Experimental Study and Reliability Assessment of Postfire Hangers at a Long-Span Suspension Bridge

Abstract

Hangers are primary load-carrying members in suspension bridges, connecting the girder to the main cable, and in case of fire accident, the bridge safety may be affected due to the deteriorated performance of hangers. In this study, a number of 160-wire specimens were tested to obtain their strengths after being heated to various temperatures and cooled down. Then the Weibull distribution was used to describe the randomness of the results. Thereafter, a statistical model was established to estimate the capacity of postfire hanger consisting of parallel steel wires. Subsequently, static tensile tests were carried out on three steel wire bundles, with each consisting of 19 parallel steel wires, to verify the model, where two bundles were heated. Based on the predicted residual capacities and field measured hanger forces, the reliabilities of postfire hangers of the Runyang Suspension Bridge were assessed. It was found that the tensile strength of hangers degraded after exposure to high temperatures, and their residual strength and reliability were highly dependent on the highest exposure temperature. Finally, the repair and replacement of the four postfire hangers on the bridge was conducted according to the assessment.