下承式钢管混凝土拱桥吊杆在风–车联合作用下疲劳响应分析
Fatigue Response Analysis of Down-Bearing Concrete Filled Steel Tubular Arch Bridge Boom under Combined Wind-Vehicle Action

吊杆是下承拱桥最为重要受力构件之一，为分析其在随机车流和风荷载联合作用下应力循环次数、应力幅及疲劳寿命。以某下承式拱桥为工程背景，建立精细化元胞自动机模型模拟随机车流并对桥梁边吊杆影响线进行加载，然后基于谐波合成法模拟桥址处风荷载的随机脉动过程和风速时程，并根据准定常气动力理论对桥梁进行非线性抖振时程分析，分别得到随机车流和风荷载作用下吊杆应力时程，最后将两者应力叠加，采用雨流计数法将应力时程曲线进行计数处理后得到风–车联合作用下吊杆应力循环次数及应力幅，通过S-N曲线法、Palmgren-Miner线性累积损伤理论分析吊杆的疲劳寿命和等效应力幅。结果表明：1) 采用谐波合成法模拟随机风场具有较高精确性，可作为研究结构风致振动的一种模拟方法；2) 桥梁非线性抖振时程分析时，拱肋横向位移RMS值远大于竖向位移和扭转位移RMS值，该构件设计时风荷载作用不可忽视；3) 风荷载作用下吊杆应力波动较小，但波动频率极为密集，证实了吊杆属于典型高周疲劳；4) 风–车联合作用下吊杆的疲劳寿命需在随机车流单独作用下的疲劳寿命乘0.8修正系数。
The spreader bar is one of the most important stress-bearing members of a down-bearing arch bridge. In order to analyze its stress cycle number, stress amplitude and fatigue life under the combined effect of random traffic flow and wind load. Then, based on the harmonic synthesis method, we simulated the random pulsation process of wind load and wind velocity time course at the bridge site, and analyzed the nonlinear jitter time course of the bridge according to the quasi-deterministic aerodynamic theory to obtain the stress time course of the boom under the action of random traffic and wind load respectively, and finally superimposed the two Finally, the two stresses are superimposed, and the number of boom stress cycles and stress amplitude under the combined wind-vehicle action are obtained by counting the stress time course curves using the rainfall counting method, and the fatigue life and equivalent force amplitude of the boom are analyzed by S-N curve method and Palmgren-Miner linear cumulative damage theory. The results show that: 1) The simulation of random wind field by harmonic synthesis method has high accuracy and can be used as a simulation method to study the wind-induced vibration of the structure; 2) The RMS value of transverse displacement of the arch rib is much larger than the RMS value of vertical displacement and torsional displacement when the bridge is analyzed in nonlinear jitter vibration time, and the wind load effect cannot be neglected when the member is designed; 3) The stress fluctuation of the boom under the wind load is small, but the fluctuation frequency is extremely; 4) The fatigue life of the boom under the combined wind-vehicle action needs to be multiplied by 0.8 correction factor under the separate action of the random traffic.