29 Structural & Civil Engineers Cite Evidence for Controlled Explosive Demolition

[Newtons Bit]

No, you were vague.
That's kinda like one hand clapping, it can't be. If the columns were only connected on one side, then there would be sets of two adjacent columns tied together but not tied to adjacent sets all the way arround the building. That boat don't float. Do you know what a moment frame is?

Exterior columns normal to the east, north and south face of the building were laterally unbraced: they were disconnected from the diaphragm. The exterior columns on the west face were still connected to the diaphragm. Geez, there's even a picture and everything.

Edit: and for the record "LATERALLY" refers to the out-of-plane direction or weak-axis of the exterior moment frames. The frames were still connected together, but had become completely disconnected from the floor diaphragm on the east face, and the east half of the north and south frames were disconnected.

 

[H'ethetheth]

My bad. Will you own up to yours?

That's impossible.

Okay good. I appreciate that.

Then I'll say that it is not impossible. I will grant that it is incorrect as it is literally formulated there without mentioning that it's about the sides of the building, not the sides of each individual column. However, in the light of the quote from p 588. it should be clear that this statement was always about walls as a whole.
There is a clear difference in buckling strength between these two scenarios, but the difference disappears rapidly as soon as something starts to buckle.
That's why I mention the 12 oz soda can. It's strong enough to hold a man, but as soon as you introduce an asymmetry in the loading, the load bearing capacity decreases dramatically and you basically fall to the ground.
Columns in lightweight buildings like the WTC highrises are just like that. I'm no building guy, so I don't know the safety factors used in the field, but I'd be surprised if the columns were built to support more than twice their every-day load. In other words, these buildings, like aircraft, are designed to operate relatively close to their limit load.

Removing lateral support from the perimeter in a situation where there is already a huge hole in it and big asymmetric loads creates a scenario where once one column buckles, the rest goes too.
And I have to say, accelerating at as good as g seemed unlikely to me too. I think everybody can see that in this thread. But if I want to know why NIST engineers don't think that's weird, I check if it makes sense using a ballpark estimate. If my estimate is in the ballpark, I'm satisfied.

 

[Christopher7]

Exterior columns normal to the east, north and south face of the building were laterally unbraced: they were disconnected from the diaphragm.

Where does it say that?
Here's what it says:
"the intact floor framing pulled the exterior columns inward . . . . and the floors pulled on the exterior columns" [588]

The exterior columns on the west face were still connected to the diaphragm. Geez, there's even a picture and everything.

The slabs are removed in the graphic.

 

[Newtons Bit]

And I have to say, accelerating at as good as g seemed unlikely to me too. I think everybody can see that in this thread. But if I want to know why NIST engineers don't think that's weird, I check if it makes sense using a ballpark estimate. If my estimate is in the ballpark, I'm satisfied.

It makes perfect sense. Read the damn report.

From Fig 3-15


Stage 1 is 8 STORIES of columns buckling and losing all of their strength. Stage 2 is the rest of the building falling those 8 floors. There's nothing left to support the upper portions of the building in those 8 stories so what happens? The whole building falls 8 stories at roughly g. Why is this a big question?

Hell, it's all explained in the report on NCSTAR1A pg. 45. READ IT.

 

[Newtons Bit]

Where does it say that?
Here's what it says:
"the intact floor framing pulled the exterior columns inward . . . . and the floors pulled on the exterior columns" [588]
The slabs are removed in the graphic.

The WEST face was pulled in by the floor diaphragm. You can't read either, can you? Or apparently look at pictures other than pretty 3d ones.

 

[beachnut]

It makes perfect sense. Read the damn report.

From Fig 3-15


Stage 1 is 8 STORIES of columns buckling and losing all of their strength. Stage 2 is the rest of the building falling those 8 floors. There's nothing left to support the upper portions of the building in those 8 stories so what happens? The whole building falls 8 stories at roughly g. Why is this a big question?

Hell, it's all explained in the report on NCSTAR1A pg. 45. READ IT.

You explained it clearly. Anyone one who persists at making this an issue cannot learn.

 

[H'ethetheth]

It makes perfect sense. Read the damn report.

From Fig 3-15
[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_163294a45444493da1.gif[/qimg]

Stage 1 is 8 STORIES of columns buckling and losing all of their strength. Stage 2 is the rest of the building falling those 8 floors. There's nothing left to support the upper portions of the building in those 8 stories so what happens? The whole building falls 8 stories at roughly g. Why is this a big question?

Hell, it's all explained in the report on NCSTAR1A pg. 45. READ IT.

I'm not sure why your panties just went where they went, but over the last few days I've been doing exactly what you just told me to do.

I last stopped participating in this forum before the WTC7 report was out, at least I believe, and I hadn't heard this claim before.
So, as you can see from my contributions to this thread, I read some of the report, wondered a little, did my estimate and when I had, I saw that it's entirely possible and that it makes perfect sense that this freefall phase should last for 8 storeys.

You'll find no argument here.

ETA: But, Newton's bit, as we're talking anyway. You can probably tell me what kinds of safety factors are usual in structural engineering. I mean design load vs. limit load.
Just curious.

 

[Christopher7]

Okay good. I appreciate that.

all perimeter columns were laterally unsupported on three out of four sides.

Then I'll say that it is not impossible. I will grant that it is incorrect as it is literally formulated there without mentioning that it's about the sides of the building, not the sides of each individual column. However, in the light of the quote from p 588. it should be clear that this statement was always about walls as a whole.
There is a clear difference in buckling strength between these two scenarios, but the difference disappears rapidly as soon as something starts to buckle.
That's why I mention the 12 oz soda can. It's strong enough to hold a man, but as soon as you introduce an asymmetry in the loading, the load bearing capacity decreases dramatically and you basically fall to the ground.
Columns in lightweight buildings like the WTC highrises are just like that. I'm no building guy, so I don't know the safety factors used in the field, but I'd be surprised if the columns were built to support more than twice their every-day load. In other words, these buildings, like aircraft, are designed to operate relatively close to their limit load.

Not so. WTC 7 design was described as "robust" made to carry several times its designed load. Not that it matters because the added weight of the core pulling down exceed that anyway.

Removing lateral support from the perimeter in a situation where there is already a huge hole in it and big asymmetric loads creates a scenario where once one column buckles, the rest goes too.

The hole had little to do with the collapse. The moment frames redistributed the loads. [NIST L pg 36] WTC 7 would have collapsed without debris damage. [Tech beat 11-20-08]

And I have to say, accelerating at as good as g seemed unlikely to me too. I think everybody can see that in this thread. But if I want to know why NIST engineers don't think that's weird, I check if it makes sense using a ballpark estimate. If my estimate is in the ballpark, I'm satisfied.

Ballpark is OK? No,no. Free fall acceleration can only happen in air, there can be no resistence. Buckling columns as shown in the graphic still give some resistance.

 

[FineWine]

Not so. WTC 7 design was described as "robust" made to carry several times its designed load. Not that it matters because the added weight of the core pulling down exceed that anyway.

The hole had little to do with the collapse. The moment frames redistributed the loads. [NIST L pg 36] WTC 7 would have collapsed without debris damage. [Tech beat 11-20-08]

Ballpark is OK? No,no. Free fall acceleration can only happen in air, there can be no resistence. Buckling columns as shown in the graphic still give some resistance.

Why do you persist in arguing with engineers? You don't know anything about the subject and refuse to learn.

 

[Christopher7]

Why do you persist in arguing with engineers? You don't know anything about the subject and refuse to learn.

Grow up and cut the personal attacks/appeal to unverified authority. This is not rocket surgery.

Free fall acceleration can only occur in air! capish?

 

[FineWine]

Grow up and cut the personal attacks/appeal to unverified authority. This is not rocket surgery.

Yes, indeed, rocket SURGERY. Well put!

You are a fraud. Real engineers have explained the aspects of the collapse of WTC 7 that you insist on distorting through misreading and cherry-picking. You are impervious to correction. We get the idea that you know nothing about engineering or physics, and you are incapable of processing information provided by qualified professionals. You have received detailed responses to your garbled accusations (of what?) and you've hand-waved them away. You bring nothing to the table. Yes, grow up.

 

[twinstead]

This is why you will forever be relegated to arguing on internet forums, Chris. You've got nothing, and you're arguing with people who do. I hope you don't wonder why the "trials" haven't started yet.

 

[Newtons Bit]

ETA: But, Newton's bit, as we're talking anyway. You can probably tell me what kinds of safety factors are usual in structural engineering. I mean design load vs. limit load.
Just curious.

It's impossible quantify on a building that you don't have all the information for, but I'll give you a break down.

Typical modern steel design (and what NIST used to check WTC 1&2 to ensure it met, or was close, to modern codes) is called Load Resistance Factored Design (LRFD). LRFD uses a maximum expected live load (and wind and earthquake and snow, etc) combined with actual dead loads. For live loads, the designer will reduce this live load based on the tributary area of the supporting members: a small floor beam or joist will likely be designed for the full effect, a girder 75% and a column 50% of the design live load. The actual in service live-load will roughly be 25% of the maximum expected live load.

The designer will take these loads and combine them with aptly named "load combinations" from ASCE7 and ensure these values are greater than the capacities of the steel. A couple of typical strength load combinations would be:

(i) 1.4 * (dead load)
(ii) 1.2 * (dead load) + 1.6 * (live load)

There is then a factor applied to the capacities of each member based on the failure mode being analyzed (0.9 for compression or tension, 0.75 for shear). These capacities use the ASTM minimum yield (or rupture) stress of the steel. The mills will always supply material with higher yield strength, sometimes significantly, sometimes not.

So the actual "factor of safety" with load combination (i), assuming that the dead load and reduced live load are the same (which will be very roughly correct for a building like WTC 7), assuming that the yield stress is ASTM spec, assuming that the original design capacity of the member is equal to the demand, the factor of safety will be be 1.4/0.9 = 1.55.

When you include the fact that the in-service live load is roughly half the reduced live load, the factor of safety becomes 2.2.

When you start including how the other items increase the "factor of safety", it's very likely 3.0.

This only applies to gravity load combinations in a gravity system. The lateral system will have higher "factors of safety" vs. gravity.

 

[Christopher7]

Yes, indeed, rocket SURGERY. Well put!

You are a fraud. Real engineers have explained the aspects of the collapse of WTC 7 that you insist on distorting through misreading and cherry-picking.

Cherry-picking is a denier term to infer that the facts presented are invalid. Such is not the case.

Free fall acceleration can only occur in air. Deal with that fact and cut the denial double talk. You are not engaging in the debate, you are engaging in personal attacks.

 

[H'ethetheth]

Not so. WTC 7 design was described as "robust" made to carry several times its designed load. Not that it matters because the added weight of the core pulling down exceed that anyway.

I'm sorry to say, but I won't take that from you. I'll need some source for that.

The hole had little to do with the collapse. The moment frames redistributed the loads. [NIST L pg 36] WTC 7 would have collapsed without debris damage. [Tech beat 11-20-08]

Sure. I'm not disputing that. But I am sure that it would have been less likely for the building to collapse at freefall over 8 floors. A hole like that is a perfect way to initiate buckling. Have you stood on an empty soda can already?

Ballpark is OK? No,no. Free fall acceleration can only happen in air, there can be no resistence. Buckling columns as shown in the graphic still give some resistance.

Sigh... that would depend on how big you make your ballpark, now wouldn't it? I would have been satisfied with an opposing (i.e. retarding) force of less than 2% of the design load bearing capacity.
This is because in my (admittedly second-hand) experience of extrapolating motion data from high-speed camera footage shot explicitly for that purpose, it is an achievement if you can determine positions with an accuracy greater than +/-1%. Differentiating numerical data like that inherently increases the errors you make in the position data.

So I try to think of a simple model that can tell me whether it is remotely possible, and what do you know: I find that it is entirely possible to weaken a structure so much that it provides no noticeable resistance to collapse.

So yes, ballpark is okay. The difficult part is finding the right ballpark.

 

[FineWine]

Cherry-picking is a denier term to infer that the facts presented are invalid. Such is not the case.

Free fall acceleration can only occur in air. Deal with that fact and cut the denial double talk. You are not engaging in the debate, you are engaging in personal attacks.

There is no debate. There is an agenda-driven fraud pretending to argue about a subject he doesn't understand. You have been told why your free-fall claim is nonsense. Get over it.

See post #604.

 

[Christopher7]

It's impossible quantify on a building that you don't have all the information for, but I'll give you a break down.

Free fall acceleration was verified by NIST. All your calculations cannot erase the fact that free fall can only happen in air. Do you understand that simple fact?

 

[Christopher7]

There is no debate. There is an agenda-driven fraud pretending to argue about a subject he doesn't understand. You have been told why your free-fall claim is nonsense. Get over it.

Free fall nonsense?

Get serious.

Are you saying free fall did not occur?

Do you think NIST lied about it?

 

[FineWine]

Free fall acceleration was verified by NIST. All your calculations cannot erase the fact that free fall can only happen in air. Do you understand that simple fact?

You don't understand anything that is explained to you.

See post #604.

 

[H'ethetheth]

It's impossible quantify on a building that you don't have all the information for, but I'll give you a break down.

...snipped for brevity...

Nice, thanks!