重载和腐蚀共同作用下钢桥的时变疲劳可靠性分析

TIME-VARYING FATIGUE RELIABILITY ANALYSIS OF STEEL BRIDGES UNDER COMBINED ACTIONS OF HEAVY LOADS AND CORROSION

提出了一种能考虑重载和腐蚀耦合作用的钢桥时变疲劳可靠性分析方法。以某钢混组合简支梁桥为例,研究了日均卡车交通量、等效荷载总重、腐蚀性等级等因素对其疲劳失效概率的影响规律,计算了其疲劳细节在多种工况下的疲劳失效概率,比较了多种腐蚀环境下基于确定性分析方法和可靠性分析方法计算的疲劳寿命结果。结果表明:该文提出的基于支持向量回归和蒙特卡洛模拟的框架可快速准确地计算腐蚀环境下钢桥的疲劳失效概率;日均卡车交通量、等效荷载总重和环境腐蚀性等级的增加会造成钢桥疲劳寿命显著缩短;当环境腐蚀性等级在C5及以下时,基于确定性分析估算的疲劳寿命趋于保守。然而,当环境腐蚀性等级到达CX时,基于确定性分析得到结果可能偏不保守,应充分考虑环境腐蚀的影响。

A time-varying fatigue reliability analysis method of steel bridges is proposed in the present study,which can consider the coupling effects of heavy loads and corrosion on the fatigue reliability of steel bridges.Taking a steel-concrete composite simply-supported bridge as an example,the investigated is the influence of average daily truck traffic,of equivalent gross vehicle weight and,of corrosivity grade on its fatigue failure probability.The calculated is the fatigue failure probability of its fatigue details under various working conditions,and the compared is the results of fatigue life calculated upon one deterministic analysis method and one reliability analysis method under various corrosion environments.The results show that:The proposed framework based on support vector regression and Monte Carlo simulation can calculate the fatigue failure probability of steel bridges quickly and accurately in corrosive environment;The increase of the average daily truck traffic,of equivalent total weight of vehicle and,of the level of environmental corrosivity will significantly shorten the fatigue life of steel bridges;The fatigue life estimated upon deterministic analysis tends to be conservative when the environmental corrosivity level is C5 and below.However,the results obtained upon the deterministic analysis may not be conservative when the environmental corrosivity reaches CX under which the environmental corrosion shall be fully considered.