Earthquake Damage Index and Fragility Analysis of Steel Damper for Seismic Isolation Bridge

Abstract

As an important component in seismic isolation bridges, steel dampers should have excellent low-cycle fatigue performance. This paper performs destructive tests of two types of steel dampers to accurately evaluate the fatigue damage of steel dampers under earthquake action. The damage index of steel dampers under the combined effect of cumulative energy dissipation and maximum deformation is established based on the damage states’ development during the testing process, which can characterize the degree and state of damage of steel dampers under earthquake action. The seismic performance of a seismic isolation continuous girder bridge is evaluated using the frequency statistical method of incremental dynamic analysis beyond the designated functional state, and the fragility analysis of steel dampers was carried out. The results show that the faster the loading rate, the more susceptible steel dampers are to fatigue failure. Under the design earthquake, the basic state of most dampers enters the energy dissipation state, realizing the seismic design goal of protecting bridge piers. The results indicate that the dampers’ overall performance state is slightly damaged, and the fatigue failure of steel dampers is not prominent in most earthquake cases.