Seismic performance of confined masonry walls with joint reinforcement and aspect ratio: An experimental study

•Contributes to the understanding of the seismic performance of confined masonry walls.•The amount of joint reinforcement and the aspect ratio of the walls was studied.•Four different aspect ratios and two amounts of reinforcement were used.•Large full scale specimens were tested, h = 2500 mm and lengths from 1710 mm to 6180 mm.•Joint reinforcement deformation were obtained using a large set of instruments. The effect of joint reinforcement, aspect ratio and their possible interaction, on the performance of confined masonry walls, was studied experimentally. Eight full scale confined masonry walls with four different height-to-length aspect ratios (hw/lw = 1.46, 1.0, 0.59, 0.4) and two different amounts of horizontal reinforcement per aspect ratio (phfyh=0.6,1.21N/mm2) were subjected to reversible cyclic shear loads and a fixed axial stress, representing the vertical load of five stories. The walls with hw/lw=1.0 were included from a previous study. The aspects ratios considered correspond to slender walls, square walls, long walls with one masonry panel and long walls with two masonry panels. Multiperforated concrete masonry units with 75% of net area were used. The performance of the walls is described in terms of strength, strength degradation, displacement capacity, ductility, dissipated energy, stiffness degradation, joint reinforcement (JR) deformation, cracking patterns, and crack opening. The results show that JR increased the shear strength of the walls and, in most cases, it had a negative impact on ductility; however, ductility increased as the aspect ratio decreased. Drift at peak strength increased with JR, and it had a clear tendency to grow as the walls were longer. Long walls tend to have a more brittle behavior. A detailed description of the experimental program and the results are given, after which, some conclusions are drawn.