Fatigue and Fracture Evaluation of a 70 Year Old Steel Bridge

Abstract

Nen’jiang No.1 Bridge has been used for 70 year, so fatigue, fracture and corrosion dominate the remaining life of this bridge. Obviously the designer did not take into consideration the fatigue problem at that time. In order to keep this bridge in service economically as long as possible, bridge owner decides to take measures to preserve its service safety. Thus the remaining fatigue life and fracture failure risk need to be evaluated. The analytical results according to the fracture mechanic based concept show that the diagonal edge members U0L1 and U9L8 have the shortest remaining fatigue life, and some members have a potential risk of brittle failure. The fracture failure risk evaluation results show that the toughness of main truss member steel is lower than the code requirement, and members such as U0L1 and U9L8 have brittle fracture failure risk in cold winter. So this bridge should be temporarily closed traffic in winter.