Moderated Steel structures cannot globally collapse due to gravity alone

[Heiwa]

Nonsense is claiming experiments using lemons, sponges, pizza boxes, and scale jumping as examples of collapse and then accepting the conclusion of controlled demolition taking down the towers.

You are right! But as examples of crush downs they are pretty useful.

Collapse follows if you hit someone below. Crush down is a result of being hit from above and a lemon, sponge or pizza box that is hit from above by another lemon, sponge or pizza box due to gravity only will not get damaged at all.

 

[MIKILLINI]

You are right! But as examples of crush downs they are pretty useful.

Collapse follows if you hit someone below. Crush down is a result of being hit from above and a lemon, sponge or pizza box that is hit from above by another lemon, sponge or pizza box due to gravity only will not get damaged at all.

Let's consider lemon structure: Is the lemon shape and strength similar to the construction design of the twin towers? Is the mass of a lemon comparable to the mass of materials used in constructing the twin towers?
No, not even close. Nor are pizza boxes and sponges similar in mass, structural design, or material

 

[Heiwa]

Let's consider lemon structure: Is the lemon shape and strength similar to the construction design of the twin towers? Is the mass of a lemon comparable to the mass of materials used in constructing the twin towers?
No, not even close. Nor are pizza boxes and sponges similar in mass, structural design, or material

Start with uniform density. WTC I upper part C has uniform density 255 kgs/m3 according BLGB - like a sponge. And shape. Yes - there are cube like sponges. Structure? A sponge consist of many internal members holding it together so it becomes elastic. WTC 1 upper part C has columns and floors holding it together making it elastic.

No, but wait! Upper part C is not elastic!! It is rigid (!!) according to NIST, Bazant and Seffen. Rigid! Indestructible. More solid than a depleted uranium bullet (with density 25 500 kgs/m3).

But how can WTC1 upper part with density only 255 kgs/m3, i.e. 100 times less than a depleted uranium bullet, and more like a sponge be rigid?

Answer is that according NIST WTC 1 upper part is rigid!

Or must be rigid! Otherwise it cannot crush down WTC 1 lower part ... that is not rigid.

If WTC 1 lower part is rigid (indestructible) evidently it cannot be crushed down by anything.

But for some strange reason only WTC 1 upper part is rigid! According NIST!

Yes you are right - it is not like a lemon! It is more like a depleted uranium bullet. How could I make such a stupid mistake? Or ...

 

[GlennB]

One of these possibilities - applicable in pomeroo's extreme scenario - would be the utter destruction of both parts. Of course.

No - not really ... even after a two mile drop and a plenty of energy/forces at impact.

So you do deny that the lower section would be destroyed, just as you did way back when pomeroo first used the extreme scenario.

Yet when this was pointed out to you just a few days ago your response went like this :

Heiwa believes that the towers would survive the upper block being dropped on them from 2 miles in the air.

Did Heiwa believe that, or you misquote? Actually Heiwa has never said anything like that

So you are now resorting to blatant, bare-faced LYING to defend the nonsense you spew. It's on record. Black and white.

Please at least have the decency to admit it.

 

[Furcifer]

Anyone who has investigated collision damages between ship (and cars) knows that the stronger parts of both objects damage the weaker parts and that there is no crush front. And evidently the destruction is arrested when it runs out of energy. To suggest that gravity alone will drive the WTC 1 & 2 destructions is also nonsense. Too little potential energy available and 100 times more strain energy/strength in parts A and C.

You have a blatant disrespect for gravity. Better yet, a blatant disregard for it.

Out of curiousity, when you picture the collapse of the towers, are they lying on their sides floating down the Hudson? It's the only way your analysis makes any sense.

 

[Furcifer]

But how can WTC1 upper part with density only 255 kgs/m3, i.e. 100 times less than a depleted uranium bullet, and more like a sponge be rigid?

What does density have to do with rigidity?

 

[Architect]

Architect argues that (Heiwa) 'argues that the lower structure should have had sufficient capacity to arrest failure of the upper section, but at no time does he carry out any meaningful analysis of the very complex structural inter-relationships. So, for example, the hat trusses help stop sway and stabilise the structure. The floors help prevent deformation of the outer loadbearing envelope. if these are damaged, then what is the overall impact on stability.'

This is standard misquoting. The argument is simply that locally damaged floors (by the columns) of both parts A and C get entangled into one another and that friction between the damaged floors will arrest further destruction.

NIST/Bazant/Seffen treat the crush down as a one-dimensional problem - pure compression, in steps, of part A, while part C remains intact and ignore e.g. friction between subparts (floors) of parts A and C. They - NIST/Bazant/Seffen - suggest that there is some magic 1-D crush front between parts A and C that can shed structure of part A only, etc, etc., but it is complete nonsense.

Bill,

This is exactly what I mean. Setting to one side whether "entanglement" is likely give the collapse pattern we see, Heiwa completely disregards the impact of the loss of key structural elements - such as the hat trusses - on the overall structural stability of the inter-related elements. So, for example, as the outer structural envelope (the facade, if you will) relies upon a restraining action from the floors for part of its stability then we can reasonably assume that loss of same will have a much wider-ranging impact.

Let me give a fairly simple example of differing characteristics. If we take a steel rod, say 15mm in diameter, and use it to deal with tensile loads then it will be very strong. It would make an ideal tie or collar in a roof truss. If, however, the loads placed upon that truss were to change significantly such that the former tie was now required to deal with large compressive loads then it would fail - and pretty fast. Or, for example, I might point to the different design requirements (notably placing) for reinforcement in a concrete floor depending upon whether its a simple span or a cantilever. The latter distinction would be quite important where, say, there was a loss of some elements of the structure.

Assessing issues such as this requires a complex, comprehensive series of structural analyses which would test most structural engineering consultants today. Computer modelling makes life a little easier. Heiwa - and others - refuse to post any such calculations of their own, and I think that you have to ask yourself how they can be so sure in the absence of any meaningful rigour.

Anyone who has investigated collision damages between ship (and cars) knows that the stronger parts of both objects damage the weaker parts and that there is no crush front. And evidently the destruction is arrested when it runs out of energy. To suggest that gravity alone will drive the WTC 1 & 2 destructions is also nonsense. Too little potential energy available and 100 times more strain energy/strength in parts A and C.

Yes, I can see the similarities between ships, cars, and tall buildings. The next time one of my clients is looking to appoint a design team then I'll suggest that he pops around to his local accident repair centre and gets one of the mechanics to help him out.

Heiwa, produce some structural calculations.

I think I explain that quite clear in my articles.

I'm thinking that this word isn't meaning what you are thinking it is meaning.

 

[Heiwa]

What does density have to do with rigidity?

It is Bazant that introduce uniform density as a parameter in his model. Uniform density of WTC1 parts A and C is 255 kgs/m3. When part C compresses a bit of part A into part B - a rubble layer - the rubble has uniform density 1025 kgs/m3.

Evidently no WTC part has uniform density: part C is 95% air + columns (density 7850 kgs/m3) and floors (density say 2500 kgs/m3), etc.

BUT in Bazant's one-dimensional world, where towers are crushed down, floors and columns are mixed with air to get uniform density of 255 kgs/m3.

Has nothing to with reality, of course, so the Bazant model is nonsense.

 

[Heiwa]

Heiwa completely disregards the impact of the loss of key structural elements - such as the hat trusses - on the overall structural stability of the inter-related elements. So, for example, as the outer structural envelope (the facade, if you will) relies upon a restraining action from the floors for part of its stability then we can reasonably assume that loss of same will have a much wider-ranging impact.

No, I do not disregard the hat truss! It is fitted on top of part C and is never in contact with part A (lower structure) at alleged contact.

So we repeat: Part C is displacing downwards and is slightly dislocated sideways so that the columns of part A contacts the bottom floor of part C except where part A columns are outside part C. I suggest that the part A columns then damages the part C bottom floor locally. The hat truss cannot prevent that!

As part A (lower structure) columns damage part C floors, I then demonstrate that part C cannot crush down part A.

According the model of NIST and Bazant it is the bottom floor of part C that crushes part A and compress part A into rubble. I consider that model rubbish.

 

[Heiwa]

Yes, I can see the similarities between ships, cars, and tall buildings. The next time one of my clients is looking to appoint a design team then I'll suggest that he pops around to his local accident repair centre and gets one of the mechanics to help him out.

Good, structural analysis is required for ship, car, aeroplane and tall building design. In the shipbuilding industry we sometimes call it naval architecture and the engineers designing ship structures are called naval architects. Very complex as the design loads applied to the structure in interface water/air are not so easy to define. But the design principles are the same for any structure. You do not find that know how at a repair centre.

 

[Heiwa]

You have a blatant disrespect for gravity. Better yet, a blatant disregard for it.

Out of curiousity, when you picture the collapse of the towers, are they lying on their sides floating down the Hudson? It's the only way your analysis makes any sense.

Sorry, gravity is one important load to consider both for structural design and structural damage analysis.

The difference between, e.g. a tall building structure designer and a naval architect is that the tall building designer mainly considers static loads (incl. e.g. snow on the roof) and some wind loads.
In naval architecture you have to consider much more loads, incl. impacts, e.g. when big waves smash into the structure. So at least I am quite familiar with the latter subject.
So when part C - upper part of WTC 1 - is alleged to smash into part A - lower structure of WTC 1 - I have a quite good feeling for it.

And in my simple view it is part C that shall be destroyed first and not part A in some funny crush down ... due to gravity alone.

I have great respect for the forces of nature and sea ... incl. gravity.

 

[Architect]

Bill,

If you look at Heiwa's post, above, you'll see thhat he claims to take account of the hat trusses however it's quite clear that - because it's not in direct contact with the lower part of the building (which he calls "A"), then he disregards its contribution to the overall structural model. But as you'll appreciate from my earlier post, this isn't how the structure works. The hat trusses actually play quite an important part in the overall stability of the building, ditto the tie action of the floors. By ignoring this, his model is fataly flawed.

I'll give another example. The gable of a house is normally tied to the roof structure. People commonly thing this is to hold the roof in place, but in fact it's to prevent movement in the masonry as the thin gable isn't braced and can wander all over the place. Now, if the roof were to collapse then the gable would be at risk of imminent failure - even if no debris had hit in on the way down. Likewise in a traditional 2 or 3 storey house, it is the floor joists which tie the outer masonry (or timber) walls together. If there were no floors then we'd need to either thicken or buttress the walls.

So, as I mentioned before, issues about whether a loose beam would punch through a floor slab are largely irrelevant. If the envelope fails, the floors fail globally. If the floors fail, then the envelope fails globally. If the hat truss fails, then loads are no longer transferred across the structure and everything goes pear shaped.

Also remember that tie bar analogy I gave above. Just because - say - a floor girder beam and pin joint work in tension doesn't mean they can work in compression (if, for example, elements of the core or envelope began to bow inwards locally). Reinforcement is also in the bottom - it was a permanent steel shutter - hence the slabs can only work in span, not cantilever. This means that if part fails then it's much harder for the floor to simply work around the problem.

This, of course, is not going to be anything like automotive design. I worry about those who found upon analysis based upon the latter being relevant to the former.

 

[Architect]

The difference between, e.g. a tall building structure designer and a naval architect is that the tall building designer mainly considers static loads (incl. e.g. snow on the roof) and some wind loads.
In naval architecture you have to consider much more loads, incl. impacts, e.g. when big waves smash into the structure. So at least I am quite familiar with the latter subject.

I'm sorry, but that's entirely misleading. Wind loads on tall structures are very complex, rather than a case of simply looking at shear loadings. One has to consider the impact of pressure differences, tangential and incidental loads leading to torsion across the structure, issues about resonance and damping, and so on. As the boys who did the Citicorp building can tell you, it's an incredibly difficult area.

It seems to me that there is a pervading presumption in your reasoning about the inherrently more complex nature of naval architecture is opposed to structural engineering. With respect, I find such an untenable position deeply worrying. You make very basic mistakes in understanding the how the various elements of the WTC structure worked with each other, for example the importance of floors and hat trusses as part of a composite system, and show little grasp of how elements are designed for credible loads.

If it's so easy, I would suggest you sit the IStructE entrance exam. You should find it easy and I will be the first to apologise. I shan't hold my breath, however, because I think that - deep down - you know you'd fail.

 

[Heiwa]

So you do deny that the lower section would be destroyed, just as you did way back when pomeroo first used the extreme scenario.

No - I just suggest that the upper section will be destroyed (shredded in small parts = rubble) first and that, after upper section is destroyed, it cannot destroy anything. You see - the upper part is quite weak and volum wise 95% air. To assume it can destroy anything - regardless of drop height - is far fetched.

It is thus quite possible that lower section is just partially damaged.

But don't forget that there can also be a bounce.

OK - I know that NIST and Bazant suggest that rubble can destroy anything, but it is rubbish.

 

[stateofgrace]

No - I just suggest that the upper section will be destroyed (shredded in small parts = rubble) first and that, after upper section is destroyed, it cannot destroy anything. You see - the upper part is quite weak and volum wise 95% air. To assume it can destroy anything - regardless of drop height - is far fetched.

.

As was the rest of the building, correct?

 

[Heiwa]

I'm sorry, but that's entirely misleading. Wind loads on tall structures are very complex, rather than a case of simply looking at shear loadings. One has to consider the impact of pressure differences, tangential and incidental loads leading to torsion across the structure, issues about resonance and damping, and so on. As the boys who did the Citicorp building can tell you, it's an incredibly difficult area.

It seems to me that there is a pervading presumption in your reasoning about the inherrently more complex nature of naval architecture is opposed to structural engineering. With respect, I find such an untenable position deeply worrying. You make very basic mistakes in understanding the how the various elements of the WTC structure worked with each other, for example the importance of floors and hat trusses as part of a composite system, and show little grasp of how elements are designed for credible loads.

If it's so easy, I would suggest you sit the IStructE entrance exam. You should find it easy and I will be the first to apologise. I shan't hold my breath, however, because I think that - deep down - you know you'd fail.

Yes - to establish the loads to apply to a structure is not easy. Particularly when they are of a dynamic, irregular nature. Actually, it is the most important aspect of the whole analysis. That's what makes naval structural engineering so interesting. But the basic principles are the same, so please do not suggest that I am not familiar with the subject.

 

[Heiwa]

If you look at Heiwa's post, above, you'll see thhat he claims to take account of the hat trusses however it's quite clear that - because it's not in direct contact with the lower part of the building (which he calls "A"), then he disregards its contribution to the overall structural model. But as you'll appreciate from my earlier post, this isn't how the structure works. The hat trusses actually play quite an important part in the overall stability of the building, ditto the tie action of the floors. By ignoring this, his model is fataly flawed.

How can the hat truss/roof of part C, prevent the solid, vertical columns of the lower structure, part A, to locally damage the thin bottom horizontal floor of part C 53 meters below the roof/hat truss in an alleged contact?

 

[Heiwa]

As was the rest of the building, correct?

Of course.

 

[GlennB]

No - I just suggest that the upper section will be destroyed (shredded in small parts = rubble) first and that, after upper section is destroyed, it cannot destroy anything.

Which leaves only the possibility that the lower section will not be destroyed by the "two mile fall". You say this now and have done so in the past. Yet you deny ever having said it.

You remain a liar.

 

[stateofgrace]

Of course.

So why are you trying to compare it to a lemon? Is a lemon 95 % air?

Also what happens if the massive dynamic weight misses the 5% of the structure below? What happens if this massive dynamic weight misses all the supporting structure and actually hits something that cannot support it?

Also why are you trying to make out that the volume of the upper block in anyway represents the actual weight of it and try to dismiss it as weak and it cannot destroy anything? What did this mass weigh ? Produce some maths to support your case that this weight can be stopped by the structure below, that by your own admission "is quite weak and volum wise 95% air".

If a massive weight is dropped onto something that by volume is 95 % air and very weak, what is going to stop it dropping?