Abstract

Reinforced masonry (RM) shear walls are commonly used in mid- and high-rise masonry buildings as the main lateral load resisting system. The seismic performance of RM shear walls can be enhanced by integrating reinforced boundary elements at the wall most stressed zone (i.e. wall ends). Evaluating the compression behaviour of the boundary elements is key for predicting the seismic response of the RM shear walls. Unlike reinforced concrete (RC), the experimental studies that focused on compressive stress-strain behaviour of reinforced masonry are scarce.
This study quantifies the stress-strain relationship of sixteen C-shape full-scale and fifty four C-shape half-scale fully grouted unreinforced and reinforced masonry boundary element (RMBE) specimens tested under concentric compression loading up to failure. The effect of changing hoop spacing, vertical reinforcement ratio, the strength of grout, and aspect ratio (height to thickness) on the axial compressive stress-strain behaviour of RMBE is investigated. Enhancement in both peak and post peak stress-strain behaviour were observed by decreasing the hoop spacing, increasing the grout strength, decreasing the aspect ratio, and increasing the vertical reinforcement ratio. Out of the studied parameters, the hoop spacing had the most noticeable effect on the stress-strain relationship.
Finite element modelling (FEM) numerical simulations are employed to simulate the compression behaviour of the full-scale RMBE. The proposed FEM procedure provides good prediction of the compression stress-strain behaviour of RMBEs and captures the influence of the confinement reinforcement ratio on the RMBE response. In addition, this study investigates the capability of three existing stress-strain models in predicting the RMBE stress-strain relationship. The considered models overestimated the enhancement in the RMBE stress and significantly overestimated the enhancement in the RMBE strain.
Finally, an analytical compressive stress-strain model capable of predicting the RMBE compressive response considering various confinement effects is proposed. The proposed empirical stress-strain model is capable of capturing the overall compressive stress-strain behaviour where a good agreement with the test results was achieved. This model can be implemented in different design and assessment frameworks aiming at better prediction of the seismic response of RM walls with boundary elements.