Design, Analysis, and Experimental Evaluation of Hybrid Precast Concrete Shear Walls for Seismic Regions

The hybrid shear wall system investigated in this dissertation is constructed by stacking rectangular precast concrete wall panels along horizontal joints above the foundation and at the floor levels. The term 'hybrid' reflects that a combination of mild reinforcing steel (U.S. Grade 60) and high-strength unbonded post-tensioning (PT) steel is used for lateral resistance across the joints. During a large earthquake, gap opening at the base joint allows the structure to undergo large lateral displacements with reduced damage. Upon unloading, the PT steel provides a restoring force to close this gap and pull the wall back towards its undisplaced position, reducing the permanent lateral displacements. The mild steel crossing the base joint is designed to yield and provide energy dissipation.

The primary goal of the dissertation is to investigate the seismic behavior and design of hybrid walls with practical details, while specifically focusing on the classification of the system as 'special' reinforced concrete shear walls according to the requirements of the American Concrete Institute (ACI). The behavior from six 0.40-scale test specimens subjected to service-level gravity loads combined with reversed-cyclic lateral loading is studied, including walls featuring multiple panels and panel perforations, both common features in practical building construction. The primary experimental variables include the detailing of the mild steel bars crossing the base joint, relative areas of the mild and PT steel, concrete confinement, and size of panel perforations. The measured behaviors of the test specimens are compared against design predictions and analytical simulations, using both detailed fiber element models and simplified finite element models created with a 'design office' philosophy.

The results demonstrate that hybrid precast walls can satisfy all of the requirements for special reinforced concrete shear walls in high seismic regions with improved performance, while also revealing important design, detailing, and analysis considerations to prevent undesirable failure mechanisms. In addition to this dissertation, a key deliverable from the project is a validated Design Procedure Document (Smith and Kurama 2012) containing detailed guidelines and tools for engineers and precast producers involved in the seismic design of ACI-compliant hybrid shear walls with predictable and reliable behavior under earthquakes.