整体式斜交桥中桥台钢桩地震响应

采用有限元分析软件SAP2000建立了某整体式斜交桥的三维结构模型，通过离散非线性弹簧单元模拟桥台-台后土以及H型钢桩-桩周土的土-结构相互作用，通过一系列双向地震作用下的非线性时程分析，研究了桩的朝向、桩周土刚度及桩头转动刚度对整体式斜交桥中H型钢桩地震响应的影响规律。研究结果表明:双向地震作用下，H型钢桩的横桥向位移显著大于纵桥向，且受桩朝向的影响更为明显，强、弱轴弯矩均呈正反双向分布，屈服面函数最大值一般位于桩顶，另一峰值则位于桩身2~4 m埋深处；钢桩绕强轴弯曲布置时，桩顶纵桥向位移相比绕弱轴弯曲时降低18.2%，但横桥向位移增大47.7%，桩顶处绕强轴弯矩增加约3.9倍，桩身反向强轴弯矩峰值降低67.0%，桩顶处绕弱轴弯矩基本不变，桩身反向弱轴弯矩峰值增加约1.0倍；随着桩周土刚度的降低，桩顶纵、横桥向位移增大，桩顶屈服面函数值降低，而桩身屈服面函数峰值增加，桩身更不易保持弹性；当桩头采用柔性连接时，桩顶纵、横桥向位移均增大，桩顶屈服面函数值降低，有利于保护桩头，而桩身屈服面函数峰值增加，当桩头转动刚度过低时甚至可能大于桩顶刚度，导致桩身在罕遇地震作用下先进入塑性。 

Seismic responses of abutment steel piles in integral skewed bridges

A three-dimensional structural model of a integral skewed bridge was established by using finite element analysis software SAP2000, and the interactions of abutment-soil behind the abutment and H-shaped steel pile-soil around the pile were simulated through a discrete nonlinear spring element. Through nonlinear time-history analysis under a series of bi-directional seismic actions, the influence rules of pile orientation, stiffness of the soil around the pile, and rotational stiffness of pile head on the seismic responses of the H-shaped steel pile in the skewed integral abutment bridge were studied. Research results show that under bi-directional seismic actions, the transverse displacement of the H-shaped steel pile is significantly greater than the longitudinal displacement, and greatly affected by the pile orientation. The bending moments around the strong and weak axes distribute in both positive and negative directions. The maximum values of yield surface function are generally located at the pile top, while the other peak values are located at the 2-4 m where the pile body is buried. When the steel pile is arranged around strong axis bending, the longitudinal displacement at the pile top reduces by 18.2% compared with that around weak axis bending, but the transverse displacement increases by 47.7%. The bending moment around the strong axis at the pile top increases by about 3.9 times, while the bending moment peak value of reverse strong axis of the pile body decreases by about 67.0%. The bending moment around the weak axis at the pile top basically unchanges, while the bending moment peak value around the reverse weak axis of the pile body increases by about 1.0 times. With the decrease in the stiffness of the soil around the pile, the longitudinal and transverse displacements at the pile top improve, and the yield surface function value at the pile top reduces slightly, while the peak value of the yield surface function of the pile body increases. The pile body is difficult to be elastic. When a flexible connection is adopted at the pile head, the longitudinal and transverse displacements at the pile top both rise. The yield surface function value at the pile top decreases, and the pile head can be protected effectively, but the peak value of the yield surface function of the pile body increases. When the rotational stiffness of the pile head is too low, the peak value of the yield surface function of the pile body may be higher than the value at the pile top, and thus the pile body may enter the plastic stage first under rare earthquakes.