How 9/11 was done

[stateofgrace]

OK, I'll accept that for a moment... but why the collapse of the core into tiny peaces?

Huh?

So are you saying the cores collapsed after the rest of the building?

ps, I know the answer.

 

[9/11-investigator]

i could have sworn floor trusses and perimeter columns were built along with the core in 1969

That's true. Point?

not horizontal load, the core was not designed to bear any horizontal load at all

Less so than the outer columns, true. What does it have to do with the vertical implosions of the core at 911?

my pants dont weigh 500,000 tons

Although obesity is rampant in your part of the world I hope your legs are not either!

The reality is that all 47 core columns where sliced in 10 m long pieces. Had this not been the case then New York either had 2 Eiffel towers of its own or several buildings more destroyed by the tilted cores.

they were not sliced, they failed at the joints where the 30 foot sections were connected during contruction

OK. But why did they fail?

it would be physically impossible for the towers or the core to tilt completely over without collapsing

There was no tilting whatsoever. The towers collapsed into their own footprint. It is physically impossible for the core to implode. We are talking about 47 columns that were heavily interconnected by horizontal beams. It was a rigid structure that maybe could tilt but not implode. And certainly not by vertically falling floors and trusses; falling parallel to the core, not against it.

 

[Grizzly Bear]

OK, I'll accept that for a moment... but why the collapse of the core into tiny peaces?

Your question was already answered... to put it simply, the columns were erected in sections, and either bolted or welded together. The connections that hold the structure together are the limiting factors for the design allowables, and they're the most prone components to fail. There's hardly anything extraordinary about that...

 

[9/11-investigator]

The can only "fall over" a bit before they collapse under their own weight.

Why would the tower collapse under its own weight at an angle of 1, 2, 5, 10 degrees if it was able to withstand collapse in vertical position. What you probably mean is that the core would break halfway (fold).

Let's grant you that. Since the towers fell into their own footprint, according to you, we should have seen an upright core of 1300 feet, that would stand upright (after the 9 seconds it took for the rest to fall), then start to tilt and then at some point would break.

But that did not happen! The core collapsed with the rest of the building at the same speed.

No, that's how it was built. 10m lengths fit nicely on a truck, it would be kind of difficult to deliver a 1300 ft. column to the job site, don't you think?

Of course not. Did I say otherwise?

 

[9/11-investigator]

I know next to nothing about physics; I'll be the first to admit that.

Stay with the spinning wheel Sabrina!

 

[defaultdotxbe]

There was no tilting whatsoever. The towers collapsed into their own footprint. It is physically impossible for the core to implode. We are talking about 47 columns that were heavily interconnected by horizontal beams. It was a rigid structure that maybe could tilt but not implode. And certainly not by vertically falling floors and trusses; falling parallel to the core, not against it.

.
please dont tell me you are confusing the kangaroo cranes in the picture you posted as being part of the building

they were interconnected by the floor trusses, which was one of the first parts to fail

Why would the tower collapse under its own weight at an angle of 1, 2, 5, 10 degrees if it was able to withstand collapse in vertical position. What you probably mean is that the core would break halfway (fold).

.
as i said before, if you dont understand this you should really educate yourelf

IIRC i read that the towers would collapse if they tilted more than 5-10 degrees off vertical

 

[9/11-investigator]

You brought it up. And now you want to drop it??

Fine. The core is not stable as a freestanding structure. Again, it requires the presence of the rest of the structure to remain standing; the core handled the gravity load and was braced against the perimeter structure. That's simply a fact of the Twin Towers construction; some buildings are built with freestanding cores, the Towers weren't. What's so hard to understand about that?

That's all correct. But if the core does not collapse while carrying half the weight of the WTC for 30 years than it should not collapse if it does not carry any weight whatsoever. Tilting maybe, but not collapse.

 

[Grizzly Bear]

Less so than the outer columns, true.

The exterior columns were design specifically to contribute to the tower's lateral stability for wind loads, as well as providing the horizontal bracing of the core via the floor trusses. Are you assuming that they are not?

OK. But why did they fail?

Loss of lateral bracing. This is an rather easy principal to demonstrate...

Essentially the longer the unbraced length of the column, the less stability it has, and thus the smaller the loads it can carry...

 

[Baylor]

The core collapsed with the rest of the building at the same speed.

No it didn't.

 

[9/11-investigator]

Your question was already answered... to put it simply, the columns were erected in sections, and either bolted or welded together. The connections that hold the structure together are the limiting factors for the design allowables, and they're the most prone components to fail. There's hardly anything extraordinary about that...

Maybe the connection points are the weakest link, maybe not (it depends on how you design it or how you weld). But that does not explain why the rigid core (due to horizontal beams) should fail.

 

[9/11-investigator]

No it didn't.

Sigh. That's not the core. Buy glasses. That's a single column of the once 47 columns core, where the detonators failed to do their job.

 

[stateofgrace]

That's all correct. But if the core does not collapse while carrying half the weight of the WTC for 30 years than it should not collapse if it does not carry any weight whatsoever. Tilting maybe, but not collapse.

Investigator,You have not answered a single post I put to you.

Huh?

So are you saying the cores collapsed after the rest of the building?

ps, I know the answer.

Yes lets.

When you are ready explain what role the core played in supporting the floors and how the floors were braced between the inner core and the external columns.Could you please explain fully what happens when the bracing between the core and external coulmns is violently removed?

When you are ready.

I had to stop after three laughing dogs.

Bracing,911, explain its role in the construction of WTC 1 and 2.How did the floors brace the core to the external columns?

On you go.

My point,dear boy, is you have absolutly no idea how these towers were built, how the were held together and why they collapsed.

Bracing, explain it, fully, and what part the floor trusses played in bracing the towers together, please include in your explanation your understanding of the tube in tube design of the towers.

On you go

You do understand what bracing is, right?

When you are ready, investigator.

 

[9/11-investigator]

The exterior columns were design specifically to contribute to the tower's lateral stability for wind loads, as well as providing the horizontal bracing of the core via the floor trusses. Are you assuming that they are not?

No, this is correct.

Loss of lateral bracing. This is an rather easy principal to demonstrate...

[qimg]http://img296.imageshack.us/img296/1899/shortlo0.png[/qimg]
[qimg]http://img367.imageshack.us/img367/7023/longmv9.png[/qimg]

Essentially the longer the unbraced length of the column, the less stability it has, and thus the smaller the loads it can carry...

Your comparison is wrong. Where is the finger equivalent during 911? Was it Gods invisible finger? The core was not a lemonade reed. The Eiffel tower is more than 300 m high:

http://middlezonemusings.com/wp-content/uploads/2007/03/eiffel-tower.jpg

No trusses and outer ring of columns necessary to keep the upper half of the tower upright. What's the difference between this and the core of the twin towers?

 

[9/11-investigator]

Investigator,You have not answered a single post I put to you.

When you are ready, investigator.

When there are a lot of posters to be answered I choose to ignore the hillbillies, my dear boy.

 

[dtugg]

How did the collapses initiate according to NIST? Answer that.

 

[Grizzly Bear]

No, this is correct.

Incorrect; Case studies provide the necessary design parameters

Data attributed to the above linked source:
Exterior perimeter columns: The wall functioned like a square tube, providing resistance to the combined effect of lateral wind and gravity loads.
Core: The columns mainly carried the gravity load.
Floor trusses: The floors supported the gravity loads and provided lateral stability to the external walls.

Your comparison is wrong. Where is the finger equivalent during 911? Was it Gods invisible finger?

It's not intended to be a one on one comparison with the trade centers. It however demonstrates the basic principal as it concerns the core coulmns' design more than sufficiently. A point which you do not appear to understand. The same concept I applied in that little experiment, is applied at the macroscopic scale in the design phase. As "playful" as the photos may convey, the concept has very serious applications in engineering.

 

[9/11-investigator]

Now that I come to think of it, the existence of the spire proves my point. A single column is able to stand upright for a moment, although it is weakened by cuts from explosives and finally folds. If the columns would not have been blown to pieces and horizontally interconnected they were even more able to stay upright (just like the Eiffel tower).

 

[9/11-investigator]

How did the collapses initiate according to NIST? Answer that.

No I will not, because you will never be sure if I googled it up.

 

[stateofgrace]

When there are a lot of posters to be answered I choose to ignore the hillbillies, my dear boy.

Really?

So you are no going to explain how the floors braced the core to the external columns?

Or are you going to ignore me, pretend I am unworthy of your attention and continue to pretend you have the foggiest idea of what you are talking about?

BTW, this is public forum everybody can read what you are posting.

Again, please explain how the core was braced to the external columns.

 

[9/11-investigator]

It's not intended to be a one on one comparison with the trade centers. It however demonstrates the basic principal as it concerns the core coulmns' design more than sufficiently. A point which you do not appear to understand. The same concept I applied in that little experiment, is applied at the macroscopic scale in the design phase. As "playful" as the photos may convey, the concept has very serious applications in engineering.

Explain to me why the upper half of the Eiffel tower does not collapse without protecting trusses and surrounding outer columns.