Technical Conference on the Federal
Building and Fire Safety Investigation
of the World Trade Center Disaster
Session VI - Structural Fire Response and
Probable Collapse Sequence and Key Findings
September 15, 2005
Building and Fire Research Laboratory
National Institute of Standards and Technology
U.S. Department of Commerce
Probable Collapse SequencesProbable Collapse Sequences
NIST adopted an approach that combined mathematical
modeling, statistical analysis, laboratory experiments, and
analysis of photographs and videos, and accounted for
uncertainty in input parameters, analyses, and observed
events, to address:
The probable sequence of events from the moment of aircraft
impact until the initiation of global building collapse.
How and why WTC 1 stood nearly twice as long as WTC 2
before collapsing (102 min vs 56 min).
What factors, if any, could...