定侧压混凝土双轴变幅拉-压疲劳累积损伤研究

为了调查混凝土在双轴拉-压交变荷载作用下的疲劳性能和累积损伤规律，利用改造的MTS疲劳试验机对变截面棱柱体混凝土试件进行了定侧压下轴心拉-压单级等幅和多级高-低、低-高变幅疲劳试验．总结了实测等幅与变幅疲劳应变与变形模量的衰减规律，基于疲劳变形模量定义了损伤变量，拟合试验结果得到了两阶段的损伤演化方程，依据损伤演变与损伤状态、加载条件间的相关性，建立了相应的疲劳累积损伤模型，并给出了利用本文模型进行疲劳损伤分析和剩余寿命预测的方法．模型预测的剩余寿命与实际试验结果的对比验证了模型的精度与有效性．

Fatigue cumulative damage of concrete under cyclic tension- compression with constant confined stress

An experimental research program was carried out with the aim of investigating the fatigue cumulative damage of concrete in axial tension - compression under constant and variable amplitude cyclic loading with constant confined stress. Forty -six tapered prismy specimens were tested on the biaxial fatigue test equipment, which was reconstructed basing on the stress -controller close -loop system of MTS. The damage variable was defined with the secant modulus of plain concrete under constant amplitude fatigue loading, and the law of cumulative damage and its two - stage evolution was obtained from the data of experiments. According to the correlation between accumulative damage and loading levels, the fatigue damage model was established. The precision and validity of the model was verified by the results of variable amplitude loading