The study analyzes the impact of openings in masonry infill walls on the lateral strength and stiffness of seven-storey reinforced concrete buildings. Using pushover analysis, the findings reveal that increasing the percentage of openings leads to higher vulnerability in the infill walls, and user-defined hinge models perform better than default models in reflecting nonlinear behavior. Recommendations are made regarding the use of hinge properties to avoid unreasonable displacement capacities in existing structures.