混凝土在三轴比例加载下的损伤特性研究

将根据Najar损伤理论建立的单轴受压条件下混凝土损伤模型推广应用到三轴受压状态、利用由Simpson积分方法建立的损伤模型，计算得到了混凝土在三轴比例加载作用下，竖向主应力方向的损伤曲线．研究结果表明，混凝土在三轴受压和单轴受压作用下的损伤有相似的发展趋势．2种类型加载历史下混凝土损伤都随着应变的增大而增大，且初始加载阶段损伤发展较快，加载末段损伤发展缓慢并趋于稳定值．但是，在相同应变历史条件下，三轴受压下的损伤值比单压下的损伤值明显变小，而且随着侧压比例的增大损伤进一步减小，说明侧压有效限制了混凝土损伤的发展．另外，三向等比例加载状态下混凝土损伤近似沿直线增长，且损伤增长速率非常小，说明这种加载状态对于充分发挥混凝土受压特性是最有利的．

Damage Evolution of Concrete under Triaxial Proportional Loading

According to the damage theory by Najar, the damage model of concrete under uniaxial compression is applied to triaxial compressive state to analysis damage evolution of concrete under various triaxial loading pattern. Based on the Simpson integral method, the damage curve of concrete in the main stress direction under triaxial proportional loading is calculated by the damage model. The damage evolution rule of concrete under triaxial and uniaxial compression shows the similar tendency. With the increase in the strain of the loading history, the incremental speed of damage becomes less and less, and finally the damage approaches a stable extreme value. Experienced the same axial strain loading history, the damage value of concrete is lower than that of under uniaxial compression, and the damage of concrete in axial direction is reduced gradually with the increase in lateral pressures, which means that the lateral pressure can reduce the damage effectively. In addition, under triaxial equi-compression loading history, the damage of concrete is found to be in linear dependence relationship with the increase of axial strain, which means that kind of loading pattern can develop the compressive feature of concrete adequately.