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World Trade Center Collapse

The truth about exactly how the World Trade Center towers collapsed matters greatly, both to the families of those who perished and to the future safety of buildings in America and elsewhere. In the spring of 2002, Congress called upon the National Institute of Standards and Technology (NIST) to conduct a thorough investigation into the disaster. Civil engineer S. Shyam Sunder served as the lead investigator. In this audio slide show, Sunder describes the series of structural and fire-related events within the towers as they progressed toward catastrophic collapse.

BySusan LewisNova

Editor's Notes

Editor's note: As a result of the study, NIST made recommendations for changes to building codes and standards. Shyam Sunder discusses these recommendations and other sobering findings of the study in a separate interview with NOVA. The edited transcript of this interview may be found under Transcript below, following the transcript of the audio slide show.

This feature originally appeared on the site for the NOVA program Building on Ground Zero.

Major funding for NOVA is provided by the David H. Koch Fund for Science, the NOVA Science Trust, the Corporation for Public Broadcasting, and PBS viewers.