Seismic retrofitting for bridges in Osaka city

In the wake of the Hanshin-Awaji Earthquake, the Osaka Municipal Government has planned and executed seismic retrofitting for bridges in Osaka. This report first discusses the present condition of bridges in Osaka, and changes in bridge design standards. Next, it explains the basic concept und erlying bridge seismic retrofitting, derived from the experience of the Han shin-Awaji Earthquake. In planning retrofitting, evaluation criteria on the importance and seismic capacity of all bridges in Osaka were established. Based on these criteria , the bridges were classified into five ranks each. Evaluation results were indicated in the form of a matrix. Using the matrix, retrofitting methods and priority were determined. Accord ing to plan, about half of the bridges in Osaka will be retrofitted.