循环荷载下考虑滞回效应的混凝土损伤模型

针对高混凝土坝地震过程中复杂的材料非线性问题,建立循环荷载下考虑滞回效应的混凝土损伤模型。模型分别选取符合混凝土实际变形特性的拉伸与压缩骨架线以考虑材料拉压异性,骨架线中含有软化段系数以适应试验结果的离散性。采用不依赖于骨架线形状的滞回效应加卸载特征点表达式,搭建能够反映混凝土循环荷载作用下软化段滞回效应的卸载路径与重新加载路径,并建议设立残余应变临界值解决残余塑性应变与卸载应变比值随应变增长的持续发散问题。模型将复杂多轴问题转化至单轴等效应变空间中求解,计算参数少,数学表达式简单,并通过混凝土循环荷载试验与Koyna重力坝的震害模拟验证了模型在非线性问题求解上的正确性与高效性。

Damage Model of Concrete Considering Hysteretic Effect Under Cyclic Loading

Starting from the dynamic non-linearity of materials for the seismic safety of high concrete dams, a damage constitutive model is established. Based on the experimental data, the tension and compression skeleton lines conforming to the actual deformation characteristics of concrete are selected to take into account the tensile and compressive anisotropy of materials. The skeleton lines contain softening section coefficients to adapt to the discreteness of the test results. The loading and unloading characteristic point expressions of the softening section independent of the skeleton line shape are adopted, and the unloading paths and reloading paths which can reflect the accumulation of damage are constructed by combining the characteristic points to describe the hysteretic effect of the softening section of concrete under a cyclic loading. It is suggested to set the critical value of residual strain to solve the continuous divergence due to the ratio of the residual plastic strain to the unloading strain increasing with the strain. The model transforms complex multi-axis problems into the uniaxial equivalent strain space with few calculation parameters and a simple mathematical expression. The correctness and efficiency of the model in solving non-linear problems are verified by the cyclic loading test of concrete and earthquake damage simulation of Koyna gravity dam.