Pedestrian Bridge Collapse and Failure Analysis in Giles County, Virginia

Abstract

A pedestrian suspension bridge over Walker Creek near Route 749 in Giles County, Virginia, partially collapsed in October of 2008, causing 10 people to fall into the creek below. The failure occurred when one of the anchors holding a suspension cable fractured. This paper presents the investigation of the failure, including a structural analysis of the bridge to determine cable forces, material property testing of the fractured anchor, laboratory testing of a different anchor from the bridge, and a simple strength evaluation of the anchor under combined axial force and moment. Based on the results of the study, it was concluded that the anchor should not have failed carrying the loads on the bridge on the day of failure. The anchor failed in brittle fracture because of a local defect in the material at the perimeter of a corrosion pit on the surface of the anchor hook. The structural analysis and laboratory testing indicated that the material around the defect was at yield before fracture initiation. The material flaws significantly influenced the bridge failure after yielding and inelastic deformation of the anchor material at the inside of the hook radius occurred.