Cyclic Loading for RC Bridge Columns Considering Subduction Megathrust Earthquakes

Current structural design philosophies rely on the inelastic capacity of structures for resisting seismic excitations. To assess such capacity, cyclic loading protocols have been used as a common practice in laboratory and numerical evaluations. The main objective was to obtain quasi-static loading protocols that reflect the increase in the inelastic demands of bridge columns subjected to long duration ground motions caused by subduction megathrust earthquakes. To study the demands imposed on the structural system, results from nonlinear time-history analyses considering numerous subduction ground motions imposed on structures with a wide range of structural periods and target ductilities were used. Because the number of inelastic cycles and the expected damage can be closely related, statistical analyses of the number of inelastic cycles and the cumulative inelastic demands were used to develop the loading protocols. Due to the observed dependence of the demand parameters on the structural period, different protocols were developed for short-, medium-, and long-period responses. The proposed cyclic deformation histories are more representative of the inelastic demands from subduction earthquakes; therefore, their application would improve the seismic assessment of bridge columns exposed to such hazards.