The Towers Had Robust Self-Supporting Core Structures

• 47 box columns a yard wide, steel 4" thick at base
• Abundantly cross-braced
• Capable of supporting the entire weight of building
• Anchored directly to bedrock
• Did not depend on floor diaphragms for support

The towers were designed to withstand 140 MPH winds.
In such cases the floor diaphragms would help transfer lateral loads loads between perimeter walls and core. Otherwise, structural function of the floors was not in play.