既有铁路钢桥剩余疲劳寿命的概率性评估

中国铁路线上大量既有钢桥承受着日益繁重的交通荷载,其疲劳剩余寿命与使用安全已受到桥梁管理部门的高度重视,为避免不必要的维护与更换,应建立合理的既有钢桥使用安全评估方法。在建立能反映铆接钢桥疲劳破坏机理的脆断和韧断概率失效模型基础上,给出了疲劳可靠性分析的极限状态方程,并合理确定了随机变量的参数取值。建立了铆接钢桥构件双角钢概率疲劳破坏模型,基于Monte Carlo算法实现了铆接钢桥构件双角钢疲劳断裂失效概率的计算,编制了相应的概率断裂分析程序DAPFF。进而将概率断裂力学评估方法应用于京九线赣江桥的时变疲劳可靠度分析,并给出了赣江桥概率疲劳剩余寿命评估结果与维护对策。

Probabilistic assessment of remaining fatigue life for existing railway steel bridges

The remaining fatigue life and service safety of existing railway steel bridges is a topic of considerable importance,particularly for their operators.An improved method for the estimation of the actual fatigue life and safety of such structures are required in order to make their continued safe use possible while avoiding unnecessary repairs or replacements.According to the fatigue failure mechanism of existing steel bridges,two probabilistic fatigue failure models -brittle and ductile are proposed.Moreover,the corresponding limit-state equation and the basic variables are identified,and the uncertainties associated with them are quantified.A double-angle probabilistic fracture failure model(DAPFFM) of riveted bridge members is proposed.Furthermore,a reliability analysis program-DAPFF,based on Monte-Carlo method,is developed to compute the fatigue failure probability of DAPFFM.Then the probabilistic fracture assessment method is used to predict the time fatigue reliability of Ganjiang Railway Bridge of Jingjiu Railway in China.According to the assessment results of main truss members,the probabilistic remaining fatigue life,inspection intervals and maintenance strategy are determined.