A comparative seismic performance assessment of a multi-span bridge isolated with elastomeric and sliding isolation systems

Resumen

The remarkable performance of seismically isolated bridges in South America during the last two major seismic events has reflected the substantial increase in the adoption of base isolation in this type of infrastructure. In this paper, a non-isolated multi-span bridge was retrofitted for continued functionality adopting seismic isolation devices. With the aim of performing a comparative assessment of the most adopted base isolation techniques, the retrofitted bridge was analyzed using elastomeric and sliding isolation devices. In this case study, Lead Rubber Bearings (LRB) and Triple Friction Pendulum Bearings (TFPB) were selected as representative cases of elastomeric and sliding isolators, respectively. In the design of these isolation systems, the values of isolated periods, post-yield stiffness and yield force of both systems were set to be almost equals. This criterion was adopted for the purpose of comparing the unique effects of each type of isolator on the bridge seismic response. A series of nonlinear dynamic analyses were carried out considering both horizontal ground motion components to perform the comparative assessment. Numerical models that consider the bidirectional response and describe the different stages of motion of the isolators were adopted and then validated reproducing a series of benchmark tests. Upper and lower limit analyses were considered to gain a comprehensive understanding of the induced response by each isolation system. From the results, it is concluded that the LRB system induces a more uniform distribution of the seismic forces into the substructure; however, it experiences greater isolator displacements in comparison with the TFPB system.