15 th International Brick and Block Masonry Conference Florianópolis – Brazil – 2012 NEW SEISMIC CONSTRUCTION CATEGORIES FOR REINFORCED CONCRETE BLOCK STRUCTURAL WALLS: ANALYSIS Shedid, Marwan 1 ; El-Dakhakhni, Wael 2 and Drysdale, Robert 3 1 PhD, Assistant Professor, Ain-Shams University, Cairo, Egypt. shedidmm@mcmaster.ca 2 PhD, Martini, Mascarin & George Chair in Masonry Design, McMaster Univ., Canada. eldak@mcmaster.ca 3 PhD, Professor Emeritus, McMaster University, Hamilton, Canada. drysdale@mcmaster.ca This sequel paper contains detailed analyses of an experimental study reported in a companion paper that was conducted to evaluate the ductility, stiffness degradation and energy dissipation characteristics of rectangular, flanged, and end-confined reinforced masonry (RM) shear walls failing in flexure. The test program consisted of seven 2- and 3-story RM shear walls, with aspect ratios of 1.5 and 2.2, tested under reversed cyclic lateral displacements simulating seismic loading effects. Documentation of the wall base curvatures, and ductility levels attained are presented. This paper focuses on determining the extent of plasticity over the wall height, identifying the trend of stiffness degradation, and quantifying the amount of hysteretic damping. The relationship between the hysteretic damping and the ratio of the post-yield to the yield displacement was found to be almost linear for the test walls. In addition, the wall stiffnesses degraded rapidly to about 60% of their gross stiffness at very low drift levels (0.1% drift). Extent of plasticity over the wall height was about 75% of the wall length. The data presented in this paper is expected to facilitate better understanding of RM wall behavior under in-plane load to researchers, practicing engineers, and code developers. The results demonstrated the benefits of the increased curvature and displacement ductility values gained by adding flanges and boundary elements to rectangular walls and are expected to facilitate adoption of the flanged and end-confined wall categories in North American masonry codes as a cost-effective technique to enhance the seismic performance of masonry construction. Keywords: Boundary elements, Concrete masonry, Ductility, Flanges; Seismic tests; Shear walls. INTRODUCTION The response of RM rectangular walls was shown to be significantly enhanced when boundary elements are added at their ends or when walls are structurally connected to intersecting walls (Shedid el al., 2012). The presence of boundary elements at the end zone of the walls allowed the use of more than one layer of vertical bars which was confined within closed ties. Moreover, structurally connecting a rectangular wall to an intersecting wall or to a boundary element limited the damage at the wall ends, provided out-of-plane stability in the same time, and resulted in increase in wall top displacement and displacement ductility (Shedid et al., 2012). In addition, a significant saving in the amount of vertical reinforcement was achieved while maintaining the same load carrying capacity of rectangular walls. The current study aims at analyzing the response of a previously reported experimental study in which seven half-scale reinforced concrete-block shear walls under quasi-static cyclic loading (Shedid et al., 2012). The focus of this paper is to extract quantitative information by analyzing and comparing these test results and identifying the effects of different test parameters on the wall behavior. Specifically, in this study, the wall curvatures, extent of plasticity, wall displacement ductility, energy dissipation characteristics, and the trend for