Performance of strengthened hybrid structures renovated from old railway steel bridges

Structural repair or maintenance technique has been a hot issue in recent years due to the increasing aging problems of old railway bridges, which have been used beyond or approaching their design service life. A strengthening method for old steel railway bridges by integrating the new structural members was adopted in engineering practice in this context. Rubber-latex mortar, GFRP plates and rapid hardening concrete were integrated with the old steel railway bridge to increase its rigidity and reduce both stress levels and structure-borne sound levels of the old steel bridge. The purpose of the present study is to investigate the mechanical performance of the renovated hybrid railway bridge. The material test on aged structural steel, the static loading test on the strengthened bridge, and the impact hammer test on the old bridge before and after strengthening, were performed to confirm the effects of present strengthening method. Moreover, three-dimensional FE models were built to make a comparison study between the strengthened and the original steel bridge. Both experimental and numerical results indicate that the renovation method can greatly enhance the stiffness and reduce the stress levels of steel members, resulting in the extension of the service life of the old steel railway bridge. Furthermore, noise reduction effects by using concrete and rubber-latex mortar were confirmed in the impact test.