Design of Rupture Strength of Side Blocks in Elevated Steel Girder Bridges with Elastomeric Bearings

Elastomeric rubber bearings with side blocks have been extensively used as a seismic response-control device in steel girder bridges in Japan. In real scenarios, the behavior of the girder bridges with elastomeric bearings are usually complex because of the complex mechanism by which the seismically induced inertia forces at concrete deck transmits to the girder bearings. Therefore, it is important to carry out seismic response analysis of a whole bridge system considering the interaction between different structural components in order to check the performance of the side blocks during an event of severe earthquakes. The objectives of the present study are to develop a detailed three-dimensional finite element (FE) model of an elevated girder bridge system and to propose a design rupture strength for the side blocks. The FE-model is constructed based on an existing plate girder bridge considering the effect of concrete slab, girders, stiffeners, rubber bearing, pier and the damage control by the side blocks. A sequence of seismic response analysis is then performed using four different rupture forces of the side blocks by considering the Level-2 design earthquake, the 1995 Kobe earthquake and the 2016 Kumamoto earthquake. The analytical investigation reveals that the side blocks should be designed to withstand a horizontal force of at least 1200 kN in order to prevent the rupture of the side blocks and to mitigate damage of bridge piers. Moreover, the damage to the critical parts of bridge superstructure can be mitigated by strengthening the side blocks. Based on the analysis results, a retrofit plan to strengthen the side blocks of existing girder bridges is proposed.