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.