Layman's terms please! Tower collapse issue

[stateofgrace]

OK - g! An amount so massive it would be possible for anybody to miss it unless you, like me, know the physics involved.

Really?

So everybody missed the enormous explosion in impact zone and the enormous explosion that completly disintegrated 33000 ton of building?

Why do you think that is?

 

[stateofgrace]

OK - g! An amount so massive it would be possible for anybody to miss it unless you, like me, know the physics involved.

Heiwa, I have revisited this thread and wish to be absolutely clear on your theory.

Just so I get this absolutely correct, please allow me to summarise it as I see it.

A massive explosion took place inside the impact zone that caused the remaining external columns and inner core to give way. As the massive static weight above became dynamic and started to fall, another massive explosion occurred which resulted in the total disintegration of 33,000 tons of building. It then follows that a top down demolition occurred by further explosives. This occurred in the centre of New York, in broad day light with the world’s media in attendance. Nobody noticed these massive explosions, except you, who looked at a video, years later.

Doesn’t this seem slightly odd to you?

 

[ElMondoHummus]

...the sinking of the Estonia (note to Merikans; the ship, not the country)...

Gee, thanks for clarifying. I was about to Google a map, just to make sure it didn't pull an Atlantis!

 

[padragan]

Ok... first of all, I'm a computer geek with very limited knowledge of design of large buildings, but from the sideline it is VERY obvious who is running from hard questions and who seems to know what they talk about (hint, the answer to one of those is HEIWA and it is not the second one).

Anyway, one thing that puzzles me greatly is why Heiwa is constantly using density in his reasoning, so I thought of an example to prove my point.

Imagine that we extended one of the towers by by 20 or 30 stories, simply by adding plastic tent walls and roof. That is, we would have a block above the impact zone with basicly the same mass as the real case, but obviously the density would be MUCH smaller, since we have so much more space.

So, the questions (and I'd appreciate answers from Heiwa as well as real professionals):

1. Would the plastic extension make a difference? Would the impact be more gentle because of the density issue?

If YES then:

2a: Could that be used as a principal of strengthening buildings in the future to prevent collapses?

If NO then:

2b. If the extension wouldn't affect the collapse, why shold the density in the real case be of any consequence? Isn't mass the only thing that actually matters?

 

[Architect]

Padragan

No the plastic extension would make very little difference as it would add little mass to the building. And you're right, density isn't an issue but rather mass, design loads, and load paths during the collapse sequence.

I did rather like the way you put it in layman's terms....

 

[Heiwa]

Heiwa, I have revisited this thread and wish to be absolutely clear on your theory.

Just so I get this absolutely correct, please allow me to summarise it as I see it.

A massive explosion took place inside the impact zone that caused the remaining external columns and inner core to give way. As the massive static weight above became dynamic and started to fall, another massive explosion occurred which resulted in the total disintegration of 33,000 tons of building. It then follows that a top down demolition occurred by further explosives. This occurred in the centre of New York, in broad day light with the world’s media in attendance. Nobody noticed these massive explosions, except you, who looked at a video, years later.

Doesn’t this seem slightly odd to you?

You have apparently not read my article about why gravity force alone cannot globally collapse a multiparts steel structure? I do not speculate about what really caused the WTC collapses, only conclude gravity force alone (PE=KE>SE) cannot do it.
One mystery is the WTC1 upper block telescoping into itself prior any damage occurs in the structure below the fire/heat zone. The upper block and its PE is supposed to be intact before, during and after the complete collapse. The collapse is supposed to start with the lower structure being crumpled due to gravity force.
Another mystery is that the wall columns in the fire/heat zone (except those cut earlier where you can see two persons looking out) are intact, when smoke and dust are ejected some seconds later. Very strange! Was only the core collapsing? Why?
One thing is certain. The vertical core columns were massive and very strong. To just bend one (I have not seen any) and then cut it off (many examples seen) requires plenty of force, work and energy applied at the right locations. Gravity force does not work like that. It slips off. So you need something else. And it need not cause a massive explosion. There are many ways to cut steel without noise.

BTW - many odd things occurred on 911. But topic is tower collapse issues and gravity alone could not do it.

 

[Architect]

Heiwa

You have ignored post after post pointing to serious flaws in your interpretation of the building structure, of the initiation sequence, and indeed of the initiation zone. All of these undermine your case.

Likewise you have been unable, or unwilling, to post real structural calculations. I believe this is because you are unable to do so, and that references to "layman's terms" and "children's explanations" are a crude attempt to disguise this.

Now, put up or shut up.

 

[Heiwa]

Ok... first of all, I'm a computer geek with very limited knowledge of design of large buildings, but from the sideline it is VERY obvious who is running from hard questions and who seems to know what they talk about (hint, the answer to one of those is HEIWA and it is not the second one).

Anyway, one thing that puzzles me greatly is why Heiwa is constantly using density in his reasoning, so I thought of an example to prove my point.

Imagine that we extended one of the towers by by 20 or 30 stories, simply by adding plastic tent walls and roof. That is, we would have a block above the impact zone with basicly the same mass as the real case, but obviously the density would be MUCH smaller, since we have so much more space.

So, the questions (and I'd appreciate answers from Heiwa as well as real professionals):

1. Would the plastic extension make a difference? Would the impact be more gentle because of the density issue?

If YES then:

2a: Could that be used as a principal of strengthening buildings in the future to prevent collapses?

If NO then:

2b. If the extension wouldn't affect the collapse, why shold the density in the real case be of any consequence? Isn't mass the only thing that actually matters?

Density? According Bazant/Seffen uniform density of the complete upper block is a basic requirement for gravity driven collapse by the same upper block of structure below. Apart from it being rigid and solid and intact all the time. It simplifies the math, we are told.

Putting up a plastic extension will evidently not change anything. Does not sound either solid or rigid .

The upper WTC1 block has a volume of 183 000 m3, weight about 33 000 tons and thus uniform density of 0.18 tons/m3 (like baled wool).

If the volume of the upper block was only 64 m3, e.g. a block 4 x 4 x 4 metres the uniform density would be ... 516 tons/m3.

Now, if you drop this latter block/mass (33 000 tons) on floor 95 of WTC1, what happens? Global collapse? Or a 16 m² hole through the building? Probably the latter. And the block is probably intact after cutting this hole through 95 floors.

The reason is that the block was only applied to the floor.

But according to Bazant/Seffen math the 64 m3 solid block (33 000 tons) would cause global collapse! But it didn't. Only a hole.

So mass didn't matter either?

So there must be a hole in the Bazant's/Seffen's math!

Or does the scientists mean that the upper mass must be uniformly applied to the lower structure? As explained earlier it is only 8.25 tons/m². But how would you do that? The upper block can never apply a uniform pressure on the lower structure. Etc, etc.

 

[einsteen]

Probably that hole would be in all floors down and the building loses its stability and the tower is doomed, there is always a debunk workaround Heiwa, think about it!

I don't know whether the uniform density is a requirement, I always thought it was a simplification in order to setup differential equations to describe the non uniform mass distribution, because everyone knows a uniform structure cannot crush down and collect mass on its way down.

 

[Architect]

Now, if you drop this latter block/mass (33 000 tons) on floor 95 of WTC1, what happens? Global collapse? Or a 16 m² hole through the building? Probably the latter. And the block is probably intact after cutting this hole through 95 floors.
.

And where, pray, do you get a 4x4m/16m2 hole from. Does the upper portion compress by a massive factor as well as magically slide off?

 

[padragan]

Density? According Bazant/Seffen uniform density of the complete upper block is a basic requirement for gravity driven collapse by the same upper block of structure below. Apart from it being rigid and solid and intact all the time. It simplifies the math, we are told.

Putting up a plastic extension will evidently not change anything. Does not sound either solid or rigid .

The upper WTC1 block has a volume of 183 000 m3, weight about 33 000 tons and thus uniform density of 0.18 tons/m3 (like baled wool).

If the volume of the upper block was only 64 m3, e.g. a block 4 x 4 x 4 metres the uniform density would be ... 516 tons/m3.

Now, if you drop this latter block/mass (33 000 tons) on floor 95 of WTC1, what happens? Global collapse? Or a 16 m² hole through the building? Probably the latter. And the block is probably intact after cutting this hole through 95 floors.

The reason is that the block was only applied to the floor.

But according to Bazant/Seffen math the 64 m3 solid block (33 000 tons) would cause global collapse! But it didn't. Only a hole.

So mass didn't matter either?

So there must be a hole in the Bazant's/Seffen's math!

Or does the scientists mean that the upper mass must be uniformly applied to the lower structure? As explained earlier it is only 8.25 tons/m². But how would you do that? The upper block can never apply a uniform pressure on the lower structure. Etc, etc.

I see that two linked questions were to hard for you to cope with... And even though you say that the extension hadn't changed anything you keep going on about the importance of density and your old worn out hay bale.

The big problem is that if your hay bale should stay any chance to survive you need to explain why density would make a difference in the real example but not with the extension.

In reality as I look at it the only thing that would matter would be:

- The mass of whatever drops
- The kinetic energy this mass can develop during the fall
- The strength of whatever is supposed to hold it up
- The size of the area that the load is distributed on
- Strength distribution (which points can best cope with the load/stress)
- The reisistance of air (which I think can be safely ignored in this case)

These are the factors that the engineers and architects in this thread have included and shown calculations about. Density is simply not a factor.

So... from the sideline it's obvious that you are wrong. Your rambling on a 64m3 block is of no use whatsoever. The area of the upper block matched the area of the lower part (duh? Same house, remember?).

 

[Apollo20]

Heiwa:

You just posted this comment: "One thing is certain. The vertical core columns were massive and very strong. To just bend one (I have not seen any) and then cut it off (many examples seen) requires plenty of force, work and energy applied at the right locations."

Well, you know this is NOT certain!

I would ask you to look at Figures 4.1 and 4.2 of NCSTAR 1-3C. These are photos of CORE columns from the impact zones of WTC 1 & 2. The column sections are badly bent and in one case the column has been torn, (yes torn!) in half.

Under the action of 30,000 tonnes of crushing force I guess those columns weren't so strong after all!

 

[Architect]

I predict more hand-waving and wanton ingoring of technical issues from our Scandanavian pal.

 

[ElMondoHummus]

I would ask you to look at Figures 4.1 and 4.2 of NCSTAR 1-3C. These are photos of CORE columns from the impact zones of WTC 1 & 2. The column sections are badly bent and in one case the column has been torn, (yes torn!) in half...

Just to help the poor, foolish readers (like ME!) who accidentally opened the NCSTAR 1-3C appendixes and couldn't figure out where the images were : The pictures Dr. Greening refers to are on pages 201 and 202 of the actual NCSTAR1-3C report. NOT the appendixes!

But in all seriousness, everyone, draw your attention to the fact that Figure 4.1 shows a pretty badly distorted column - bent and twisted around its long axis - and figure 4.2 shows one bent back on itself. Dr. Greening - and everyone else who's been commenting on this issue - has a strong point about the forces involved in the collapse.

 

[X]

Density? According Bazant/Seffen uniform density of the complete upper block is a basic requirement for gravity driven collapse by the same upper block of structure below. Apart from it being rigid and solid and intact all the time. It simplifies the math, we are told.

Putting up a plastic extension will evidently not change anything. Does not sound either solid or rigid .

The upper WTC1 block has a volume of 183 000 m3, weight about 33 000 tons and thus uniform density of 0.18 tons/m3 (like baled wool).

If the volume of the upper block was only 64 m3, e.g. a block 4 x 4 x 4 metres the uniform density would be ... 516 tons/m3.

Now, if you drop this latter block/mass (33 000 tons) on floor 95 of WTC1, what happens? Global collapse? Or a 16 m² hole through the building? Probably the latter. And the block is probably intact after cutting this hole through 95 floors.

The reason is that the block was only applied to the floor.

But according to Bazant/Seffen math the 64 m3 solid block (33 000 tons) would cause global collapse! But it didn't. Only a hole.

So mass didn't matter either?

So there must be a hole in the Bazant's/Seffen's math!

Or does the scientists mean that the upper mass must be uniformly applied to the lower structure? As explained earlier it is only 8.25 tons/m². But how would you do that? The upper block can never apply a uniform pressure on the lower structure. Etc, etc.

You are arguing two completely different situations.

1) The upper block, weighing 33,000 tons with a square cross-section of 63.4 meters to a side (4020 m²).

2) A very dense block weighing 33,000 tons but measuring 4 meters to a side (16 m²).

These are not the same.
The static pressure loads will be completely different. As will the applied forces.

Further, the reason the simplified model was chosen has been explained to you repeatedly.


Now, you are willing to admit your tiny block will cause damage (holes in the floor).

Yet you maintian that the upper block will fall into the floors, impacting sans impact, and will somehow stop.

Provide calculations showing that the tower has enough strength to stop a 33,000 ton mass moving downwards at an appropriate speed.

 

[Heiwa]

In reality as I look at it the only thing that would matter would be:

1. - The mass of whatever drops
2. - The kinetic energy this mass can develop during the fall
3. - The strength of whatever is supposed to hold it up
4. - The size of the area that the load is distributed on
5. - Strength distribution (which points can best cope with the load/stress)
6. - The reisistance of air (which I think can be safely ignored in this case)

These are the factors that the engineers and architects in this thread have included and shown calculations about. Density is simply not a factor.

So... from the sideline it's obvious that you are wrong. Your rambling on a 64m3 block is of no use whatsoever. The area of the upper block matched the area of the lower part (duh? Same house, remember?).

1. There are many masses that drop - connected to one another one way or another. Do not simplify and say it is one mass (like Bazant/Seffen/Nist). Let's say that the number of masses of the upper block are n.

2. Yes, if these masses drop, their PE becomes KE. Each mass n has its own PE/KE due to gravity. And each mass starts at different locations.

3. The lower structure is fairly complex - 280+ columns, 94 floors, etc. Cannot be treated as one spring or a party ballon or similar (like Bazant/Seffen/Nist)

4. Here is a crunch! The columns only occupy 0.14% of the total cross area of the tower. What loads are put on them? None? OK. The uppermost floor of the lower structure thus occupy 99.86% of the cross area. What loads are put on it and where and when? See 1. There are many masses dropping down. Which one will be applied first? Right - the one that was closest above. Will there be ONE impact or many?

5. ?? The strength of the lower intact structure (all parts/connections, etc) is known. And according 4. we know the various loads n that are put on the uppermost floor of the lower structure in a certain order (depending where the started from).

So we start with load number 1 (the one that is applied first!). What happens to the uppermost floor! Any deformations? Local failures? Is the floor still connected the 280+ columns? Then we apply load number 2, etc. Some loads may drop down beside the building. After a while the uppermost floor in the intact structure will probably collapse, serious local failure, and then we have to see what happens at the next floor applying the n loads there in proper order. The first collapsed floor will probably deflect many of the loads coming first and later from above outside the structure or inwards, against each other causing jamming and entanglement of these loads/masses. Too complicated to calculate? Not really. As long as you realize that it is not one, solid, rigid mass (one PE/KE) that impacts one 'structure' below with one SE, you will agree that the Bazant/Seffen/Nist simplifications are just nonsense.

In my view the first 5% of the loads/masses from above applied on the uppermost may locally damage the uppermost floor of the intact structure. The horizontal floor then becomes sloping. The first 5% loads/masses will probably then change direction from vertical to sideways due to the slope and may be stopped, e.g. entangled in the columns. Some may drop on the next floor, but it will obviously resist or only fail locally where the loads/masses are applied!

You need all the 5% of the first loads to damage one floor. The next 5% of the loads/masses coming dropping from above will not hit the uppermost floor, but something else, guess? Yes, the mess of the first 5% of the loads/masses. Some sort of compacting of these 10% masses should now take place due to gravity. There is a lot of damping, friction, etc. in this mess.

But I agree - the second uppermost floor may alse collapse, similar to the uppermost floor when the next 5% of the masses above have dropped on the first 5% load/mass/mess. The second floor will also deflect the loads from above as the first. After a while, in my opinion, the top part of the lower structure is completely jammed with the first 10% of the loads/masses that have dropped down and have been deflected. I doubt very much that the remaining 90 % masses will do much harm. Some will drop down outside. The rest will rest on top. No global collapse. This is the beauty of airy tower steel structures of non uniform density. Some local parts my fail (e.g. floors) and then any other lose parts just get entangled in the mess.

6. You can forget the air (and any Bazant/Seffen simplifications - they are just air).

 

[Heiwa]

You are arguing two completely different situations.

1) The upper block, weighing 33,000 tons with a square cross-section of 63.4 meters to a side (4020 m²).

2) A very dense block weighing 33,000 tons but measuring 4 meters to a side (16 m²).

These are not the same.
The static pressure loads will be completely different. As will the applied forces.

Further, the reason the simplified model was chosen has been explained to you repeatedly.


Now, you are willing to admit your tiny block will cause damage (holes in the floor).

Yet you maintian that the upper block will fall into the floors, impacting sans impact, and will somehow stop.

Provide calculations showing that the tower has enough strength to stop a 33,000 ton mass moving downwards at an appropriate speed.

Applying the Bazant/Seffen theories and math it evidently doesn't matter if the 33 000 tons upper block has uniform density 0.18 tons/m3 (like a bale of wool) or 518tons/m3 (of superdense material). Global collapse is always assured and ensues when all of it is suddenly applied to the lower structure. But evidently it is neither true, not so easy. Apply common sense.

Re Provide calculations showing that the tower has enough strength to stop a 33,000 ton mass moving downwards at an appropriate speed - read my article. Using certain assumptions the 33 000 tons will bump into the lower structure and elastically compress it ... and then be stopped and pushed up a little. The bump may cause some local failures of the top floors - see previous - message, but a global collapse will never start.

 

[Newtons Bit]

Using certain assumptions the 33 000 tons will bump into the lower structure and elastically compress it ... and then be stopped and pushed up a little. The bump may cause some local failures of the top floors - see previous - message, but a global collapse will never start.

Can you provide the section number in your article of that? Thanks.

 

[Heiwa]

Heiwa:

You just posted this comment: "One thing is certain. The vertical core columns were massive and very strong. To just bend one (I have not seen any) and then cut it off (many examples seen) requires plenty of force, work and energy applied at the right locations."

Under the action of 30,000 tonnes of crushing force I guess those columns weren't so strong after all!

Read my article - an intact wall column carries 70 tons and can handle 350 tons. An average itact core column carries 280 tons and just to compress it to yield you need a force of 1000 tons.

Where would it come from? Dropping from the sky? How would it be applied to the column?

 

[Heiwa]

Can you provide the section number in your article of that? Thanks.

No! Suggest you re-read the whole article from start as it is being improved at regular intervals thanks to you.