A case study of seismic response analysis on an approach light bridge in airport

It is difficult to understand seismic behavior of approach light bridges because they have been hardly damaged in past earthquakes. Some approach light bridges had been constructed in the sea with installing piers into the seabed ground which consists of soft marine sedimentary layers, and moreover, they had often been connected to a seawall enclosing a man-made island by reclamation. Thus, its seismic behavior might be received influence of the displacement by the surrounding ground and the seawall. This study shows a case study of seismic response analysis based on a multiple-support excitation method to confirm the behavior of the approach light bridge during an earthquake. As results, the seawall greatly moved to the sea side due to liquefaction occurred around the seawall. This movement can not be ignored compared to the space between the abutment and the bridge. To confirm influences caused by this movement in the bridge analysis, two cases were examined. In the first case, the seawall pushes the bridge out by the displacement of the amount that exceeds the space. In the second case, the seawall does not push the bridge out exceeding the limitation based on passive earth pressure. It is concluded that the liquefaction resistance of the soil around the seawall is predominant for the displacement at the seawall and damages which the bridge received by the seawall is depend on the strength of the spring element between the abutment and the land fill.