Rehabilitation and Strengthening of Aged Steel Railway Bridges in Japan

In Japan, nearly a half or even more of the existing bridges with a span exceeding 15 meters were predicted to be over 50 years old in next 10 years. Appropriate repair, strengthening, or replacement work should be performed on aged steel bridge structures to ensure their performance in service condition. A novel strengthening method using rubber-latex mortar, glass fiber reinforced polymer plates, lightweight rapid hardening concrete, and reinforcement bars is proposed for strengthening short-span steel railway bridge superstructures and for improving the seismic performance of aged column structures. To confirm the effectiveness of the strengthening method, loading tests were performed on test specimens for short-span steel railway bridges, longitudinal-lateral beam connections as well as steel columns. Numerical models were also built to simulate the structural behavior of both original and strengthened steel structures. According to the obtained results, the present renovation method can significantly enhance both rigidity and load carrying capacity of short-span steel bridge superstructure, connections, and column structures, resulting in the extension of the residual fatigue service life of bridge tarp structures and improvement of seismic performance of column structures.