Cyclic in-plane shear behaviour of reinforced concrete masonry walls with single and double layered reinforcement

Recent changes in the Australian reinforced concrete design standards (AS 3600) specify that reinforced concrete (RC) shear walls should have double layers of reinforcement (horizontally and vertically) to achieve a ductility factor of two in earthquake design. The practice of centrally placed single layered RC walls is limited by specifying the ductility factor of one in AS 3600. However, the Australian masonry design standards (AS 3700) continue to allow single layered reinforcement as a conventional practice in reinforced masonry (RM) walls and permit the use of a ductility factor of two in earthquake design. Subsequently, there is a renewed concern on the performance of single layered reinforced masonry walls compared with double layered reinforced masonry walls and their associated ductility levels. This research aims to experimentally investigate the cyclic in-plane shear behaviour of RM walls with single- and double-layer reinforcements. Four RM walls were tested with three different reinforcement layer configurations: (1) single layer of vertical and horizontal bars, (2) single vertical with double layers of horizontal bars and (3) double layers of vertical and horizontal bars. Dimensions of all tested walls were 1590 mm (length) × 1600 mm (height) × 190 mm (thickness). Experimental outcomes revealed that the change in reinforcement detailing did not substantially affect the failure patterns and ductility of the tested walls. All the walls depicted typical combined flexural-shear cracking patterns. Among the walls tested, the double layered RM walls showed moderately higher initial stiffness (40%), in-plane shear load (20%) and energy dissipation (31%) capacities compared to the single layered RM walls. The general perception that double layered reinforcement could always improve the strength and ductility of RM walls should be considered cautiously as geometrical and mechanical parameters of the walls can also have an influence.