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Go to Editorial ManagerThe principle aim of this research is concentrated to analyze the effect of cracks and their propagations on the mechanical behavior of a quasi-brittle material such as concrete. The singularity (stress concentration to infinity at the tip of crack) is avoided by using the principal of fracture energy with the fictitious crack approach. The concrete crack is divided into two major zones; the first one is the fracture zone (a combination of bridging effect and the cohesive microscopic cracking) which obeys a special law permitting the transmission of stress across the two faces of crack, this zone is considered as partially cracked concrete. When the opening of the crack exceeds a specific value, this zone is converted to a real crack (an open crack) and cannot transmit any stress across the two faces of a crack. The program of finite element used in this research is prepared by the researcher using discrete-crack approach with the experimental data obtained from the flexural test on notched beam loaded under three-point bending, where fracture mode I is dominated. The response of the applied load-crack mouth opening displacement (CMOD) with appropriate fracture energy is selected. The results show that the cohesive microscopic cracking zone for the plain concrete is very wide. The cohesive stress distributions across the microcracks with the corresponding crack openings are drawn from the first crack appearance till the beam failure.
In this investigation, the bond stresses between the reinforcement and concrete was studied by using non-material interface elements that are able to produce the bond stresses for the reinforced concrete beam gradually loaded from zero to failure. Depending on (Jawad) program, which is a non-linear analysis program of plain and reinforced concrete beams through a discrete-crack approach by using the finite element method. The stiffness matrix derivation of the interface element and the way of non-linear treatment were explained. The distribution of bond stress drawings along the steel reinforcement for different values of loading was achieved before and after cracking.