Quasi-static testing of concrete masonry shear walls with different horizontal reinforcement schemes

Constructions built with partially grouted reinforced masonry (PG-RM) shear walls are common in several countries, and consequently, different construction solutions can be expected. In this context, one of the main differences detected is the type of horizontal steel reinforcement used. The most traditional options consist of bed-joint reinforcement and bond-beam reinforcement. Despite the advances in this research area, there is little experimental evidence to determine which of these horizontal reinforcement schemes exhibits a superior performance under seismic loads. Thus, the research described in this paper focused on assessing and comparing the seismic performance of PG-RM shear walls with different horizontal reinforcement options. For this purpose, four concrete masonry walls with an aspect ratio of 0.86 were tested undergoing constant axial pre-compression and quasi-static cyclic incremental lateral displacements. The tested walls had the same horizontal reinforcement ratio but different layouts (only bed joint reinforcement, only bond beam reinforcement, and a combination of them). The other design characteristics remained constant. The obtained results were analyzed in terms of the force-displacement curves and seismic performance parameters such as the maximum resistance, stiffness decay, energy dissipation, and equivalent viscous damping ratio. In addition, a comparative analysis of damage progression of the tested walls was carried out using the digital image correlation (DIC) technique. The tested walls experienced progressive deterioration of the lateral stiffness in proportion to drift increments regardless of the reinforcement scheme. Once achieved the lateral resistance, the degradation of the behavior accelerated, turning into a rather unpredictable response. Employing different horizontal reinforcement layout showed no influence on the lateral capacity of the walls when the same horizontal reinforcement ratio and material qualities are used. It was also observed that the distributed bed-joint reinforcement was better than the bond-beam reinforcement layout in controlling crack widths. Additionally, a combination of bond-beams and bed-joint reinforcement seems to be the most suitable reinforcement strategy based on hysteretic behavior, energy dissipation capacity, and ductility. The presented experimental evidence is promising, although further studies are required in order to promote its use in design codes and construction projects