中文摘要：

为了分析及深入探讨混凝土在受拉加载及卸载情况下的力学特性,基于随机损伤本构关系提出了一种混凝土轴拉加卸载模型,推导出了混凝土加卸载的应力-应变关系表达式.为了印证理论表达式,进行了混凝土轴向拉伸及加卸载的试验研究,测得了混凝土的材料参数及其相应的轴拉加卸载应力-应变曲线.结合模型的计算结果,对混凝土的轴拉加卸载试验结果进行了对比分析,结果表明：混凝土轴拉加卸载模型能够预测混凝土的极限强度,同时能描述混凝土的强度软化、加载过程中的弹模折减及卸载后的塑性变形.

英文摘要：

To analyze the mechanical properties of concrete in the case of tensile loading and unloading, a stochastic elastoplastic tensile damage model of mesoscopic springs was proposed for the axial loading and unloading of concrete, with the loading and unloading stress-strain relationships of concrete deduced. To validate the rationality and accuracy of the model, an experimental research on axial tensile loading and unloading of concrete was carried out, where the concrete parameters and the stress-strain relationships were measured. Comparison between the experimental results and the calculation model results shows that, the model can well predict the ultimate tensile strength, meanwhile nicely depict the strength softening, the residual strain after unloading and the elastic modulus degradation of concrete.