World Trade Center Disaster: Damage/Debris Assessment

LZA Technology (LZA) was retained on behalf of Silverstein Properties, a lease-holder of the World Trade Center (WTC) site, to perform structural investigative services in connection with the World Trade Center attacks. Our work included a review of all relevant available photographic evidence (still photos and video) and utilization of the knowledge LZA gleaned through our continual site observations from September 11, 2001 through July 2002, as the New York City Department of Design and Construction's lead engineering consultant. This paper summarizes LZA's evaluation of the following: 1) Structural damage sustained by the exterior frames of WTC 1 and WTC 2 due to the aircraft impacts, 2) Debris distribution resulting from the collapses of WTC 1 and WTC 2. This includes an assessment of which tower's debris damaged the remaining World Trade Center buildings and other nearby buildings, and 3) Structural damage sustained by WTC 1 due to the collapse of WTC 2.