Researchers model effects of bomb blasts

Progressive collapse of the Alfred P. Murrah Federal Building in Oklahoma City caused many deaths compared to similar bombing incidents. Lawrence Livermore researchers are analyzing computer models to find out why.

Courtesy of the Oklahoma Bombing Investigation Committee

High-performance government computers are testing retrofitting schemes to make large buildings resist terrorist bombs, Robert M. Ferencz said recently at the annual meeting of the American Association for the Advancement of Science in Denver.

Ferencz, a researcher in the Defense Technologies Engineering Division of the Energy Department's Lawrence Livermore National Laboratory, said buildings are too vulnerable to progressive collapse after the loss of one load-bearing column or wall.

The Alfred P. Murrah Federal Building in Oklahoma City suffered progressive collapse from a truck bomb in 1995, leading to 168 deaths, he said. But when the Khobar Towers housing U.S. troops in Saudi Arabia was hit by a truck bomb in 1996, only 19 died because there was no progressive collapse.

'The blast analysis problem is technically challenging, both empirically and computationally,' Ferencz said. Scientists can simulate the physics of shock waves, he said, and engineers know how to model buildings, but they do not yet understand the interactions between a shock wave and a complex 3-D structure.

The Army's Engineer R&D Center in Vicksburg, Miss., is combining blast models developed by Energy's Sandia National Laboratories with Livermore's ParaDyn structural mechanics application to simulate bomb effects on buildings with retrofitted reinforcement, Ferencz said.

Livermore researchers are using another 3-D hydrodynamics application to examine blast vulnerabilities of various buildings and potential retrofits. It's common for the design and coding of a blast model to take several months, plus a week to compute results on a supercomputer.

'This is the computational equivalent of building a building and then blowing it up in the middle of a desert,' Ferencz said.

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