Experimental investigation of concrete masonry prisms reinforced with in-line stiffening cages under concentric and eccentric loading

This study investigates the axial and flexural behavior of fully grouted masonry prisms reinforced with pre-tied in-line steel cages. The research examines the influence of reinforcement configuration, tie spacing, and load eccentricity on strength, and stiffness, addressing gaps in the existing literature regarding confinement effects and stiffness evaluation in cage-reinforced masonry. A total of forty fully grouted masonry prisms were tested under concentric and eccentric compression. The specimens were categorized into three groups: reinforced masonry with pre-tied cages (RM-T), conventionally reinforced masonry with central bars (RM), and unreinforced masonry (URM). Axial stiffness under concentric loading was quantified using a secant stiffness approach, while effective flexural stiffness ( ) under eccentric loading was evaluated using strain-based curvature measurements. For concentrically loaded specimens, results show that RM-T prisms exhibited higher axial load capacity and stiffness with lower variability than URM prisms, with tie spacing showing only a small influence on stiffness and axial capacity. For eccentrically loaded specimens, the RM-T prisms consistently showed greater load-carrying capacity than the RM prisms at the same eccentricity, demonstrating the benefit of distributing reinforcement across the section. Increasing eccentricity resulted in a reduction in both and load-carrying capacity for all reinforcement configurations. Across all eccentricities, the measured at failure exceeded the values prescribed by the Canadian standard for masonry structure (CSA S304:24), indicating that the standard-based stiffness is conservative for prism-scale members. • Cage reinforcement improved axial stiffness and enhanced confinement of grouted prisms • Stiffness enhancement was governed primarily by grout confinement rather than the direct axial contribution of longitudinal steel. • Under eccentric loading, cage prisms provided greater moment resistance than single-bar prisms • CSA S304:24 stiffness provisions proved conservative for all tested prisms • A confinement-modified stiffness formulation improved agreement with experimental results and rationalized observed stiffness gains.