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Lessons From Ground Zero: Understanding Why the Twin Towers Collapsed and Engineering Solutions to Prevent Future Tragedies
Supported by NSF, University of California-Berkeley professor and expert on steel buildings Abolhassan Astaneh-Asl is recovering critical evidence from the site of the collapsed World Trade Center (WTC) towers. Steel fragments from the WTC hold valuable clues for understanding why the buildings collapsed, including the relative contributions of impact and heat stresses. Such knowledge can help prevent future tragedies by enabling construction of buildings more resistant to earthquakes, bombs, and other catastrophic forces.
Important information that might have been lost to the rapid removal and recycling of steel from the WTC site has instead been captured for future analysis. Thanks to the swift, effective action of NSF staff, especially Priscilla Nelson and Joy Pauschke, funding was approved a mere three days after the terrorist attacks. Within a week, Astaneh was in New York City, gathering perishable data. He initially spent 20 days at ground zero, followed by a further six days in late October.
Amidst 40,000 tons of twisted steel, Professor Astaneh located and recovered an internal column apparently hit by one of the planes. This piece of steel reveals what may have happened to internal columns when the planes collided with the twin towersbuildings that were "almost perfectly constructed," according to Astaneh. He has collected heat-deformed specimens resembling "something from a Salvador Dali painting." The heat was so intense that fire proofing on the steel melted into a thin, glasslike layer.
With separate funding, Professor Astaneh plans to undertake various analyses of his WTC data [see www.ce.berkeley.edu/~astaneh]. He and his colleagues will examine cross-sections of steel specimens under an electron microscope to determine how much heat they were subjected to and for how long. With David McCallen of Lawrence Livermore National Laboratory, he will construct a realistic computer-simulation model of the WTC, calibrate it using data gathered on site, and examine alternative crash scenarios (e.g., planes with less fuel aboard, 747s instead of 767s, planes hitting the building lower or higher, etc.). The researchers aim to apply lessons learned from this tragedy to new and existing high-rise construction to lessen damage and save lives in future disasters.
Astaneh has received prior NSF support to develop an innovative technology of his own design using concrete-and-steel composite shear walls to make buildings more bomb- and earthquake-resistant. In a separate project, he is investigating application of a cable-based technology to prevent "pancaking" of floors during bombings and other events that remove internal columns. Tests in mid-2001 demonstrated successful use of the technology in new construction. NSF-supported testing, scheduled for early 2002, will assess its use in retrofit applications.
For more information, contact Abolhassan Astaneh-Asl at astaneh@ce.berkeley.edu, 510-642-4528.
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Photo credit: Abolhassan Astaneh-Asl
Caption: An internal column from the World Trade Center, which appears to have been hit by a round object.
Photo credit: Abolhassan Astaneh-Asl
Caption: This mangled I-beam can help expose the chain of events leading to the collapse of the twin towers of the World Trade Center.
Photo credit: [Abolhassan Astaneh-Asl]
Columns from Building 7 of the World Trade Center.
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