He can speak for himself. I'm familiar with steel construction but not aware of any structural member that would be 4" thick. Deep or wide or cross section, sure...but not thick. Aircraft carrier flight deck, maybe. It goes to his credibility.
Columns and beams are fabricated from same material essentially...wide flanged I-beam material. size, cross sections and connections can differ, but they don't taper. It's all kinda a big lego set. You maybe be thinking of the floor trusses which tie the whole mess together. These taper to practically nothing at either end and would be the weak link in a fire. I think the wtc also had a series of box columns around the exterior.
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