| Many road bridges were damaged in the 2016 Kumamoto earthquake. On the main regional road Kumamoto Takamori Line, despite bridges that were seismically designed based on the 1996 road bridge specifications, there were cases in which the recovery of the function could not be performed quickly. In the 1996 Road Bridge Specification, Level 2 ground motion was specified based on the lessons learned from the Hyogoken-Nanbu Earthquake. Level 2 ground motion type II follows the current road bridge specifications specified in 1996, and it is not possible to clarify the damage factors of bridges designed based on the 1996 road bridge specifications. Therefore, it is very important in considering future seismic design methods.In this paper, we will investigate the damage caused by the seismic action of road bridges that were seismically designed based on the 1996 road bridge specifications damaged by the Kumamoto earthquake. The purpose is to make an estimation based on the damage traces found in the previous survey. Looking at the strong motion displacement records around the bridges covered in this paper, we can see that the displacement was north, east, and downward, and the displacement remained. When this is compared with the acceleration record, it can be seen that a large displacement occurred during the main movement.The substructures of the bridges were moved about 1 m each, and the amount of movement was different for each substructure. The rubber bearing had a large residual displacement, and its direction was different for each fulcrum. In addition, the finger joints were engaged with each other in a state shifted in the direction perpendicular to the bridgeaxis. A displacement limiting structure installed on the abutment was sheared.The damage was analyzed especially focusing on ground displacement. As a result, it was confirmed that damage estimated to be due to the effect of ground displacement was observed. The substructure will follow and move at least due to the ground displacement at the time of the earthquake. It became clear that there was a possibility that the part and the superstructure were damaged. Based on this experience, in the future construction of road bridges, it is necessary to investigate the possibility of ground displacement during an earthquake and to minimize the impact on the bridge at each stage of the route planning and structural planning. Therefore, it is considered necessary to conduct appropriate examination. |
