New Technologies in Retrofitting and Strengthening of Ageing Steel and Composite Bridges in Japan

Abstract Steel railway and road bridges have widely been used for the past century in Japan. Many are still in use but have deteriorated. New technologies have been developed to repair, strengthen or renovate these bridges to extend their service life. Steel members often suffer from fatigue cracks and corrosion, which can be tackled by new technologies, including: a new pavement system using steel fibre reinforced concrete at steel decks; a strengthening system using steel plates with holes at the corner of steel piers; and a new repair method using carbon fibre reinforced polymer sheets at the girder end. When deterioration is serious, bridges can be renovated or replaced with new structures. Railway girder bridges are renovated by the integral bridge with nail-reinforced soil method, a deteriorated viaduct in a marine environment has been renovated to a steel plate girder bridge, and deteriorated composite slabs are replaced with precast prestressed concrete slabs connected with epoxy-resin-coated reinforcing bars. Many bridges have been seriously damaged by strong earthquakes and ageing bridges must be retrofitted. Some examples are shown, including: replacing hinged columns with hybrid towers and rubber bearings, strengthening pivot bearings, installing dampers and devices to prevent girders falling off.