Importance of UPS in South Tower

[pgimeno]

I've seen some recent discussion relative to the catenary forces that pulled the perimeter columns in WTC 2. I was wondering if this has been taking into account:

http://undicisettembre.blogspot.com/2007/06/ups-on-81st-floor-of-wtc2.html

I think NIST didn't consider that factor directly, as the references to the UPS system reduced merely to stating that it existed and caused the tenants to reinforce the floors.

Could that extra weight have a significant role in the pulling of the perimeter columns?

 

[BCR]

So are you saying that UPS delivered the package the bomb in it?

 

[PB2007]

deleted

 

[Dave Rogers]

I think NIST didn't consider that factor directly, as the references to the UPS system reduced merely to stating that it existed and caused the tenants to reinforce the floors.

It appears from Henry's website that NIST didn't consider it directly because they didn't have any documentation of the strengthening applied or the loads present.

Could that extra weight have a significant role in the pulling of the perimeter columns?

Could have, but it appears that the extra weight was applied mostly in the two-way trussed corner section, where any catenary action would have primarily caused a lateral deflection of the one-way trusses. I would expect it to have less effect on the perimeter columns than additional weight near the mid-point of a floor side.

Dave

 

[jaydeehess]

It appears from Henry's website that NIST didn't consider it directly because they didn't have any documentation of the strengthening applied or the loads present.



Could have, but it appears that the extra weight was applied mostly in the two-way trussed corner section, where any catenary action would have primarily caused a lateral deflection of the one-way trusses. I would expect it to have less effect on the perimeter columns than additional weight near the mid-point of a floor side.

Dave

Interesting read.
The TV company I work for has two medium sized UPS units. One is 750VA the other 1500 VA. The former, with the additional optional battery pack weighs 600 pounds. The other is approx double that. These can keep our TV station and the cable TV head end (including a dozen computer servers) running for about one hour.
The weight of these units is the equivalent of nine 200 pound men but they do not utilise the battery type shown in the article. They use 12V batteries that resemble the ones found in automobiles.

On the other hand I used to work for Transport Canada and we replaced the old RUPU (Rotary Uninterruptible Power Supply), which was a large electric motor that turned a heavy flywheel and an AC generator. the AC generator supplied the radar equipment. The flywheel would keep the generator turning, in the event of a power failure, long enough for the diesel to start up and supply current to the electric motor (almost perfect isolation from line spikes and surges). This RUPU was replaced with a battery bank of the type shown in the article. IIRC 72 batteries were needed to run the radar long enough for a diesel genset to kick in. There was another bank of 24 of this type that supplied back up for the radio equipment.

 

[MG1962]

Even if the reinforcing of the flooring played no part in the collapse. At least we have a good alternate answer to that material flow. The NIST always said their answer was an educated guess.

Great peice of research

 

[BigAl]

Interesting read.
The TV company I work for has two medium sized UPS units. One is 750VA the other 1500 VA. The former, with the additional optional battery pack weighs 600 pounds. The other is approx double that. These can keep our TV station and the cable TV head end (including a dozen computer servers) running for about one hour.
The weight of these units is the equivalent of nine 200 pound men but they do not utilise the battery type shown in the article. They use 12V batteries that resemble the ones found in automobiles.

I ran a data center with a 60kva load, the UPS was good for 20 minutes. The battery room looked like something out of a diesel-electric submarine. I couldn't imagine how many tons of lead we had in there.

It would be easy to imagine a comparable data center and UPS in the Fuji Bank facility (is that what it was?) on 9/11.

 

[Sam.I.Am]

I ran a data center with a 60kva load, the UPS was good for 20 minutes. The battery room looked like something out of a diesel-electric submarine. I couldn't imagine how many tons of lead we had in there.

Unless there were 126 4' tall, 18" square battery cells crammed into a space so tight that you had to crawl on top of the batteries to get around then it probably looked nothing like a submarines battery well.

 

[pgimeno]

It appears from Henry's website that NIST didn't consider it directly because they didn't have any documentation of the strengthening applied or the loads present.

Sad how sometimes some important factors that we can't see or don't have data about them turn out to be crucial to understand an event. I'm not saying it's the case here though.

Could have, but it appears that the extra weight was applied mostly in the two-way trussed corner section, where any catenary action would have primarily caused a lateral deflection of the one-way trusses. I would expect it to have less effect on the perimeter columns than additional weight near the mid-point of a floor side.

I see. I suppose that some lateral deflection would be expectable in that case, which was not observed AFAIK. So it seems we can in principle rule out a significant role of that extra weight in the collapse.

 

[BigAl]

Unless there were 126 4' tall, 18" square battery cells crammed into a space so tight that you had to crawl on top of the batteries to get around then it probably looked nothing like a submarines battery well.

Was this on a nuke? I assume a nuke needs backup power.

 

[Sam.I.Am]

Was this on a nuke? I assume a nuke needs backup power.

Yes. All nuke boats have a diesel generator (DC) and batteries as well as the nuclear power plant. They also have 2 other modes of propulsion using DC (one is independent of the main shaft) so that we could always limp back into port if something happened either to the reactor or the main shaft.

The batteries are your final power source and the technology is proven through decades of use on hundreds of boats since before WWII. They have improved the cells somewhat since then but that had more to do with changing the plating than anything else. The size and configuration is the same.

 

[Dave Rogers]

I see. I suppose that some lateral deflection would be expectable in that case, which was not observed AFAIK. So it seems we can in principle rule out a significant role of that extra weight in the collapse.

I doubt we can be certain either way, really. Any lateral deflection of the one-way bridging trusses would be inside the building, and hence unobservable from outside. It would cause some pull-in, from simple geometry, but I think it would be impossible to separate which bit of weight caused how much of the total pull-in.

Dave