Evaluation of the seismic performance of a highway bridge considering the subsidiary fracture of the rubber bearings

The 2011 earthquake off the Pacific coast of Tohoku occurred on March 11^th. Several natural rubber bearings of the viaduct in the Tohoku district were fractured due to this earthquake. This type of damage was the first experienced in Japan. In this research, a three span continuous plate girder bridge with reinforced concrete piers was selected as a structure for examination. Natural rubber bearings were set up on the top of each pier. A fracture model of the natural rubber bearing was proposed in this research. Dynamic response analysis of the highway bridge considering the hardening and the fracture of the natural rubber bearing was conducted using TDAP III. The observed record of the nearest point to the damaged highway bridge in Sendai was selected as seismic input motion. From the results of the dynamic response analysis of the highway bridge, an increase of relative displacement in the natural rubber bearing, depending on the fractured bearing was confirmed in a longitudinal direction. The possibility of a fracture progress of the natural rubber bearing was verified. The relative displacement of the natural rubber bearing in the transversal direction was confirmed, the rotational motion of the girder occurred after the fracture of natural rubber bearings. From these results, the response of the highway bridge considering hardening and fracture of the natural rubber bearing was determined.