急流条件下钢栈桥水流力数值模拟研究

Numerical Simulation of Flow Force for Steel Trestle in Rapids

在急流中搭建临时钢栈桥,水流力是影响栈桥安全性的关键因素,现有相关设计规范对钢栈桥水流力作用考虑不足。以下部结构为3排钢管桩的某临时钢栈桥工程为研究对象,通过计算流体动力学方法对桩周水流场进行数值模拟,分析作用于钢管桩上的瞬时水流力特征。研究结果表明,水流在绕过栈桥钢管桩后分离形成回流漩涡,水流作用于桩身的阻力和侧向力均存在脉动成分;前桩对中桩和后桩具有遮挡效应,使得前桩的平均阻力大于中桩和后桩,平均阻力模拟结果与《港口工程荷载规范》建议值较吻合;3个管桩的平均侧向力均接近于0,瞬时侧向力峰值与平均阻力处于同一量级,若单纯对钢管桩水流力按静力进行结构设计,可能偏于不利。

During the construction of temporary steel trestle bridge in the rapids,the flow force is the key factor affecting the safety of trestle bridge.In this paper,a temporary steel trestle bridge with three rows of steel pipe piles is taken as the study object.The flow field around the piles is simulated by the computational fluid dynamics method,and the characteristics of instantaneous flow forces acting on the steel pipe piles are analyzed.Results show that the flow separates and forms a backflow vortex after passing by the steel pipe piles of trestle bridge.The resistance and lateral force of the flow acting on the pile have pulsating components.The front pile has shielding effect on the middle pile and the back pile,so the average resistance of the front pile is greater than that of the middle pile and the back pile.The simulation results of average resistance are in good agreement with the recommended values in the Load Code for Harbour Engineering.The average lateral forces of the three pipe piles are close to zero,and the peak value of instantaneous lateral forces is in the same order of magnitude as the average resistance.It may be unsafe to design the structure of steel pipe pile purely according to the static force.