Response of model pile-supported bridge to near-fault pulse-type ground motions

Two comparative scaled shaking table tests were conducted to investigate the influence of near-fault pulse-type ground motions on pile-supported bridge system. Two sets of pulse-like (PL) and non-pulse like (NPL) ground motions with identical response spectra were applied as inputs to evaluate the dynamic response and damage modes of the system under different intensity levels. The results indicate that the natural frequency of the system decreases significantly and the damping ratio increases continuously with the increase of loading intensity, reflecting stiffness degradation and enhanced energy dissipation dominated by pile-soil interaction. PL ground motions do not significantly amplify the peak acceleration but remarkably increase the velocity and displacement responses, with flexible components such as the bridge deck being more sensitive. The overall frequency-domain response is controlled by the matching degree between the input spectrum and the dominant frequency of the system. Pulse identification using the wavelet energy concentration method reveals that pulses are concentrated in the early stage of ground motions and dominated by low frequencies, which are strongly correlated with large structural displacements. Hysteretic and energy analyses show that the pulse-containing cases exhibit an impact-type response mechanism with instantaneous energy concentration, while the non-pulse cases present a cyclic cumulative type. This study provides experimental basis and theoretical reference for the seismic design of bridges in near-fault regions. • High-quality shaking table data were obtained for a pile–soil–bridge system. • Pulse and non-pulse motions with identical spectra and duration were compared. • Structural responses were evaluated from local to global and time to frequency. • Velocity pulses were identified using wavelet energy concentration analysis. • Pulse effects were interpreted from hysteretic energy dissipation mechanisms.