Capacity-based inelastic displacement spectrum for reinforced concrete bridge columns

This paper aims to construct inelastic displacement spectra associated with corresponding damage state (i.e., the capacity-based inelastic displacement spectrum) for RC bridge columns using a new smooth hysteresis model proposed by the authors. Nonlinear time history analysis of SDOF systems having different hysteretic behaviors identified from the tested columns with various design parameters and subjected to 15 far-field and 15 near-fault pulse-like ground motions was conducted. The considered design parameters include the ratios of longitudinal reinforcement and transverse reinforcement, aspect ratio, as well as axial load ratio of columns, and the effects of these parameters on deteriorated hysteretic behaviors of RC bridge columns was discussed. Failure criteria was made because columns analyzed using the model proposed by the authors could fail under one or more than one of the earthquake records especially when subjected to near-fault ground motions. Furthermore, the effects of various design parameters of column and earthquake types on the computed spectra were presented and the well-known inelastic displacement ratio formula in the literatures were evaluated using the computed spectra. Finally, formulae for inelastic displacement ratio and corresponding damage state as a function of structural period, strength ratio, and various design parameters were established for far-field and near-fault ground motions, respectively.