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Cracks have a serious impact on the safety of concrete structures, and the tensile behavior of concrete is the key to control generation and propagation of crack. To improve the safety of concrete structures, it is crucial to understand the mechanical properties of cracked concrete under uniaxial tensile load. In this article, dynamic tensile test and tensile test after different fatigue damage were conducted to investigate the mechanical properties of cracked concrete. First, the damage evolution law of cracked concrete under dynamic tensile load was investigated by means of [Formula: see text] ([Formula: see text]: crack mouth opening displacement) control mode whereupon the relationship of stress– dCMOD considering rates effect was obtained. Then, the change law of cracked concrete under uniaxial tensile load after fatigue damage was studied by analyzing four mechanical parameters including tensile strength, elastic modulus, critical displacement, and fracture toughness. The empirical formulas of the four parameters with numbers of fatigue cycles are given. Furthermore, acoustic emission technology was applied additionally.

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This paper studies the method of determining the fracture parameters of pre-notched concrete beams with horizontal pre-set cracks and the influence of fracture intersection on fracture characteristics of concrete based on the three-point bending test. Pre-notched concrete beams with horizontal pre-set cracks were designed as 13 groups according to the different positions, lengths and widths of horizontal pre-set cracks. The fracture toughness was calculated on the basis of the cohesive force model of concrete, and the crack opening displacement obtained by using the digital image correlation technique. The study's results indicate that the distance between the pre-set crack and the notch tip as well as the pre-set crack length and width have various influences on the fracture propagation of edge mode I crack, the bearing capacity and unstable fracture toughness of concrete beams owing to varying degrees of loss of cohesion in the fracture process zone (FPZ). The study also finds that a large lack of cohesion in the FPZ indicates a high possibility of a reduction in the bearing capacity and unstable fracture toughness of concrete beams.