WTC 1 & 2. What happened after collapse initiation?

PhantomWolf said:
Well then oh great font of wisdom, what exactly is the state between hollow and solid? Sorta hollow? Hollow but for a few bits that aren't? Not really quite hollow cause I can't possible admit that I'm wrong?
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Porosity does not exist in your world? Would you say Vulcano stone is hollow? alot of air and penetrations in it. is it solid or holow?
 
but hey , i dont want to further discuss it.

pls call it hollow if you think that is correct.
i also say it was a CD cause i think that is correct :)

bye bye
 
Would you say Vulcano stone is hollow?
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Im still trying to come to terms with just how bad that analogy is.
Do volcano stones generally have cavities that run straight through them vertically?
 
scissorhands said:
Im still trying to come to terms with just how bad that analogy is.
Do volcano stones generally have cavities that run straight through them vertically?
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not straight as a elevator shaft, but as straight as stairs did, yes.
 
Not correct. You were the one complaining about extremes, but you are the one that thinks that for something to be hollow it must have nothing inside it at all. Look again at the definition. "Having a space or gap or cavity." If it more than one space, gap or cavity, it's still hollow. You're fighting not only a losing battle here, but an irrelevant one and making yourself look even more trollish that usual. In fact honestly I don't know why I'm bothering to try and educate you, you have no interest in learning so it's pointless.


To go back a looooong way the floor truses are far more important in the collapse because that is where the majority of the mass hit. The cores have less mass and less flooring to fall on top of what's there. The expected result is that the floor trusses would be broken off their seating and pushed down into the next floor by the upper section creating for want of a better description the pancake effect (and before you start on about NIST saying that didn't happen, go read it again, they said that the collapse initiation wasn't caused by pancaking, they never said it didn't happen AFTER the collapse had started.) The core, with less to fall on it and deal damage would most likely survive the initial collapse but rather collapse under its own weight. The outer walls, without the linking to the core, would fall outwards.

Now compare that to what was seen and what was recovered afterwards. The outer walls fell outwards, the core stood for 30 seconds after the collapse, the truss seats on the coloumns were all bend downwards by a force applied from above, and the floors were compressed together in the tower footprint. Strange that.


edited to add, and on that note, I'm going to bed
 
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Sparky said:
Heiwa,

AA. If I were to use your logic, wouldn't a CD have also been arrested by friction?

BB. How do you think the towers came down and weren't arrested by friction?

CC. Do you seriously believe that the buildings could have possibly been wired with enough high explosive to not only take out the columns but also acres upon acres of floor space?

DD. Don't you think someone would have noticed?
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AA. No, using CD you destroy primary structure in critical loactions with known result - global collapse. WTC1 local primary structure up top could not have been destroyed by fire/heat and if it had happened it would only cause local damages to floors, followed by arrest due friction.

BB. Some type of CD was used (in several places).

CC. What is wrong with remote control (no wires)?

DD. Answer no. These criminals were quite clever and ruthless.
 
Heiwa said:
Seems? Evidently when two bodies (structures) A and B come in contact, the force F of body A on the other body B, produces an opposite reaction force, Fo of body B on body A. Google on Isaac Newton for more info. F = Fo = equilibrium.
Depending on the properties of A and B, F may damage or deform B or Fo may damage or deform A. There are plenty of possibilities but quite easy to analyse what happens after this initiation contact.

After each damage or deformation of A or B you have to redo the analysis, step by step, to see what happens then with the forces involved. Luckily there is always equilibrium to simplify the analysis. Normally some of the new forces that develop after initiation contact produce friction forces, so you have to include those in a complete analysis.

NIST and Bazant suggest without any evidence that A destroys B. NIST suggests that B lacks strain energy to absorb the energy transmitted by A to B without any calculations to back up the suggestion. Bazant suggests that A crushes down B, while A remain intact. Neither has heard about friction!

It seems neither NIST nor Bazant has any knowledge of structural damage analysis (like many participants on this thread). Reason is that very few universities teach the subject. Bazant has written 400+ scientific papers but none about structural damage analysis. He has still a lot to learn.

I on the other hand that have investigated and analysed 100's of steel structural damages due to contacts (ship collisions - also groundings and ships colliding with quays and fixed objects) have some experience. Structural damages occur every day so it is not a new phenomenom! On the contrary.

Some 13 (?) years ago some Japanese made a complete damage analysis of a serious contact A against B using Finite Element Models + plenty of computer capacity. The destructions followed the A+B contact would in reality take 5 seconds, but the analysis split this events in 5000+ sub-events (how the further damages developed and were arrested) and it took the computers three weeks to do the full analysis.

When the analysis was done they actually arranged a real A + B contact and found good agreement between theoretical analysis and the real thing.

Interesting stuff. I wrote a positive review about that project in a serious English engineering monthly journal published by the Royal Institute of Naval Architects in London.
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TheRedWorm said:
And you can do calculations to back this...assertion up?
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...
 
Dictator Cheney said:
would you say the WTC Cores was hollow?
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Uhh, yes. The whole building was "hollow". To use an extremely poor analogy, they are hollow the same that a bunch of cardboard boxes stacked together are hollow.

Why the heck would they not be?
 
An interesting problem

It has been argued that the bottom section of WTC1 would have been able to withstand the impact of the top section dropped from a height of one floor such that the top section would just bounce on the lower part with both parts acting like a spring. For this to happen, of course the collision must be considered elastic.

Thus, the building is split into two sections. The top part is dropped onto the lower part such that the impact velocity is 7.1 m/s (a = 0.7g over a fall of 3.7m as observed in WTC1). Assume the bottom part is 384m high and the collision is elastic. Assume the entire lower part (and the upper part if you think that makes a difference) behaves as a linear spring.

In order to halt the top part before the elastic limit is reached, what would the minimum force required in the spring at maximum deflection?

Solve for force in terms of mg (the mass of the upper part times gravity).
 
Heiwa said:
As the bodies have masses, they are attracted to each other by gravity according Newton. But there are also other origins of forces!

So when the upper block of WTC1 displaces by gravity and contacts the lower structure other forces develop, e.g. friction. Not too difficult to understand but completely ignored by NIST and Bazant.

Bazant is a really comical figure with his indestructible upper block. According his theory the upper block should continue to the centre of the earth and, after crush down of the structure below, continue making a big hole in the ground, etc, etc.

Somebody should ask Bazant why his upper block suddenly stops at the soft ground at the surface of the earth.
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Hi

Do you know that buildings can't float?
 
GregoryUrich said:
It has been argued that the bottom section of WTC1 would have been able to withstand the impact of the top section dropped from a height of one floor such that the top section would just bounce on the lower part with both parts acting like a spring. For this to happen, of course the collision must be considered elastic.

Thus, the building is split into two sections. The top part is dropped onto the lower part such that the impact velocity is 7.1 m/s (a = 0.7g over a fall of 3.7m as observed in WTC1). Assume the bottom part is 384m high and the collision is elastic. Assume the entire lower part (and the upper part if you think that makes a difference) behaves as a linear spring.

In order to halt the top part before the elastic limit is reached, what would the minimum force required in the spring at maximum deflection?

Solve for force in terms of mg (the mass of the upper part times gravity).
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Oddly enough, Heiwa has already performed this calculation (with gross assumptions in favor of collapse prevention) and determined that the upper floor of the lower block would fail.

He hasn't figured out what that means yet.
 
Heiwa said:
AA. No, using CD you destroy primary structure in critical loactions with known result - global collapse. WTC1 local primary structure up top could not have been destroyed by fire/heat and if it had happened it would only cause local damages to floors, followed by arrest due friction.

BB. Some type of CD was used (in several places).

CC. What is wrong with remote control (no wires)?

DD. Answer no. These criminals were quite clever and ruthless.
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Hi Heiwa,

Do buildings float?
 
GregoryUrich said:
It has been argued that the bottom section of WTC1 would have been able to withstand the impact of the top section dropped from a height of one floor such that the top section would just bounce on the lower part with both parts acting like a spring. For this to happen, of course the collision must be considered elastic.

Thus, the building is split into two sections. The top part is dropped onto the lower part such that the impact velocity is 7.1 m/s (a = 0.7g over a fall of 3.7m as observed in WTC1). Assume the bottom part is 384m high and the collision is elastic. Assume the entire lower part (and the upper part if you think that makes a difference) behaves as a linear spring.

In order to halt the top part before the elastic limit is reached, what would the minimum force required in the spring at maximum deflection?

Solve for force in terms of mg (the mass of the upper part times gravity).
Click to expand...

Spring against spring.

Assume two springs 1 and 2!

Spring 1 has length L1 and spring constant C1 and spring 2 has length L2 and spring constant C2.

Spring 1 is fixed at one end and spring 2 is attached to the other end of spring 1.

A force F is applied to the free end of spring 2. What happens?

Evidently both springs compress and a reaction force -F develops at the fixed end of spring 1.

Compression d1 of spring 1 is d1 = F/C1

Compression d2 of spring 2 is d2 = F/C2

The energy E1 required to compress spring 1 is E1 = (d1)² C1/2

The energy E2 required to compress spring 2 is E2 = (d2)² C2/2

The total energy E to compress the two springs is E = E1 + E2

Now release spring 2 from spring 1.

Instead of applying a force to the two springs, spring 2 is now moving with a kinetic energy E and is colliding with the free end of spring 1. We assume a soft collision.

What happens then? Both springs compress as if a force F was applied to them and a reaction force -F develops at fixed end of spring 1.

What happens then? One possibility is that both springs decompress and that spring 2 bounces back! Another is that one of the springs break due to overload. A third possibility is that both springs break simultaneously but it is unlikely. If something breaks it is the weakest link.

What do you think?
 
"Spring is in the air"

In my experience normal springs being extended risk passing their elastic limit, but springs being compressed approach becoming metal tubes and actually gaining in strength as "spring rolls". Springs don't seem to illuminate the issue. But I could easily be talking cobblers. If so, blame it on the ouzo.
 
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