Moderated Steel structures cannot globally collapse due to gravity alone

[Gravy]

In the Twin Towers they were bolted into 1300 foot units and assemblies closely spaced and braced against the concrete floor slabs at 12' intervals. top to bottom and all around.

No, they were welded into 3-story sections that were then bolted together (and in a few stories welded) at their ends and spandrels. I don't know what you mean by "braced against the concrete floor slabs."

When the truss seats below the impact zones were examined by NIST, all were found to be bent downward. This can be seen in many photos. To what do you attribute this effect?

In this configuraton they gave the building tremendous strength and considerable flexibility- just not to the point of the box columns kinking though.

The NIST report goes into great detail about the ability of the towers to resist various forces. Do you disagree with any of it?

 

[tfk]

C7,
Ever hit a nail with a hammer & had it fly off sideways?

Yes. Entirely different conditions.
I'll add that analogy to the Big Mac file.

Nope. It's not "entirely different conditions" in the slightest. It is exactly the same.
A long, slender, semi-restrained element hit hard, but not perfectly aligned to the vertical axis of the nail, from above.

Another entirely different mechanism and a VERY valid analogy, is the tiddly-wink. Rotational motion is converted to linear motion by virtue of a single collision of one end of the "wink" (is that what it's called?) with the surface of the table. Notice when this happens, there is NO high velocity motion in either wink before the one wink gets shot off at high speed. There is NO "conservation of speed" principle. It is conservation of energy. And conservation of energy can, and often does, allow high speed events coming out of stored energy involving low speed inputs. (e.g., spring loaded guns).

Another different mechanism is simply the lever, as exemplified by jumping spoons on a table. Hit downward on the edge of the bowl of a spoon & you can shoot it with high velocity. Higher than your hand comes down.

if a 4 ton beam asembly is thrown to the side with enough horizontal velocity to make it 400 - 500 feet, then, BY DEFINITION, it has enough energy to embed itself into whatever it might contact at that point.

Correct. All that energy directed sideways was not caused by the top section of the tower falling straight down.

You missed my point. If the part has been thrown that far, then it ALREADY HAS all the energy it needs to embed itself in whatever it hits.

And in spite of your somewhat contrarian responses, you don't appear to appreciate the mechanical principles that are involved.

It is trivial to change slow motion into fast motion. It's called a lever.

It is trivial to change motion in one direction to motion in a different direction. It's called a collision.

It is trivial to change rotational motion to linear motion and back. It's also called a collision.

And, in spite of what Mr. Smith says, steel box columns WILL bend & store energy elastically. And then give it back in a rebound.

Even if cardboard box columns are particularly bad at it. (Of course, cardboard ones will, too. You just have to be very careful not to kink them.)

tk

 

[Gravy]

All carefully calculated of course and with a very large margin of safety built in.

I'll bet you don't know what the margin of safety for the perimeter and core columns was, under normal circumstances.

Anyway, there was no "margin of safety" designed for the perimeter columns in the event that 30,000 tons of building came crashing through itself. The structure fails at its weakest connections. Lots of them.

 

[Christopher7]

Chris7, sitting here a while back I dropped yet another pencil on the edge of my desk. It ended up a good 3' from it's original "destination" just below its original direct line of fall. That is, it deflected sideways. It bounced. There was, no doubt, some flexing and torsion and whatever involved. We all know this happens routinely when things fall and hit other things along the way.

When a falling solid object meets solid a stationary object, one or both compact slightly. As they return to their original shape to the best of their ability, the formerly falling object is propelled back up or in another direction. This is called "bouncing".

That's all very nice but it does not apply to a steel frame building that is 95% open falling on same.

The building below gave way, there was no bouncing.

Bazant did not mention the "bounce factor".

His theory requires all the debris* be compacted to the max and applied evenly to each successive floor.
*-20% ejected

This is not what happened in the south tower.

His theory does not explain how the south tower collapsed.

 

[bill smith]

Bill, you're running into Christopher 7 territory here. The towers were tubes, the outer walls of which consisted of tightly-bound sections. When those tubes are violently destroyed from the inside by millions of pounds of accumulating, accelerating, falling debris, and the walls of the tubes essentially burst, which way do you expect the wall sections to travel?

Next, how far should such wall sections travel in a collapse that's not aided by anything but gravity? If you don't know how to answer that, you need to reconsider your objections to the videos and physical evidence.

Next, tossing thousands of tons of steel around would require explosives thousands of times larger than are used in building demolitions. The idea that such enormous detonations are undetectable is absurd on its face. If you disagree, then please explain what weapon you think was used to destroy the towers, and the effects we'd expect to see from it. I'm very curious to know how you think this might be possible. Christopher 7 and Heiwa can't answer that question, and they've been doing this for years.

Hi Gravy- there are so many areas of 9/11 that do not add up in my opinion. With three thousand dead it needs to be cleared up. The 9/11 Commission report was entirely unsatisfactory and there was- and is no will for an independent enquiry.

To me we only have to establish beyond doubt that the gvernment story is false in many serious respects. We don't have to prove how exactly how it was done. An independent enquiry will ferret that out quickly enough but we will need to force one somehow. I have theories about many of the events which we may get into at some point.

 

[GStan]

When a falling solid object meets solid a stationary object, one or both compact slightly. As they return to their original shape to the best of their ability, the formerly falling object is propelled back up or in another direction. This is called "bouncing".

That's all very nice but it does not apply to a steel frame building that is 95% open falling on same.

The building below gave way, there was no bouncing.

Bazant did not mention the "bounce factor".

His theory requires all the debris* be compacted to the max and applied evenly to each successive floor.
*-20% ejected

This is not what happened in the south tower.

His theory does not explain how the south tower collapsed.

Is it your contention that the ejected debris distribution could not have been achieved without the use of explosives? Is it your contention that if there were no added explosive forces available to eject the debris, that the entirety of the building would have fallen within its own footprint?

 

[BenBurch]

Really? How in this case, not some comparison,
was the energy redirected?

Buckling. And compressed air.

Take a long wooden match stick score it about halfway though in the middle to represent the joints, compress it between your fingers. Most of the time the bits go flying out.

 

[ElMondoHummus]

Hi Gravy- there are so many areas of 9/11 that do not add up in my opinion. With three thousand dead it needs to be cleared up. The 9/11 Commission report was entirely unsatisfactory and there was- and is no will for an independent enquiry.

To me we only have to establish beyond doubt that the gvernment story is false in many serious respects. We don't have to prove how exactly how it was done. An independent enquiry will ferret that out quickly enough but we will need to force one somehow. I have theories about many of the events which we may get into at some point.

Oh, my, not again...

Sir: The 9/11 Commision Report was not meant to be a definitive explanation of the towers collapse. The NIST report was. Since this entire thread is concentrating on the engineering issues behind the collapses (more specifically, C7's and Heiwa's misapprehensions of them), and since you were replying specifically to a post concerning itself with specific issues about the collapses, then I'm at a loss as to why you invoked the 9/11 Commision Report. There's no real engineering in that work; it discusses the hijackers and the events of the day, not the details of how the towers structurally failed.

Perhaps you should continue along the line of the structural issues, vis-a-vis the NIST reports. Posts about how the columns should have acted cannot be supported by criticism of the 9/11 Commision Report because the failures of the structures are not seriously discussed there. They're discussed elsewhere.

 

[Gravy]

Bill, the title of this thread is "Steel structures cannot globally collapse due to gravity alone." Until your last, completely evasive, "JAQ and demanding answers!" post, you were participating in the discussion about the collapses.

Second time:

When those tubes are violently destroyed from the inside by millions of pounds of accumulating, accelerating, falling debris, and the walls of the tubes essentially burst, which way do you expect the wall sections to travel?

Next, how far should such wall sections travel in a collapse that's not aided by anything but gravity? If you don't know how to answer that, you need to reconsider your objections to the videos and physical evidence.

Next, tossing thousands of tons of steel around would require explosives thousands of times larger than are used in building demolitions. The idea that such enormous detonations are undetectable is absurd on its face. If you disagree, then please explain what weapon you think was used to destroy the towers, and the effects we'd expect to see from it. I'm very curious to know how you think this might be possible.

Please show that you've put more thought into your claims than have Christopher 7 and Heiwa. Thanks.

 

[phunk]

When a falling solid object meets solid a stationary object, one or both compact slightly. As they return to their original shape to the best of their ability, the formerly falling object is propelled back up or in another direction. This is called "bouncing".

That's all very nice but it does not apply to a steel frame building that is 95% open falling on same.

The building below gave way, there was no bouncing.

Bazant did not mention the "bounce factor".

His theory requires all the debris* be compacted to the max and applied evenly to each successive floor.
*-20% ejected

This is not what happened in the south tower.

His theory does not explain how the south tower collapsed.

But we're not talking about the upper block of the building bouncing, we're talking about individual components like the box columns that were "ejected". Is it your claim that if 2 columns collide they can't bounce off each other?

 

[Christopher7]

The towers were tubes, the outer walls of which consisted of tightly-bound sections. When those tubes are violently destroyed from the inside by millions of pounds of accumulating, accelerating, falling debris, and the walls of the tubes essentially burst, which way do you expect the wall sections to travel?

So, the buildup of debris pushed out on the exterior walls enough to make them burst while busting through floors in a small fraction of a second?

Bazant did not mention this bursting much less calculate the energy necessary to do it.

Did you pull this out of your . . . imagination?

 

[DGM]

bill smith;

Have you changed your mind on the columns not "being able to store energy" (paraphrased}? You seem to be trying to shed that argument while trying to not miss a step (dodging). It's OK for adults to admit they were wrong.(I'm not sure why I felt the need to say that)

 

[Christopher7]

But we're not talking about the upper block of the building bouncing, we're talking about individual components like the box columns that were "ejected". Is it your claim that if 2 columns collide they can't bounce off each other?

Actually, we are talking about exterior frame sections that did not bounce off of anything. They were ejected laterally at 50+mph.

 

[tfk]

Very astute observation. Framework sections being torn apart in a violent and chaotic collapse would also have jagged, splayed ends, not finished, machined (i.e., straight) ends.

The ends of all these columns have been cut, not torn apart.

You're right.

They WERE cut.

They were cut in approximately 1964. When they were manufactured for the construction of the towers.

When you cut a beam using explosives, there are obvious tell-tale signs that include rough, ragged edges, thinning of the material, melted & resolidified edges, obvious high strain rate crystal deformations (that you cannot see except under a microscope), etc.

These beams show none of these indications. They were NOT cut by charges. They were NOT cut by thermite. They were, quite simply, NOT cut. Period.

They failed at their weak link: the bolts that joined them together.

And that helps explain how some of them were thrown outside the structure:

The beams were NEVER intended to take any significant bending loads. Long slender beams don't do that very well.

They were intended to take only compressive & tensile loads. Similarly, the bolts holding them together were not intended to take bending loads either. Due to the damage & tipping of the upper section, suddenly they were asked to take enormous bending loads. They resisted for quite some time.

But when they failed, some of the beams were bent over by the descending block of the tower. They bent, and bent, and bent, storing more & more energy, until the bolts gave way. In essence, this is EXACTLY how a fighter jet is launched off of a carrier deck. A "weak link" member (called a 'dog bone') is inserted between the shuttle (that shoots the jet) and a hard point. The pressure is built up & up & up, until the dog bone simply fractures.

It is an EXCELLENT system for storing energy and then suddenly flinging a heavy object with great speed.

tk

 

[DGM]

Actually, we are talking about exterior frame sections that did not bounce off of anything. They were ejected laterally at 50+mph.

Why is this NOT possible (by gravity)? Did I miss your calculations?

 

[ElMondoHummus]

So, the buildup of debris pushed out on the exterior walls enough to make them burst while busting through floors in a small fraction of a second?

Bazant did not mention this bursting much less calculate the energy necessary to do it.

That's not really true, Chris. It's been pointed out to you that the BLBG paper specifically dealt with issues of mass shedding, and found that they did not contradict the overall conclusion. This "bursting" is a consequence of the columns - the primary load-bearing components of the system - failing. Any other effect is a consequence of that. Bazant et. al. may not have directly addressed minute points about how the failures manifested, but you're splitting semantic hairs to imply that a failure to specifically mention "bursting" is equivalent to not accounting for the energy involved at all. How individual failures manifest is indeed something he did not address, but the fact that the energy was there was.

 

[GStan]

Actually, we are talking about exterior frame sections that did not bounce off of anything. They were ejected laterally at 50+mph.

Could they have been ejected laterally at any speed that would not be suspicious to you?

 

[tfk]

Try it yurself if you have a suitable cardboard box. Any size as long as it is long and slender.

You may, or may not, realize it, but cardboard is a REALLY lousy model for steel.

Why don't you do your test with a metal box, preferably steel. Soft metals i.e., copper brass, aluminum, etc) aren't very good either, but they are MUCH better than cardboard.

If I were cynical, I might suspect that you chose cardboard for the express purpose of getting the (wrong) answer that you wanted all along.

Ah, who am I kidding...

... I've extremely cynical, bill.

tk

 

[DGM]

You may, or may not, realize it, but cardboard is a REALLY lousy model for steel.

Why don't you do your test with a metal box, preferably steel. Soft metals i.e., copper brass, aluminum, etc) aren't very good either, but they are MUCH better than cardboard.

If I were cynical, I might suspect that you chose cardboard for the express purpose of getting the (wrong) answer that you wanted all along.

Ah, who am I kidding...

... I've extremely cynical, bill.

tk

And he was proposing this experiment to a builder/iron worker (Me). Condescending was the word that came to my mind.

 

[bill smith]

Bill, the title of this thread is "Steel structures cannot globally collapse due to gravity alone." Until your last, completely evasive, "JAQ and demanding answers!" post, you were participating in the discussion about the collapses.

Second time:

When those tubes are violently destroyed from the inside by millions of pounds of accumulating, accelerating, falling debris, and the walls of the tubes essentially burst, which way do you expect the wall sections to travel?

Next, how far should such wall sections travel in a collapse that's not aided by anything but gravity? If you don't know how to answer that, you need to reconsider your objections to the videos and physical evidence.

Next, tossing thousands of tons of steel around would require explosives thousands of times larger than are used in building demolitions. The idea that such enormous detonations are undetectable is absurd on its face. If you disagree, then please explain what weapon you think was used to destroy the towers, and the effects we'd expect to see from it. I'm very curious to know how you think this might be possible.

Please show that you've put more thought into your claims than have Christopher 7 and Heiwa. Thanks.

Gravy - I wasn't being evasive. And I AM looking for answers which requires asking questions. If I hear something that definately invalidates one of my notions then so be it. There is little point in not taking it on board if any progress is to be made. That dosn't mean accepting whatever I'm told though

Without necessarily accepting your premise I would expect the wall sections to be pushed outwards.

I don't think he wall sectons would travel very far in a gravity driven collapse.

Although there are a lot of indicatons against explosives for the reasons you mention, there seems to be a case for additionl energy coming from somewhere,somehow to eject- for instance he 4-ton chunk the 500 feet we were talking about earlier.