Layman's terms please! Tower collapse issue

[Apollo20]

Heiwa:

Sure there may have been some "telescoping" of the upper block of WTC during the first few seconds of collapse, but the mass of the upper block remained essentially the same. And you are incorrect when you say "nothing happens at the the initiation zone floors 93-98" at the start of the collapse. I would say that it's almost impossible to see what is going on between floors 95-99 after the first second or so of collapse... Can you see through all that smoke, dust and debris Heiwa? I can't!

[X]:

Density has the dimensions of mass/volume. I think some posters have used kg/m^3 while others have used g/cm^3, so we may have some inconsistency in this thread...

It's usually self evident what the implied units are when people say a density of 1 although they should really specify g/cm^3 (or use the term specific gravity).

 

[Newtons Bit]

[X]: It appears Heiwa is using specific gravity, not density. It's unitless.

 

[tsig]

OT of course, but cargo ships often carry cargoes with density >1 or even >4 (ore). And they do not sink! Arkimedes explained why >200 years BC. Smart guy. Google Arkimedes! He is still around!

Note: only cargo has density >1. Would sink like a stone. That's why we have cargo ships to carry cargo with density >1. They float.

FYI, it is quite easy to load a ship (wrongly) and it breaks apart in two pieces, both of which float! Why is that? Local failure. Fairly easy to put the two parts together again. After analysis why failure took place.

Same thing and exactly the same principles for WTC1. Start to explain the local failures. Then I will explain why the structure below will still stand.

You say: Ships are a classic case of structures that require high structural strength at low average density.

At low average density?

No serious person uses such words in engineering. Low? Average? Density? Seffen uses uniform density! Even worse! Low average density!! Have I have to laugh.

Heiwa

Only a fool laughs at tragedy.

 

[rwguinn]

Only a fool laughs at tragedy.

Someone needs to tell Heiwa's hypothesis to the folks on the various boats and ships in WWII that got cut in half, or blown in two, or to the Edmond Fitzgerald, the Titanic, and numerous other boats that broke in half and sank, or just sank.

 

[Heiwa]

Heiwa:

Sure there may have been some "telescoping" of the upper block of WTC during the first few seconds of collapse, but the mass of the upper block remained essentially the same. And you are incorrect when you say "nothing happens at the the initiation zone floors 93-98" at the start of the collapse. I would say that it's almost impossible to see what is going on between floors 95-99 after the first second or so of collapse... Can you see through all that smoke, dust and debris Heiwa? I can't!

Why would there be telescoping of the upper block for three seconds prior collapse at all? The gravity collapse has not begun! The gravity collapse begins at the initiation zone and continues downwards ... and assumes a rigid upper block (no telescoping) that free falls (not seen by a normal observer, like me) into the initiation zone because all the columns there have disappeared (not seen by me and not explained by Nist, Bazant, Seffen, Spoof & Co - just assumed).

And the rigid upper block shall then first make this solid impact (not seen) over 4000 m², no damping allowed by e.g. crunched columns left behind and second produce a shock wave (it takes 0 seconds as it is instant but assumes perfect hit on 4 000 m² - if not, no shock wave) and then third drive the gravity collapse or rather a crush front downwards, where all 280+ columns at each floor below are crunched, crumpled and crushed (and removed - columns ripped apart at two ends), accelerated to participate in the mess as a beta L part all the time during the collapse (10-15 seconds) of the lower structure. The upper block, rigid, cannot break up because then there is nothing to drive the avalanche and the crunching, crumpling, crushing and ripping aparts of columns ... so that the floors can drop one after the other.

You have to look at the videos frame by frame. Suddenly, at initiation, you see a row of smoke puffs split by ... I assume, intact columns. But the columns should have been gone then. Don't ask me how! Free fall = no columns, no smoke puffs. Floors dropping down as per Nist latest fairy tale? OK, but then the columns are intact. OK, you can't see that! Did you assume it?

I always wonder how gravity can throw away sideways a big block of a wall with numerous columns and spandrels! Doesn't look as gravity collapse to me.
A crush front cannot throw away a 10 storey tall wall piece that is 30 metres wide! And the squibs and fire works preceeding the crush front. Nothing can preceed the crush front! Etc, etc. Looks like assistance (extra energy input) of some kind was provided.

You don't really know what a gravity driven collapse are, do you? They are rare and do not occur in steel structure buildings. The gravity force applied from above has a tendency just to slip off the steel structure after a small local failure and hit the ground instead. Quite basic actually.

 

[Heiwa]

Only a fool laughs at tragedy.

Low average density is comedy. Music hall. Hollywood.

 

[tsig]

Someone needs to tell Heiwa's hypothesis to the folks on the various boats and ships in WWII that got cut in half, or blown in two, or to the Edmond Fitzgerald, the Titanic, and numerous other boats that broke in half and sank, or just sank.

Steel can't weaken, therefore Catch22.!

 

[X]

[X]: It appears Heiwa is using specific gravity, not density. It's unitless.

An odd thing to use for buildings, IMHO, but it would explain the numbers dancing around 1. Maybe he wanted numbers that were impressively small?

Which raises the question of why Heiwa, of all people, is talking about ships carrying cargoes of >1 spec. grav.

The overall density of the ship must still be <1. Probably considerably less for safety.

 

[Heiwa]

Someone needs to tell Heiwa's hypothesis to the folks on the various boats and ships in WWII that got cut in half, or blown in two, or to the Edmond Fitzgerald, the Titanic, and numerous other boats that broke in half and sank, or just sank.

Isn't that a little too late and OT? And Titanic? She surely hit an ice berg? Result? Local failure in the sheel plate (long fracture). No global collapse. She sank as she lost buoyancy due to inflow of water into the hull. 1500+ persons died because the ship lacked proper LSA and associated procedures/training.

 

[Heiwa]

An odd thing to use for buildings, IMHO, but it would explain the numbers dancing around 1. Maybe he wanted numbers that were impressively small?

Which raises the question of why Heiwa, of all people, is talking about ships carrying cargoes of >1 spec. grav.

The overall density of the ship must still be <1. Probably considerably less for safety.

In the shipping industry we never use the term 'overall density of the ship'. It is really comical.

 

[DGM]

Isn't that a little too late and OT? And Titanic? She surely hit an ice berg? Result? Local failure in the sheel plate (long fracture). No global collapse. She sank as she lost buoyancy due to inflow of water into the hull. 1500+ persons died because the ship lacked proper LSA and associated procedures/training.

Surely frozen water can't hurt solid steel. LOL

 

[Minadin]

In the shipping industry we never use the term 'overall density of the ship'. It is really comical.

In the building industry we never refer to the 'uniform density' of a structure, either. There are specific loads and specific loading conditions and there are the various structural elements arranged in a certain way to handle them as efficiently as the design allows while still meeting the requirements for the useful occupancy of the building.

 

[Architect]

Well - evidently you have not read my paper because the structural design of WTC1 (or at least its upper part) is well described.

You know that I have, and no it wasn't well described.

One conclusion then is that the outer envelope, you mean the four outer walls consisting of 63 columns each

Your failure to grasp basic structural terminology is not my concern.

The outer envelope does not need any floors to stand.

With respect, that is a blatantly false proposition for anyone with a grasp of building structures. It would be uneconomical to upsize structural members of the envelope sufficiently to resist the typicaly dead and imposed loadings on any building as tall as WTC. This is implicit on all the discussions of the structure including NIST, Edinburgh, Sheffield, Arup, and so on.

If you cannot grasp basic structural concepts that what hope do you have that you can rigorously analyse the collapse itself?

In face, have you read any of the studies by the four I name above?

Quite the opposite, the floors need the outer envelope to hang on (via bolts). Remove all floors and the walls stand.

The envelope supports the floors but the floors in tunr restrain the outer facade. This is basic stuff, you know.

The initiation zone is apparently where the collapse started - no problem for me, except that the roof of WTC1 drops 20-25 meters and there is still no big damages at the initiation zone.

By definition the initiation zone is the point where collapse first occurs. You seem to be confusing it with immediate impact zone, which suggests you fail to grasp the fire modelling issues arising from NIST and other studies. This too is basic stuff.

The initiation sequence? One thing is sure - no mention that the upper block disintegrates prior to collapse below the initiation zone starts.

It's a shame your wrong about that, isn't it? I suggest you watch the video evidence again.

Is 'initiation' a technical term? Sound more like magic and secret society to me!

Not so hot at English, eh? Bummer. I remember that stage, at school. Keep working hard at it, mate.

The performance of steel in fire is described (with a link) in the paper. The steel gets hot, etc! Strength is hardly affected below 500°C. Core column integrity! Yes, it is a mystery how 47 strong core columns were destroyed.

Whilst encouraging that you now conceed steel fails in fires, despite your failure to address the point initially, you grossly underestimate the temperature and effect of fires. Why do you persist in doing so, in the face of all the evidence?

Well the uniform density of the upper block is less than that of wool, so I think it is a useful comparison.

A tonne of WTC in bits ways the same as a tonne of WTC and one bit. Do not waste our time with whollly irrelevant structural analogies.

The use of concrete of floors. I thought you thought I did not know that there were concrete floors? Anyway - they poured concrete on the steel floors pans held by trusses to even them out, provide noise and fire insulation, etc.

"Pans"? You're really struggling with this terminology issue.

And do you really think that the concrete was only to provide accoustic and fire insulation together with a level top surface? Really?

I know Nist suggests that 6 or 11 floors fell down suddenly into the initiation zone and initiated the collapse, but it is nonsense. Only fools believe that.

Who said that this was the collapse mechanism? Provide us with a page reference from NIST then?

 

[Dave Rogers]

Which raises the question of why Heiwa, of all people, is talking about ships carrying cargoes of >1 spec. grav.

Because it's his MO. Look through all the possible physical parameters of a system, and pick the one that superficially appears to support his latest argument while ignoring (a) the fact that it doesn't and (b) all the other physical parameters.

I've also noticed another fallacy Heiwa is committing, which is based on semantics: he's defining processes to exclude specific events, then stating that the absence of those specific events from the process is contradictory. Here are a couple of examples.

1. Heiwa claims that there was no initial drop prior to the collapse. He therefore defines collapse initiation as all the processes that take place before there is any drop of the structure. Since there is no drop of the structure during the collapse initiation process, collapse cannot initiate. This is an absurd argument, in that it claims the anomaly that there is no collapse before the collapse starts.

2. Heiwa claims that there was no initial drop of the upper block into the collapse initiation zone, but rather there was a collapse of the lower floors of the upper block. This is a little more subtle; he's effectively defining the upper block so as to include what everyone else defines as the collapse initiation zone, and then defining the collapse initiation zone as being the top few floors of the lower block. This is an equally absurd argument, in that it claims that the first floors to collapse are not in the collapse initiation zone, when the collapse initiation zone is properly defined as the first few floors to collapse; in effect Heiwa is arguing that the first few floors to collapse were not the first few floors to collapse.

As for "average density", I don't particularly care what engineers do and don't talk about. The concept is trivially simple to understand. And Heiwa, as others have pointed out, your comments on "uniform density" are themselves laughable; nobody sane would seriously argue that the upper block of the North Tower was a homogeneous object of constant density, even though this might be used as a simplification in order to model the effects of its fall.

Dave

 

[Architect]

Seconded, Dave.

Ironically I'm in Manchester, waiting for rain and wind to ease off (ha!) in order that I can go on a site visit on a .... wait for it ......tall building somewhere near Deansgate. But hell, what would I know about building such things, eh?

Anyone got a boat I can design?

 

[uk_dave]

Hmmmmm 'Architect' is in Manchester at the same time as Manchester's chief Constable decides to go off and commit suicide during a period of unseasonal strong storms indicating that the 'weather modification' chemtrails are having the desired effect of pushing oil prices to a record high resulting in Warren Buffet becoming the new supreme ruler of the world and commissioning a new office building in Manchester.

Join the dots, people.

 

[Hokulele]

Seconded, Dave.

Ironically I'm in Manchester, waiting for rain and wind to ease off (ha!) in order that I can go on a site visit on a .... wait for it ......tall building somewhere near Deansgate. But hell, what would I know about building such things, eh?

Anyone got a boat I can design?

Sure! I am at the shipyard working on a newer version of one of these this week. They just raised the derrick, and it should be ready for commissioning this fall. Funny how they are really, really concerned about fire protection issues, seeing as how fire has no effect on steel . . .

 

[Architect]

Hmmmmm 'Architect' is in Manchester at the same time as Manchester's chief Constable decides to go off and commit suicide during a period of unseasonal strong storms indicating that the 'weather modification' chemtrails are having the desired effect of pushing oil prices to a record high resulting in Warren Buffet becoming the new supreme ruler of the world and commissioning a new office building in Manchester.

Join the dots, people.

I've worried that the winds will damage the C4 coated reinforcement in the Tower and that it might not collapse into Deansgate when we press the button. And after the £millions we spent buying-off all the workers, too.....

 

[peteweaver]

A structure can only be as strong as the bolts which hold it together.

 

[rwguinn]

A structure can only be as strong as the bolts which hold it together.

Conversly:
A Conspiracy theory is only as strong as the nuts that keep the loose screws from falling out...