Seismic Performance Assessment of Partially Grouted, Nominally Reinforced Concrete-Masonry Structural Walls Using Shake Table Testing

An experimental program has been carried out to study the performance of partially grouted, nominally reinforced (PG-NR) concrete block structural walls under in-plane seismic loading on a shake table. Five reduced-scale structural walls were constructed and tested under scaled versions of the 1940 El Centro, California earthquake, using its N-S component record with a constant axial compression load that represented a single-story building. The test walls were grouped into three categories. Type I and III walls had reinforcement at the wall end cells only, with vertical reinforcement ratios of 0.07 and 0.12%, respectively, based on the gross cross-sectional area of the walls. Type II walls were similar to Type I walls, but with an additional reinforcement bar located midlength of the wall with a vertical reinforcement ratio of 0.10%, also based on the gross cross-sectional area of the wall. The experimental results were documented and discussed with respect to wall lateral load capacity, stiffness degradation, period shift, displacement ductility levels attained, and relevant seismic-force reduction factors. The test results showed that PG-NR masonry walls can comprise a ductile seismic force-resisting system. Subsequently, PG-NR masonry walls have the potential to bridge the gap between unreinforced and reinforced masonry systems. The use of PG-NR masonry also results in a reduced cost compared with traditional reinforced masonry systems used in seismic zones that are typically fully grouted within the plastic hinge zones and require higher reinforcement ratios.