I-5 Skagit River Bridge Collapse Review

Abstract

On May 23, 2013, a truck-tractor with a flatbed semitrailer hauling an oversized container was traveling south on Interstate 5 (I-5) near Mount Vernon, Washington. While crossing the Skagit River, the oversized container struck portions of the through-truss bridge, which resulted in a 49-m (160-ft) simple-span section of the 339-m (1,112-ft) bridge collapsing into the river. This collapse occurred even though the oversized container had a permit authorizing the travel route and was being escorted by a pilot vehicle. This paper (1) identifies some key transportation issues related to this scenario, e.g., permitting, route databases, signage, buffer between posted and actual clearance, insurance coverage, and pilot car requirements/operation; and (2) presents a structural analysis of the impact that provides insight into the truss design, damage sequence, failure mode, and potential techniques to increase the robustness of this class of bridge.