Degradation overload vibration, single-connection failure, gusset plate failure, tension member cracking and a lack of redundancy in the structural design are among the factors that may have contributed to the partial collapse of the Union Pacific Salt River Bridge in Tempe, Ariz., says Arizona State University professor Barzin Mobasher. "It also is not yet clear if any structural health monitoring tools, including fatigue crack monitoring, were done to assess the existing condition," he says.
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