Dimensional Estimation of Residual-Drift Demands for Bilinear Bridges under Near-Fault Ground Motions

Residual drift of bridge columns is an important performance measure for structural damage and postearthquake repair decisions. Yet there are very limited models available for estimating the residual drifts accurately. This paper presents an innovative method to realistically predict the residual drifts (including their trend and upper bound) of bilinear bridge deck-column systems directly from their inelastic mechanical properties and ground motion characteristics. The proposed estimation originated from the rigorous dimensional analysis of nonlinear time-history responses of various bilinear bridge deck-column systems under near-fault ground motions. Under this framework, the peak inelastic drifts and residual drifts were presented in dimensionless forms and showed remarkable order and correlation with structure-to-pulse frequency and the dimensionless nonlinearity index that accounts for the preyielding strength, ground motion amplitude, and softening or hardening postyielding behavior. Regressive equations for maximum displacement and residual-drift demands were proposed and validated. The corresponding error of this approach was shown to be lower than those of the existing codified methods.