the 9-11 Commission knows and does not know. I think that the Commission actually was informed as to how the building was constructed in the first place, no guess work required. I don't see what 911 Research is trying to prove, either.

[johnp]

Demonstration that towers core were not a hollow steel shaft...

I would accept "hollow steel shaft" as a description of a box column.

Good point
However one should ask why
FEMA Misrepresented the Towers' Construction ?
http://911research.wtc7.net/wtc/evid...lueprints.html

[johnp]

Apparently 911Research doesn't like hotlinking images. Regardless...

I looked at the pic and the other link. They look pretty dang hollow to me. They don't resemble any solid rectangular device I've seen.

Look at the picture closely. The steel that is running from left to right behind the worker looks like a steel rectangular column. Looking at the link, they show a diagram of such a column. The image of the WTC being constructed is too small and grainy to show what's really going on there.

Better images here
http://911research.wtc7.net/wtc/evid...struction.html
Edited to add
They don't resemble any solid rectangular device I've seen.
Take a look at these images seem pretty solid
http://911research.wtc7.net/wtc/evid.../wtccons2.html

[PhantomWolf]

I'm not sure what you are contending here. If the cores themselves were not hollow, how do you explain them housing the elevator shafts and stairwells? If you are contending that the core columns themselves were not hollow, how do you explain the images you previously posted that show exactly that?

[johnp]

I'm not sure what you are contending here. If the cores themselves were not hollow, how do you explain them housing the elevator shafts and stairwells? If you are contending that the core columns themselves were not hollow, how do you explain the images you previously posted that show exactly that?

The point is that the way it is presented -by the 9/11 Commission Report as well as the Fema report-... the only role of the central core section was for housing elevators.
Edited to add -....-

[Photon]

Hi johnp

Surely the blueprints of the towers would have been used in determining how they collapsed. Or weren't they?

[Chainsaw1]

The point is that the way it is presented -by the 9/11 Commission Report as well as the Fema report-... the only role of the central core section was for housing elevators.
Edited to add -....-

The Central Core was designed to allow load transfer, from the outer walls allowing the building to sway slightly in the wind. It also supported one end of the floor trusses. IN theory it could have supported the buildings entire weight, on top of the central core, as long as there was not side movement to collapse it! Kind of like setting a book on a drinking straw, it however required reinforcement to keep it from collapsing from the side.
The problem is most people can not tell the difference between what the Builders said when the building was built and what the reality was!
The bracing is the key, the bracing of the central core itself and the bracing and stiffness it received not only from the steel but from the concrete creating a rest Mass as well.
The concrete was an important factor in the design as well the concrete above the floor trusses help to resist movement itself.
The whole building had to work together to function properly, that is what Broke down after the planes hit, the codependency of the structure to provide structural integrity.
It is a perfect example of the old saying,
Fore want of a nail, a horse shoe was lost, fore want of a shoe, a horse was lost, fore want of a horse, a Knight was lost, fore want of a Knight a battle was lost, and in that battle a Kingdom was lost!
Modern buildings are a struggle, between Redundancy, and codependency, every one of them is a compromise between those competing forces.

[JayUtah]

However one should ask why
FEMA Misrepresented the Towers' Construction ?

911 Research assumes that FEMA intended those diagrams to be accurate framing plans. I see no evidence of such intent. Twice now your source has pasted their own interpretation on the source material in a cheap-shot attempt to create an anomaly. In fact, their entire approach to the prevailing science seems to be based on the cheap shot. That is why I long ago gave up on them as serious researchers.

[JayUtah]

They don't resemble any solid rectangular device I've seen.
Take a look at these images seem pretty solid [/b]

You're looking at the crane derricks, not part of the WTC structure. Why do you insist on trusting the judgment of people who can't distinguish construction equipment from framing? Are these people really more qualified than practicing engineers to investigate a collapse?

[JayUtah]

...the only role of the central core section was for housing elevators.

I see no evidence for the claim they said that was the core's only role. Again that's your web site pasting their interpretation on what was said. Why are you constantly letting them do your thinking for you?

[JayUtah]

Surely the blueprints of the towers would have been used in determining how they collapsed.

Not all diagrams you see in government-sponsored reports derive from original engineering drawings or framing plans. They shouldn't be considered accurate to scale and in all details. You have to look at how the diagram is being referred to in order to judge whether it's an accurate enough depiction.

However, the models used in the detailed finite-element analysis, where accuracy counts, were prepared according to the original framing plans as well as subsequent knowledge of the as-built condition. Keep in mind this is still proprietary information. The government must have it in order to carry out its investigation, but that does not necessarily entail revealing it in detail to the public where competing structural engineers can exploit it for commercial advantage.

[PhantomWolf]

to the original framing plans as well as subsequent knowledge of the as-built condition.

I want to point something out to those that don't understand the difference here. Blueprints (or other plans) and "As-Built" are often two totally different things. The Blueprint Plans are what you wanted to have built. The "As-Built" is far more important because that is what the contractor actually gave you. Having just spend a LOT of time wading through P&I Diagrams for a Gas Production Station, I very quickly found this out.

[Chainsaw1]

Some one please call me an Idiot, after reading this article http://chronicle.com/temp/reprint.ph...jn728rfkn21t9lI contacted the author, the arthor after I contacted him, he had me contact Thomas W. Eagar, Dr Eagar seems quite interested in the work I did with thermite, and Burning Aluminum,
"I am not at my computer so I cannot see your attachments until I return to my office this weekend (I am using a Blackberry). But I am sure you are right." The only problem is that I was convinced after talking with people here that I was doing bad Science and dumped the work to recycle the hard Drive videos pictures almost everything gone.
Thousands of dollars and hours of time wasted and here I might have had a missing key all along, I am such an Idiot, I should have held on to the documentation and stuck to my guns!
I feel so bad about this I just do not know what to do, the experiments are dangerous, but if I have to I will do them again.
Motion force was the key all along to forming thermite, or getting boiling or burning Aluminum.
I had the key and I threw it away!

[JayUtah]

For example, in some places the WTC contractor was allowed to hang stronger steel than what was specified because the stronger steel was on hand and the weaker steel was delayed. The schedule was preserved and the the allowable-stress design method was preserved. The construction was no less safe than the design. But if you want to model the behavior of the actual building, you have to identify the stronger steel in your model even if the plan says something different.