Seismic Design, Analysis, and Behavior of Reinforced Concrete Coupled Shear Wall Systems with Post-Tensioned Coupling Beams

The seismic design, analysis, and large-scale experimental evaluation of a novel multi-story coupled shear wall system with post-tensioned coupling beams are presented in this dissertation. In this new system, high-strength unbonded post-tensioning (PT) strands are used to couple (i.e., link) reinforced concrete (RC) shear wall piers for primary lateral load resistance in building structures. Reversed-cyclic quasi-static testing of two 40%-scale coupled wall specimens with the proposed details were conducted to evaluate the system according to the requirements of the American Concrete Institute (ACI). The laboratory specimens represented the most critical bottom three stories of an eight-story prototype structure, consisting of two C-shaped wall piers, six coupling beams (two beams at each floor level), tributary slabs at each floor, and the foundation. The other (less critical) regions of the eight-story structure were simulated analytically.

To validate the seismic design methodology, selected important design parameters were varied between the two 40%-scale test specimens. The two primary parameters were: (1) coupling beam depth; and (2) use of energy-dissipating (ED) ductile mild steel reinforcement crossing the beam-to-wall joints (i.e., partially post-tensioned versus fully post-tensioned coupling beams). The measured behaviors of the test specimens were compared against design predictions and analytical simulations using fiber element models. Overall, both test specimens performed well and significantly better than previous tests of conventional RC coupled shear wall structures. The specimens achieved ductile behavior through the completion of three full cycles at or exceeding the “validation-level” lateral roof drift prescribed by ACI, thus demonstrating the classification of these structures as “special” RC shear walls. In addition to a dense array of conventional sensors, the deformations of the specimens were monitored using up to 14 two- and three-dimensional digital image correlation (DIC) sensors, providing unprecedented near-full-field response data of the most critical regions of the structures. Ultimately, the high-fidelity data from these tests support the ACI validation of the design procedures and modeling/prediction tools for the use of post-tensioned coupled shear wall structures as primary lateral load resisting systems in moderate and high seismic regions of the U.S.