Influence of Confining Element Stiffness on the In-Plane Seismic Performance of Confined Masonry Walls

Confined masonry (CM) construction is being increasingly adopted for its cost-effectiveness and simplicity, particularly in seismic zones. Despite its known benefits, limited research exists on how the stiffness of confining elements influences the in-plane behavior of CM. This study conducted a comprehensive parametric analysis using experimentally validated numerical models of single-wythe, squat CM wall panels under quasi-static reverse cyclic loading. Various cross-sections and reinforcement ratios were examined to assess the impact of the confining element stiffness on the deformation response, the cracking mechanism, and the hysteretic behavior. The key findings included the observation of symmetrical hysteresis in experimental CM panels under cyclic loading, with a peak lateral strength of 114.3 kN and 108.5 kN in push-and-pull load cycles against 1.7% and 1.3% drift indexes, respectively. A finite element (FE) model was developed based on a simplified micro-modeling approach, demonstrating a maximum discrepancy of 2.6% in the peak lateral load strength and 5.4% in the initial stiffness compared to the experimental results. The parametric study revealed significant improvements in the initial stiffness and seismic strength with increased depth and reinforcement in the confining elements. For instance, a 35% increase in the lateral strength was observed when the depth of the confining columns was augmented from 150 mm to 300 mm. Similarly, increasing the steel reinforcement percentage from 0.17% to 0.78% resulted in a 16.5% enhancement in the seismic strength. These findings highlight the critical role of the stiffness of confining elements in enhancing the seismic performance of CM walls. This study provides valuable design insights for optimizing CM construction in seismic-prone areas, particularly regarding the effects of confining element dimensions and reinforcement ratios on the structural resilience.