混凝土循环加卸载动态损伤演化推移分析及损伤值估计模型

Analysis of Dynamic Damage Evolution Translation and a Model of Estimating Damage Value of Concrete under Cyclic Loading and Unloading

利用多功能三轴仪进行了不同应变速率下的混凝土循环加卸载试验,对声发射信号与应力水平的关系进行了分析,并从声发射撞击数的角度对混凝土损伤演化规律特性进行研究,进一步构建了只含循环次数的单参数损伤值估计模型。研究结果表明:在不同的应变速率下,混凝土损伤演化的路径各不相同,当应变较小时,混凝土前期损伤累积程度较大,后期平缓,出现水平段;随着应变速率的提高,混凝土损伤演化路径前移,后一种应变速率相对于前一应变速率所对应的损伤推移值随着累计残余应变的增大呈现出先增大后减小的规律,当累计残余应变一定的情况下,随着应变速率的提高,相邻2种应变速率对应的损伤推移程度在不断减弱;混凝土循环加卸载损伤演化规律具有三阶段损伤模式,统计密度函数能较好地反映循环加卸载损伤演化规律。

Concrete samples were tested by multi-function triaxial instrument under cycle load condition with different strain rates. The relationship between acoustic emission signals and stress level was analyzed,and the damage evolution regularity was researched from the aspect of acoustic emission hit number. Furthermore,a single-parameter model that only contains cycle number was established to estimate damage value. The results show that 1) under different strain rates,the paths of damage evolution are not identical. Damage accumulation degree at earlier stage is bigger than that at later stage when the strain is small,and damage curve is flat at later stage; 2) the damage evolution path moves forward with the increase of strain rate,and the value of damage development along with the increase of strain rate presents a regularity that first increases then decreases with the increase of cumulative residual strain. When cumulative residual strain is certain,the damage development degree at two adjacent strain rates weakens with the increase of strain rate; 3) the regularity of concrete damage evolution under cyclic loading and unloading is featured with three phases,which can be reflected by statistical density function.