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willravel, apologies for the confusion . . .. the steel lattice I refer to is not the external lattice of the facade (which purpose is to take out wind loads), but the prefabricated lattice trusses which made up the floor plates. These were light-weight steel sections, prefabricated into zig-zag truss beams (to save weight and allow services to pass through) and were connected to the central core. It was supposedly the failure of these light-weight floor plate trusses (at their connection with the core)which resulted in the floor collapse. Once just one part of one floor starts crashing down, the whole thing is going to go down like a pack of cards. Strong as the building was . . . the large span floor plates were not designed to withstand the impact of a concrete floor from above dropping down 12' . . and even if it could, you would now have the weight of TWO concrete floors bearing on weakened connections with fires still raging. Stunned as I was at the time . . in hindsight, the collapses are not really hard to understand.
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Where your talents and the needs of the world cross . . there lies your vocation.
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