WTC collapses discussion thread IV

Quote:

I wish I could read minds...

Then again, maybe not.

I wish you could stop trying.

About dt:

Pants-of-dog, I think your argument about a constant or varying v is beside the point. Garcia uses v(initial)=-7.7m/s and dv=.5m/s. He then says that for the floors to fail, they (or any portion of them) need to be deflected by only ~7cm=~.07m. The time for this to occur is not more than the distance divided by the slowest velocity, which is ~0.01s.

Fidel, the dt in Garcia is the time for the floor to break, not the time for the entire tilted floor to pass through the position held by the lower floor before the lower floor broke. Thus, the argument using trigonometry is completely irrelevant. (Pants is basically right on this point. I'm not sure if the mod's agree with him or simply don't want to take a side in an honest argument. It's simply not fair to call Pants-of-dog a troll for disagreeing with you.)

(I'm using ~ to mean approximately. In this case, not off by more than 10%. Since there can never be complete certainty in estimate, this is commonly used in this sort of discussion. I expect this will be familiar to most readers, but I've not seen it used on the boards before, so I thought I'd say it now to avoid confusion.)

jas wrote:

Hang on there, pardner.

What do you mean by "Wineglasses stacked a hundred million miles high"? How many upper wine glasses would be crushing through how many lower ones, and how would this occur?

 

Please explain also how a "house of cards" built with panes of glass would crush through itself from the top down with the removal of a few panes of glass, leaving a rubble pile of broken glass.

Bjorkman claimed that no type of construction can crush the same type of construction. I assume that we all agree that a tower of wine glasses (or glass sheets) a hundred million miles high will crush itself under its own weight.

I didn't make any claim about upper and lower blocks, but, since you asked, I'll have a go.

There's a house of cards built of sheets of glass. Let's say nice big sheets. They are artfully balanced on top of each other, so that at each point where the balanced sheets of glass meet, the two lower pieces support the weight of one or two horizontal pieces, the two upright upper pieces above them, and the weight of the house of cards above. I remove one of the horizontal pieces. Let's say, above half way, but not right at the top. The sheets that were resting on it start to fall. All the ones above them start to fall. The two that initially started to fall hit the lower uprightl pieces beneath them. Glass is not too bad at supporting weight or resisting force edge on, but if you hit it in the middle of the pane, it smashes. The lower upright pieces shatter. The other horizontal pieces they were supporting start to fall. All the unsupported upright pieces above them start to fall. These new upright pieces smash into the middle of the horizontal planes of glass that used to be a full layer beneath them. These upright pieces, or others, or the pieces of the smashed horizontal pieces smash through the next set of even lower upright pieces. The falling upper layers continue to smash the horizontal layers on the lowel levels. Sometimes the falling sheets break two, but there's plenty of other falling sheets, and a even half or a quarter of a falling sheet can smash a horizontal sheet of glass. The whole lower structure is crushed from the top down. There are panes of glass falling everywhere. Some of them smash into lower sheets of glass. Some of them hit each other while falling and shatter eachother. Some of them fall off the side and smash to pieces when they hit the ground.

(Sorry this got a bit complicated in the middle. I had to take into account that a house of cards has a triangular lattice.)

It's a house of cards; once it starts to fall; it's all going to come down. It's made of glass; the pieces break when they hit each other or the ground. It's a house of cards made of glass. How can you imagine that if you remove a couple sheets of glass you are going to end up with anything other than a pile of broken glass?

jas wrote:

PB66 wrote:

 

Bjorkman claimed that no type of construction can crush the same type of construction. I assume that we all agree that a tower of wine glasses (or glass sheets) a hundred million miles high will crush itself under its own weight.

Why do you assume this? Why does the tower need to be a hundred million miles high?

 

Wait, are you saying that you don't believe a tower of wine glass a hundred million miles high will crush itself under its own weight?

 

I said a hundred million miles high because it is such an absurd figure, I assumed -apparently incorrectly- that we would all agree it would crush itself. I don't know how strong wine glasses are, maybe you need a stack 5 metres high, maybe you need one 25 metres high. My point was that if you want to understand whether a structure can crush itself under its own weight, then you need to understand it's strength and density. Bjorkman's assumption that there is no imaginable configuration of weights and strengths which will crush itself is is plain wrong

 

Do you really believe that a stack of wine glasses a hundred million miles high wouldn't crush itself under its own weight?

 

PB66 wrote:

About dt:

Pants-of-dog, I think your argument about a constant or varying v is beside the point. Garcia uses v(initial)=-7.7m/s and dv=.5m/s. He then says that for the floors to fail, they (or any portion of them) need to be deflected by only ~7cm=~.07m. The time for this to occur is not more than the distance divided by the slowest velocity, which is ~0.01s.

I see. Thank you.

Pants-of-dog wrote:

I have never read the phrase "upper block pile driver" except in your posts. I would like you to define it clearly before I make a decision as to what the "official report" says.

Think of a hammer smashing a dinner plate and without any tilting of the hammer face whatsoever. Our carpenter is from Finland and never-ever tilts his hammer just for argument's sake.

Now imagine you're on planet earth where Newtonian laws of gravity are in play, and the upper block of WTC2 tilted by as much as 23 degrees according to several different video recordings.

Pile driver, hammer -  what's the difference, Pants? Or is there a quantum explanation for the dual hammer-dinner plate effect of some sort? Spooky. It's as if steel buildings were made of glass, or a house of cards so to speak.

PB66 wrote:

I agree that you and Griscom used the same trigonometric argument to calculate dt. The dt that both of you calculated is a measure of the length of time a tilted, falling floor would take to pass through the position original held by a lower, stationary floor. What is needed for Garcia's equation is the time it takes for a portion of the falling material to break the portion of the floor that was directly beneath it. These are different.

As you said, Garcia omits any mention of the angle. This is because it doesn't affect the time he estimates for the falling material to break the portion of the floor that it is falling on.

Tilting of the upper block would effect duration of impact absolutely. As Griscom said, impact occurs in a straight line on the point of impact. If the concrete slab is tilted by just one degree, then the impact has to begin with the low end of the slab and march 64 meters to the high end of the floor.

But none of this would matter for several reasons. Bazant claims that the upper block imparted a 30 g dynamic load on the lower block after an unimpeded free fall of 3 metres. Tony Szamboti said he originally read about the 30 g dynamic load and didn't think anything more of it. That was until his mechanical engineering experience kicked-in. He realized that Newton's laws of motion and gravity do not support Bazant's hypothesis. For a 30 g dynamic load to break through the floor below, there would have to be both a loss of velocity and deceleration. Garcia admits to a loss of velocity of 0.5/m/s. Szamboti says there should have been veleocity loss of 5.3m/s and deceleration of 304m/s^2 after a jolt for which there was no opposing jolt as per Newton's third law and conservation of momentum. And Szamboti's inclusion of calculations for just three energy sinks are most conservative by his own admittal. There were probably more energy drains on the initial impulse. A 30g dynamic force should have destroyed the upper block after the initial impulse, and which it most likely did, and which photographic evidence tends to suggest actually happened. Rigid upper block as pile driver is very probably a US government endorsed whitewash of what really happened on 9/11.

PB66 wrote:

Fidel wrote:

Tilting of the upper block would effect duration of impact absolutely. As Griscom said, impact occurs in a straight line on the point of impact. If the concrete slab is tilted by just one degree, then the impact has to begin with the low end of the slab and march 64 meters to the high end of the floor.

Once the lower floor is broken, it's not clear to me that it offers any resistance. I'm not saying I believe in a rigid upper block model, but if we were to take that model, I would assume that anyone who has used a knife will recognise that it is easier to cut through with the sharp point end first and then slide across, rather than use the entire blade in one go. According to the  trigonometric argument put forward by Griscom, it should always be easier to use the whole blade all at once.

If you can imagine a knife that is 64 metres long and tens of metres wide, I suppose it might be more realistic. Could you handle a knife that long?  A knife is designed to slice through meat, fish, bread, and maybe some cheese. 250 steel columns and steel flooring girders are a lot more substantial than a fish fillet or chicken sandwich. A credible theory for collapse initiation has to satisfy Newtonian laws of physics. None of the four or five variations on NIST pancaking through pile driver theories do though. And that's the problem. More information is needed, A new investigation should happen, like there were subsequent investigations into the death of just one man murdered on Novemeber 22nd, 1963. The last official US Government investigation into JFK's murder concluded that Oswald probably did not act alone and that it probably was a conspiracy.

That's right, Jas. Even if the 12 floors of WTC1 did remain intact as a "rigid upper block", it still could not have crushed the other 80 percent of the much more massive and stronger part of itself. However, video evidence does not support the rigid upper block theory. There was no significant deceleration, which means that there was no crushing of the lower block occurring, and Newton's laws of nature were "circumvented" in some way on 9/11/01.

al-Qa'bong wrote:

Quote:

PB66, you do not seem to understand the concept. We are not talking about things crushing under their own weight, The Twin Towers did not crush under their own weight; if they did, we would have seen a large upper block crushing a smaller, weaker lower block.

 

But it did. The top section of the towers fell onto one floor, then that floor and the original block fell onto the next floor, etc., etc.

- one of the obvious questions people seem to be missing is - if you want the upper block to fall onto 'one floor' of the lower block - how is that it's not only one floor of the upper block impacting one floor of the lower block, and thus one floor of the lower disentigrates, and one floor of the upper?? Exactly the same 'physics' would apply, wouldn't they? (I'll understand if you avoid this, as there's no actual 'physics' readily discernible anywhere in this whole redqueen "I make whatever rules I want!!!' discussion ... )

jas wrote:

Please provide evidence for this statement. Don't worry - there's more to this you'll need to explain.

Please provide evidence that the upper block has disintegrated.

My evidence is that you see the upper block before it falls. Assuming the mass does not magically disappear, the upper block must still be there. Of course, it is possible that it has been reduced to rubble, but the mass of the falling rubble would still conceivably had a pile-driver effect. But it probably was not turned to rubble, as Bazant has shown in his equations concerning velocity of the shock wave.

You have yet to provide any evidence that the upper block crumbled. Please provide it now.

Quote:

Please cite where Bazant makes the claim that I have bolded.

As I said above, I don't dispute that things were ejected outwards. This is what could happen if crushing were actually occurring--obviously, on a lesser scale. This would also happen with other events occurring. It's not a game of semantics, Pants. Bazant uses the term "crush" because he has no other choice. It's still grossly inaccurate.

No. The only inaccurate thing is your depiction of Bazant's model as some sort of claim that the towers were universally pulverised.

jas wrote:

Do you know what "upper block" means?

Do you know what "piledriver" means?

Do you understand that the theory you are defending claims that the upper blocks crush through the intact buildings, effectively serving as piledrivers? If you don't like the terms "piledriver" or "crushing down", what term would you use to describe what the upper blocks (in your theory) are doing to the intact bulk of the building.

A pile driver is a specific tool used by pile installers. It hammers the pile into the ground. The pile is then buried vertically, and intact.

Since you are not claiming that the WTC towers are actually perfectly intact and buried in the earth at ground zero, you are obviously using "pile-driver" in some sort of metaphor.

I would say that the upper block destroyed the lower storeys, or hammered them perhaps.

siamdave wrote:

- one of the obvious questions people seem to be missing is - if you want the upper block to fall onto 'one floor' of the lower block - how is that it's not only one floor of the upper block impacting one floor of the lower block, and thus one floor of the lower disentigrates, and one floor of the upper?? Exactly the same 'physics' would apply, wouldn't they? (I'll understand if you avoid this, as there's no actual 'physics' readily discernible anywhere in this whole redqueen "I make whatever rules I want!!!' discussion ... )

There are two reasons.

One is that the rubble between th eupper block and lower block would have cushioned the impact between the upper block and lower block.

The second is more complicated, and deals with the velocity of the crushing fronts going up and going down. Bazant shows how the velocity of the wave going up into the upper block decelerated very swiftly.

The mathematical evidence for an essentially rigid upper block of storeys begins at the bottom of page 15/29, and ends on the subsequent page. The figure 9 that Bazant mentions during the mathematical discussion is on page 29/29.

http://wtc7lies.googlepages.com/Bazant_WTC_Collapse_What_Did__Did_No.pdf

Writer, I wanted to thank you for the videos you posted. They were very informative.

If you need help finding your cat's head, let me know.

Bjorkman's axiom, that you paraphrased, is that a small portion of a structure cannot cause a global collapse by falling onto a larger structure made the same way.

This is not universally true. Exceptions to Bjorkman's axiom are a house of cards, a structure of wineglasses stacked a hundred million miles high, an exact replica of the WTC made of chocolate, etc.

You have exluded some of these examples and others because they do not "crush" through the lower structure, but destroy the lower structure in oher ways. This contradicts the first post you made on this page where you claim that "crush-down" includes many events including toppling, and does not mean solely crushing.