Comparison of Hybrid and Emulative Precast Concrete Shear Walls for Seismic Regions

This paper compares the measured lateral load behavior of a 0.4-scale "hybrid" precast concrete wall test specimen with the behavior of a second precast specimen designed to emulate monolithic cast-in-place reinforced concrete shear walls. Both walls have the same overall geometry and are constructed by placing rectangular wall panels across horizontal joints. The lateral resistance at the joints of the "emulative" system is provided by mild [i.e., Grade 400 (U.S. Grade 60)] steel bars, whereas the hybrid wall features a combination of mild steel bars and high-strength unbonded post-tensioning (PT) strands. The mild steel reinforcement at the base of both systems is designed to yield and provide energy dissipation, while the unbonded PT steel in the hybrid system also provides self-centering capability to reduce the residual lateral displacements of the structure after a large earthquake. The comparisons between the two walls focus on the applied lateral load versus displacement behavior, energy dissipation, behavior of the steel reinforcement, and behavior along the critical horizontal base-panel-to-foundation joint. Due to the lack of PT steel, the emulative specimen developed a residual uplift along the entire base-panel-to-foundation joint, resulting in excessive horizontal slip, large strength and stiffness degradation, and significant residual lateral displacements. In contrast, the hybrid specimen showed significantly smaller residual uplift, horizontal slip, and strength and stiffness degradation, resulting in excellent re-centering and energy dissipation with ductile behavior over much larger lateral deformations.