Did Bush watch plane hit the first tower ?

[defaultdotxbe]

Please explain the exact difference between a controlled demolition and what happened to the towers other than securing the area ?

dozens of other buildings damaged (6 destroyed or damaged beyond repair) 16+acre debris field, raging fires burning for months, 8 month clean up operation...

 

[Cl1mh4224rd]

Please explain the exact difference between a controlled demolition and what happened to the towers other than securing the area ?

Seriously? You can't tell the difference between the collapses of WTC1 and WTC2 and that of a controlled demolition? Ouch.

A building subjected to controlled demolition collapses inward, not outward, as the Twin Towers did.

 

[Non Believer]

As to the demolition question- you can only have a controlled demolition when there are no buildings located within a certain range of the building to be demolished. where is evidence that the spreading of the debris out radially from the towers was greater than average for a building of its size. Certainly the collapse into the footrint is as good as could be expexcted from a regular controlled demolition.
As for your point Horatius, you are aware that NIST rejected the pancake theory correct? And yes you are right demolitions are usually done from the bottom as in the case of 7. But my point is that if they will fall so neatly from just releasing the floor trusses near the top why are they bothering with these fancier type demolitions.

 

[Non Believer]

Cl- The cloud of dust blows outward wherever the demolition charges are placed.

 

[uk_dave]

As for your point Horatius, you are aware that NIST rejected the pancake theory correct? And yes you are right demolitions are usually done from the bottom as in the case of 7. But my point is that if they will fall so neatly from just releasing the floor trusses near the top why are they bothering with these fancier type demolitions.

Only as far as the collapse initiation.

There were always two possible events which initiated the collapse:

1. Floor assemblies letting go of the columns and falling down through the building

or

2. Columns failing through being pulled by the sagging floor assemblies

Evidence compiled by NIST indicates that the latter was the culprit.

After initiation the collapse itself is too chaotic to be accurately modelled to the degree that NIST would have to in order to provide a blow by blow account of how the structure collapsed. But since that wasn't their brief anyway and it served no useful purpose in establishing whether any building codes required changing, they did not carry out such a detailed model.

But an educated knowledge of framed structures informs any architect or structural engineer of the processes which occured durng the progressive collapse.

 

[Architect]

As for Architect TFA- you tell me I don't have a good argument, I don't think you even understand my argument. So here is the main argument - Remaining building structures below areas of damage still have their structural integrity intact, and offer resistance to the collapsing portion above. It seems likely that this resistance to collapse is measurable. We can estimate the weight of the top 20 or so floors, and measure their likely acceleration. So where are those numbers?

You claimed that asserting a building that has suffered a partial initial collapse of a floor would automatically lead to global collapse. As in your quote-

Progressive collapse under the imposed loadings is exactly what we would expect. Are you claiming that the lower structure should have resisted the loadings? I should warn you that this would be quite at odds with normal structural expectations.

I should warn you that is exactly what happened in one of the major high rise fires in Spain. a portion of the building collapsed, but the floors below held. Why does it make any sense that buildings that were built to withstand huge live loads (estimated to be 2000 times in the perimeter columns) would have no chance to withstand the collapse of the portion of the building above? I asked before to show evidence of your quote above, and you haven't. Instead you just repeat obvious understandings about the construction of the building, and then claim I am somehow ignorant of all this. Get it together mate.

1. Ronan Point.

2. Windsor did not have a completely steel frame, nor did it have the hat trusses providing an element of support.

3. Failure of the structure under the additional shear loadings is exactly what we would expect. Numbers are un-necessary.

 

[Non Believer]

Well that seems pretty fair UK. Yes, You cannot have it both ways. The floors cannot break away at the joints with the columns and simultaneously be pulling the columns laterally. There is an obvious tradeoff in these two forces There is clearly enough lateral support in the lattice form of the exterior columns to not collapse with this pancaking (joint breaking theory). Additionally the interior core would have remained standing as well. Did the lateral bracing of the floor trusses to the exterior give the interior columns additional strength? Yes. Would the interior columns have remained standing with a pancake type collapse? Yes as well. They would have been weakened but would have remained standing.
So in a sense, I believe we are closer to a similar understanding of these events U.K (and NIST's explanation of them). I think we can go on to argue about the calculations for initial collapse, but I would like too try to close the book on the question of global collapse.
I know we cannot completely distinguish between initial collpse and global. Whatever the conditions of initial collapse are, they will dictate the calculation for global collapse. For example the initial collapse on the 94th floor may have been a simultanoues at all points in the structure on the floor (which seems to be the needed assumption considering the symmetry of the collapse), or it may have been a portion of the floor. there is that floor term again. Can we consider the term floor to mean the entire structure at a certain level, and refer to the floor trusses as such.
Anyway, what it comes down too is that you claim that global collapse is a given, but cannot really be modeled due to the uncertainty and chaos. Of course I have a problem with both of these positions. Maybe it is commonly understood that any type of major initial collapse will automatically bring down the rest of steel framed buildings, but show me the pre 9-11 statements in this regard then. As for the too chaotic part, i will give you that it may be complicated. And it may be that we can never model it in a complete blow by blow manner, but too be able to simply say that instability spread throught the building is so ambiguous it defies credibility.

 

[Gravy]

So what you have said to contradict me Gravy. I didn't say a floor or two, I said twenty. The buildings were built to support these floors initially (or did you forget that). Yes there is going to be additionally force with collapse, but the structure was built to withstand additional force.

No, the Twin Towers were not build to survive the tops of the buildings falling through the bottoms. You keep talking about floors. We're talking about the entire top of the building.

As for your Windsor example, what is that supposed to prove?

That you have no idea what you're talking about, as I said.

it looks like several of the floors collapsed, but then stopped.

And the core, NonBeliever? Did that collapse? And the construction below the fire-affected area, how does it differ from that above?

So it actually helps my point, that initial collaspse does not lead automatically to global collapse.

No, it shows that you need to read for comprehension.

So I am going to repeat if you guys want to claim that I don't know what I am talking about, please refer to the exact quote I have made and how it is mistaken.

See above.

 

[Cl1mh4224rd]

Cl- The cloud of dust blows outward wherever the demolition charges are placed.

Dust, yes, an a bit of debris. None of this is in any way similar to the large amounts of debris we all saw falling away from the towers.

Buildings subjected to controlled demolition fall as "cleanly" as they do because of the amount of work that goes into the "controlled" part of the demolition. The tower collapses were a mess...

Besides, when was the last time you saw a building demolished from the top down?

 

[Non Believer]

Gravy- I think were done here. You don't seem to offer anything other than you think I am stupid. As I have asked please spell out how so ? The difference between the floors below the damage and those above is that those below were structurally intact. Thefore we are not prone to guesswork as to the amount of damage done (and therfore their structural integrity) as in the damaged floors.
Do you think if just the top floor collapsed the whole building would have collapsed? Or maybe if just one joint collapsed the whole building was bound to go. Ya I'm being sarcastic, but at what floor did it become obvious that the floors below couldn't handle a collapse There has got to be some actual science here.

 

[Bell]

Gravy- I think were done here. You don't seem to offer anything other than you think I am stupid. As I have asked please spell out how so ? The difference between the floors below the damage and those above is that those below were structurally intact. Thefore we are not prone to guesswork as to the amount of damage done (and therfore their structural integrity) as in the damaged floors.
Do you think if just the top floor collapsed the whole building would have collapsed? Or maybe if just one joint collapsed the whole building was bound to go. Ya I'm being sarcastic, but at what floor did it become obvious that the floors below couldn't handle a collapse There has got to be some actual science here.

We are not talking about 1 floor or 1 joint. We are talking about +/- 30 floors of building for WTC2 and +/- 15 floors of building for WTC1 falling down on the rest of the buildings.

 

[Non Believer]

As I asked Bell, at what point does the damage above become unsupportable for the structure below? One floor, two. Five elephants put in one of the offices after dinner. Give me something.

Cl-To answer your question. Yes the one and only time I saw it was Sept 11. Here is one for you - When was the last time you saw a steel framed building collapse that wasn't from demolition

 

[Cl1mh4224rd]

Gravy- I think were done here. You don't seem to offer anything other than you think I am stupid. As I have asked please spell out how so ? The difference between the floors below the damage and those above is that those below were structurally intact.

No surprise, but Gravy's correct:

The building totalled 32 storeys, with 29 floors above ground and three below. A concrete core and concrete frame supported the first 16 floors. Above that was a central support system of concrete columns, supporting concrete floors with steel perimeter columns. An additional feature was the presence of two 'technical floors' - concrete floors designed to give the building more strength. One was just above the ground level and the other at the 17th floor.

[...]

The fire eventually finished 26 hours later, leaving a complete burn-out above the fifth floor. The steel-glass façade was completely destroyed, exposing the concrete perimeter columns. The steel columns above the 17th floor suffered complete collapse, partially coming to rest on the upper technical floor.

[...]

Preliminary findings suggest that a combination of the upper technical floor and the excellent passive fire resistance of the tower's concrete columns and core prevented total building collapse.

concretecentre.com/main.asp?page=1095

 

[babazaroni]

Do you think if just the top floor collapsed the whole building would have collapsed? Or maybe if just one joint collapsed the whole building was bound to go. Ya I'm being sarcastic, but at what floor did it become obvious that the floors below couldn't handle a collapse There has got to be some actual science here.

The outer columns buckled around the impact point. The hat truss will transfer the entire load the outer columns were supporting (including the outer columns themselves) to the core columns.

The damaged core cannot support this massive load and the dynamics associated with the transfer. And of course the individual floors below cannot as well.

 

[Cl1mh4224rd]

When was the last time you saw a steel framed building collapse that wasn't from demolition

news.bbc.co.uk/2/hi/uk_news/england/hereford/worcs/6105942.stm

[A spokesman for the fire service] added: "Intense heat buckled the steel girders holding the roof."

And this building didn't even suffer structural damage and likely had its fireproofing intact. Unless you want to argue that the British government demolished a toilet paper plant...

 

[Bell]

As I asked Bell, at what point does the damage above become unsupportable for the structure below? One floor, two. Five elephants put in one of the offices after dinner. Give me something.

I have no idea about numbers, and can't cite the NIST report from head, as some members can

But uk_dave touched upon this some posts up:

You don't understand that the floor assemblies are only designed to support their own dead load and the live load inposed upon them by normal office activities?

 

[Horatius]

As for your point Horatius, you are aware that NIST rejected the pancake theory correct? And yes you are right demolitions are usually done from the bottom as in the case of 7. But my point is that if they will fall so neatly from just releasing the floor trusses near the top why are they bothering with these fancier type demolitions.

Okay, I think you completely missed my point. My bad for assuming you knew how to read sarcasm. The collapse of the towers was different from a CD in that they caused enough damage to WTC7 to cause it to burn and collapse, similar to what others mentioned about other buildings. That doesn't (or at least, shouldn't) happen in a "controlled demolition". That's what the "Controlled" part means.

And even if you believe the collapse of WTC7 wasn't directly linked to the damage caused by the towers, will you admit the fires and other damage were so linked? Because even that much damage to WTC7 puts the lie to the CD hypothesis.

 

[Gravy]

As I asked Bell, at what point does the damage above become unsupportable for the structure below? One floor, two. Five elephants put in one of the offices after dinner. Give me something.

We on this forum may not know what the minimum would be, but we know that when an entire 12-story section (plus a 350-ton antenna) buckles, rotates, and collapses, that is sufficient for the collapse to progress. And we know that a 30-story section buckling, rotating, and collapsing, as below, is more than sufficient.

​

 

[Woody-]

To Woody- I went to your link. there is a lot of info there. Could you please just tell me where that quote comes from ?

They person that wrote the article interviewed Mark Loizeaux, what part of that do you not understand. Here is the full quote if your interested.

"First of all, you've got the obvious damage to the exterior frame from the airplane—if you count the number of external columns missing from the sides the planes hit, there are about two-thirds of the total. And the buildings are still standing, which is amazing—even with all those columns missing, the gravity loads have found alternate pathways. O.K., but you've got fires—jet-fuel fires, which the building is not designed for, and you've also got lots of paper in there. Now, paper cooks. A paper fire is like a coal-mine fire: it keeps burning as long as oxygen gets to it. And you're high in the building, up in the wind, plenty of oxygen. So you've got a hot fire. And you've got these floor trusses, made of fairly thin metal, and fire protection has been knocked off most of them by the impact. And you have all this open space—clear span from perimeter to core—with no columns or partition walls, so the airplane is going to skid right through that space to the core, which doesn't have any reinforced concrete in it, just sheetrock covering steel, and the fire is going to spread everywhere immediately, and no fire-protection systems are working—the sprinkler heads shorn off by the airplanes, the water pipes in the core are likely cut. So what's going to happen? Floor A is going to fall onto floor B, which falls onto floor C; the unsupported columns will buckle; and the weight of everything above the crash site falls onto what remains below—bringing loads of two thousand pounds per square foot, plus the force of the impact, onto floors designed to bear one hundred pounds per square foot. It has to fall."

To UK Dave- so what you are saying is that as long as you get some (or maybe one) of the floor trusses to collapse that will bring down the whole building because that that floor truss will fall on the one below (which cannot support it) and thus lead to global collapse. Makes it sound like it would be pretty damn easy to bring these puppies down then. Why do demolition teams go to such efforts to bring them down when just dropping a couple of floor trusses should do the trick.

Maybe because when the drop them on purpose the want to "control" where they fall. They dont want them damaging every other structure for several hundred feet around.

Please explain the exact difference between a controlled demolition and what happened to the towers other than securing the area ?

Your kidding aren't you? The big differences would be the damage or total destruction of WTC3, WTC4, WTC5, WTC6, WTC7, WFC3, WFC4, St. Nicholess Church, Bankers Trust building, Verizon Building, etc etc.

Cl- The cloud of dust blows outward wherever the demolition charges are placed.

The cloud of dust is generally not from the explosives, its from the falling structure expelling trapped air.

 

[Non Believer]

Cl- I'll start with you. you have got to be kidding if you think that taco stands roof collapsing is even in the ballpark. Maybe some of rolls of toilet paper stacked up kept the roof from coming down completely. O.K lets change it too when was the last time you saw a high rise steel framed building collapse completely that wasn't a demolition.
As to your point on windsor, why didn't the collapse spread laterally as you say happened in WTC.
Horatius- Do you really believe you could bring down the towers in a controlled demolition without damaging the nearby buildings. Good luck.