Seismic design of self-centering bridge piers considering soil-structure interaction

Abstract

This paper presents the seismic design method for self-centering (SC) bridge piers considering soil-structure interaction (SSI) based on the inelastic displacement ratios (CR). The pier is simplified to a single-degree-of-freedom (SDOF) system characterized by flag-shaped hysteretic behavior. The cone model is adopted to simulate the dynamic behavior of the elastic homogeneous soil half-space below the foundation. Firstly, nonlinear time history analyses are conducted by subjecting the soil-structure interaction systems to 20 synthetic ground motions matched to the design response spectra. The effects of different parameters including the fundamental period of the fixed-base superstructure Tfix, strength reduction factor R, secondary stiffness ratio α, energy dissipation ratio of the flag-shaped model β, structure-to-soil stiffness ratio a0, and the height of the pier hs on the inelastic displacement ratios are studied. The analysis results show that the inelastic displacement ratio of the self-centering pier is generally underestimated when SSI is ignored. Specifically, the analytical relationship among CR, R, and Tfix is developed through regression analysis and used to estimate the inelastic displacement demands of the soil-structure systems during the design process. Next, the effects of soil on the elastic structural base shear force are investigated using the base shear effect coefficient RSSI and a simple equation is developed through regression analysis to estimate the RSSI value. A seismic design procedure of the self-centering piers considering soil-structure interaction is then proposed. Finally, a design example demonstrates the application of the proposed.design procedure, and 12 natural ground motions are used to perform nonlinear time history analyses of the designed self-centering pier. The analysis results verify the effectiveness of the proposed seismic design method.