中文摘要：

Najar能量法定义了损伤耗散能和无损应变能,并通过两者的比值确定了混凝土单轴受压情况下的损伤变量。该方法原理清晰,但不能在宏观上很好地描述混凝土单轴受压破坏的实际过程。针对此问题改进了Najar能量法,将混凝土受压过程中的弹性变形和塑性变形剥离开来,定义了一个新的损伤变量。为了对比分析改进前后的方法,进行了不同加载速率下的混凝土单轴压缩试验,并对试验数据加以拟合。以拟合后的试验数据为基础,分别利用改进前后的两种方法计算了混凝土受压过程中损伤变量,得到了改进前后损伤变量随应变变化的关系曲线。对比分析发现,改进后的Najar能量法在计算上更为简便,而且在宏观上更符合混凝土单轴受压的一般破坏规律。同时,这一关系曲线也反映了混凝土材料的应变率效应。

英文摘要：

Najar energy method defines damage dissipation energy and nondestructive strain energy,and the ratio of those two is defined as the damage variable. The principle of the method is clear,but the method can ＇t well describe the actual process of concrete uniaxial compression failure. In this paper,this method is improved,the delamination of elastic deformation and plastic deformation in the process of concrete compressiona is done,and a new damage variable is defined. In order to make a comparison between those two methods, the uniaxial compression tests of concrete under different loading rates are carried out,and the experimental data are fitted.Based on the fitted data,the damage variables in the compression process of concrete are calculated by those two methods,and the relationship curves between the damage variables and strain are obtained from the experimental studies. It is found from the experimental studies that the improved Najar energy method is more simple and more convenient than the conventinoal methods,and it is also more conformable to the general failure law of concrete under the uniaxial compression. At the same time,the relationship curves also reflect the strain rate effects of concrete.