Abstract Summary
Tsujun bridge is a stone arch bridge in Kumamoto Prefecture, which has been designated as an important cultural property of Japan. Tsujun bridge suffered slight damage during 2016 Kumamoto earthquake. No stones fell down, but wall stones were pushed out in the transverse direction of the bridge. Moreover, cracks were found in the soil which was filled between stone canals and wall stones. Those damages were found not in the central part of the stone arch but between the arch end and the bridge end. This study explains the damage mechanism of Tsujun bridge due to Kumamoto earthquake though microtremor observation and numerical simulations. First, input ground motions for Tsujun bridge during Kumamoto earthquake was estimated by microtremor observations. Next, an analytical model of Tsujun bridge was created based on the observed natural frequencies. Then, the seismic response of Tsujun bridge was simulated using the refined distinct element method. The actual damage situation that observed damage was not found in the central part of the stone arch but between the arch end and the bridge end could be simulated, and its reason was explained. Moreover, a simple countermeasure to reduce the bridge deformation without ruining historic values was considered and its effect was investigated.
