Experimental Investigation on Hybrid Steel-Grout Vertical Joints with Steel Anchor Rings for Precast Concrete Shear...

Vertical joints are commonly required in precast concrete shear walls when large wall panels are divided for fabrication, transportation, and erection. To reduce on-site work and improve assembly efficiency, this study proposes and investigates a hybrid steel-grout vertical joint, namely a steel-anchor-ring grouted connection, which uses embedded threaded sleeves, steel anchor rings, an inserted vertical bar, and high-strength grout to transfer shear between adjacent wall panels. Monotonic direct shear tests, cyclic shear tests under normal tension and compression, and cyclic loading tests on precast shear wall specimens were conducted to investigate its mechanical behavior. The load-slip behavior, observed interface debonding, and final shank fracture in the direct shear tests suggested that grout-panel interface bond contributed substantially to the pre-peak response, whereas anchor-ring action became increasingly important after bond degradation. Comparison of the cyclic shear specimens suggested that normal tension promoted interface opening and bond degradation, leading to slip-dominated behavior, whereas normal compression enhanced interface contact and post-peak stability. For the specimens tested, the measured-to-calculated resistance ratios based on the code-based expression were 1.97-2.70 under direct shear and compression-shear conditions, but decreased to 1.20-1.31 under tension-shear loading. Wall-level demand analysis showed that the shear transferred across the vertical joint was significantly affected by both joint location and wall shear span ratio; larger shear span ratios increased the joint shear demand, whereas offset joint layouts reduced the demand. The wall specimens, designed relative to the code-based resistance, exhibited limited joint-related cracking and stable hysteretic behavior, and failed by wall-base flexural damage, indicating the shear-transfer effectiveness of the proposed joint under the tested configurations.