Engineering Inc. - November/December 2009 - 19

n just a few horrifying seconds in 2007, the nation’s fifth-busiest bridge— the I-35 West Mississippi River Bridge in Minneapolis, responsible for carrying 140,000 vehicles daily—dropped into the water below, killing 13 people and injuring 145. Almost as soon as rescue crews and emergency personnel appeared at the scene, a select group of engineers and design experts from government and private industry began combing through the debris. They reviewed video and analyzed the steel and concrete that once constituted the 1,097-foot span in order to find clues about how and why the structure failed. A team of individuals—led by highly skilled forensic engineers—worked to unravel complex engineering puzzles and identify any design flaws, maintenance errors or general misuse that might have contributed to the disaster. Forensic engineering isn’t anything new. Public officials, manufacturers, engineers, architects, attorneys and others have long searched for answers in the event that a product or structure breaks down, resulting in injury, death or catastrophic failure. In today’s high-tech world, these investigators rely on new devices, systems and science to boldly go where no engineer has gone before— inside buildings, tunnels, levees, motors and more—in order to pinpoint the cause of a problem and, where possible, to prevent disaster from striking twice. It’s no simple task. “Forensic engineers must be one-half detective and one-half engineer,” says Edward W. Pence, Jr., president of Stroud, Pence & Associates, Ltd., a Virginia Beach, Va.–based firm that specializes in forensic engineering. “Investigations can take weeks, months, even years. They can involve complex processes and tests. But, ultimately, making sense of everything and finding definitive answers requires solid engineering skills and experience. Someone must interpret all the information.” Though films, books and television shows, such as CSI: Crime Scene Investigation, glamorize forensics, the discipline remains rooted in three basic principles: persistence, patience and hard work. “The work can be dirty and unpleasant. It can involve long hours and tedious work that you would never see in a show like CSI,” says Randy Down, president and CEO of Down Forensic Engineering, Inc., in Cary, N.C. “But a good forensic engineer can sift through piles of data and information and help solve extremely tough cases.” Beyond Failure I (top) Down Forensic Engineering, Inc., provided this image of a damaged gear from a recent mechanical failure investigation. (below) Forensic engineers at Forensic Analysis & Engineering Corp. helped determine the cause of this structure collapse. ricane Katrina. There have been other failures. The 1981 Hyatt Regency Hotel walkway collapse in Kansas City and the I-35 West Mississippi River Bridge (officially known as Bridge 9340) have left an indelible mark on engineering’s legacy. Each failure was followed by months of painstaking investigation. In the case of Bridge 9340, forensic engineers and orensic engineers must be one-half detective and one-half engineer. EdwArd w. PEncE, Jr. Stroud, Pence & ASSociAteS, Ltd. History will not soon forget when the levees broke in New Orleans after Hur- the National Transportation Safety Board (NTSB) used computer modeling, digital image analysis, photo analysis, X-rays, mechanical and corrosion testing and oldfashioned inspections of metal and debris to understand how and why the collapse occurred. (The analysis indicated that fractured steel gusset plates significantly contributed to the bridge’s failure, although that conclusion is being questioned.) Several industries now use forensic engineering to determine the cause of accidents, failures and other problems. Robert K. Kochan, president, CEO and principal technical consultant for Forensic Analysis & Engineering Corp. in Raleigh, N.C., says his firm uses forensic engineering to probe a mélange of issues, including industrial safety, vehicular collisions, electrical equipment, mechanical systems, mold and mildew causation, fires and explosions, marine accidents, product defects, structural analysis and material and metallurgical analysis. But not all accidents require a forensic engineer, Kochan says. “If a person cuts a strap with a pocket knife and a load of November / December 2009 eNGINeerING INc. AP Photo MAndEL nGAn/AFP/GEtty IMAGEs

Engineering Inc. - November/December 2009

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