In Reply to: SurePlate steel building connections WTC?? posted by JWmHarmon on January 08, 2002 at 10:45:35:
Noting that some comments questioned why or whether the lower chord attachments of the trusses were necessary to the tower, I returned to look at Ngon Nguyen's posts from last September and October. He seems to make a case that the VE attachment also served to transmit some vertical loads, I believe, and thus was not redundant. On this premise, I went back to sketching a new scenario:
In (1) two floors w. trusses are shown, w. VEDs (A), as fuel spreads across floor and collects against wall.
In (2) the ignited fuel quickly goes up wall and burns through
the VED adhesive at (B). This causes sagging of truss and cracking of concrete membrane.
In (3) truss falls further and fractured concrete falls to lower
floor, breaking it, and so forth...