Structurally, the South Tower fared worse than its twin. The plane severed thirty-three exterior steel columns and ten core columns, causing the South Tower to immediately lean slightly to the southeast above the impact zone. The crash stripped fire-suppressing insulation from dozens of core columns and steel trusses that supported the building’s concrete floor slabs. Like the North Tower, the building absorbed the impact and remained upright, as promised by the dreamers and designers who built it. But the severed steel columns and the loss of fire-suppressing insulation portended a disaster
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