PSI - Issue 70

Chaitra Shree V. et al. / Procedia Structural Integrity 70 (2025) 67–73

71

contrast, the analytical MATLAB model offers a more generalized prediction based on assumed failure criteria and hence refers to it as diagonal cracking without explicitly classifying the crack type (shear vs. flexural). The diagonal shear cracking used in the ANSYS model emphasizes that the cracking was induced by significant shear stresses along the diagonal, which is a refined interpretation aligned with observed deformation and crack paths. Both results are consistent in identifying the diagonal direction as the primary failure path, confirming the reliability of the predictions. The simulation results demonstrate good agreement with the analytical model, showing only a ±6% deviation, which can be attributed to the additional confinement effects realistically captured in the finite element analysis. The load – displacement response indicates moderate ductility, aligning well with experimental observations for unreinforced masonry infill walls. The initial stiffness reflects strong wall-frame interaction, where the majority of the load is resisted during the pre-cracking phase. Crack initiation corresponds to tensile failure along the mortar joints, as evidenced by the equivalent plastic strain (PEEQ) contours. The dominant failure mode — diagonal shear cracking — is consistent with established experimental findings under combined axial and lateral loading. Notably, the model also captures residual post-peak strength, attributed to frictional contact and partial confinement from the surrounding RC frame. These results collectively justify the effectiveness of the Drucker-Prager model in simulating compressive shear yield behavior of masonry with high fidelity. The equivalent plastic strain (PEEQ) contour revealed that cracks initiated near the bottom corners of the infill and propagated diagonally towards the top corners — typical of diagonal shear failure. This mode of failure occurs when the shear stress exceeds the tensile strength of the material, which was accurately captured by the Drucker-Prager model due to its pressure-sensitive nature. High principal stress regions were observed along these diagonal zones, confirming the onset of tension-induced cracking. Additionally, the out of-plane effects, though limited in this 2.5D simulation, showed minor stress concentrations near the central panel, highlighting the need for full 3D modeling in future studies for thicker walls.

Fig. 4. Finite Element Analysis (FEA) model in ANSYS illustrating the progressive failure mode and displacement contours

4.1 Comparison with Analytical Results Using MATLAB, the shear capacity was estimated using the Coulomb-based equation [Equation (1)]: V=τ 0 A+μN (1) Where τ 0 =0.2 MPa (cohesion), A=0.75 m 2 , μ= tan(30°) ≈ 0.577, and axial load N=200 kN. V=0.2×0.75×1000+0.577×200=150+115.4=265.4 kN Considering partial stress transfer and confinement effects, only 60 – 70% of the full analytical capacity is mobilized in actual walls. This brings the estimated peak shear capacity to approximately 153.6 kN, which closely matches the simulation output of 162.4 kN. The small deviation (+5.7%) can be attributed to numerical confinement effects and realistic plasticity modelling offered by Drucker-Prager compared to rigid analytical formulas. Considering partial