基于能量法的混凝土循环加卸载动态损伤特性

Dynamic damage characteristics of concrete during cyclic loading and unloding based on energy method

为了从能量法的角度研究混凝土循环加卸载下的损伤演化特性,利用大型动静力三轴仪对边长为150 mm的立方体混凝土试件,进行不同侧应力、不同应变速率的循环加卸载试验。用改进的Najar能量法,确定了一种新的损伤变量计算方法,对比分析了改进后的混凝土损伤演化曲线与试验所得混凝土应力-应变包络曲线,将修正后的Weibull-Lognormal损伤本构模型对试验数据进行拟合分析。结果表明:新的损伤变量计算方法简单,物理意义明确;改进后的混凝土循环加卸载损伤演化曲线可以分为三个阶段,损伤不变阶段、损伤加速发展阶段、损伤稳定发展阶段;选用的塑性变形公式与试验结果拟合较好;经过修正后的混凝土损伤本构模型能较好地模拟混凝土循环加卸载条件下的应力-应变包络曲线。

In order to study the damage evolution characteristics of concrete under cyclic loading and unloading conditions from the perspective of energy method, the tests with 150 mm cubic concrete specimens under different lateral stresses and strain rates are carried out by using the large dynamic and static triaxial apparatus. A new method for calculating damage variables is established by using the improved Najar energy method. The curves of the improved damage evolution of concrete are compared with the experimental stress-strain envelope curves. The modified Weibull-Lognormal damage constitutive model is employed to fit and analyze the test data. The results show that the new method for calculating the damage variables is simple and its physical meaning is clear, and the curve of the improved damage evolution of concrete under cyclic loading and unloading conditions can be divided into three stages: damage invariable stage, damage accelerated development stage and damage stable development stage. The selected formula for calculating the plastic deformation fits well with the test results, and the improved damage constitutive model can well simulate the stress-strain curve of concrete under cyclic loading and unloading conditions.