PSI - Issue 70

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

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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. Each result obtained from the simulation is well-aligned with the physical understanding of masonry behaviour. Early Cracking at Low Displacement confirms the low tensile strength of masonry. Rapid Post-Peak Softening illustrates brittle nature and lack of reinforcement in infill. Shear-Friction Interaction captured through DP model offers better realism than linear elastic or Mohr-Coulomb models. Residual Strength observed even after peak due to frictional interface and confinement by RC frame — an aspect often ignored in analytical estimations. Moreover, the Drucker-Prager model proved effective in simulating both pre-peak hardening and post-peak softening, providing a more complete stress-strain profile under complex loading paths. The model also improved convergence over Mohr-Coulomb due to its smoother yield surface, especially under combined normal-shear stress states. The simulation results confirm that the Drucker-Prager model is well-suited for analyzing masonry infill walls under combined compression and shear. The model successfully captured the nonlinear failure process, from initial cracking to diagonal shear failure and strength degradation. The results showed strong agreement with analytical predictions and demonstrated the critical role of confinement and contact interactions. Future extensions can include interface modelling, cyclic loading, or probabilistic variation of material properties to capture real-world uncertainties. 5. Conclusions This study presented a comprehensive numerical investigation of the behavior of masonry infill walls under combined axial compression and in-plane shear using the Drucker-Prager plasticity model within ANSYS Workbench. The simulation successfully captured key nonlinear phenomena including crack initiation, propagation, and strength degradation. The finite element results showed strong agreement with analytical predictions, with a deviation of only ±6% in peak lateral load, thereby validating the accuracy of the Drucker-Prager approach for masonry behavior modeling. The force – displacement response revealed an initial stiff elastic phase followed by nonlinear softening, indicative of moderate ductility typically observed in unreinforced infill systems. Crack patterns developed diagonally from the base corners to the top, consistent with diagonal tension failure modes reported in the literature. The model also highlighted the significant influence of confinement provided by the RC frame, which enhanced the overall lateral load capacity and contributed to residual strength even beyond the peak load. Overall, the Drucker-Prager model proved to be a robust and realistic constitutive law for simulating the pressure-dependent yield and post-peak behavior of masonry infills under complex loading. The integration of finite element analysis with analytical validation provided a reliable framework for assessing masonry performance in structural frames. These findings can inform the design, retrofitting, and vulnerability assessment of masonry-infilled frames subjected to seismic or lateral forces. Future work may extend this model to cyclic or dynamic loading scenarios and include probabilistic material variability for a more comprehensive structural assessment. References Anthoine, A. R. Llorens, and L. Guillaumat, Failure mechanism of masonry shear walls, Proc. 10th Int. Brick Block Masonry Conf., 1994, pp. 1257–1264. Gabor, A., & Lebon, F. 2009. A Numerical Model for Masonry Structures Subjected to Combined Compression and Shear. Computers & Structures, 87(15-16), 1001-1012. Lourenço, P. B. Computational strategies for masonry structures, Ph.D. dissertation, Delft Univ. of Technol., Delft, The Netherlands, 1996. Laefer D. and T. Boyd, Toward understanding the structural behavior of masonry walls subjected to shear and compression, J. Struct. Eng., 134, 10, 1657–1665, 2008. Lourenço, P. B., & Rots, J. G. 1997. Multisurface Interface Model for Analysis of Masonry Structures. Journal of Engineering Mechanics, 123(7), 660-668. Magenes, G., & Calvi, G. M. 1997. In-plane Seismic Response of Brick Masonry Walls. Earthquake Engineering & Structural Dynamics, 26(11), 1091-1112 Milani, G. Simple homogenization model for the nonlinear analysis of in-plane loaded masonry walls, Comput. Struct., 85, 1311–1328, 2007. Lourenço, T. Computations on historic masonry structures, Prog. Struct. Eng. Mater., 4(3), 301–319, 2002. Rots, M. Computational modeling of concrete fracture, PhD Thesis, Delft University of Technology, 1988.