Experimental study on cyclic tensile behaviour of concrete under various strain rates

摘要

Owing to difficulties relating to the direct tension test on concrete, few test data are available. To study the effect of strain rate and unloading stress on the mechanical properties of concrete, three strain rates of 10(-6)s(-1), 10(-5)s(-1) and 10(-4)s(-1) and four unloading stresses are considered in this cyclic tensile-compressive test and the theoretical analysis is performed. In the paper, the non-classical strain is used to describe the tensile-compressive behaviour of plain concrete. Experimental results indicate that the residual strain and the non-classical compressive strain amplitude increase gradually with the increase of the unloading non-classical strain, which is a form of damage evolution. Meanwhile, the non-classical tangent modulus degrades with the reduction of the unloading stress. This means that the accumulation of non-classical deformation accompanies the stiffness degradation of the material during the process of continuous cyclic loading. This paper proposes a model to describe the stress-strain relation of concrete under cyclic tensile-compressive loading at various strain rates. Finally, the Weibull distribution model is introduced to make a statistical analysis of the damage evolution of concrete under post-peak monotonic and cyclic loading. The Weibull distribution model is shown to be a reasonable method to describe the post-peak damage evolution of concrete.