Federal Investigators: Determining Cause of Minneapolis Bridge Collapse Could Take A Year

DETERMINING what caused Minneapolis' I-35 bridge to collapse may take a year or more due to the complexity of the investigation, federal officials stated.

Investigators with the National Transportation Safety Board (NTSB) have questioned construction crews that were working on the bridge when it collapsed last week. Employees of Progressive Contractors Inc., which was conducting a project to repair sections of the heavily traveled highway, helped investigators in efforts to establish the locations of its equipment, vehicles, and materials at the time of the accident, and how much each piece weighed.

NTSB officials said they will conduct computer analysis of the loads placed on the bridge during the construction. They will use a computer model designed to test failure scenarios to help establish whether the structure was initially cut or pulled apart.

Investigators also plan to use high-definition cameras from helicopters to examine the bridge's north end on Aug. 6 to look for clues to the collapse. The investigation also will involve reassembling portions of the bridge on land near the river and reviewing video of the collapse.

The bridge's main span collapsed into the Mississippi River during evening rush hour, sending dozens of vehicles, tons of concrete and metal into the waters of the Mississippi River 64 feet below. At least five people were killed and about 100 injured. Police have released an official list of eight people still missing, but officials said that number could increase.

The bridge collapse has prompted U.S. Secretary of Transportation Mary E. Peters to call on all states to immediately inspect any steel deck truss bridges similar to the bridge that collapsed.

"Even though we don't know what caused this collapse, we want states to immediately and thoroughly examine all similar spans out of an abundance of caution," Peters said.

According to Federal Highway Administration (FHA) data, there are 756 of the relatively unique steel deck truss bridges in the United States. FHA issued the guidance to all state transportation agencies and bridge owners strongly advising them to conduct an inspection or, at minimum, review inspection reports to determine if further action is needed.

Peters also has requested the Department of Transportation's Inspector General to conduct a rigorous assessment of the National Bridge Inspection Program. "What happened in Minnesota is simply unacceptable," Peters said. "We must have a top-to-bottom review of the bridge inspection program to make sure that everything is being done to keep this kind of tragedy from occurring again."

Peters called for the Inspector General to determine if the current federal program delivers the highest level of bridge safety. And, if needed, the Inspector General will make recommendations for future changes to the program.

Fro a state listing of steel deck truss bridges, visit http://www.fhwa.dot.gov/pressroom/sdtblist.htm. An inventory of steel deck truss bridges can be found at http://www.fhwa.dot.gov/pressroom/sdtbinv.htm.

According to the American Society of Civil Engineers, the collapse is a "glaring example" of the nation's infrastructure crisis. As outlined in the group's 2005 infrastructure report card, about 159,000 of the country's 590,750 bridges are deficient or obsolete. In the wake of the disaster, ASCE says it is proactively providing information and technical expertise and is calling for public policy action to make the nation safer and sustainable for future generations with an "Infrastructure Action Plan" that spells out steps Congress should take to shore up problems. The Reston, Va.-based group estimates it will cost $9.4 billion over the next 20 years to repair all faulty bridges.

ASCE's 2005 report card gave U.S. bridges an overall grade of C, which was one of the higher marks. The report gave U.S. infrastructure as a whole a grade of D. For more information, visit http://www.asce.org.

The American Society of Safety Engineers responded to the bridge collapse by adding an informational link to its Web site that includes facts and resources about bridge safety. Access it at http://www.asse.org/newsroom/bridgesafety.php.

The link includes tools and information for finding out more about bridge safety and construction, including articles such as "Bridge Construction-Related Deaths in West Virginia, 1990 - 1999," "Bridges and Tunnels in the Nation's Largest City"; an interview with Metropolitan Transportation Authority's acting president Martha Walther; and links to the U.S. Fish and Wildlife Service's information on bridge design, the Truss Plate Institute's design specification for bracing metal plate-connected wood trusses, and various standards and recommendations relating to bridge safety.

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  • OHS Magazine Digital Edition - July August 2020

    July August 2020

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