The World Trade Center Collapse – A Case Study

Abstract:

One needs to understand how the World Trade Center was constructed, to comprehend why the towers collapsed.

When the World Trade Center was designed, most skyscrapers were built with a dense grid of steel beams and columns that had limited open floor space on each floor.The architect and engineers for the World Trade Center used a revolutionary design and construction method to maximize the open floor spacing and still build as high as possible.

The structural steel framework design was the most significant feature of the towers. Most buildings spaced the vertical steel columns evenly across the floor. The tower design was different, and called for the columns to be moved to the exterior walls and the central core of the structure. These columns supported the buildings weight, but without lateral or side to side support from the floors, these columns would have buckled. Therefore, the floors were built upon trusses, similar to beams, which connected and bridged the distance between the core columns and the exterior columns. The trusses were connected to the columns with bolts on each end. The result of this design created a large open floor area without column interferences.

This case study will attempt to clarify various details of the collapse, indicating that the building was not structurally deficient, but still the towers collapsed.
We will examine the design, the airline impact, the fire, the ultimate collapse, and the lessons learned from the collapse.

Speaker

• Neil Schulman