Reply #56: were connected to the ACTUAL CORE COLUMNS [View All]

the horizontal beams between the core columns were there only to help keep the columns straight locally. The actual crossbracing, the actual part of the building dealing with lateral loads, was in the perimeter structure.

"The tube-frame design, earlier introduced by Fazlur Khan, was a new approach which allowed open floor plans rather than columns distributed throughout the interior to support building loads as had traditionally been done. The World Trade Center towers utilized high-strength, load-bearing perimeter steel columns called Vierendeel trusses that were spaced closely together to form a strong, rigid wall structure, supporting virtually all lateral loads such as wind loads, and sharing the gravity load with the core columns."

http://en.wikipedia.org/wiki/World_Trade_Center#Structural_design