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Steel Shots: Touring 4 World Trade Center
Posted by Tasha Weiss on February 17, 2012 at 1:17 PM.


The 44th level of 4 WTC features a belt truss system that transitions the structure from a parallelogram to a trapezoid. Photo: Jacinda Collins


Steel erection is now complete up to the 62nd floor of 4 World Trade Center, planned to be the fourth tallest skyscraper envisioned for the WTC site. Back in December, DCM Erectors provided AISC Regional Engineer Jacinda Collins with a tour of one of the newest additions to the New York City skyline. These are some of her observations:


“4 WTC is the smallest of the skyscrapers at the WTC site, however, it contains a number of unique features. It has a concrete core and utilizes steel and composite outriggers, as well as belt trusses, at the mechanical floors of the structure. The column-free spans from the core to the perimeter are approximately 45 ft with web openings for mechanical, electrical, plumbing (MEP).


The 44th story is the belt truss level and has a lot going on including a lot of welding.


4 WTC also has a number of super columns and is designed to resist blast and progressive collapse. For erection, DCM created steel platforms for the ironworkers to work at higher levels. The 3-5 story platforms allow the working level to rise with the columns and not the decking.”


A journal paper from the World Academy of Science, Engineering and Technology explains the belt truss concept. You can read the PDF here.


According to, 4 WTC is located on the southeast corner of the 16-acre WTC site and will face directly onto the World Trade Center Memorial Park to the west. Scheduled for completion at the end of 2013, it will rise 977 ft from street level to 72 stories. The tower is intended to assume a quiet but dignified presence at the site while also serving to enliven the immediate urban environment as part of the redevelopment efforts of downtown Manhattan.


For more information about the World Trade Center’s rebuilding progress, including the latest construction images and video, visit A photo by Jennifer Hardyniec, a first-year structural engineering graduate student at Virginia Tech, shows another perspective of 4 WTC and received an Honorable Mention in the 2011 AISC Student Photo Contest. You can view the photo in our previous news post at

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