Seismic Rehabilitation of Steel Arch Bridges Using Nonlinear Viscous Dampers: Application to a Case Study

Abstract

Old steel arch bridges commonly need rehabilitation interventions because of their insufficient lateral resisting capacity against seismic loads. A localized strengthening method is not always applicable to such bridges because of high costs and the lack of convenient access to the structural members, and 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. This study analyzed NVDs localized within the end bracing members of a steel arch bridge (Qotour Bridge, Iran) as a case study. Because the selection of NVD properties and the optimal location of the NVDs require several extremely time-consuming nonlinear analyses, a design strategy was outlined using linearization of the structural system. The linearization was performed by developing novel concepts of equivalent damping ratio and damping correction factor for the structure rehabilitated with localized NVDs, and the proposed design strategy was applied to the real steel arch bridge. The complimentary nonlinear analyses (nonlinear time-history and pushover analyses) conducted showed that the proposed design method is reasonably accurate in the prediction of the maximum response of the rehabilitated bridge. Moreover, the results showed that by using the proposed linearization method, the NVD characteristics can be adjusted suitably so that the seismic demand on the existing members and connections remains below an allowable limit, and the nonlinear deformations and energy dissipation are localized mostly in the NVDs.