Discrete crack propagation analysis of reinforced concrete beams under shear

The investigation of crack growth in concrete structures without shear reinforcement is an active field of research for decades. To date, there is no consensus on the influence of the critical shear crack and its contribution to the shear force transfer, so that numerous shear force models take its magnitude differently. While one group assigns the largest amount mainly to the compression zone and less to the crack friction, the other group assigns it to the crack force transmission due to aggregate interlock. This paper presents an investigation of the influence of the critical shear crack on the load-bearing behavior of concrete beams without stirrups based on a discrete analysis using the extended finite element method (XFEM) for one or more discontinuities (cracks). The concrete damage plasticity (CDP) is used to represent a real material response. For the damage evolution of the discrete cracks, various softening models for the crack process zone are considered (linear, bilinear and nonlinear). The accuracy and computational intensities of different cases are compared. Based on experimental results, it is shown that XFEM in combination with CDP provides realistic data with respect to load-bearing behavior, stresses in the concrete model, crack propagation, crack kinematics, and resulting crack aggregate stresses.

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Discrete crack propagation analysis of reinforced concrete beams under shear