Abstract
Due to the tsunami triggered by the 2011 Great East Japan Earthquake on 11 March 2011, Tohoku area suffered tremendous destructions. Shizugawa area (Minamisanriku Town) is taken as the study area. From simplified evaluations of bridge outflow, β1 and β2 values (ratio between bridge resistance and impact force) are confirmed to be efficient for evaluation of bridge girder and pier. From the investigation by recording videos, tsunami height was rising in relatively small pace inferring the wave shape not to be the bore type. Further, precisely evaluated β1 can explain the survival of Hachiman Bridge in both two mechanisms (one as tsunami just acted on girder and did not submerge it, with consideration of hydrodynamic and static force; other as girder was impacted and entirely inundated, using the maximum velocity during the inundation and considering hydrodynamic force and buoyancy).
