Numerical Simulation Of Static And Dynamic Mechanical Performance Of Concrete On Micro-Level

In this paper, concrete was taken as three-phase composites consisting of aggregate, bond and mortar matrix on micro-level. Based on the second development of finite element software Marc, numerical simulation of mechanical performance and failure process was studied for the uniaxial concrete specimen of Dongjiang arch dam, three-graded-concrete supported beam and three-graded-concrete beam of Xiaowan arch dam under static and dynamic load, and the relation of micro-damage and macro-failure were simply discussed.The number of all kinds of aggregate was decided according to the actual gradation of aggregate of three-graded-concrete and Walraven formula. The location of aggregate was random generated by Monte Carlo method, and the random aggregate model was established by the compiled program with Fortran language. The mesh division of aggregate, bond and mortar matrix was carried out respectively by Advancing Front method. Mechanical parameters of each phase material were considered as constant values when the uniaxial concrete specimen were simulated, the results indicate that the bond is weak links, the micro cracks appears in the bond first before they enter the mortar matrix, then the specimen failed because of the expand, combination of micro cracks. The tensile strength and the elastic modulus were assumed to obey Weibull and logarithmic normal distribution and the other mechanical parameters were taken as constant values in the simulations of three-graded-concrete supported beam. The random aggregate random parameters model was established, which is very close to the actual structure. The results show that the nonlinear behavior of higher homogeneous specimen appears later obviously; the influence of random distribution of elastic modulus on the mechanical character is very little in linear range, while great in nonlinear range; random distribution of tensile strength affects the strength and the damage threshold of concrete obviously. The results of simulations of three-graded-concrete supported beam under dynamic load show that in the impact load the carrying capacity improved and the displacement decreased when specimen failed, and without inial static load, it is dangerous that material tensile strength and elastic modulus were improved to its 1.3 times in the code. In the last, the three dimensional random aggregate random parameters model was established. The tensile strength and elastic modulus of bond element surrounding same aggregate were taken as constant value, but those of bondelement surrounding different aggregate were assumed to obey Weibull distribution. In order to reduce the efforts of calculation, small aggregate and mortar were considered as one material and its equivalent mechanical parameters were decided by the method of equivalent inhomogeneity. Based on method of Mori-Tanaka and two-phase tandem method, mixed method was presented to calculate the equivalent mechanical parameters. The comparison between results of three dimensional simulations and those of two dimensional simulations show that the numerical simulation method in this paper is feasible and the results are reasonable.