WTC 1 & 2. What happened after collapse initiation?

[Heiwa]

The result, as every sane human realizes, will be a pile of rubble.

You are quite mad.

Hm, it appears that this plane (structure) that dropped on a field at Shanksville, PA, did not even provide a pile of rubble but just a little bomb crater in the ground ... and no rubble anywhere. Another first on 9/11!

Of course, after digging for a while they found an FDR in the bomb crater but it appears now that NTSB cannot confirm that the FDR they recieved to analyse originated from the plane in question. OT for this thread, OC.

 

[Grizzly Bear]

I know you would be surprised. Doesn't change anything. You were in error. Happens all the time. That's why we discuss so you and other non-engineers and sect members will learn a little about the real world.

The silly irony is... you aren't in tune with the real world physics. Non-engineers are able to see your errors, yet you are quite oblivious to them.

 

[tsig]

BTW: All you "Equal forces" nuts:
By the same logic (dropping a glass on a table) you have shown:
If you drop a table on a glass, why does the glass break? The forces are equal and opposite, are they not?

Looks like we're back to NET FORCE=ZERO.

"Will the circle be unbroken
By and by, by and by?
In a better home awaiting
In the sky, in the sky?"

{old hymn}

 

[Newtons Bit]

I have seen many bolts dropping out causing local damage to my welded steel structures.

Reasonable confidence level! Can't you do better than that?

Better is first to establish the design loads involved. It can be tricky.

Then you apply these loads to the structure/component and establish the resulting stresses everywhere.

Then you adjust the structure/component so that the combined stress is, say, 1/3 of the maximum permissible stress (e.g. yield) to obtain a FoS of 3.
Then you have a nice safety margin and redundancy allowing for wear and tear, misalignment, manufacturing faults, errors in load estimations, fatigue, etc, etc. Oh yes, in my steel construction business we use FoSs like that - always based on stress calculations. Only 40+ years experience.

Of course I can slender down the structure allowing one static stress level and another dynamic (short term) stress level and permitting that some deformation will take place (due short term dynamic loads), etc, etc. There are many variations.

Heiwa, if you actually have something to say that is backed up by calculations, let me know. If not, stop wasting my time. You and I both know that you don't know what you're talking about. The only real question that remains for me is what possesses you to never admit that you can make mistakes. But that doesn't relate to 9/11, just to kooks.

 

[Grizzly Bear]

Hm, it appears that this plane (structure) that dropped on a field at Shanksville, PA, did not even provide a pile of rubble but just a little bomb crater in the ground ... and no rubble anywhere. Another first on 9/11!

[derail] They found debris, of course since the plane hit ground at high velocity and at a steep angle there wasn't much recognizable debris left of it...[/derail]

Plus you have a nasty habit of using weak analogies... Apples to apples please... I keep asking and you never give, how does a plane hitting the ground at 800 ft/second comapre to a 30 story section of building hitting another section of building made of the exact same materials? Scratch Apples and orange I'll wager you're going for comparing apples to planets

 

[AZCat]

And no, if bolts move around they won't just shear off and fall away, assuming the bolt is actually installed correctly. You do know that bolts are pre-tensioned beyond their yield strength and thus form a bond through friction with the connecting surface right? This is the slip resistance of the bolt. It is less than the bearing capacity (direct shear on the bolt shank) but much, much greater than 1 kip.

I didn't know that. Or if I did, I forgot it a long time ago.

 

[Heiwa]

Heiwa, if you actually have something to say that is backed up by calculations, let me know. If not, stop wasting my time. You and I both know that you don't know what you're talking about. The only real question that remains for me is what possesses you to never admit that you can make mistakes. But that doesn't relate to 9/11, just to kooks.

I missed your calculations of the bolt strength. FYI - it is you wasting your time with bolts and nuts, nutty OT OC.
What mistakes of mine are you hinting at in sectarian style?

 

[tsig]

I know you would be surprised. Doesn't change anything. You were in error. Happens all the time. That's why we discuss so you and other non-engineers and sect members will learn a little about the real world.

In the real world buildings are designed to resist gravity not float on water.

BTW your continued reference to members of this forum as a "sect" is insulting and deliberately provocative.

 

[Myriad]

The WTC tower floors were bolted to the columns. That's why bolts are relevant.

In just this one case, though, one of Heiwa's comments might actually make sense in the context he claims he usually works in. I can see where bolted connections between surfaces that are frequently subject to significant flexing, such as in ship's hulls, might be prone to working loose and therefore considered unreliable.

Respectfully,
Myriad

 

[tsig]

The WTC tower floors were bolted to the columns. That's why bolts are relevant.

In just this one case, though, one of Heiwa's comments might actually make sense in the context he claims he usually works in. I can see where bolted connections between surfaces that are frequently subject to significant flexing, such as in ship's hulls, might be prone to working loose and therefore considered unreliable.

Respectfully,
Myriad

I can see where a welder would have a hard time understanding a bolted connection. Or he could have welded too much magnesium in enclosed spaces.


If he could just be convinced that a building is not just a ship set on it's end then progress could ensue. LOL

 

[Heiwa]

And no, if bolts move around they won't just shear off and fall away, assuming the bolt is actually installed correctly. You do know that bolts are pre-tensioned beyond their yield strength and thus form a bond through friction with the connecting surface right? This is the slip resistance of the bolt. It is less than the bearing capacity (direct shear on the bolt shank) but much, much greater than 1 kip.

Hm, pre-tensioning beyond yield produces plastic deformations of the threads, so the bolt threads are deformed. If that produces friction is very doubtful. On the contrary. It is the friction that deforms the threads. And then the bolt can be pretty useless regardless if it is fitted in a nut or threaded hole. I agree - it must actually be correctly installed - not so easy. If not ... anything may happen; normally the bolt drops down or pops away - hopefully at installation and not later due to just being partly overloaded/deformed at installation.
That's why I never trust a bolted connection. Or its 'design strength' (sic).
So what is the 'design strength' of a bolt. According your table or depending on correct installation?

I like that you recognize FRICTION with connecting surfaces as an important factor. It would have arrested the WTC1/2 failures very soon.

The upper block is just like a bolt that you try the screw into the lower structure. After a while it is arrested. All due to FRICTION.

 

[Heiwa]

BTW your continued reference to members of this forum as a "sect" is insulting and deliberately provocative.

Partly correct. Some participants behave like sect members that do not accept, e.g. Newton or basic physics and have some 'better' ideas ... very obscure. They often use foul language and insults and ignore the argument and attacks the arguer. Easy to spot. But I am never insulting anybody. Provocative, yes. With Newton's support, that's easy.

 

[R.Mackey]

You write, "In your pictures, the fall is already underway." So in this picture, all the columns have already been severed?

Yes. It is extremely likely that all connections between the upper and lower block have sheared at this instant. If by some miracle there are some badly deformed members hanging on, they have already lost all meaningful material strength, i.e. already buckled.

So the upper block tilts slightly, then the 3.7 meter fall occurs and the upper block continues to rotate as it falls. Then this rotation stops and the upper block falls vertically. So what causes the upper block to stop rotating after it begins to fall?

Nothing does. It rotates more. In my whitepaper, I explain why there is some opposition to more rotation, since more rotation means more impact with lower floors on that side, but we expect this to slow the rotation, not necessarily stop it.

You write in your paper, "Since the upper block tilts, it first comes in contact with the lower structure at the down-tilted corner."

If this is the case then why do we notice the lower block being destroyed with a high degree of radial symmetry?

We don't.

"Radial symmetry" really only applies in cylindrical or spherical situations, I think what you mean is "reflective symmetry," i.e. the same destruction on opposite faces. But it isn't. The timing of destruction is slightly different opposite the hinge. There are slight differences all the way down the Tower, but since the rotation is minor and the lower block is all connected, it's not enough to notice. What symmetry there is in the destruction exists because the structure itself starts as largely symmetric, and there are only slight force differences caused by the tilt.

 

[Heiwa]

The silly irony is... you aren't in tune with the real world physics. Non-engineers are able to see your errors, yet you are quite oblivious to them.

My objective is evidently the assist non-engineers to understand some basic physics, structural analysis, etc. Tough job, though.

 

[Grizzly Bear]

My objective is evidently the assist non-engineers to understand some basic physics, structural analysis, etc. Tough job, though.

Then please feel free to explain why these columns on the south tower began to buckle and why they have been drawn inward. Your model ignores both by assuming that they would be able to not only stand strong against lateral shear forces, but also in doing so impart friction to slow the collapse to a halt

LINK

The same observation is made in the north tower.

NISTalso details the various failure modes of recovered columns showing spandrel connection failures in addition to failure of the connections of the columns themselves.
Did you read NCSTAR 1-3C, or even glance at it?

This is basic physics Heiwa, why are you ignoring it?

 

[pomeroo]

I know you would be surprised. Doesn't change anything. You were in error. Happens all the time. That's why we discuss so you and other non-engineers and sect members will learn a little about the real world.

What is the sense in attempting to engage someone who clearly is missing several cards from his deck? People are making sophisticated arguments that he can't begin to comprehend and he continues to insist that Newton wouldn't understand that dropping the top third of a building onto the rest of it destroys the whole structure.

 

[pomeroo]

My objective is evidently the assist non-engineers to understand some basic physics, structural analysis, etc. Tough job, though.

Let's make one last despairing attempt:

I have two china vases filled with sand or water (take your pick), one four feet tall and the other two feet, the smaller resting on top of the larger. I lift up the smaller vase and drop it from a height of ten feet onto the larger vase. We all get the idea that the forces balance. Now,

1) The smaller vase smashes, leaving the larger vase intact;

2) Neither vase breaks (a new equilibrium is established);

3) Only the larger vase breaks;

4) Both vases get smashed.


Choose one of the four possible answers.

 

[pomeroo]

I know you would be surprised. Doesn't change anything. You were in error. Happens all the time. That's why we discuss so you and other non-engineers and sect members will learn a little about the real world.

He calmly, with glassy eyes and a lopsided, deranged grin, asserts that 1 + 1 = 7.

 

[Heiwa]

Then please feel free to explain why these columns on the south tower began to buckle and why they have been drawn inward. Your model ignores both by assuming that they would be able to not only stand strong against lateral shear forces, but also in doing so impart friction to slow the collapse to a halt

LINK

The same observation is made in the north tower.

NISTalso details the various failure modes of recovered columns showing spandrel connection failures in addition to failure of the connections of the columns themselves.
Did you read NCSTAR 1-3C, or even glance at it?

This is basic physics Heiwa, why are you ignoring it?

Evidently I have read the NIST-report(s). I quote from them in my articles. Evidently fire/heat cause local failures/deformation prior initiation but if they in turn cause free falls or impacts is not proven anywhere. And very unlikely. Topic is however what happens after initiation and that's where NIST goes wrong.

 

[Heiwa]

Let's make one last despairing attempt:

I have two china vases filled with sand or water (take your pick), one four feet tall and the other two feet, the smaller resting on top of the larger. I lift up the smaller vase and drop it from a height of ten feet onto the larger vase. We all get the idea that the forces balance. Now,

1) The smaller vase smashes, leaving the larger vase intact;

2) Neither vase breaks (a new equilibrium is established);

3) Only the larger vase breaks;

4) Both vases get smashed.


Choose one of the four possible answers.

Aha, now a multiple answers quiz! What is the purpose of that? Desperation? But good that you agree that the forces developing at contact are in equilibrium, i.e. the downward, gravity force is balanced by an opposite reaction force of equal size. You have learnt something!!

Now if the larger, imobile vase is very strong and the the smaller, dropping vase is very weak 1) may occur. On the contrary, if the large vase is very weak and the small one is very strong, 3) may occur.
If both vases are very weak 4) may happen.
If both vases are very strong, 2) may happen, i.e. the small vase bounces on the large vase and continues somewhere else. It is unlikely that the small vase lands on top of the large on. The small one will slip off.

It is thus not possible to choose one of the four possible answers as all answers are possible.

According NIST, if the potential energy released by the small vase, exceeds the strain energy that can be absorbed by the vases, global collapse ensues.

A fifth possibility is however that the small vase is partly damaged in its base and the big vase is partly damaged at its top at contact and that the small vase gets stuck in the top part of the large vase due to friction developing.

Why did you eliminate the fifth possibility? Sectarian elimination of dangerous facts?

When doing structure damage analysis you must evidently consider all possibilites. NIST failed doing that.