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Investigation of the Collapse of WTC 7… how do we know NIST got it right?

CEE 298 Winter Seminar Series
John Gross, NIST
Tuesday, January 30, 2018 - 4:30 pm
Shriram 104
September 11, 2001, will be remembered for the spectacular and unpresented structural collapse of the World Trade Center “twin towers” where close to 3000 building occupants and first responders lost their lives.  Also that day, the 47-story World Trade Center 7, which was not hit by a commercial aircraft, collapsed completely due to, what would commonly be described as, “normal office content fires.” Over a period of six years, from 2002 to 2008, the collapse of these three buildings was studied by the National Institute of Standards and Technology. The collapse of WTC7 proved to be particularly challenging since, after the collapse of the twin towers, lower Manhattan was evacuated, and few eyewitness accounts, photographs or videos were available making re-construction of the spread of the fires difficult. The presenter will address the uncertainties in estimating the growth and spread of fires, the effect of the fires on the structural components, the complex failure modes of the steel frame, and the propagation of these uncertainties.  Through investigation of a video of the collapse, the speaker will attempt to answer, “how do you know that NIST got it right?”
 
Dr. John Gross recently retired after 34 years working for the National Institute of Standards and Technology. Dr. Gross’ research interests include the behavior of steel structures under earthquake and wind loads, fracture mechanics, stability, and fire performance of structures. Since joining NIST, Dr. Gross has either led or contributed to seven failure investigations. Among his many recognitions, Dr. Gross was named among the "Top Ten Federal Engineers of the Year" by the National Society of Professional Engineers and was awarded the DOC Gold Medal in 2005 and Special Act Award in 2008 for his contributions to the World Trade Center failure investigations.