路用水泥混凝土疲劳损伤的可靠度分析

Fatigue Damage Reliability Analysis of Cement Concrete for Highway Pavement

为获得路用水泥混凝土在高应力比作用下疲劳可靠度的变化规律,首先推导了水泥混凝土疲劳寿命等单调随机变量的概率密度,然后推导了Miner,Chaboche-Zhao和修正Chaboche-Zhao疲劳损伤模型的损伤概率密度;借助疲劳试验结果,获得这3种模型的疲劳损伤概率密度函数,最后将荷载循环作用次数代入上述函数,从而获得水泥混凝土疲劳可靠度随荷载循环作用次数的变化规律.结果表明:随着荷载循环作用次数增加,相同应力比下,疲劳可靠度从几乎为100%逐渐衰减为0%;无论何种应力比,在荷载循环作用初期,疲劳可靠度均有一个较稳定阶段,但随着应力比的增加,该阶段逐渐减小,且可靠度为0%时对应的荷载循环作用次数也减小;在可靠度衰减阶段,对于相同荷载循环作用次数,应力比越高,则可靠度越低;此外,Miner疲劳损伤模型比修正Chaboche-Zhao疲劳损伤模型偏安全.

In order to obtain the changing law of the fatigue reliability of cement concrete for the highway pavement under high stress ratios, firstly the probability densities of monotonic random variables including cement concrete fatigue life were deduced. And then the fatigue damage probability densities of the Miner, Chaboche-Zhao and modified Chaboche-Zhao models were deduced. By virtue of the fatigue test results, fa- tigue damage probability density functions of the three models were obtained. Finally, substituting load cycles into the functions the changing law of cement concrete fatigue reliability with load cycle was ac- quired. The results show that under the same stress ratio, with the increase in the load cycle the fatigue re- liability declines from almost 100% to 0% gradually. Under any stress ratio, in the initial stage of load ac- tion, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the phase diminishes gradually and the load cycle corresponding to reliability of 0% also decreases. In de- scent phase of reliability, the higher stress ratio is, the lower concrete reliability is for the same load cycle. Besides, relative to the modified Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.