Monday, June 01, 2009
Yep, there were explosions in WTC7, nuff said?
7 World Trade Center was a 47-story building, designed by Emery Roth & Sons, with a red granite façade. The building was 610 feet (186 m) tall, with a trapezoidal footprint that was 330 ft (101 m) long and 140 ft (43 m) wide. Tishman Realty & Construction managed construction of the building, which began in 1983. In March 1987, the building opened, becoming the seventh structure of the World Trade Center. The building was constructed above a Con Edison substation that had been on the site since 1967. The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing 600,000 sq ft (55,700 m²). The final design for 7 World Trade Center was for a much larger building covering a larger footprint than originally planned when the substation was built. The structural design of 7 World Trade Center included features to allow a larger building than originally planned to be constructed. A system of gravity column transfer trusses and girders was located between floors 5 and 7 to transfer loads to the smaller foundation. Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The fifth floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the seventh 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.
The last part of this video shows, in slow motion, more detail of the column of windows that were blown out during the collapse and also some debris being thrown upward from above where the windows were, along with some bright flashes that look like small explosions. Hmm...?
See Barry Jennings testimony of an explosion where the stairway was destroyed when he was descending from the sixth floor.