Quick Question About The Fireproofing On The WTC Outer Columns

[WildCat]

Just came across a pic on this page taken during construction. Is the yellow material fireproofing or something else?

 

[Gravy]

Tarps to keep the weather out.

 

[AZCat]

Just came across a pic on this page taken during construction. Is the yellow material fireproofing or something else?

Tarps to hide the use of C4-coated rebar from prying eyes.

 

[WildCat]

Tarps to keep the weather out.

Ah, yes that is what it is! Found a better pic here.

nvm

 

[Brainster]

I don't think there was any fireproofing on the outer columns, only the inner ones and of course the steel trusses supporting the weight of each floor above.

 

[WildCat]

I don't think there was any fireproofing on the outer columns, only the inner ones and of course the steel trusses supporting the weight of each floor above.

Yeah, it looks like they just put the aluminum cladding directly on the columns.

Maybe the location of the outer columns means that heat can't build up enough around them for it to be a concern?

 

[DGM]

I don't think there was any fireproofing on the outer columns, only the inner ones and of course the steel trusses supporting the weight of each floor above.

The exterior columns were insulated with a combination of plaster board and blaze-shield. I don't have time to look up the reference now but this is stated in the NIST report.

 

[Gravy]

I don't think there was any fireproofing on the outer columns, only the inner ones and of course the steel trusses supporting the weight of each floor above.

Yes, the exterior columns were covered with SFRM beneath the aluminum cladding (this also helped reduce thermal expansion from the sun). On the interior they were covered with SFRM and gypsum wallboard.

Note the rating on the trusses: 1/2" = 3 hours? Not quite.

 

[Alferd_Packer]

Ah, yes that is what it is! Found a better pic here.

nvm

Did you check out the zoom in of that photo with the contractor's name and the date?

 

[leftysergeant]

I just picked up on another intertesting feature of the cap on the building. Are those white box-like structures inside the framing concrete? Part of the sway damping mechanism? They look heavy. Since sway-damping involves a free-floating weigh, AFAIK, would not any imbalance in the way it was supported shift the weight permanently to one side, further stressing the core columns?

 

[Gravy]

I just picked up on another intertesting feature of the cap on the building. Are those white box-like structures inside the framing concrete? Part of the sway damping mechanism? They look heavy. Since sway-damping involves a free-floating weigh, AFAIK, would not any imbalance in the way it was supported shift the weight permanently to one side, further stressing the core columns?

The towers didn't use tuned mass dampers. They employed many small viscoelastic (rubbery) dampers that connected the lower chords of the floor trusses to the exterior columns, to act as shock absorbers. Worked well.

 

[Thunder]

cant it just be called "thermal insulation"? steel does not burn.

 

[leftysergeant]

Okay. So what might those concrete-looking structures be? They do look heavy.

 

[Gravy]

Okay. So what might those concrete-looking structures be? They do look heavy.

In which photo?

 

[Unfit4Command]

I don't think there was any fireproofing on the outer columns, only the inner ones and of course the steel trusses supporting the weight of each floor above.

A lot of the fire protective insulation on the outer columns in the impact areas was removed by the planes. It's easy to see some intact insulation on some of the columns in the photographs below. I'm not 100% sure what "weatherproofing" is.

​

 

[A W Smith]

I just picked up on another intertesting feature of the cap on the building. Are those white box-like structures inside the framing concrete? Part of the sway damping mechanism? They look heavy. Since sway-damping involves a free-floating weigh, AFAIK, would not any imbalance in the way it was supported shift the weight permanently to one side, further stressing the core columns?

No but the Citigroup Center uses a huge tuned mass damper

As well as Trump Tower, Random House tower, and the Bloomberg tower, all in NYC,

 

[Gravy]

The weatherproofing kept water from penetrating at the cladding seams.

 

[Gravy]

No but the Citigroup Center uses a huge tuned mass damper

As well as Trump Tower, Random House tower, and the Bloomberg tower, all in NYC,

The coolest one is in Taipei 101!

Edit: sorry, didn't see that you also linked to wikipedia.

 

[StoneRook]

Gravy, here is a question to you.

I sort of remembering reading in one of the reports that the interior side of the outer columns had material on them that help transfer the interior temperature to the outer side to help it maintain some sort of thermal balance to the steel.

At the time, I thought that this property would transfer alot more of the fire heat than anticipated in the original construction.

I have to dig up where I read that, but perhaps you can shed some light on this for me?

(to much data to take in sometimes :>)

 

[Gravy]

Gravy, here is a question to you.

I sort of remembering reading in one of the reports that the interior side of the outer columns had material on them that help transfer the interior temperature to the outer side to help it maintain some sort of thermal balance to the steel.

At the time, I thought that this property would transfer alot more of the fire heat than anticipated in the original construction.

I have to dig up where I read that, but perhaps you can shed some light on this for me?

(to much data to take in sometimes :>)

Edit: did a little checking. Yes, a higher thermal conductivity inner panel appears to have been used.

"For the inside face of the columns, Alcoa proposed to apply a high "k" value (thermal conductivity) material. This application would provide thermal protection while permitting heat migration from the room air to the column steel under service conditions."

Read more about this at NIST NCSTAR 1-6A, p. 16

Note that there's an error in the labeling above. "Aluminum window" should say "insulation" or somesuch.