混凝土抗压疲劳寿命概率模型试验研究

Experimental study on probability model of concrete compressive fatigue life

对27个强度为C30、尺寸为150mm×150mm×300mm的混凝土棱柱体试件进行了疲劳寿命试验,推导了利用小样本数据对对数正态分布和三参数Weibull分布进行参数估计的方法。基于试验数据,利用相关系数优化法,分别用对数正态分布和三参数Weibull分布对混凝土疲劳寿命的概率模型进行拟合,回归得到其分布参数,从而确定了C30混凝土疲劳寿命概率模型。运用得到的混凝土疲劳寿命模型对算例进行了疲劳可靠度的计算。拟合的结果表明,混凝土疲劳寿命基于这两种概率分布模型都拟合较好,但三参数Weibull分布拟合精度更高。对混凝土疲劳损伤的研究表明,混凝土结构疲劳累积损伤所对应的可靠度随加载周期大致呈现二次抛物线下降的趋势,混凝土结构的疲劳损伤随着加载周期的增加而发展得越来越迅速。

Fatigue life test was carried out to 27 concrete prism specimen whose strength were C30,the parameter estimation method using small sample data for lognormal distribution and the three parameter Weibull distribution was deduced.Based on the test data,combined with the relative coefficient optimization method,probability models of concrete fatigue life were fitted by lognormal distribution and the three parameter Weibull distribution,the fatigue life models of C30 concrete were determined by fitting the distribution parameters,fatigue reliability of an example was calculated by those concrete fatigue life models.The fitting results show that the concrete fatigue life based on the two probability distribution models are both well fitted,but the three parameter Weibull distribution has higher fitting precision.Research on fatigue damage shows that the reliability level of repeated damage caused by concrete structural fatigue,in an inverse ratio to the loading period,roughly follows the downward tendency of the second-degree parabola,and the damage,in direct ratio,speeds up rapidly in accord with the cycle of loading time.