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WTCCS Spreadsheet Crush-Down Model

Analysis of airplane impacts, fires and collapse theories and examination of related evidence.

Re: WTCCS Spreadsheet Crush-Down Model

Postby OneWhiteEye on Fri Jul 10, 2009 7:13 pm

femr2 wrote:You've lost me there. I'll wait for your next segment, no pressure.

Keith Seffen mentions an effective residual capacity P* with a suggested value (early in the paper) of 0.03. So, given an FOS of 5 and determining capacity at a level by summing the loads above, multiply that figure by 0.03 times the distance dropped. I said Seffen-ish because that's not what he did, but the idea of 0.03 over the distance (same as full capacity times 3% of the distance) came from his paper. This enfolds elastic and plastic ranges along with an intrinsic reduction in capacity based on the notion of propagation of failure - in other words, it's a figure pulled out of my ass.

It's the lowest number that seems reasonable without something both-hands-waving-vigorously to make it lower.

The other E1 figure I used was simply 0.03*0.5*P + 0.07*P(y) where P(y) is the peak capacity determined as above, FOS*sumOfLoad(y). That's supposed to represent a linear elastic phase with max of P plus a constant plastic phase at P. The total displacement of 10% of story height for structural resistance is, to my vague lay understanding, quite generous under the circumstance. Naturally, the energy sink difference compared with your run to get arrest at 51 is proportionally less than the first method.

Taken together with inelastic collision losses, I didn't bother adding any more sinks - not that they don't exist or whatever, but more to keep it simple for a baseline of comparison to get a gross sense of the power dissipated by your model as a multiple of structural resistance. Notice I didn't say energy this time.

I could hang-out in the central core....YEP !

Haha, OK, you get the job! Can you imagine Bazant hogtied in a nearby building with a stick of dynamite in his mouth, dependent on the crush front to destroy a radio-timer-detonator on the first floor way below you - within 20 seconds of initiation? Survivor gets big monetary reward. Now that's a game show!

(Hey, just kidding, I'm really not that bloodthirsty - but some TV execs are so I kinda regret putting that out into the aethers, but not enough to erase it. Moderator, Moderator, come save me from my own tasteless bend)
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Re: WTCCS Spreadsheet Crush-Down Model

Postby femr2 on Fri Nov 20, 2009 7:41 pm

psikeyhackr wrote:But according to an engineering magazine from 1970 the heaviest exterior wall panel was 22 tons.

We must be very careful to ensure that we don't make too many assumptions.
Do you have a reference to the magazine article ?
We must know what KIND of wall panel it was. I think you said it was from floor 9, though now it's *the heaviest*. There are numerous wall panel configurations, especially towards the base, and around the mechanical floors.

So why isn't EVERYBODY demanding that the NIST tell us the weights and quantities of ALL TWELVE TYPES OF PANELS?

Because they are not listening. Why not ask them for the full WTC AnSys data while we're at it :wink:
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Re: WTCCS Spreadsheet Crush-Down Model

Postby femr2 on Sat Nov 21, 2009 12:18 am

psikeyhackr wrote:
femr2 wrote:We must be very careful to ensure that we don't make too many assumptions.
Do you have a reference to the magazine article ?
We must know what KIND of wall panel it was. I think you said it was from floor 9, though now it's *the heaviest*. There are numerous wall panel configurations, especially towards the base, and around the mechanical floors.


The largest contract for fabrication of structural steel is held by Pacific Car and Foundry Co., of Seattle. It is $21.79 million for 55,000 tons of steel for the towers' bearing wall panels from the ninth floor up.

In all there are 5,828 of these panels, each about 10 ft wide, 36 ft high, with the heaviest individual panel weighing about 22 tons. Each panel consists of three box columns, 14 in. square, made up of plate up to 3 in. thick and, connected by 54-in, deep spandrels.


Eng News Record

psik

Hmm.

I imagine it would be one of the lower mechanical floor region panels.

I'll have to think about how it may scale relative to others.

Thanks.
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