Efforts of Seismic Retrofit: The Future Challenge of Innoshima Bridge Beyond 40 Years of Service

Innoshima Bridge, which was opened for traffic in 1983, is a three-span, two-hinged stiffening truss girder suspension bridge with a center span of 770 meters, featuring a double-deck structure with the upper level for motor vehicles and the lower level for bicycles and pedestrians. In response to large-scale earthquakes, the bridge is required to have the performance that limits seismic damage to a minimum and enables a swift rehabilitation of its functionality. The results of the seismic performance evaluation revealed damage to various members in the bridge. Therefore, it is decided to conduct seismic retrofit to the damaged members, such as installation of viscous dampers to reduce the seismic forces, addition and replacement of the structures around the wind tongues, and some other reinforcements. This paper presents a report on the seismic performance verification and retrofit design of Innoshima Bridge.