NEWS & UPDATE
OTHER ARTICLES IN THE WTC SERIES
Why Did the World Trade Center Collapse? Science, Engineering, and Speculation by Thomas Eagar and Christopher Musso
Better Materials Can Reduce the Threat from Terrorism by Toni G. Maréchaux
An Initial Microstructural Analysis of A36 Steel from WTC Building 7 by J.R. Barnett, R.R. Biederman, and R.D. Sisson, Jr.
When the World Trade Center towers collapsed, a mission was created for researchers
affiliated with the National Science Foundation (NSF). That organization,
within weeks of the event, awarded grants of $300,000 to engineering and social
science researchers to conduct a variety of assessments at the site, some
to reconstruct the events of September 11 to uncover the exact cause of the
failure of the twin towers, others to improve the postdisaster response. Additional
grants were expected to be awarded late this year to continue the research.
The projects were a continuation of NSFs ongoing funding of disaster and hazards research, said Amber Jones of the foundations office of legislative and public affairs. Although the projects are diverse, they ultimately can be combined to provide comprehensive disaster-response research, not only for naturally occurring phenomena, such as earthquakes, but also for urban disasters, such as explosions, and for the steady deterioration of buildings and urban centers, said Priscilla Nelson, director of the NSF Civil and Mechanical Systems Division. With proper planning, a variety of technologies can be combined for a cohesive, advanced disaster response, Nelson said.
Although the grant recipients have been working independently of one another, they will soon have a chance to pool their knowledge as a first step toward that combined response.
One of the things we want to do here at the NSF is to pull all the researchers together to talk about what theyve been doing, Nelson said. A workshop will be held December 12 and 13 at New York University, during which each grant recipients will present summaries of their work and findings, Nelson said. By February 7, all recipients of the original grants will have submitted a written report of their work.
Following are descriptions of the grant projects.
Laser Mapping Adds a New Dimension to Disaster Analysis
David Bloomquist, University of Florida, led a team at the WTC using a laser system to produce high-resolution three-dimensional (3-D) maps of the interior and exterior of damaged buildings (Figures 1a and 1b). The technology is especially useful for identifying displacements and cracks.
Normally, when a building is damaged, its condition is determined through
conventional survey techniques. That process is time-consuming, and the resulting
information is incomplete, according to Bloomquist. The new technique combines
airborne laser swath mapping with groundbased scanning laser technology. That
combination provides hundreds of millions of laser range measurements of precise,
3-D positions of points covering the surface of the ground, buildings, and
rubble at the disaster site, Bloomquist said.
Twelve days after the attack, the University of Florida-led team collected ground observations from a 25,900 square kilometer area around the World Trade Center. Aerial data, collected through laser and digital photography, further enhanced the images.
The immediacy of the technology could prove invaluable in future disasters,
One of the main issues we have . . . is getting a rapid assessment, Nelson said. With the laser technology, damage can be quickly identified, down to the centimeter, especially if the mapping can be combined with pre-disaster global positioning system maps, she said.
The University of Florida has spent more than four years studying applications for airborne laser swath mapping, including landslide detection and monitoring, sinkhole assessment, and hurricane damage.
Figure 1. (a-left) A laser map image of the former site of the World Trade Center and surrounding buildings, and (b-right) a close-up view of the leveled buildings. (Image courtesy of University of Florida College of Engineering.)
Professor Investigates the Mechanical and Structural Properties of the
Abolhassan Astaneh-Asl, University of California at Berkeley, is, with a colleague, collecting data on the mechanical and structural properties of the WTC towers, particularly steel affected by heat, fire, and impact.
At the WTC site, Asteneh-Asl has examined the wreckage, looking for clues in the heaps of burned, bent metal to the collapse of the twin 110-story towers. The goal is to determine where failure occurred and how to improve the structural integrity of new buildings so they can better withstand fires, explosions, earthquakes, and other hazards, according to the NSF.
Asteneh-Asls examination of the debris found that steel flanges, once an inch thick, became paper-thin after the disaster. He reportedly found pieces of structural steel with gouge marks identifying where a Boeing 767 struck, including one segment that appears to have been sliced by an airplane wing, and another by the planes nose. Asteneh-Asl is also part of a team assembled by the American Society of Civil Engineers to investigate the trade center site and reconstruct the failure of the buildings.
We will be able to learn many valuable lessons from this tragedy to improve our structural design and construction and (to understand) the effects of fires on steel structures to avoid such a catastrophic and complete collapse and tragic loss of life, Asteneh-Asl said in early October.
Asteneh-Asl, who has studied bomb-resistant building designs, said he plans to continue researching how to protect steel structures from terrorist attacks. One option he has tested involves bolting reinforced concrete plates to steel shear walls. If a plane hit such a wall, Asteneh-Asl said, it would probably not penetrate the building. Instead, it would probably fold up, accordion-style, with its fuel remaining outside the building.
Compact Technology Puts Information in the Palm of Investigators Hands
J. David Frost, Georgia Institute of Technology, and a team collected data on the structural damage at the WTC using handheld technology developed for use after earthquakes. The equipment includes a global positioning system, a digital camera, and a handheld computer loaded with PQuake, software designed to assess damage after earthquakes. The software was developed by Frost, a professor of civil engineering at the Georgia Institute of Technology, and his research group.
Frost was brought to the scene to collect and analyze data on structural engineering and damage assessment.
The process involves three-person teams, each including a structural engineer, that collect and input digital data, digital photos, and global positioning system coordinates into a Palm Pilot computer. The information is then uploaded into a geographic information systems database and examined for detailed synthesis and analysis of damage. The assessment will document the type of structure as well as specifics of damage, both structural and non-structural.
Frost has served on a number of postearthquake reconnaissance teams. He combined that experience with his civil engineer training to develop the PQuake systems, according to Georgia Tech.
Other NSF Quick Response Research awards went to
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