Crack propagation modeling in quasi-brittle materials such as concrete is essential for improving the reliability and load-bearing capacity assessment. Crack propagation explains many failure characteristics of concrete structures using the fracture mechanics approach. This approach could better explain the softening behavior of concrete structures. A great effort has been made in developing numerical models; however, some models involve complex expressions with too many parameters, and the

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... lts are in some cases inaccurate. In this investigation, a numerical approach is developed to model the fracture process zone (FPZ). Based on the modified crack closure integral (MCCI) method, a new nonlinear spring is proposed to be placed between the interfacial node pairs to model crack propagation. A new strain energy release rates for Mode I is calculated as a function of opening in the softening part. Two benchmark beams are simulated by the ABAQUS software for the accuracy of cohesive zone model. The model decreases complexity of predicting crack propagation. It is observed that the cohesive zone model is robust, accurate and able to model the crack growth in the concrete beam. The prediction of the crack path is close to the experimental results (up to 90%). The peak loads had approximately 7.7% difference compared with the previous experimental loads. The accuracy of displacement in the present study is 15.9% compared with previously model at the same load intensity.