Seismic rehabilitation of steel arch bridgesusing nonlinear viscous dampers: Application to a case study

چکیده مقاله

Old steel arch bridges commonly need rehabilitation interventions because of their insufficient lateral resisting capacity against seismic loads.A punctual strengthening method is not always applicable to such bridges because of high costs and the lack of convenient access to the structural members, while replacement of the existing arch supports with base isolators is extremely difficult and risky. As an alternative and convenient retrofitting method, energy dissipation systems in the form of nonlinear viscous dampers (NVDs)can be adopted. In this study, NVDs are localized within the end bracing members of a steel arch analyzed as case study. Since the selection of NVD properties and the optimal location of the NVDs require a great number of extremely time-consuming nonlinear analyses, a design strategy is outlined using linearization of the structural system. The linearization is performed by developing novel concepts of equivalent damping ratio and damping correction factor for the structure rehabilitated with localized NVDs. The design strategy is employed for a real steel arch bridge as a case study. The complimentary nonlinear analyses(nonlinear time-history and pushover analyses) conducted in this paper show that the proposed design method is reasonably accurate in prediction of the maximum response of the rehabilitated bridge. Moreover, the results show that by using the proposed linearization method, the NVD characteristics can be suitably adjusted so that the seismic demand on the existing members and connections lies under an allowable limit, and the nonlinear deformations and energy dissipation are mostly localized in the NVDs.