The Minato Bridge is a long-span truss bridge with a length of 980m and located in the Hanshin Expressway at the Osaka Port, Japan. Although damageto this bridge from the 1995 Hyogo-ken Nanbu Earthquake had not been so serious, seismic design for highway bridges was revised after the earthquake. Seismic performance of the bridge was evaluated by dynamic analysis applying revised ground motions and its seismic risk was found to be at non-negligible level. In this project, several types of retrofit structural systems with three different performance levels were considered and evaluatedusing seismic life-cycle cost (S-LCC). S-LCC consists of retrofitting cost and seismic risk. Several risks were calculated using the damage probability obtained from the hazard and fragility curves as well as cost data. As a result, the damage-controlled structure with minimized S-LCC was employed to achieve rational retrofit from a viewpoint of risk management. The concept was to differentiate main members which support vertical load fromsub-members for lateral force such as seismic force. In this design, mainmembers were required to be within linear region and sub-members were allowed to perform nonlinearly to provide damping. This structural system should allow early reopening of the bridge to traffic even after a severe earthquake so that it will serve as a part of lifeline and reduce social loss. For the covering abstract see ITRD E139491.
Samenvatting