IPB




POSTS MADE TO THIS FORUM ARE THE SOLE RESPONSIBILITY OF THE AUTHOR AND DO NOT NECESSARILY REFLECT THE VIEWS OF PILOTS FOR 911 TRUTH
FOR OFFICIAL PILOTS FOR 9/11 TRUTH STATEMENTS AND ANALYSIS, PLEASE VISIT PILOTSFOR911TRUTH.ORG

WELCOME - PLEASE REGISTER OR LOG IN FOR FULL FORUM ACCESS ( Log In | Register )

3 Pages V  < 1 2 3  
Reply to this topicStart new topic
Collapse Hypothesis

mrmitosis
post Sep 29 2010, 02:19 AM
Post #41





Group: Private Forum Pilot
Posts: 228
Joined: 11-February 10
From: Australia
Member No.: 4,909



QUOTE (SanderO @ Sep 28 2010, 05:03 PM) *
I think you are correct. A new investigation will air some very dirty laundry and that would be unacceptable.


http://labvirus.files.wordpress.com/2010/0...n-id1084585.pdf

^^^

I only learnt about this Cass Sunstein character earlier today. It seems that Obama is determined to carry the torch passed over from the previous administration (as if there were ever any reason to believe otherwise).

SanderO, I'm not sure if I understand the nuances in your analysis, and I am sure that you understand the physics better than I do.

However, there are a couple of details which I suspect you have misinterpreted. For example, are you suggesting that once the collapse sequence had been initiated in the case of the North Tower, that the destruction which ensued can be explained without speculating about the use of explosives?

To my understanding, the damage caused to the towers resulting from aircraft impacts would in fact result in a decreased capacity for the upper portion to crush what lies beneath it. David Chandler explains it pretty well -

http://www.youtube.com/watch?v=28ds5sFvTG8...feature=related

In other words, not only was there insufficient energy available for the collapse to begin - there was not enough for it to continue, either.

Perhaps this is not what you are arguing, and perhaps I need to brush up on my own understanding of the forces involved. Apologies in advance if this is the case dunno.gif
Go to the top of the page
 
+Quote Post
SanderO
post Sep 29 2010, 06:09 AM
Post #42





Group: Troll
Posts: 1,174
Joined: 23-December 09
From: NYC
Member No.: 4,814



I believe in this case Chandler is wrong. My explanation is based on the simple fact that there was more than sufficient mass in the upper section of the towers to destroy the FLOORS once that mass was dis associated from the columns. Chandler's basic physics concept is correct, but he is not actually describing what happened. He reduces the problem to a small block crushing a big one or essentially why would columns which supported X mass not supported it mysteriously on 9/11 after the plane strike?

But the fact is that those columns - the core - were not involved in the collapse of the floors. The columns would be the path of most resistance, but the floors fell, not on or through (crushing) the columns, but onto one another. The floors were connected to the sides of the columns and they had each been designed for a 100 #/SF load (mechanical floors more) and with the upper floors coming down on them this was exceeded by a factor way beyond the safety margin of the FLOOR design. The floors failed and did so chaotically and the failure progressed rapidly and became less stoppable as more and more floors added to the descending mass. Neither the core columns not the facade columns were involved nor could prevent the collapse of the floors.

This is basic statics and something that engineers who design structures understand and principles they use all the time. A floor slab, and in this case the trusses which support it, and the connections to the columns which support the trusses are designed to carry anticipated loads (in this case 100#/sf for the slabs) with a safety factor. The floors themselves weighed more than 100#/sf without adding the live load. So each floor could conceivable represent 200#/ sf of added load when it feel to the floor below. Some of the mass went over the side and some into the core so this is the upper limit of added mass contributed by each floor. But some of the core columns might fall outside the core and add to this mass. Regardless in a few seconds AFTER collapse initiation the conditions for floor collapse were met and the top floor supporting all that extra mass sagged past its elastic limit and shattered dropping down and presenting the floor below with even more extra mass and it failed quickly and so on to the ground. This was not pancakes as the over loading of the floors did not have to happen simultaneously over the entire floor area, but in a short period of time all the mass above came more or less straight down and overcame the entire area of each floor.

Proof that the core columns were not involved in the floor collapse is the spire which stood for a bit after the floors collapsed. Not all the core but at least 40% and up to 50 floors and 501 stood over 7o. The longest surviving core columns were the ones supporting the north (long span side) of the floors outside the core.

Also confirming that the columns were not involved is the fact that the facade columns were found un buckled and can be seen falling away in huge sheets of up to 150 tons flat and made up of 20 or more 10x36 facade panels. This strongly indicates that they peeled away after the floors had collapsed with the growing floor mass providing the horizontal force to push them away.

All the air in the building was rapidly displaced by the compacting crushing falling debris and this is seen by the huge cloud of dust which propagated away from the bottom after the collapse hit the ground. Some of the air pressure shattered the glass and carried smaller pulverized debris in streams of air laterally as the collapse progressed.

Some lighter elements were strung off the building such as the light aluminum skin of the facade columns and even some steel sections so it was not like pouring sand down a chute. It was a very chaotic and energetic even involving the collapse of hundreds of thousands of tons of material.

Getting this all started is where the engineering took place. But once it was started it was nature that destroyed the structure. This is analogous to the use of explosive to set of avalanches. Once they get started they are completely natural phenomena.

This post has been edited by SanderO: Sep 29 2010, 06:15 AM
Go to the top of the page
 
+Quote Post
mrmitosis
post Sep 29 2010, 10:00 PM
Post #43





Group: Private Forum Pilot
Posts: 228
Joined: 11-February 10
From: Australia
Member No.: 4,909



I'm well and truly out of my depth here, but perhaps I can paraphrase your argument as I understand it in dot form, respond briefly, and you can correct me if I have misinterpreted anything. (I hope you don't consider this too much of a tedious exercise.)

In essence, what I gather you are saying is that:

(i) the structural integrity of the tower floors was dependent on the strength of what was bracing them to the columns, and the M x A of what came crashing down onto them.

(ii) the scenario you describe was distinguishable from pancaking because the floors were not ripped from the columns as whole blocks, but in a more random (but close to simultaneous) fashion. Basically, the concrete was smashed apart and brought down by the descending material from above, which naturally accumulated as the collapse sequence gained momentum.

The part which does not square with my observation is the fact that such a small proportion of the steel columns remained standing and intact after the rest of the building came down. You mention that at least 40% of the core remained post-collapse, but from my perspective, I find it difficult to explain how ANY steel below the impact point could be destroyed so cleanly and rapidly, at least by virtue of tumbling concrete. As you say, this was the path of most resistance, and so an additional source of energy is required.

You also point out that there was enough bulk sitting above the point of impact to separate the floors from the columns, bringing those floors and the ones below down with them. I have no reason to dispute this, but I don't think this is what Chandler was referring to.

When he raises the matter of a "small block crushing a big block", I think he is drawing attention to the impossibility of this as an explanation (not the reality of it) as far as the building's core is concerned. Setting aside any of the mechanisms involved in separating the floors from the columns and trusses, how are we to explain the destruction of the columns themselves? The steel was sliced and diced neatly and uniformly, and a lot of it was visibly and forcibly ejected sideways as the structure fell. Something was breaking the steel apart and shooting it out horizontally - what was it?

On a slightly unrelated point, it's interesting that on every piece of footage I've seen, the camera shudders violently about 12 seconds before the north tower comes down, although we hear nothing on the audio track. Hmmm.
Go to the top of the page
 
+Quote Post
SanderO
post Sep 29 2010, 11:00 PM
Post #44





Group: Troll
Posts: 1,174
Joined: 23-December 09
From: NYC
Member No.: 4,814



I break up the destruction of the towers into separate phases which blend into one another as opposed to discrete steps though parts of the collapse do involve discrete elements of the structure.

What we have is the plane strikes which damage some columns and then some fires which seem to cause local damage but are not hot enough to melt of seriously weaken enough steel for the tops to come down. That is where the engineered intervention comes into play and though I can propose various ways to accomplish that it would be speculation be cause I believe this involves the perimeter core columns and we can't see them.

What we see is the next phase where the top appears to be descending downward after tilting a bit with the antenna leading the descent. But descent is perhaps a bit misleading. The top IS descending but the bottom of the top "block" is not descending and it appears to be "disappearing" into the top of the bottom. It almost looks as the top is collapse at its bottom as it falls down through the plane strike zone onto the largely undamaged top of the lower section at about the 92nd floor. At the same time we see "ejections" all around the building at this impact zone between the top and the bottom. The upper part seems to hang together and it appears to be under little internal stress and in fact its initial descent accelerates at or close to free fall indication that there was nothing stopping its descent or nothing we could measure.

What is likely happening in the early stages of the collapse of the upper part is that it has been dislodged from the columns which supported it and naturally it drops, much like WTC 7 as it drops it brings the lowest floor say 93 in contact with floor 93 and the 94 is added and so on. These are not added a pancakes or uniform slabs and the collisions are energetic, not perfectly aligned contain dislodged steel columns and so forth which shatters the floors as the collide. Some of them crash through multiple floors related to the aircraft damage.

The destruction of the top takes about 4 seconds and the huge antenna moves ahead. It required the hat truss to distribute its loads to multiple columns and without that it is like a spear dropping through a grid of beams. The ones just below it were not very strong and the hat truss was used to assist those columns. It did other structural things such as act as an end plate stiffener for the square tube facade. But when the hat truss was compromised the antenna was "on its own" and down it went. In destroying the center of the core it also caused the lateral beams in the core to pull at the perimeter of the core and that in turn caused weakening and separation from the floor system.

As a static structure the loads were engineered to be travel to the columns and then down to the foundation. As columns and lateral beams were compromised and then unloaded others say increased loads and this also could progress to a runaway overloading and failure scenario.

In any case the top section came apart and descended on to the upper part of the lower section. When it did some of the material "splashed" over the side and pushed the facade columns away. Some of the facade columns in the initial moments of the descent were buckled and sprung from the building leaving the floors with no out board support. Some of the facade was displaced and in descending the meeting facade columns then severed the connects to the floor system. This was a chaotic event and 80,000 tons of concrete, steel and heavy HVAC equipment came tumbling down. The floor upon which this material began to fall was quickly overloaded... at least parts of it were and then all of it was. As parts were overloaded because of the somewhat random nature of the collapsing floors and mass from above they collapsed onto the floor below them 17 floors of material came "raining down" in those first few seconds.

As an area of floor saw the load exceeding its yield strength it shattered. This could be concrete breaking, or truss chords snapping or beam seats shearing, or bolts and welds parting. But it took perhaps 6 - 10 floor masses to destroy an intact floor which was designed for 100 PSF.

The floors began to fall down/ collapse inside the the top of the lower section. Pretty soon large areas of floors were failing at once dropping and some dropped in huge sections forcing the air outward breaking the glass and the the flimsy shaft walls of the core which had the express elevators arrayed the length of the long side of the core along with HVAC shafts.

The mass now plunged down floor by floor as an avalanche slow at first but eventually reaching a speed of over 60 MPH The gathering mass pushed against the facade and it toppled over in huge sheets as the bolts between columns and spandrels were not designed for that sort of shear load. The stripped off facade panels rolled over and sailed to the ground broke apart on impact.

A similar avalanche destroyed the floors and many of the cross beams which supported them in the core. Like the collapsing floors outside the core, the collapsing floors inside the core raced down leaving many of the columns behind. Some still connected to each other by surviving lateral beams. But these columns were unstable and had inadequate lateral support - too tall and thin to stand on the own and with the chaotic collapse around them they were jostled and began to oscillate, sway and buckle - breaking at the weakest points - the connections between one 36' long column to the next. The core columns in the lower sections show no signs of burning, melting, cutting, or explosions. They fell apart like pick up sticks. Examine the debris photos.

None of the facade panels achieved more than 34mph as it fell away from the towers. Chandler traces something which he clocks at 70 mpg - a point on / leading a dust plume taken from across the Hudson River at Liberty Landing. We can't identify this as a facade panel or know the weight of the projectile. I'm sure pieces were sprung violently in the collapse and there were things within the building such as refrigerant in the HVAC system which surely exploded in the collapse and there were 12 mechanical floors in 4 separate heights in the building. The only identifiable facade panels are clocked at much lower speeds which is supports the idea that they fell off or we pushed off by the collapsing floors.

To understand the design of the floor system imagine four legs of a table, but the top is not ON the legs but rests on little support blocks on the side of the legs. If you put too much weight on the table top the top might buckle or the blocks would break of the top would shear at the blocks. But whatever happened to the top it would not damage the leg except to perhaps push it over of pull it in. The floors were not designed to carry 17 floor masses.

So the collapse was completely natural, but the initiation was likely engineered and it need only involve perhaps as few as 14 - 36 foot tall columns in the upper section. That is speculation. The gravitational collapse AFTER initiation is basic engineering and physics.

The observed spire columns were the strongest and were the ones which supported the floors outside the core. All the weaker core columns in the center of the core did not survive in the spire. This tells us that the collapse was not the result of destruction of the perimeter core columns. The initiation of collapse likely involved those columns above the strike zone. But below it the gravitational collapse destroyed the floors, stripped the support from almost all facade columns which feel away and the the spire remained but too tall and thin to stand without lateral support
Go to the top of the page
 
+Quote Post

3 Pages V  < 1 2 3
Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 




RSS Lo-Fi Version Time is now: 23rd July 2014 - 02:03 PM