What Technology Was Used to Build the Twin Towers in New York City?

When completed in the early 1970s the twin towers of New York City's World Trade Center were the tallest buildings in the world. Building such tall towers at the edge of a major river in lower Manhattan required some complex and groundbreaking technology.

The Bathtub

• The site where the twin towers were built was located on 16 acres of landfill along the Hudson River that needed to be excavated. A primary concern was keeping water out of the foundation. This problem was solved by building what commonly became known as "the bathtub." This process involved digging a 70-foot deep slurry trench down to bedrock around the perimeter of the site and filling it with concrete.

Outer Support Columns

• Unlike most skyscrapers of the time, major support columns for the twin towers were erected on the outside of the building. Since the towers were going to be so high, this "hollow tube" approach, using newly available high-strength steel, could handle the high gravity load from above, as well as strong wind gusts.

Damping System

• To decrease the natural swaying effect of the high towers in the wind, a new technology known as a damping system was incorporated. Dampers made of visco-elastic material were placed between floor trusses and columns of the towers to reduce the sway, much like shock absorbers on cars reduce the impact of a bump.