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Highway bridges are widely designed with extended pile-shafts due to their cost-effectiveness compared to conventional pile foundations. However, while pile foundations are generally designed to remain elastic under earthquakes, extended pile-shafts with similar diameters to bridge columns are susceptible to localized seismic damage below ground level. This poses challenges for post-earthquake damage inspection of foundations and contributes to the complex seismic behavior of the bridge system. The complexity also results from the column-pile-shaft-soil interaction effect, where substantial variations exist in soil properties, and design details of column, pile-shaft, and bridge superstructure. To address the complexity and deal with the uncertainties, this study develops probabilistic numerical models to examine the seismic performance of extended pile-shaft-supported highway bridges through cyclic pushover analyses and nonlinear response history analyses (NRHAs). Two-dimensional (2D) finite element models of the column-shaft-soil system are developed in OpenSees, where 320 model samples are generated using Latin Hypercube Sampling to capture uncertainties in bridge design and soil profile. In each model, fiber-type force-based beam-column elements are used to model the column and pile-shaft, whereas p-y and t-z springs are utilized to simulate the soil behavior. Cyclic pushover analyses are performed on the 2D models to elucidate the column-shaft coupling effect in seismic response and damage. In addition, seismic capacity limit state models in terms of curvature ductility of column-shaft are developed by relating the global responses to material-level behaviors. Furthermore, high-fidelity three-dimensional (3D) models of the bridge-column-shaft-soil systems are developed to capture the dynamic interplay among column, pile-shaft, soil, deck, and various abutment components. NRHAs are then carried out against the 3D models when subjected to a large suite of ground motions, enabling a comprehensive investigation of seismic responses of column-shaft. The results indicate that column-shaft deformation, characterized by curvature ductility, is concentrated at two critical locations: the column top and the pile-shaft below ground level. This study provides insights to analyze and design extended pile-shaft-supported highway bridges under earthquake loading.

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Seismic Response Analyses of Highway Bridges Designed with Extended Pile-Shafts

  • 会议论文

  • 发表日期：

    2025年

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  • Sirui Song,
  • Yazhou Xie

摘要

Highway bridges are widely designed with extended pile-shafts due to their cost-effectiveness compared to conventional pile foundations. However, while pile foundations are generally designed to remain elastic under earthquakes, extended pile-shafts with similar diameters to bridge columns are susceptible to localized seismic damage below ground level. This poses challenges for post-earthquake damage inspection of foundations and contributes to the complex seismic behavior of the bridge system. The complexity also results from the column-pile-shaft-soil interaction effect, where substantial variations exist in soil properties, and design details of column, pile-shaft, and bridge superstructure. To address the complexity and deal with the uncertainties, this study develops probabilistic numerical models to examine the seismic performance of extended pile-shaft-supported highway bridges through cyclic pushover analyses and nonlinear response history analyses (NRHAs). Two-dimensional (2D) finite element models of the column-shaft-soil system are developed in OpenSees, where 320 model samples are generated using Latin Hypercube Sampling to capture uncertainties in bridge design and soil profile. In each model, fiber-type force-based beam-column elements are used to model the column and pile-shaft, whereas p-y and t-z springs are utilized to simulate the soil behavior. Cyclic pushover analyses are performed on the 2D models to elucidate the column-shaft coupling effect in seismic response and damage. In addition, seismic capacity limit state models in terms of curvature ductility of column-shaft are developed by relating the global responses to material-level behaviors. Furthermore, high-fidelity three-dimensional (3D) models of the bridge-column-shaft-soil systems are developed to capture the dynamic interplay among column, pile-shaft, soil, deck, and various abutment components. NRHAs are then carried out against the 3D models when subjected to a large suite of ground motions, enabling a comprehensive investigation of seismic responses of column-shaft. The results indicate that column-shaft deformation, characterized by curvature ductility, is concentrated at two critical locations: the column top and the pile-shaft below ground level. This study provides insights to analyze and design extended pile-shaft-supported highway bridges under earthquake loading.