Layman's terms please! Tower collapse issue

[rwguinn]

The 'A' columns might 'not hit anything' as they fall outside the structure, but the floors that were attached to them will pancake and overload the floors below them. They will cause the columns below the 'A' columns to be pushed and pulled out of alignment so that they can not carry any more load.<<<<snip>>>>

I snipped all that because you were using factual data and inferrences, which are strictly forbidden when dealing with troofers.
It causes them to change the subject, run away, and/or hide.
It certainly has no bearing on their reality...

 

[Heiwa]

In the core, when the upper section falls between the columns instead of directly aligned with them, there is nothing to slow it down. It won't just become entangled and stop. As as the upper section of the core falls between the columns, it's mass will easily break loose the horizontal members it encounters, as those are not designed to carry any vertical load. The mass will also impact against the sides of the core columns, pushing them out of alignment (very easily as the horizontal members are being removed also). The mass of the upper core section, if not aligned with the columns below, will easily 'unzip' the core all the way down.

You do not really believe that? 47 core columns suddenly failing, pieces of solid columns being removed, misalignment and then ... free fall of mass above + impacts? On what. And then impacts from the sides. By gravity?
Gravity is at work all the time! And deform the failing parts. Local failures! And always in equilibrium due to reaction forces in intact structure. No free fall ever. And no impacts in any direction. The failed parts will just get entangled with other parts. No unzipping!

Only Bazant, Seffen, Nist and of course JREF greenhorns believe in 280+ simultaneous, local failures of low stressed load bearing columns, free fall + a big first impact - not seen on any videos - followed by multiple impacts on the floors below caused by an intact, rigid, with uniform density upper block that remains intact all the time during the destruction driving the collapse and that finally lands on the rubble ... intact. Not seen on any videos of course.

Luckily steel structures and gravity do not work like that. Except in NWO physics, of course.

 

[Heiwa]

The 3 meter free fall is not even necessary. All you need is to shift the columns of the upper block out of alignment with the columns of the lower block. Just a few degrees tilt of the upper block will do, for example if one of the outer walls buckles as we saw happen.

You saw one of the outer walls buckles? You mean a deformed wall on an enhanced photo before destruction. When did it finally buckle and fail? Synchronized with the roof dropping?

 

[Architect]

You do not really believe that? 47 core columns suddenly failing, pieces of solid columns being removed, misalignment and then ... free fall of mass above + impacts? On what. And then impacts from the sides. By gravity?
Gravity is at work all the time! And deform the failing parts. Local failures! And always in equilibrium due to reaction forces in intact structure. No free fall ever. And no impacts in any direction. The failed parts will just get entangled with other parts. No unzipping!

You have impressively failed to grasp the nature of structural collapse or, consequently, the mechanisms which would cause structural collapse.

As far as I can tell, you make a number of fundamental (and mistaken) assumptions in support of your hypothesis;

• That the external envelope was self supporting and can be meaninfully compared to a cage-type structure. In particular you believe that the floors played no part in stabilisation of the envelope against buclking failures. This is just plain wrong. You've been challenged to post caluclations to prove your case, but have refused.

• Having finally accepted that steel is susceptible to fire induced failure, you have suggested that localised collapse would result in redistribution of loads to adjacent structural members and hence no more than localised failure. However this is also blatantly over-simplistic, assuming as it does that these adjacent members have sufficient capacity to carry the new loads - many of which will, for example, follow markedly different load paths. If you want to argue it, you're going to have to post some (wait for it) calculations.

• You then go on to argue that the design capacity of the lower part of the building had sufficient excess capacity to withstand the collapse of the upper section. This too shows an astounding ignorance of structural design. Firstly, the new load is dynamic in anture resulting significant orders of magnitude greater than normal static loadings. Secondly joints, members, etc. are designed to accommodate credible load paths; just because a joint can support a certain vertical load does not mean that it can support the same load horizontally as the structure collapses.

• The final aspect of your argument I'd like to focus on is your apparent believe that, because the collapse resulted in a crush-up/crush-down failure, the debris field would not have caused failure despite being of similar mass. 30,000t is 30,000t. This is something so simple that even a child could see it, and there is little hope if you cannot grasp that concept.

Only Bazant, Seffen, Nist and of course JREF greenhorns believe in 280+ simultaneous, local failures of low stressed load bearing columns, free fall + a big first impact - not seen on any videos - followed by multiple impacts on the floors below caused by an intact, rigid, with uniform density upper block that remains intact all the time during the destruction driving the collapse and that finally lands on the rubble ... intact. Not seen on any videos of course.

Ah, there we go again.....all the experienced engineers in the world are wrong except you. NIST, Bazant, Greening, Arup, Edinburgh, Sheffield, the authors of the Eurocodes, NCE, everyone. All wrong. All greenhorns. Except you.

And yet you seem to believe that the NIST model requires 280 simultaneous failures. You believe that the building fell at free fall speeds. Wrong wrong wrong wrong wrong.

You're still running away from my challenge re: awards. Scared?

Luckily steel structures and gravity do not work like that. Except in NWO physics, of course.

Says the alleged naval architect.

 

[Heiwa]

You have impressively failed to grasp the nature of structural collapse or, consequently, the mechanisms which would cause structural collapse.

As far as I can tell, you make a number of fundamental (and mistaken) assumptions in support of your hypothesis;

• That the external envelope was self supporting and can be meaninfully compared to a cage-type structure. In particular you believe that the floors played no part in stabilisation of the envelope against buclking failures. This is just plain wrong. You've been challenged to post caluclations to prove your case, but have refused.

• Having finally accepted that steel is susceptible to fire induced failure, you have suggested that localised collapse would result in redistribution of loads to adjacent structural members and hence no more than localised failure. However this is also blatantly over-simplistic, assuming as it does that these adjacent members have sufficient capacity to carry the new loads - many of which will, for example, follow markedly different load paths. If you want to argue it, you're going to have to post some (wait for it) calculations.

• You then go on to argue that the design capacity of the lower part of the building had sufficient excess capacity to withstand the collapse of the upper section. This too shows an astounding ignorance of structural design. Firstly, the new load is dynamic in anture resulting significant orders of magnitude greater than normal static loadings. Secondly joints, members, etc. are designed to accommodate credible load paths; just because a joint can support a certain vertical load does not mean that it can support the same load horizontally as the structure collapses.

• The final aspect of your argument I'd like to focus on is your apparent believe that, because the collapse resulted in a crush-up/crush-down failure, the debris field would not have caused failure despite being of similar mass. 30,000t is 30,000t. This is something so simple that even a child could see it, and there is little hope if you cannot grasp that concept.

Ah, there we go again.....all the experienced engineers in the world are wrong except you. NIST, Bazant, Greening, Arup, Edinburgh, Sheffield, the authors of the Eurocodes, NCE, everyone. All wrong. All greenhorns. Except you.

And yet you seem to believe that the NIST model requires 280 simultaneous failures. You believe that the building fell at free fall speeds. Wrong wrong wrong wrong wrong.

You're still running away from my challenge re: awards. Scared?



Says the alleged naval architect.

Subject is collapse. The floors, secondary structure transmitting load to the primary load carrying columns, are still attached. Evidently, as long as they are attached/bolted to the columns, they can also transmit horizontal windloads on one wall to another and prevent transverse movement of the columns. Nobody argues about that. Clear from the article.
And evidently heat affects the properties of the steel. 500°C and yield is reduced a little. Clear from the start! Strange that you cannot quote properly!
But heating some columns in a fire does not cause free fall of an upper block! The upper block and the lower structure are still attached by the alleged failed columns (none seen on any video) and gravity does not produce free fall of connected parts!
Gravity will only deform the alleged failing columns due fire. No free fall is possible of the upper block. And not seen on any videos.
Free fall 3.7 m before impact takes 0.8-0.9 seconds. Not seen on any video.
As a consequence an impact on a lower structure caused by an upper block after free fall is not possible. And not seen on any videos.
So there is no new vertical gravity load on the lower structure. The gravity load is always the same on the lower structure, while the connecting columns are being deformed. Quite basic. That's why steel structures never collapse due to gravity unless you suddenly destroy vital connections, like in CD. Fire can never suddenly destroy vital connections like CD does.
That is why CD companies never put the top of a steel building on fire and hope that it will collapse. It doesn't work like that.

But, if free fall actually occurs and if the released energy is actually applied on the lower structure, which is very unlikely, I demonstrate that it will only temporarily compress the lower structure and cause some local failures at the top of the lower structure. After that all potential energy released is consumed and lost. In reality no free fall/impact occur and all potential energy is consumed deforming the intermediate columns.

Bazant and Seffen and Nist are wrong when demonstrating anything else using false assumtions; rigid upper body, uniform density, upper body intact all the time, simultaneous failure/disappearance of 280+ columns, free fall, impacts, shockwaves, no redundancy in lower structure, etc. Clearly shown in my article.

Recommendation is that Bazant and Seffen redo their analysis using correct assumptions. No big deal really. Only that the conclusion will be that no global collapse ensues!

 

[Newtons Bit]

Subject is collapse. The floors, secondary structure transmitting load to the primary load carrying columns, are still attached. Evidently, as long as they are attached/bolted to the columns, they can also transmit horizontal windloads on one wall to another and prevent transverse movement of the columns. Nobody argues about that. Clear from the article.
And evidently heat affects the properties of the steel. 500°C and yield is reduced a little. Clear from the start! Strange that you cannot quote properly!
But heating some columns in a fire does not cause free fall of an upper block! The upper block and the lower structure are still attached by the alleged failed columns (none seen on any video) and gravity does not produce free fall of connected parts!
Gravity will only deform the alleged failing columns due fire. No free fall is possible of the upper block. And not seen on any videos.
Free fall 3.7 m before impact takes 0.8-0.9 seconds. Not seen on any video.
As a consequence an impact on a lower structure caused by an upper block after free fall is not possible. And not seen on any videos.
So there is no new vertical gravity load on the lower structure. The gravity load is always the same on the lower structure, while the connecting columns are being deformed. Quite basic. That's why steel structures never collapse due to gravity unless you suddenly destroy vital connections, like in CD. Fire can never suddenly destroy vital connections like CD does.
That is why CD companies never put the top of a steel building on fire and hope that it will collapse. It doesn't work like that.

But, if free fall actually occurs and if the released energy is actually applied on the lower structure, which is very unlikely, I demonstrate that it will only temporarily compress the lower structure and cause some local failures at the top of the lower structure. After that all potential energy released is consumed and lost. In reality no free fall/impact occur and all potential energy is consumed deforming the intermediate columns.

Bazant and Seffen and Nist are wrong when demonstrating anything else using false assumtions; rigid upper body, uniform density, upper body intact all the time, simultaneous failure/disappearance of 280+ columns, free fall, impacts, shockwaves, no redundancy in lower structure, etc. Clearly shown in my article.

Recommendation is that Bazant and Seffen redo their analysis using correct assumptions. No big deal really. Only that the conclusion will be that no global collapse ensues!

Just stop Heiwa, please.

Your "paper" has been debunked. Not that there was really anything much to debunk. You only provide conjecture, false metaphors and inaccurate bordering fraudulent simplistic calculations that do not represent the tower. You want Bazant, Seffen, etc to do calculations with your assumptions? Perhaps you should do them. You think yourself up to the intellectual task of pointing out the flaws in their calculations, why don't you try doing them yourself with baseline assumptions that you think should be used. Let's see some math. Put your money where your mouth is. Think of the fame that awaits you if you can actually prove inside job.

We've challenged you to show that you are an actual engineer and not just someone pretending to be. I've offered to personally defend your abilities as being in line with that of an engineer if you answered that challenge correctly. You haven't even acknowledged that said challenge even exists. I can only imagine that, after some attempted research on your part, you found the task too difficult.

Move on. Try doing some actual calculations. Put together some full-scale 3-d models. You claim to be an engineer, you should have access to this kind of software. Follow what I've done here with regards to fire and the exterior wall buckling. Open your mind to the possibility of actual, real truth. Not this farce that the "Truth Movement" believes. A movement that is so fractured and full of mutually contradictory theories that the only thing that they can agree on is that their initial gut reaction to seeing debunked films, like "Loose Change", is right. This, perhaps, is the tie that binds all "Truthers" together: the inability to ever admit they've made an error.

 

[X]

Subject is collapse. The floors, secondary structure transmitting load to the primary load carrying columns, are still attached. Evidently, as long as they are attached/bolted to the columns, they can also transmit horizontal windloads on one wall to another and prevent transverse movement of the columns. Nobody argues about that. Clear from the article.
And evidently heat affects the properties of the steel. 500°C and yield is reduced a little. Clear from the start! Strange that you cannot quote properly!
But heating some columns in a fire does not cause free fall of an upper block! The upper block and the lower structure are still attached by the alleged failed columns (none seen on any video) and gravity does not produce free fall of connected parts!
Gravity will only deform the alleged failing columns due fire. No free fall is possible of the upper block. And not seen on any videos.
Free fall 3.7 m before impact takes 0.8-0.9 seconds. Not seen on any video.
As a consequence an impact on a lower structure caused by an upper block after free fall is not possible. And not seen on any videos.
So there is no new vertical gravity load on the lower structure. The gravity load is always the same on the lower structure, while the connecting columns are being deformed. Quite basic. That's why steel structures never collapse due to gravity unless you suddenly destroy vital connections, like in CD. Fire can never suddenly destroy vital connections like CD does.
That is why CD companies never put the top of a steel building on fire and hope that it will collapse. It doesn't work like that.

But, if free fall actually occurs and if the released energy is actually applied on the lower structure, which is very unlikely, I demonstrate that it will only temporarily compress the lower structure and cause some local failures at the top of the lower structure. After that all potential energy released is consumed and lost. In reality no free fall/impact occur and all potential energy is consumed deforming the intermediate columns.

Bazant and Seffen and Nist are wrong when demonstrating anything else using false assumptions; rigid upper body, uniform density, upper body intact all the time, simultaneous failure/disappearance of 280+ columns, free fall, impacts, shockwaves, no redundancy in lower structure, etc. Clearly shown in my article.

Recommendation is that Bazant and Seffen redo their analysis using correct assumptions. No big deal really. Only that the conclusion will be that no global collapse ensues!

I've highlighted the important part.

Yes, the weight remains the same (if you ignore the sudden addition of the weight of the airplane).

But now the upper block is moving.
I'm sure you know that moving objects have momentum, right?
All that potential energy from the weight sitting at that height is going to rapidly become kinetic energy, from the weight moving.

You know there is a difference. I would be very surprised if you were willing to hold a bowling ball 6 inches over your head, then drop it. But b your logic here, since it didn't hurt to hold it, it will not hurt when it falls on your head.

And I should point out (I don't know why it is necessary to point this out again...) that it was more than fire affecting the columns and trusses. There is the tiny detail of them being hit by an airliner going pretty darned fast. I've seen columns get cut by a forklift moving only a few kilometers an hour (some people just shouldn't be allowed to drive those things). Imagine what a plane going well over 700 kilometers per hour could do.

Now, Heiwa, instead of merely asserting that the assumptions used by Bazant, Seffen and Nist are wrong, are you willing to go out ad prove it?
Bazant, Seffen and Nist would be capable of supporting their assumptions. Are you? This is not a board populated by children, Heiwa. It is a board populated by people who know what they are talking about.
You assert that all the people who disagree with you are novice greenhorns. It's a pretty bold claim to make, Heiwa. Especially given your reluctance to provide any calculations for scrutiny.
Look at it this way: If you provide the calculations, and you show everyone else has been wrong, you will be a hero. Most of the professionals who were wrong will apologize (I say most, since I can't speak for everyone). You will be able to get any job you want, having shown yourself to be an engineer par excellence.

So, do you have anything to offer besides rhetoric?

 

[Architect]

Come on, Heiwa. The boys have put it well. Provide some real structural calculations. Put up, or shut up.

 

[LashL]

Come on, Heiwa. The boys have put it well. Provide some real structural calculations. Put up, or shut up.

[My bolding]

I'm pretty confident in predicting that Heiwa will do neither.

 

[Heiwa]

Come on, Heiwa. The boys have put it well. Provide some real structural calculations. Put up, or shut up.

?? All real calculations are in the article! Very simple ones - static intact stresses in structure (<20-30% yield), amounts of PE/KE available (not very much = 40 litres of diesel oil), effects on intact structure, if this PE/KE is applied to it (as a spring); deformation, force, stress, buckling properties of columns, etc. Will not cause global collapse! What else do you need? Lobster and champagne?
Main purpose is of course to debunk Nist, Bazant and Seffen in layman's terms. Their assumptions behind collapse are 100% incorrect; rigid upper block of uniform density being intact all the time during destruction, free falling, impacting, shock waving, compressing the lower, intact structure only by gravity, etc.
I am quite pleased with the article. Only some greenhorns at JREF are upset as expected but have not shown that these ridiculous assumptions are correct.

 

[Heiwa]

But now the upper block is moving.
I'm sure you know that moving objects have momentum, right?
All that potential energy from the weight sitting at that height is going to rapidly become kinetic energy, from the weight moving.

You know there is a difference. I would be very surprised if you were willing to hold a bowling ball 6 inches over your head, then drop it. But b your logic here, since it didn't hurt to hold it, it will not hurt when it falls on your head.

Yes, strange that the upper block is suddenly moving. Free fall? Shouldn't really do that being connected with the lower structure via supposedly failing columns. Steel does not allow it, even if heated.
You make the mistake comparing the upper block with a bowling ball! It is not! Using the assumptions of Bazant and Seffen it is more like a bale of wool. Mostly air. It will not hurt!

 

[Heiwa]

Now, Heiwa, instead of merely asserting that the assumptions used by Bazant, Seffen and Nist are wrong, are you willing to go out ad prove it?
Bazant, Seffen and Nist would be capable of supporting their assumptions. Are you?

Haven't I done all that in the article? Rigid upper block? Uniform density of same? Free fall? Impact on lower structure? 100% alignment? Enormous amount of kinetic energy transmitted? Enormous impact velocity? Shock wave in lower structure? No support exist for these assumptions.

 

[pomeroo]

Subject is collapse. The floors, secondary structure transmitting load to the primary load carrying columns, are still attached. Evidently, as long as they are attached/bolted to the columns, they can also transmit horizontal windloads on one wall to another and prevent transverse movement of the columns. Nobody argues about that. Clear from the article.
And evidently heat affects the properties of the steel. 500°C and yield is reduced a little. Clear from the start! Strange that you cannot quote properly!
But heating some columns in a fire does not cause free fall of an upper block! The upper block and the lower structure are still attached by the alleged failed columns (none seen on any video) and gravity does not produce free fall of connected parts!
Gravity will only deform the alleged failing columns due fire. No free fall is possible of the upper block. And not seen on any videos.
Free fall 3.7 m before impact takes 0.8-0.9 seconds. Not seen on any video.
As a consequence an impact on a lower structure caused by an upper block after free fall is not possible. And not seen on any videos.
So there is no new vertical gravity load on the lower structure. The gravity load is always the same on the lower structure, while the connecting columns are being deformed. Quite basic. That's why steel structures never collapse due to gravity unless you suddenly destroy vital connections, like in CD. Fire can never suddenly destroy vital connections like CD does.
That is why CD companies never put the top of a steel building on fire and hope that it will collapse. It doesn't work like that.

But, if free fall actually occurs and if the released energy is actually applied on the lower structure, which is very unlikely, I demonstrate that it will only temporarily compress the lower structure and cause some local failures at the top of the lower structure. After that all potential energy released is consumed and lost. In reality no free fall/impact occur and all potential energy is consumed deforming the intermediate columns.

Bazant and Seffen and Nist are wrong when demonstrating anything else using false assumtions; rigid upper body, uniform density, upper body intact all the time, simultaneous failure/disappearance of 280+ columns, free fall, impacts, shockwaves, no redundancy in lower structure, etc. Clearly shown in my article.

Recommendation is that Bazant and Seffen redo their analysis using correct assumptions. No big deal really. Only that the conclusion will be that no global collapse ensues!

People who are far more competent than you have corrected your errors repeatedly. Does anything ever sink in?

 

[pomeroo]

?? All real calculations are in the article! Very simple ones - static intact stresses in structure (<20-30% yield), amounts of PE/KE available (not very much = 40 litres of diesel oil), effects on intact structure, if this PE/KE is applied to it (as a spring); deformation, force, stress, buckling properties of columns, etc. Will not cause global collapse! What else do you need? Lobster and champagne?
Main purpose is of course to debunk Nist, Bazant and Seffen in layman's terms. Their assumptions behind collapse are 100% incorrect; rigid upper block of uniform density being intact all the time during destruction, free falling, impacting, shock waving, compressing the lower, intact structure only by gravity, etc.
I am quite pleased with the article. Only some greenhorns at JREF are upset as expected but have not shown that these ridiculous assumptions are correct.

The pleasure you take in an article that demonstrates your incompetence to discuss these matters strongly suggests that you are not a real engineer.

 

[Newtons Bit]

?? All real calculations are in the article! Very simple ones - static intact stresses in structure (<20-30% yield),

Your calculations are bunk. This has been explained. All you have done is taken the total weight over the total area. You have not accounted for severed columns. You have not accounted for individual columns with larger tributary areas will have somewhat higher stresses.

amounts of PE/KE available (not very much = 40 litres of diesel oil), effects on intact structure, if this PE/KE is applied to it (as a spring); deformation, force, stress, buckling properties of columns, etc. Will not cause global collapse!

Terribly fake analogy. Though one that is interesting to look at. If you have a crane that has 100% efficiency, it will take 40 litres of fuel to raise the upper block roughly 3m. That's like having a car with a fuel efficiency of 0.000075km/liter. This is quite significant. You did not calculate the amount of energy required to buckle the columns. You just waived your hand.

I am quite pleased with the article. Only some greenhorns at JREF are upset as expected but have not shown that these ridiculous assumptions are correct.

I've even offered you a challenge in which you could prove that you are not just a silly little kid in Sweden trying to challenge real engineers. You ignored that challenge. And yet you still call us greenhorns? I laugh at this.

We've pointed out the problems in your paper over and over again. I can only conclude, that you have pushed your fingers so far into your own ears that you have squished out what little critical thinking skills you posses.

 

[Architect]

?? All real calculations are in the article!

No, they're complete bunkum. As has been shown here. You have included absolutely no structural analysis, nor do we see detailed analysis of the performance of the individual members required to support your bizarre hypothesis.

I do not believe you are at all qualified in engineering.

 

[Heiwa]

Your calculations are bunk. Terribly fake analogy. Though one that is interesting to look at. If you have a crane that has 100% efficiency, it will take 40 litres of fuel to raise the upper block roughly 3m. That's like having a car with a fuel efficiency of 0.000075km/liter. This is quite significant. You did not calculate the amount of energy required to buckle the columns. You just waived your hand.

Yes, a big crane can lift 33 000 tons 3.7 metres in six seconds and for that it requires about 40 litres of diesel oil. Quite big engine, though in the crane. Explained in my article incl. calculation.

Energy required to buckle a column? Can also be calculated. Let's assume the column has low slenderness ratio and will not buckle before yield. So first you have to compress elastically the column to yield! Assume it is a spring! The energy/force formula is in the article. After that it becomes a little more complex. The column will deform plastically somewhere depending on its configuration and supports, so you have to establish, where this deformation takes place. But then you can calculate the work required for this plastic deformation. Not too difficult.

Evidently the plastic deformation modifies the configuration and maybe the supports of the column, so you have to allow for that, until buckling finally takes place, be it bucklebending, torsionbuckling or crumpling up.

I wonder why Nist didn't do it? It helps to retrieve some failed columns from the initiation zone also. Quite incompetent not doing either. Just saying PE/KE > SE without any calculations/evidence of any sort!

But topic is collapse ... and Bazant's/Seffen's assumptions. You still maintain the upper block was perfectly aligned with the lower structure during the gravity collapse? Look at WTC2! Aligned? I just put in a photo of WTC2 in my article about it.

100% alignment between upper block (with rigid, uniform density, mass that drives the gravity collapse!) of lower structure is an ABSOLUTE requirement for a gravity collapse, like an avalanche. If no alignment the upper block slides off the lower structure due to gravity = no gravity collapse or avalanche.

And for same reason no rigidity of upper block = no gravity collapse or avalanche possible

And of course no uniform density of upper block = no gravity collapse or avalanche possible.

We are not talking about a rigid bowl hitting something! Remember the upper block was mostly air! Many persons forget that.

 

[DGM]

..Snip....Yada..Yada...
We are not talking about a rigid bowl hitting something! Remember the upper block was mostly air! Many persons forget that.

Why don't you save your typing fingers and just say you don't know how to calculate (don't understand) what Newtons Bit asked?

 

[Newtons Bit]

Energy required to buckle a column? Can also be calculated.

THEN DO IT. I've already asked you a dozen times. You keep saying your calculations are in your paper, and now you admit it's not. What's the problem? Do the calculation!

 

[Architect]

100% alignment between upper block (with rigid, uniform density, mass that drives the gravity collapse!) of lower structure is an ABSOLUTE requirement for a gravity collapse, like an avalanche. If no alignment the upper block slides off the lower structure due to gravity = no gravity collapse or avalanche.

For crying out loud......

How often have you been told that column-column collision is not required for collapse? How often have you been told what part the floors play? How often have you been asked why - nay, how - the upper debris field would magically "slide" off the lower section?

Is reading comprehension a major problem for you?