Failure mode in WTC towers

[Furcifer]

What interests me is the first 4 seconds of the WTC collapse initiation with the roof dropping and apparently the upper part above the fire/initiation zone telescoping into it, while the outer walls appear straight. Assuming a 60/40 weight distribution walls/core (20 000 tons walls/14 000 tons core above fire zone) and compression <30% yield in the structure, even if all core columns are disconnected/dislocated in one location each (how(?) and cannot transmit any load to the core below) and 100% of the weight above is then carried by the walls, the walls would only compress to <50% yield ... and still hold. They would not crumple up and any outward bendingbuckling would be prevented by the spandrels (like a waist belt).

Do you ever go by the last name Ross? You and him have a horrible understanding of how things work. You have a preconceived idea of what should have happened based soley in your own warped reality. Forget what you think you know and listen to some of the very intelligent and learned people in this forum.

 

[GregoryUrich]

No, the pan caking speed is not momentum limited. In fact, the simple failure of floors due to weight would proceed and accelerate as you see in the actual failure on 9/11. The floors can only hold 29,000,000 pounds, and then they fall. The core can hold the whole building along with the shell, and both need the floors! This is the unique design of the WTC and its incredible strength. With just a pancake collapse of floors only, the event would be as fast as 12 to 16 seconds, leaving the exterior and core alone. Silly model, but very true. I have to run the numbers but the floor would instantaneously fail with over 29,000,000 pounds, and when the next floor is reached, it fails and adds to the mass, which accelerates at g, and we have a very rapid destruction. Do not fall for the lies of idiots in 9/11 truth. Run a simple model and see how the WTC fails very quickly, just the floors. BTW, as seen on 9/11 parts of core, 50 stories, were still standing for sometime after the floors had left for the ground! So that make your ideas kind of wrong.

The compressed air took a fireman on the stairs and blew him down 5 stories! He was in the core of the collapsing WTC, and he was picked up and moved. An explosion blast would have killed him, a compression of air due to the collapsing front would blow him down! You must study the WTC more to understand the big picture. You can not have preconceived ideas, you must find the answers from a neutral mind, not a CT idiot induce trance of stupid.

You are wrong about the floors, you can see them in a video falling and compressing air outward. The floors are the weak link, the core and shell alone hold all the weight of the WTC! It is the floor that can only hold 29,000,000 pounds. That means any more than the weight and force of 6 floors moving down a floor would fail a single floor; or if you just place 11 more floors (just the floors, does not count parts of core or shell helping) on one floor, just put that weight on a single floor, you have failure! So the floors were failing as fast, or faster than the overall failure front because the floors were overloaded as the mass of not only the upper floors impact them, but parts of the core are coming down too and overloading each floor. I hate to imagine what was going down the elevator shafts and stairwells. What made the fireman fly 5 floors down? Air pressure due to the falling building. Just remember the guys rescued from the fallen WTC core were not blown up, one guy was blown down due to wind gusts from the collapsing building. Proof also there were not explosive charges in the core, or building, these guys would have heard the RDX going off. I hope you understand the sound of real explosives, and blast effects on humans.

The compression of air was accelerating and would show up many floors below, in fact it would show up quickly; very quickly; look up something on your own! Propagation of pressure in a vessel, oops, like when you close the front door of your house and the back door flies open; go do a speed check now! Physics experiment 1,000,054; the slam front door, opens back door. Quick.
Darn, why is it when I drop a box in another box, air rushes out the bottom of the box as soon as the other box falls into it (it ran out the top too, it looked like an explosion with all the flour pouring out all over, up and out the bottom too). And these boxes are not tight! Loose fitting box in another box, and air comes out as soon as the box begins to fall! OH, I was in the subway tunnel, a train many blocks away entered my tunnel and the air was rushing by me well before the train came. Why?
OOPS, I was in a building and felt air moving out of the elevator door while it was closed and the elevator was 35 floors up moving down! Why?

Congratulations on your first substantial post.

The floors in general were designed for max 100 psf plus their own weight, giving approximately 4,200,000 pounds. The floors can probably hold twice that, but you are giving them a safety factor of 7.

I'm not sure what you mean by your momentum statement. Pancaking speed is definitely reduced by momentum transfer in the quasi-inelastic collisions.

Being a skeptic, I would need to see calculations regarding propagation of the air pressure to account for this:

 

[bofors]

I'm inclined to say that this is the most pathetic, incredible reach I've yet seen from the Truth Movement. Let's see these "Statistics" of yours, or you are seriously talking out of your hat.

Exactly, we have every reason to suspect that the magically disappearing building-top pushing the fire-induced gravity driven collapse would tightly focus its air pressure in a very small number of locations midway down the tower. It's not like the air pressure is higher at the bottom of the tower or something. Someone just happened to leave windows open at these locations, just like people did after they jumped out of the buildings.

The facts that these so-called "squibs" shift periodically, appear in structural significant locations like near the absolute lateral center of the towers and are otherwise consistent with CD are meaningless. We know these facts are meaningless because we know these are fire-induced gravity collapses, any evidence to the contrary is merely coincidental.

Fair warning, I am quite conversant in statistics and experimental technique. Don't try to snow me.

Thank God! We have a rocket scientist to save us. Hurrah!!!

 

[Norseman]

Maybe this video of the collapse of WTC 2 would help you to understand what happened at collapse initiation in WTC 1. The collapse mechanism was the same in both towers. The south wall of WTC 1 failed first and caused the upper block to rotate south. While the east wall of WTC 2 failed first and caused the upper block to rotate east and slightly south at the same time.

So this is what the collapse of WTC 1 would have looked like if there had been a camera zoomed in on one of the south corners at collapse initiation:

This shows the northeast corner of WTC 2 just before collapse initiation.

The collapse that started at middle of the pulled in east wall has reached the columns of the northeast corner of WTC 2, the columns has started to bend in and collapse.

The bending/collapse of the northeast corner of WTC 2 has progressed further and the exterior columns of the upper block on the north side is now clearly bending eastwards as the upper block is rotating. What do you think the core columns are doing at this moment.

At this point all the columns of the east wall and the east part of the south and north walls must have ruptured. What do you think the column edges of the upper block is doing inside the lower block now Heiwa? And of course the columns to the west will soon fail like their neighbors to the east did, as the collapse initiation continues west. Then the whole upper block will be free to continue down inside the lower block ripping off floor connections, pushing sideways on core and exterior columns.

Here is the complete video:


Notice the remaining north exterior wall section of the lower block that is still standing for a moment after the rest of the tower has collapsed.

Here is two videos of the collapse initiation of the east wall that you have been shown before Heiwa:

Notice how the east wall of the lower block is pivoting out of the dust cloud at the end, what caused it to do that.

 

[uk_dave]

Exactly, we have every reason to suspect that the magically disappearing building-top driving the obvious fire-induced gravity driven collapse would focus its air pressure in a very small number locations midway down the tower.

Yep. You lack the imagination to consider what is happening inside the building during the collapse and you lack the rudimentary technical knowledge to consider how air from the upper stories might be funneled to particular locations around the buildings perimeter.

It's not like the air pressure is higher at the bottom of the building or something.

The facts that these so-called "squibs" shift periodically, appear in structural significant locations like the near absolute lateral center of the towers and are otherwise consistent with CD are meaningless.

You mean when we see a real controlled demolition the only 'squibs' are slow moving jets of dust and debris in a handful of places? Please do share your proof of this.

We know these facts are meaningless because we know these are a fire-induced gravity collapse, any evidence to the contrary is merely coincidental.

Yes, your 'facts' are meaningless.

Thank God! We have a rocket scientist to save us. Hurrah!!!

Inferiority complex showing?

 

[GregoryUrich]

A couple of comments, as this is the first time I've looked at this thread.

Consensus on this question would have quite an important effect, of course, on collapse time calculations. Since the column splices were at every third floor, then even assuming the plastic deformation energy to splice failure is the same as the energy for a column - which we assume not to be true because of the assumption that all failures occurred at the splices - this means that the assumed failure mode is a plastic hinge at every third floor, giving a three-hinge failure over nine floors rather than one. This reduces the plastic deformation energy by a factor of nine, and even this is an overestimate. If I plug that into Gregory's spreadsheet I get a collapse time of about 13 seconds.

It's rather a lot different to Cherepanov, really - he assumed that the initial impact destroyed the entire structure. I'd be a little wary of giving him too much attention.

And I thought I'd highlight the rare occurence of Bofors actually getting something right.

Dave

I think the 3 hinge buckle would be over 6 floors (includes three splices). Due to the tilting and that we don't see a 3 floor freefall in the videos, we have to assume that the failures are asymmetrical. realcddeal is working on a video analysis showing this. The plastic energy would likely need to include tension failure in nearly all of the horizontal core members, which number 82 per floor and, near the top, are nearly as strong as the columns.

 

[einsteen]

Norseman, at the other side a piece of mass is ejected with about 13m/s, that's more than is possible with the released elastic energy which was 50 J/kg if I remember well (theoretical upper limit). Great video btw. It shows exactly what happens if the core is destroyed first. And that was also what the NIST spokesman said in the interview with Jeff Hill, the core failed first. Did he make a misstake ?

 

[GregoryUrich]

Norseman, at the other side a piece of mass is ejected with about 13m/s, that's more than is possible with the released elastic energy which was 50 J/kg if I remember well (theoretical upper limit). Great video btw. It shows exactly what happens if the core is destroyed first. And that was also what the NIST spokesman said in the interview with Jeff Hill, the core failed first. Did he make a misstake ?

Isn't the "core failed first" idea based on that it appears that the antenna drops? Has anyone actually checked that taking the tilting into account?

 

[Norseman]

Norseman, at the other side a piece of mass is ejected with about 13m/s, that's more than is possible with the released elastic energy which was 50 J/kg if I remember well (theoretical upper limit). Great video btw. It shows exactly what happens if the core is destroyed first. And that was also what the NIST spokesman said in the interview with Jeff Hill, the core failed first. Did he make a misstake ?

Go and read the NIST report. There you will find that as the core was heated up it sagged and it started to transfer its weight through the hat truss to the exterior walls. This was a slow motion process, but the towers did not collapse before one of the exterior walls failed.

 

[Dave Rogers]

Isn't the "core failed first" idea based on that it appears that the antenna drops? Has anyone actually checked that taking the tilting into account?

I can't remember where, but I've seen an analysis of this that concludes that the apparent movement of the antenna is completely accounted for by rotation as the top block tilts, so in effect there is no antenna drop.

Dave

 

[Walter Ego]

Maybe this video of the collapse of WTC 2 would help you to understand what happened at collapse initiation in WTC 1. The collapse mechanism was the same in both towers. The south wall of WTC 1 failed first and caused the upper block to rotate south. While the east wall of WTC 2 failed first and caused the upper block to rotate east and slightly south at the same time.

So this is what the collapse of WTC 1 would have looked like if there had been a camera zoomed in on one of the south corners at collapse initiation:

[qimg]http://www.internationalskeptics.com/forums/imagehosting/18141479b8f52812ab.jpg[/qimg]
This shows the northeast corner of WTC 2 just before collapse initiation.

[qimg]http://www.internationalskeptics.com/forums/imagehosting/18141479b8fcb75d4d.jpg[/qimg]
The collapse that started at middle of the pulled in east wall has reached the columns of the northeast corner of WTC 2, the columns has started to bend in and collapse.

[qimg]http://www.internationalskeptics.com/forums/imagehosting/18141479b8feceda52.jpg[/qimg]
The bending/collapse of the northeast corner of WTC 2 has progressed further and the exterior columns of the upper block on the north side is now clearly bending eastwards as the upper block is rotating. What do you think the core columns are doing at this moment.

[qimg]http://www.internationalskeptics.com/forums/imagehosting/18141479b901f9d835.jpg[/qimg]
At this point all the columns of the east wall and the east part of the south and north walls must have ruptured. What do you think the column edges of the upper block is doing inside the lower block now Heiwa? And of course the columns to the west will soon fail like their neighbors to the east did, as the collapse initiation continues west. Then the whole upper block will be free to continue down inside the lower block ripping off floor connections, pushing sideways on core and exterior columns.

Here is the complete video:


Notice the remaining north exterior wall section of the lower block that is still standing for a moment after the rest of the tower has collapsed.

Here is two videos of the collapse initiation of the east wall that you have been shown before Heiwa:

Notice how the east wall of the lower block is pivoting out of the dust cloud at the end, what caused it to do that.

That is the BEST collection of stills and videos I've seen on this forum (post #84). Thank you!

Controlled demolition my ass! (Can we say ‘ass’ here?) ;-)

 

[Dave Rogers]

I think the 3 hinge buckle would be over 6 floors (includes three splices).

Not for the second and subsequent buckles - the top splice has already fractured, so the top end is free to rotate. It's either 3 splices every 9 floors, or 2 splices every 6 floors, otherwise you're double-counting every second splice.

Are the horizontal members failing in compression, tension, shear, bending or some complex combination of the four?

Dave

 

[Furcifer]

Heiwa
Basic! Shear force is the accumulation of vertical load (500 kgs/m²) on the floor truss that is transmitted to the column via the truss' end connection. It adds to the compression of the column. The shear force also produces bending of the truss around its neutral axis. Depending on the truss' end connection the bending moment may be transmitted to the column. If the end connection is, e.g. a pin joint - just one bolt - no bending moment is transmitted. If the end connection is a bolt + a small angle support some bending moment may be transmitted. I will now transfer to the 'Failure mode in WTC Towers thread.

So in the impact area there was no end connection and the bending moment was transmitted to the column. So doesn't it follow then, that there was a substantial amount of force being transmitted to the core, at a location that was already damaged? Wouldn't you agree that this was well out of design parameters?
I'm just trying to follow your logic, because you seem to understand and yet make wild jumps that nobody else can grasp. My apologies for the "warped reality" comment as well, I was getting frustrated. Plus my reality was a tad warped at the time.

 

[Newtons Bit]

Well, maybe he can help you understand the difference between conservative design using pinned connections and whether the columns had any level of being fixed.

You didn't win this argument last time.

Stop putting words into my mouth. I never said it was a pinned connection and I never treated it as such. That is your mistake, not mine. I suppose this is the typical truther justification for everything. Lie about what someone you disagree with says, and then say that your mistake is their mistake. I'm sure it works great with the teenagers who can't be bothered to verify your bs.

I have a hard time believing that you can look at two charts, one says "moment frame" and the other says "braced frame" and picked the "braced frame" chart for a moment frame system. You were confronted with a two answer multiple choice question:

The question: Pick the answer that says a.

Answers:
a.
b.

And you picked b. I suppose that's the limit of your intellectual capacity since answer "a" invalidates your religion.

 

[uk_dave]

The question: Pick the answer that says a.

Answers:
a.
b.

And you picked b. I suppose that's the limit of your intellectual capacity since answer "a" invalidates your religion.

Some people see only what they want to see, even when it doesn't even exist. One day it's a post by another member, another day it's a 'confession' on tv by the owner of wtc7.

There is an apparent pattern to this behavior. Trouble is, this is something the person in question will never see.

 

[GregoryUrich]

Not for the second and subsequent buckles - the top splice has already fractured, so the top end is free to rotate. It's either 3 splices every 9 floors, or 2 splices every 6 floors, otherwise you're double-counting every second splice.

Are the horizontal members failing in compression, tension, shear, bending or some complex combination of the four?

Dave

OK, I see what you are saying, 2 splices every three floors. However the top is not free to rotate because there are 2 to 4 substantial horizontal member and floor diaphrams keeping them in place.

NIST has very little data regarding horizontal members, but most were fractured in the member. The failure mode is unknown, but I guess shear and bending for the most part. My thinking is that since the columns were most likely not impacting columns due to tilting, that would mean that the beams were impacting beams at least in the core.

 

[beachnut]

Congratulations on your first substantial post.

The floors in general were designed for max 100 psf plus their own weight, giving approximately 4,200,000 pounds. The floors can probably hold twice that, but you are giving them a safety factor of 7.

I'm not sure what you mean by your momentum statement. Pancaking speed is definitely reduced by momentum transfer in the quasi-inelastic collisions.

Being a skeptic, I would need to see calculations regarding propagation of the air pressure to account for this:

You are not a skeptic you are a truther. You post the ultra stupid "squib" photo, which had no sound of blast from an explosive, and no blast effects, but does have ALL the characteristics of air pressure, not blast pressure. You also FAILED to tell us how many floors have fallen. Can you tell me what floor that is? Your small charges would not even blow out a window would they, and they are of course silent as a mouse.

Where did the air GO? There are a few floors smashed together, where did the air go?

BTW, momentum transfer gives a time of 12 seconds, and matches the speed of Greening at 51.2 m/s; my speed matches Greenings estimate, and I used floors failing in a gravity field, onto other floors. Sorry, 9.1 seconds for an object dropped and only 12 seconds for each floor smashing into all the floors. Yes 9.1 seconds is slowed to 12 seconds. That is significant, but why do truthers call it faster than freefall? Why is 9/11 truth so stupid?

Take the top 11 floor and place them carefully on the 99th floor, you get instantaneous failure of the mass falling a field of gravity at a=g. This mass hit floor 98 in .87 seconds at 8.52 m/s and this floor fails and the floor with the total mass begins acceleration to floor 97 at an initial speed of 7.86 m/s, reaching floor 97 in .397 seconds at a speed of 11.6 m/s. There is no stopping the train as we only loose 7 percent of our speed at each impact at the beginning and that percent is dropping as we gain MASS. At the bottom that falls to less than 1 percent in velocity reduction. This is not new, many different models present the same overall time for collapse, using different means. I have left out the energy of the initial mass, only using the weight! The initial KE is left for other tasks of destruction.

Where did the air go? These guys found out, as some of the air helped displace them in the WTC stairwell!

That was when the wind started, even before the noise. “No one realizes about the wind,” says Komorowski.

The building was pancaking down from the top and, in the process, blasting air down the stairwell. The wind lifted Komorowski off his feet. “I was taking a staircase at a time,” he says, “It was a combination of me running and getting blown down.” Lim says Komorowski flew over him. Eight seconds later—that’s how long it took the building to come down—Komorowski landed three floors lower, in standing position, buried to his knees in pulverized Sheetrock and cement.
Lim landed near Harris. “If Josephine doesn’t slow me down, I’m dead,” he’d later say. “I figured this out.” That captain who’d urged Lim to go ahead didn’t make it. “Josephine Harris saved my life,” he says definitively. Harris landed on her side, clinging to the boot of Billy Butler.

With the shell acting as a container, and the falling debris a piston, there was plenty of air pressure in the WTC to do all the stupid "squibs" you see, and that is why some of them increase speed, due to increased pressure. And that is why you do not see BLASTS, or hear BLASTS from charges that were not there.
I expect you to point to the "squib" as you do; this makes you a liar since you can not support your implication, but I have presented facts to make your implications lies.
Come up with blasts effects, and blast sounds from explosions.

Some "squibs" from falling buildings. And air pressure example. Did you see those cutter charges?

Look at the evidecne of thermite! lol. If you watch you can see some "squibs" going off to destroy the evidence!You got to admit, there are some real dumies in 9/11 truth.

Please Greg, never point to the air escaping the WTC without evidence. It makes your ideas real stupid. Please try to use evidence before being dumb.

 

[jhunter1163]

GregoryUrich:

Can you link the video that still comes from? Maybe it's just me, but that looks like a streetlight. I'd assume the "squib" is more noticeable in full motion.

 

[bofors]

GregoryUrich:

Can you link the video that still comes from? Maybe it's just me, but that looks like a streetlight. I'd assume the "squib" is more noticeable in full motion.

See time index 1.00 for the squib in question:

 

[jhunter1163]

Bofors:

That link is broken, is there another?