B.R. Robazza, S. Brzev,  T.Y. Yang, K.J. Elwood,  D.L. Anderson,  and W. McEwen,

B.R. Robazza, Corresponding author, Ph.D. Candidate, Dept. of Civil Eng., Univ. of British Columbia (UBC) 2329 W Mall, Vancouver, BC, V6T 1Z4, Canada, E-mail : brook.robazza@civil.ubc.ca, Phone: 778-840-3773
S. Brzev, Former Faculty, Dept. of Civil Eng., British Columbia Institute of Technology, 3700 Willingdon Ave, Burnaby, BC, V5G 3H2, Canada, E-mail: svetlana.brzev@gmail.com
T.Y. Yang, Professor, Dept. of Civil Eng., UBC, 2329 W Mall, Vancouver, BC, V6T 1Z4, Canada, yang@civil.ubc.ca
K.J. Elwood, Professor, Dept. of Civil Eng., Univ. of Auckland, Auckland 1142, PB 92019, NZ, k.elwood@auckland.ac.nz
D.L. Anderson,  Emeritus Professor, Dept. of Civil Eng., UBC, 2329 W Mall, Vancouver, BC, V6T 1Z4, Canada, dla@civil.ubc.ca
W. McEwen, Former Exec. Director, MIBC, 3636 E 4th Ave., Vancouver, BC, V5M 1M3, Canada, info@masonrybc.org

Reinforced masonry shear walls (RMSWs) have been demonstrated to possess adequate ductility and energy dissipation characteristics for seismic design applications. However, slender RMSWs, characterized by high height-to-thickness (h/t) ratios, may be vulnerable to out-ofplane instability under in-plane seismic loading. Out-of-plane instability is a failure mechanism that affects RMSW end-zone regions subjected to cycles of tensile strain, followed by compressive strain during load reversal. This failure mechanism has the potential to cause unexpected and rapid strength degradation or collapse, if not considered in design. The Canadian masonry design standard, CSA S304-14, prescribes h/t limits for the seismic design of RMSWs to prevent out-of-plane instability, however, no experimental testing verifies these limits. Moreover, the h/t limits are independent of the cross-sectional shape of the RMSW, despite the wall response being significantly influenced by this parameter. At a given drift demand, Tshaped RMSWs, i.e. rectangular RMSWs with flanged boundary elements at one end-zone, tend to produce higher strains at the end-zone without flanged boundary elements as compared to the end-zones of rectangularly-shaped RMSWs. This may increase the risk of out-of-plane instability affecting T-shaped RMSWs. This paper describes the findings of an experimental test-series aimed to identify the effects of flanged boundary elements on the response of slender RMSWs subjected to in-plane seismic loading. The paper presents a summary of qualitative observations and test results, as well as a discussion on the key differences in response characteristics of slender RMSWs with T-shaped compared to those of rectangular cross-sections.