桥上纵连板式无砟轨道HRB500钢筋概率S-N曲线研究

为研究桥上纵连板式无砟轨道HRB500钢筋的疲劳特性,对HRB500钢筋标准试件进行对称循环荷载下轴向拉压疲劳试验,得到不同应力水平下HRB500钢筋标准试件的疲劳寿命及其累积失效概率.在此基础上,以相关系数p和Theil不等系数u作为估计精度评价指标,对3种常用的三参数威布尔分布参数估计方法进行对比研究,并用精度最高的灰色预测法对HRB500钢筋标准试件疲劳寿命的威布尔分布参数进行估计,得到不同应力水平下HRB500钢筋疲劳寿命分布函数.最后,基于Kohout-Vêchet方程,建立全应力水平范围内可靠指标为4.2的HRB500钢筋概率S-N曲线.本文的研究成果可为服役期间组合荷载下桥上纵连板式无砟轨道HRB500钢筋疲劳寿命预测模型的建立提供试验依据.

Research on Probabilistic S-N Curve of HRB500 Reinforcing Bar of Longitudinal Connected Slab Track on Bridge

To study the fatigue properties of HRB500 reinforcing bar in longitudinal connected slab track on bridge, fatigue tests under symmetric axial alternating tension-compression cyclic loads for standard specimens of HRB500 reinforcing bar were conducted, and then the fatigue life and its cumulative failure probability of standard HRB500 reinforcing bar at different stress levels were obtained. On this basis, the correlation coefficient p and Theil''s inequality coefficient u were used as indexes of estimation accuracy to evaluate three methods which are widely used to estimate parameters of three-parameter Weibull distribution. And the grey prediction method, whose prediction accuracy is the highest among the three methods, was used to estimate the parameters of three-parameter Weibull distribution for the fatigue life of standard HRB500 reinforcing bar, and the distribution functions for the fatigue life of HRB500 reinforcing bar at different stress levels were obtained. Ultimately, the probabilistic S-N curve of HRB500 reinforcing bar in the longitudinal connected slab track on bridge with reliable index of 4.2 based on Kohout-Vêchet equation in the full stress range was established. The research can provide experimental basis for the establishment of fatigue life prediction model of HRB500 reinforcing bar in the longitudinal connected slab track on bridge under combined loads during service life.