Seismic Response Evaluation of Ductile Reinforced Concrete Block Structural Walls. II: Displacement and Performance–Based Design Parameters

Abstract

A typical seismically designed reinforced masonry building is composed of structural walls, constructed following the same prescriptive detailing requirements corresponding to a code classified seismic force resisting system (SFRS). However, due to architectural requirements (i.e. to allow for requirements such as openings and wall intersections), some of these walls might have the same overall aspect ratio but differ in their cross-section configurations. The companion paper presented the experimental results and force-based seismic design parameters for walls that fall under the Canadian Standards Association (CSA) ductile shear walls and the Masonry Standards Joint Committee (MSJC) special-reinforced walls SFRS classifications. The current paper utilizes the experimental results to extract key displacement-based seismic design parameters, including wall yield and ultimate curvatures, wall displacements at yield and at the post-yield stages, stiffness degradation, period elongation, and equivalent viscous damping. The paper also identifies different damage states and links them to wall drift levels, as well as the extent of plasticity within the wall base region as key performance-based seismic design parameters. The study showed that using a mechanics-based approach, the curvature ductility values were at least double the theoretical code values predicted for most walls. In addition, within the same SFRS classification, walls having the same overall aspect and reinforcement ratios will possess significantly different displacement-based seismic design parameters, which would subsequently influence their predicted response under seismic events. Moreover, the results showed that slab-coupled masonry walls showed an enhanced overall performance compared with the rectangular and flanged walls tested. Subsequently, it is suggested that future editions of the CSA and MSJC account for the effects of varying the wall cross section and slab coupling influence on the seismic response of ductile/special walls SFRS classifications.