Merged Applicability of Bazant's model to the real world

[Oystein]

Whatever was left over from the fireball, of the 10,000 gallons of fuel the aircraft had on them, was aerosolized and spread as a film. It was then burned up within minutes, NIST even admits that. If half of it made it into the towers and spread over just two floors it would have put a 1/16" film on things. So much for the vaunted jet fuel.
...

No need to push a strawman.
No sane person, and certainly not NIST, claims that any jet fuel was still burning when the collapses began.
No one even claims that the burning fuel contributed very much to the overall weakening of steel members: The office contents contained a lot more heat, and released it in huge raging fires.

 

[GlennB]

Your insistence that some insight would be gained by creating this simple 2-D column model with a 180 degree fold is somewhat baffling. It seems you believe the top and bottom hinges would somehow twist away from each other about the vertical axis and no longer be in vertical alignment. There is no mechanism to cause that and the geometry of the fall indicates that the columns would impact in a natural collapse.

The insght would be in the realisation that no natural collapse could lead to that perfectly symmetrical configuration. That your presumption of a jolt being necessary in natural collapse is unjustified.

I can only repeat once more, and then give up -- you are attempting to apply purely theoretical concepts of mathematical symmetry to a chaotic event.

 

[Oystein]

The situation we are dealing with in a building collapse is where the lower supporting structure is designed to support several times the load it is carrying. In that case the only way the insufficient load above can cause failure to the lower structure is if it is amplified.

This can happen in a fall if the impacting upper load decelerates at a rate greater than gravity. Of course, we see that this did not happen in the measurable fall of WTC 1.
...

No.

Here is a simple experiment everyone can do:

Buy a pack of short drinking straws.
Place a few of them vertically on your desktop.
Rest your ellbow on the desk, place your palm on top of the straws, and relax
Figure out the minimum number of straws that will support the weight of your lower arm.
Now double the number of straws.
Lift your hand to twice the previous height
Let hand fall on top of straws (hold these lightly with other hand)
Observe what happens!

I have straws here that I cut to about 12cm.
3 of these will carry my hand.
6 of them did nothing at all to stop my falling hand. No jolt, no discernible deceleration. The 6 straws were simply overwhelmed in an instant.

 

[Oystein]

...
In the case of your dixie cup and bowling ball, the dixie cup is not designed to support even the static weight of the bowling ball and it would fall right though it.

Now imagine your bowling ball was supported by a steel cylinder about two inches in diameter and 1/8" diameter wall thickness. Then imagine that it turned into paper and the bowling ball accelerated right through it. The paper cylinder would still be applying some small resisitance to the fall of the bowling ball but not nearly enough to support the static load. That is what appears to have happened to the upper section of WTC 1.

The short answer to your question is that if the supporting structure below cannot support the static load there will be no deceleration.

If the dixie cup can't holt the bowling ball at all, the 1/8" diameter wall thickness cylinder clearly is waaaaaaay to strong.

Make that an empty soda can instead: A grown person can stand on it, if he's really careful. A bowling ball surely can squash it.
Again, find the largest bowling ball that a soda can can support.
Then take one that is half as heavy, and drop on the can.
Yesm there will be a short jolt, before the ball picks up speed again and crushes through the crumpling can.
BUT that jolt is only there because you have one single inpact point and a totally rigid top assembly.

The falling ball is MUCH more than the can can absorb. Only a small fraction of it's mass is needed. And that corresponds to some elastic and some inelastic buckling of the top portion of the WTC upon first and second impact. That buckling, and the fact that the impact is really spread out, ensures that you won't see a jolt at the roof.
After 2 or so floors, the mass and momentum of the compacted layer is enough to buckle the remaining columns.

 

[ergo]

No.

Here is a simple experiment everyone can do:

Buy a pack of short drinking straws.
Place a few of them vertically on your desktop.
Rest your ellbow on the desk, place your palm on top of the straws, and relax
Figure out the minimum number of straws that will support the weight of your lower arm.
Now double the number of straws.
Lift your hand to twice the previous height
Let hand fall on top of straws (hold these lightly with other hand)
Observe what happens!

What happens?

I have straws here that I cut to about 12cm.
3 of these will carry my hand.
6 of them did nothing at all to stop my falling hand. No jolt, no discernible deceleration. The 6 straws were simply overwhelmed in an instant.

You're talking about different materials here: a hand versus plastic straws. You're also using probably the flimsiest example you could possibly come up with for your so-called supports. Also, downward hand movement cannot be spontaneous, unless you're dead. So how are you going to measure deceleration here? How is any of this even remotely analogous?

 

[ergo]

I

Make that an empty soda can instead: A grown person can stand on it, if he's really careful. A bowling ball surely can squash it.

The above doesn't even make any sense, as a human adult is surely heavier than a bowling ball.

Again, find the largest bowling ball that a soda can can support.
Then take one that is half as heavy, and drop on the can.
Yesm there will be a short jolt, before the ball picks up speed again and crushes through the crumpling can.

Do you know this would happen? Depending on the height you're dropping it from, I think the can would partly crumple and the bowling ball would either sit on top or roll off. It wouldn't be able to crush the can completely flat, mainly because of the can's cylindrical shape.

And that corresponds to some elastic and some inelastic buckling of the top portion of the WTC upon first and second impact.

There was a second impact?

That buckling, and the fact that the impact is really spread out, ensures that you won't see a jolt at the roof.

Genuine question here: Wouldn't the action of buckling imply a jolt? How does something that is supporting something else buckle without causing a jolt?

After 2 or so floors, the mass and momentum of the compacted layer is enough to buckle the remaining columns.

If so, then in both the upper and lower building portions.

 

[pgimeno]

Make that an empty soda can instead: A grown person can stand on it, if he's really careful. A bowling ball surely can squash it.

I already showed this to Tony before:

 

[ergo]

Yes, my hypothesis confirmed. How is this example analogous to the Twin Towers? And how has deceleration been measured in this instance?

 

[beachnut]

Yes, my hypothesis confirmed. How is this example analogous to the Twin Towers? And how has deceleration been measured in this instance?

When will you take your work on the WTC and expose Bazant's model as very close to reality? lol, you can't do more than fail at engineering. But it is cool seeing your failure unfold. Better throw in some big engineering words to make it more humorous.

Have you written up your concerns and emailed Bazant? Write a letter and do what Heiwa did. Why did Heiwa fail? Where is your model?

 

[Oystein]

What happens?



You're talking about different materials here: a hand versus plastic straws. You're also using probably the flimsiest example you could possibly come up with for your so-called supports. Also, downward hand movement cannot be spontaneous, unless you're dead. So how are you going to measure deceleration here? How is any of this even remotely analogous?

I can repeat that with a book, if you like, and film it?

Why would the different materials matter? The WTC structural elements are steel, the impacting floors are a mix of concrete, steel, gypsum, furniture, people... Different materials, too.

It is very analogous: Structural elements that carry half their design static load, a falling load that falls through the length of a column, elastic and inelastic buckling of the columns...

 

[Oystein]

The above doesn't even make any sense, as a human adult is surely heavier than a bowling ball.

Sorry, I meant a falling bowling ball

Do you know this would happen? Depending on the height you're dropping it from, I think the can would partly crumple and the bowling ball would either sit on top or roll off. It wouldn't be able to crush the can completely flat, mainly because of the can's cylindrical shape.

No. Like I said, a person can stand on a soda can. So a 140lb bowling ball would, too. So drop a 70lb ball.
We'd have to actually do it, as everyone might gave a diffetent intuition here. Mine tells me: A 70lb ball will squash the can and hardly eben notice it was there.

There was a second impact?

Sorry to confuse you, I meant top-part-on-floor impact. The first was 95th floor, and then there'll be about 94 more impacts.

Genuine question here: Wouldn't the action of buckling imply a jolt? How does something that is supporting something else buckle without causing a jolt?

A "jolt" as in "change of acceleration"? Yes. But a very small one. We actually find that acceleration changed all the time. Just not by as much as Tony would like to see. Which ich because the top assembly is elastic, and doesn't hit the structural elements below all at once.

If so, then in both the upper and lower building portions.

No. Because after very few floors (about 2), the velocity of the rubble layer is much closer to that of the top part than to that of the bottom part.
That is precisely what Bazant and Zhou have shown. I know it is counter-intuitive. But imagine yourself standing on a fat slab of concrete, falling down, and crushing through stuff. Imagine your worst enemy on the other side of the slab. You'll understand that you'll be much better off then he is.

 

[Oystein]

I already showed this to Tony before:

[qimg]http://www.formauri.es/personal/pgimeno/xfiles/11-s/Julio-static-dynamic.jpg[/qimg]

Well, you are supporting Tony's claim there: Obviously, the brick decelerates after it hits the can. But that is little wonder: its mass is only like 11% of the design load. Had only 11% of the top block columns failed, we might not have seen a total collapse. But as it were, 100% started tumbling.

Try this with a 45-kg boulder.

 

[Myriad]

The structure of every story below was capapable of supporting several times the load above it. In other words, in the 110 story buildings the 98th story structure was capable of supporting 36 stories or more, the 95th was capable of supporting at least 45 stories, etc.

Sigh. So in the end, it still comes down to caveman intuition.

"Steel strong. Steel not break. Witch doctor do bad magic on steel, make steel break."

The problem with caveman intuition in this case is that compared to everyday objects, large buildings are extremely weak and fragile in proportion to their own weight. "Able to support three times its actual normal load" might sound strong. But if everyday objects were made of components that were only able to support three times their actual normal load, they would be extremely fragile. They would break every time you tried to lift them, tilt them, or rest anything comparable to their own weight on top of them. Soup cans would have thinner walls at the top than the bottom (since the top has so much less weight to support) so stacking one on another would crush or distort the top half of the lower one. Stemware glasses would snap if you tipped them a few degrees off vertical (since that increases the stresses on the stem by a factor of way more than 3). A chair would fall apart if you tried to pick it up by its seat (since that puts significant tensile loads on parts that are normally only bearing miniscule or no tensile loads).

Buildings survive despite their extreme fragility because they stay put where they have evenly distributed support. (They're a bit like those medical cases where someone weighs 800 pounds and cannot get out of bed because their bones would break if they tried to stand.) We don't care that buildings aren't strong enough to be picked up, tilted, or stacked on one another because we don't need them to be. But once a building or a significant portion of a building does start moving, for whatever reason, suddenly the building is subjected to some of the same kind of insults an ordinary small-scale object is. Tilting, colliding, all kinds of forces in unplanned-for directions. (Kind of like if you forced the 800 pound guy to get out of bed and do cartwheels.) When that happens, a "three times" strength factor is not enough to make much of a difference.

"What is the riddle of steel? Steel is weak. Gravity is strong. What is steel, compared to the ground that supports it?" -- Thulsa Doom, if he'd been a structural engineer.

Respectfully,
Myriad

 

[pgimeno]

Well, you are supporting Tony's claim there: Obviously, the brick decelerates after it hits the can. But that is little wonder: its mass is only like 11% of the design load. Had only 11% of the top block columns failed, we might not have seen a total collapse. But as it were, 100% started tumbling.

Try this with a 45-kg boulder.

Sorry, I misunderstood your point reading your post too quickly, because Tony has shown problems understanding static vs. dynamic load. The above image can be perhaps compared to WTC7 as it decelerated.

 

[carlitos]

After listening to the mock debate, Tony's point appeared to be that a "jolt" is necessary for a dynamic load to be applied. Therefore, no "jolt" = no dynamic load.

Is that a fair characterization of his position?

 

[Oystein]

Sigh. So in the end, it still comes down to caveman intuition.

"Steel strong. Steel not break. Witch doctor do bad magic on steel, make steel break."

The problem with caveman intuition in this case is that compared to everyday objects, large buildings are extremely weak and fragile in proportion to their own weight. "Able to support three times its actual normal load" might sound strong. But if everyday objects were made of components that were only able to support three times their actual normal load, they would be extremely fragile. They would break every time you tried to lift them, tilt them, or rest anything comparable to their own weight on top of them. Soup cans would have thinner walls at the top than the bottom (since the top has so much less weight to support) so stacking one on another would crush or distort the top half of the lower one. Stemware glasses would snap if you tipped them a few degrees off vertical (since that increases the stresses on the stem by a factor of way more than 3). A chair would fall apart if you tried to pick it up by its seat (since that puts significant tensile loads on parts that are normally only bearing miniscule or no tensile loads).

Buildings survive despite their extreme fragility because they stay put where they have evenly distributed support. (They're a bit like those medical cases where someone weighs 800 pounds and cannot get out of bed because their bones would break if they tried to stand.) We don't care that buildings aren't strong enough to be picked up, tilted, or stacked on one another because we don't need them to be. But once a building or a significant portion of a building does start moving, for whatever reason, suddenly the building is subjected to some of the same kind of insults an ordinary small-scale object is. Tilting, colliding, all kinds of forces in unplanned-for directions. (Kind of like if you forced the 800 pound guy to get out of bed and do cartwheels.) When that happens, a "three times" strength factor is not enough to make much of a difference.

"What is the riddle of steel? Steel is weak. Gravity is strong. What is steel, compared to the ground that supports it?" -- Thulsa Doom, if he'd been a structural engineer.

Respectfully,
Myriad

Awesome.
Nominated.

 

[ozeco41]

After listening to the mock debate, Tony's point appeared to be that a "jolt" is necessary for a dynamic load to be applied. Therefore, no "jolt" = no dynamic load.

Is that a fair characterization of his position?

It is a key part of his position.

He relies on the fact that the top block started to fall and therefore was moving. From there he wrongly applies two assumptions of Bazant and Zhou:

1. That the falling columns of the top block would land on their corresponding column parts in the lower tower; AND
2. The resistance presented by those lower parts of columns would cause a "jolt" which would be discernible as deceleration of the top block.

Since there was no jolt he makes a massive leap of faith to "no jolt means unnatural causes".

The more appropriate step is to read "no jolt means column ends missing each other".

Since it is obvious that two things are occurring:

• The top block and lower tower are both elastic flexing structures where columns landing on or near columns can flex sufficiently to bypass; AND
• The top block moving proves that the majority of column ends are not "end for end" - column ends failed by buckling simply will not stay in end for end contact the deformed surfaces will automatically cause the falling end of column to slip off the deformed end of the lower column.

Those are the key facts which Tony has to ignore to "prove" that his "Missing jolt" means demolition.

Hence he is evading any response to my several times stated claims about the moving top block means no significant end for end contact AND also replying to other members pretending that end for end contact is possible in a scenario with the top block falling.

Then it is also clear that he has no overall scenario to support his hypothesis - in recent posts he has switched horse by responding to claims about the initial collapse stage and, when questioned, claiming that he was talking about the "continuing collapse.

He obviously has no coherent explanation of the Twin Towers collapses and tries to evade discussion by repeating his items of mantra about jolts.

 

[pgimeno]

Since there was no jolt he makes a massive leap of faith to "no jolt means unnatural causes".

The more appropriate step is to read "no jolt means column ends missing each other".

Aren't there other possible causes for "no jolt"?

Like, "no jolt measured in the perimeter means that the perimeter's movement was damped with respect to that of the core, making the jolt too small to be measured".

 

[femr2]

To answer your concerns you needn't look any further than right across the street from the Twin Towers, as WTC 7's upper section was about 33 stories, it had a significant observable deceleration and velocity loss just like the Verinage demolitions, and it was a steel framed tube in a tube design building.

Please indicate where on this velocity graph all instances of *a significant observable velocity loss*...

WTC 1 came down at about 2/3rds the rate of gravity and it never decelerated.

A couple of scenarios...

1) Sequential floor-by-floor explosives remove columns, which SHOULD result in periods of freefall, but don't as they are very clever and make sure the non-rigid NW corner maintains a pretty constant 2/3g, somehow.

2) After initiation a huge number of collisions of lower magnitude than you are expecting are occurring at all times, averaging out in terms of NW corner at 2/3g descent, for a while, whilst it's visible, though of course ROOSD crush fronts end up attaining a terminal velocity after about 4s.


Which do you prefer ?


Crush front terminal velocity without decelleration ? How would you work that one out Tony ?

 

[femr2]

Like, "no jolt measured in the perimeter means that the perimeter's movement was damped with respect to that of the core, making the jolt too small to be measured".

There are other factors of course, but I think it's clear that is one of them.

For reference, *mini-jolts* have, for all intents and purposes, already been identified...

The lower graph is velocity. Correctly scaled and aligned on the horizontal time axis (s), but arbitary on the vertical axis.

The vertical axis applies only to the upper position/time curve (ft).