Many of the existing multi-span simply supported bridges in New York State, U.S., are susceptible to earthquake damage and need to be retrofitted to reduce their seismic risk. In this study, seismic retrofit of a five-span simply supported bridge with typical high-type fixed and expansion steel rocker bearings is conducted. A refined three-dimensional (3D) finite element model of the bridge is developed in ANSYS by considering foundation impedances. Multi-support time history analyses have been implemented in the seismic retrofit design for two levels of ground motions: 1,000- and 2,500-year return period earthquakes. The site-specific ground motions with consideration of the spatial variation are generated based on the geotechnical information. Seismic retrofit by replacing existing steel bearings with lead-rubber bearing (LRB) isolators has been adopted. The parameters of the isolators are determined by considering factors such as the seismic performance and translational resistance during normal service. The vulnerability of structural members and seismic retrofit effectiveness are quantified by the demand-to-capacity (D/C) ratio for the combined demands at the extreme limit state. The analyses show that after seismic isolation retrofit the pervasive vulnerabilities in pier columns and cap beams are eliminated. Comparing with strengthening the vunerable structural members, seismic isolation is proved a cost-effective retrofit solution. The overall seismic isolation design and analysis procedures presented in this study can help guide future seismic retrofit of similar types of bridges.

美国纽约州许多现有的多跨度简支桥梁都容易受到地震破坏，因此需要对其进行翻新以降低其地震风险。在这项研究中，对具有典型的高型固定式和膨胀型钢摇臂轴承的五跨简支桥进行了抗震改造。考虑到基础阻抗，在ANSYS中开发了桥梁的精制三维（3D）有限元模型。在地震翻新设计中，已针对两个级别的地震动进行了多支撑时程分析：1,000年和2,500年的返回期地震。基于岩土信息生成考虑空间变化的特定地点地面运动。通过采用铅-橡胶轴承（LRB）隔离器代替现有的钢轴承，进行了抗震改造。隔离器的参数是通过考虑正常使用期间的抗震性能和平移阻力等因素确定的。结构构件的易损性和抗震加固的有效性通过极限状态下组合需求的需求容量（D / C）比率进行量化。分析表明，在进行隔震改造后，消除了墩柱和顶梁中普遍存在的漏洞。与加强易损结构构件相比，地震隔离被证明是一种经济高效的改造解决方案。本研究中提出的总体地震隔离设计和分析程序可以帮助指导类似类型桥梁的未来地震改造。