考虑冲刷深度影响的大跨悬索桥主塔群桩基础的抗船撞分析

Ship collision analysis of pile group foundations of a long‑span suspension bridge considering the scour depth

船撞是航道桥设计中必须考虑的偶然作用,当桥梁基础受到水流冲刷后,船舶的撞击会对其产生更加严重的影响。以张靖皋长江大桥南航道桥为研究对象,建立悬索桥全桥模型,分析了在冲刷和船撞共同作用下大跨悬索桥的非线性结构动力响应,根据得到的内力结果,对桩基进行截面弹塑性分析和抗船撞能力评估。结果表明:桩顶弯矩、剪力随冲刷深度基本呈线性关系,桩顶轴力、位移随冲刷深度基本呈指数关系,当冲刷深度超过一定深度后时,桩顶位移显著增加。在运营阶段应及时关注基础的冲刷深度,避免因桩基水平刚度不足引起的损失,桩顶位移也应作为桥梁抗撞评价的主要指标。

Ship collision is an accidental action that must be considered in the design of channel bridges.When the bridge foundation is scoured by the current,the ship collision will have a more serious impact on it.This paper takes the south channel bridge of the Zhangjinggao Yangtze River Bridge as the background,and establishes a full-bridge model.Then it studies the nonlinear structural dynamic response of the long-span suspension bridge under the combined effect of scouring depth and ship collision.According to the obtained internal force,the section elastic-plastic analysis and the ship collision performance of the pile are carried out.The results show that the pile top bending moment and shear force have a linear relationship with the scour depth,and the pile top axial force and displacement have an exponential relationship with the scour depth.When the scour depth exceeds a certain value,the pile top displacement increases significantly.In the operation stage,attention should be paid to the scour depth of the foundation in time to avoid losses caused by insufficient horizontal stiffness of the pile foundation.The pile top horizontal displacement should also be used as the main evaluation index of the bridge collision.