This is a study of the collapse of the 47-story World Trade Center Building 7 (WTC7) at 5:20 P.M. on September 11, 2001. This building was a steel-frame office building located north of Vesey Street in the World Trade Center Complex in New York City’s Financial District. The World Trade Center Complex opened on April 4, 1973, and, at the time of completion, the featured Twin Towers (WTC 1 and WTC 2) were the tallest buildings in the world. WTC 7 was later completed in 1987. Other buildings in the complex included the Marriott World Trade Center (3 WTC), 4 WTC, 5 WTC, and 6 WTC.
Consider that on the morning of September 11, 2001, two jets were flown into WTC 1 and WTC 2 in a coordinated act of terrorism. At 8:46 A.M. Eastern Time, American Airlines Flight 11 crashed into the north face of WTC 1. At 9:03 A.M., United Airlines Flight 175 crashed into the south face of WTC 2. Soon after, these two buildings collapsed, WTC 2 at 9:59 A.M. and WTC 1 at 10:28 A.M. These attacks killed 2,753 people. It is reported that falling debris produced structural damage to the remaining buildings in the World Trade Center Complex. It is also reported that falling debris from the collapse of WTC 1 caused damage to WTC 7 and that fires ignited by debris from WTC 1 burned for nearly 7 hours in the building. At 5:20 P.M., this 47-story building also collapsed.
The National Institute of Standards and Technology (NIST) opened an investigation into the collapses of WTC 1, WTC 2, and WTC 7 in August 2002. NIST released its final report on WTC 7 in 2008, finding that the fires that were ignited by falling debris from WTC 1 caused the collapse of WTC 7. Independent researchers, however, have assembled evidence that has raised profound questions regarding the notion that WTC 7 collapsed because of fire.
Architects & Engineers for 9/11 Truth provided funding to the University of Alaska Fairbanks (UAF) to evaluate if fire caused the collapse of WTC 7 and to examine what may have occurred at 5:20 P.M. on September 11, 2001. Therefore, the UAF research team evaluated the structural response due to the reported fire. A structural framing virtual model of WTC 7 was used to conduct the study. The reported failure was simulated using three-dimensional finite element computer models of the building. The research team studied the building’s response using two finite element programs, ABAQUS and SAP2000 version 18. At the micro level, three types of evaluations were performed. In plan-view, the research team evaluated: 1) the planar response of the structural elements to the fire(s) using wire elements; 2) the building’s response using the NIST’s approach with solid elements; and 3) the validity of NIST’s findings using solid elements. At the macro-level, progressive collapse, i.e., the structural system’s response to local failures, is being studied using SAP2000 with wire elements, as well as with ABAQUS, and it is near completion. The findings thus far are that fire did not bring down this building. Building failure simulations show that, to match observation, the entire inner core of this building failed nearly simultaneously.
