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Old 05-07-2013, 09:05 PM   #12
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Join Date: Apr 2006
Posts: 11,522

Originally Posted by Rohirrim View Post
Interesting that even Wiki tells the story of WTC7. Not difficult to figure out:

The building was constructed above a Con Edison substation that had been on the site since 1967.[6] The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing 600,000 sq ft (56,000 m2).[7] The final design for 7 World Trade Center was for a much larger building than originally planned when the substation was built.[8] The structural design of 7 World Trade Center therefore included a system of gravity column transfer trusses and girders, located between floors 5 and 7, to transfer loads to the smaller foundation.[9] Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The 5th floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the 7th floor, the building's structure was a typical tube-frame design, with columns in the core and on the perimeter, and lateral loads resisted by perimeter moment frames.[7]
Don't know what the point of yer post is, and I suspect, neither do you.

FYI, here is what NIST said about the Con Edison sub station:

25. Did the electrical substation beneath WTC 7 play a role in the fires or collapse?

No. There is no evidence that the electric substation contributed to the fires in WTC 7. The electrical substation continued working until 4:33 p.m. on Sept. 11, 2001. Alarms at the substation were monitored, and there were no signals except for one event early in the day. No smoke was observed emanating from the substation.

Special elements of the building's construction—namely trusses, girders, and cantilever overhangs, which were used to transfer loads from the building superstructure to the columns of the electric substation (over which WTC 7 was constructed) and foundation below—also did not play a significant role in the collapse.
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