Dimensional and orientational analysis of seismic responses of single-column rocking piers under near-fault pulse-like ground motions

The promising design philosophy of rocking isolation was adopted to retrofit the aged bridges with single-column piers, namely single-column rocking piers. To estimate its seismic responses to near-fault pulse-like ground motions, the seismic demand model was devised. However, the existing demand model is of complicated formulation due to the higher-order rocking terms. This paper investigates this issue by using dimensional analysis and orientational analysis, and proposes a new demand model for predicting the seismic responses of single-column rocking piers subjected to near-fault pulse-like ground motions. Firstly, the dimensional analysis of seismic responses is performed by utilizing the recently advanced intrinsic length scale to obtain compact dimensionless formulas. Next, the sensitivity analysis is utilized to distinguish those dimensionless parameters of marginal effects on the seismic responses. It is shown that both pulse phase and damping ratio are excluded from the seismic response prediction, without destroying the dimensional homogeneity and orientational homogeneity. Dimensionless formulas can be further simplified based on the additional information derived from orientational analysis. Finally, the complete solution of seismic response, namely new demand model, is proposed from multiple linear regression. It is indicated that the new demand model has simpler expression and sounder theoretical basis and can provide more credible prediction for the seismic responses of single-column rocking piers.