交通载荷作用下跨海桥梁-电缆组合结构随机振动分析

电缆沿桥跨海铺设是海缆铺设的一种新的形式, 针对由汽车和列车交通载荷诱发的沿跨海桥梁敷设电缆的振动问题, 建立了桥梁-电缆的整体组合结构分析模型, 将汽车和列车的作用载荷简化为移动的随机集中载荷序列, 发展虚拟激励法(pseudo-excitation method, PEM)用于分析移动随机载荷作用下电缆位移和应力响应的标准差及演变功率谱 (power spectral density, PSD), 并研究了汽车和列车运行速度对电缆动力响应标准差的影响. PEM将移动随机载荷问题转化为特定频率简谐移动载荷作用下的动力响应分析, 能够计算得到与Monte Carlo (MC) 方法非常吻合的电缆动力响应标准差, 但所需的时域响应分析次数远少于MC方法. 数值结果表明, 随着汽车和列车运行速度的提升, 电缆位移和应力标准差呈现增大的趋势; 在汽车和列车交通载荷作用下, 铝护套的位移标准差和功率谱的值比缆芯要大, 这可能会使得电缆的疲劳破坏首先发生在铝护套层, 本文工作对电缆沿桥跨海铺设实际工程具有一定的借鉴意义. 

RANDOM VIBRATION ANALYSIS OF A SEA-CROSSING BRIDGE AND POWER CABLE COMPOSITE STRUCTURE UNDER TRAFFIC LOADS1)

Laying power cables along the bridge is a new way of laying submarine cables across the sea. This paper focuses on the vibration of power cables laid on sea-crossing bridges induced by automobile and vehicle traffic loads. The overall combined structural analysis model of the bridge and cable is established, and the automobile and vehicle loads are simplified into random moving concentrated load sequence. The pseudo-excitation method (PEM) is developed to calculate the standard deviation and evolutionary power spectrum density of displacement and stress responses of the cable under random moving loads. The influence of automobile and vehicle speed on the standard deviation of cable dynamic response is studied. The PEM transforms the problem of random moving loads into dynamic response analysis under simple harmonic moving loads with specific frequencies, and it can calculate the standard deviation of dynamic response of the cable which is very consistent with Monte Carlo (MC) method, but the number of time-domain response analysis required is far less than that of MC method. The numerical results show that the standard deviation of displacement and stress of the cable increases with the increase of automobile and vehicle running speed. Under automobile and vehicle traffic loads, the standard deviation and power spectrum of displacement of aluminum sheath are larger than that of the cable core, which may make the fatigue failure of the cable occur in the aluminum sheath layer first. This work has a certain reference significance for the actual project of cable laying along the sea-crossing bridges.