对尺寸为300mm×300mm×300mm立方体混凝土试件进行了4中应变速率下的单轴循环加卸载试验，分析了加卸载过程中混凝土耗散能及塑性应变随加卸载次数之间的关系。结果表明：低应变速率下耗散能随循环次数的增加先增大后减小，高应变速率下耗散能则逐渐增大；耗散能与试件破坏程度密切相关，耗散能越大试件破坏所呈现出的结构面越多，破坏程度越大；在整个循环加卸载过程中混凝土的塑性应变增量较为稳定，与耗散能之间并不呈现明显的正相关性；加卸载循环历程中混凝土塑性应变几乎均匀增加，且与加载速率无关。

The single-axis cyclic plus unloading test at 4 strain rate is carried out on the size of 300mm×300mm×300mm cube concrete specimen，and the relationship between the dissipation energy of concrete and the plastic strain，with the times of adding and unloading，is analyzed. The results show that the dissipation energy at the low strain rate increases first and then decreases with the number of cycles increasing，and the dissipation energy increases gradually under the high strain rate. The dissipation energy is closely related to the damage degree of the specimen， and the greater the dissipation energy， the more structural surface， and the greater the damage degree；In the whole cycle of loading and unloading process，the plastic strain increment of concrete is stable，and there is no obvious positive correlation between the dissipation energy and the loading rate. The plastic strain of concrete increases almost evenly in the whole cycle plus unloading，and it is independent with the loading rate.