交通荷载对拉索钢丝疲劳寿命的影响

Traffic Load Effects on Fatigue Lives of Cable Wires

钢丝的疲劳寿命主要受到荷载(特别是交通荷载)作用的影响.从疲劳裂纹扩展以及临界裂纹长度两个方面研究交通荷载对疲劳寿命的影响.首先从Paris公式出发对裂纹扩展量计算公式进行简化,指出疲劳应力幅概率分布对疲劳寿命的影响主要由其均值决定;接着采用Rice公式提供的临界交通荷载分布规律对疲劳寿命的影响进行分析,给出了疲劳寿命的失效概率计算公式.通过将以上方法应用于实桥的拉索钢丝,发现应力幅的变异性对疲劳寿命的影响可以忽略.计算结果还显示,交通荷载极值对于疲劳寿命有一定影响,其标准差可达9周以上.

The fatigue lives of wires are mainly affected by live loads, especially traffic load. This paper studies the fatigue lives of wires on account of the traffic load effects on the fatigue crack growth and the critical crack length. First, the Paris Law is simplified for the analysis of crack growth, which shows that the mean value of stress range has great effects on the fatigue lives despite of the distribution function of the stress range. Then, based on the distribution of maximum traffic load from Rice equation, the traffic load effects on the critical crack length are analyzed and the failure probability of fatigue lives is proposed. The above approaches are applied to stayed-cable wires of an actual bridge. It is found that the variability of stress range has little effect on the fatigue lives. And it can be drawn from the results that the maximum traffic load has some effects on the fatigue lives and the standard deviation of fatigue lives can be up to 9 weeks.