Experimental evaluation of seismic performance of Coiled Cable Restrainer on bridges isolated by Unbonded laminated rubber bearings

Abstract

Girder bridges isolated by unbonded laminated rubber bearings (ULRBs) may suffer severe damages or even collapse due to the bearing sliding under strong earthquakes. The main objective of this paper is to investigate the effect of cable restrainers on the seismic performance of ULRBs isolated bridges considering the sliding of bearings. A superstructure restraining device named Coiled Cable Restrainer (CCR), which can restrain the girder-pier longitudinal relative displacement bi-directionally, is described in detail. Force-displacement relationship of the device was derived from pseudo static tests. 1/15 scaled shake table test was carried out on a ULRBs isolated two-span continuous girder bridge model with and without CCRs. Numerical analysis using finite element models (FEMs) were conducted as well. Test results indicate that the bearing displacement can be effectively mitigated and the residual displacement can be mostly eliminated with the implementation of CCRs. However, increased girder acceleration and pier-bottom stress were found because of the increased restoring force of the restrainer. Numerical results are in consistent with experimental outcomes, which demonstrates that the FEMs can be used to predict seismic responses of bridges equipped with CCRs for further research.