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Earthquakes and Structures
  Volume 19, Number 4, October 2020 , pages 273-286

Nonlinear response of the pile group foundation for lateral loads using pushover analysis
Yongliang Zhang, Xingchong Chen, Xiyin Zhang, Mingbo Ding, Yi Wang and Zhengnan Liu

    The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.
Key Words
    chigh-speed railway bridges; pile group foundation; nonlinear calculation model; pile group effect; pushover analysis; seismic performance
Yongliang Zhang, Xingchong Chen, Xiyin Zhang, Mingbo Ding, Yi Wang and Zhengnan Liu:School of civil engineering, Lanzhou Jiaotong University, Anning West Road 88, Lanzhou, Gansu, China

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