In-plane strength of masonry wall panels: A comparison between design codes and high-fidelity models

The susceptibility of masonry structures subjected to in-plane loads is determined by the failure mechanisms that might occur, which are governed by the material and geometric properties of the masonry. In practice, masonry walls are usually analysed using design codes, which are derived from analytical (code-based) methods. However, design codes may be overly simplistic and conservative, necessitating re-evaluation and modifications. This paper aims to compile and review various existing design codes for determining the in-plane strength of masonry walls and assess their validity when predicting masonry wall panels’ in-plane strength with different geometry and material properties. For this purpose, Monte Carlo simulations were used to vary the geometric and material properties of walls and understand how these affect their in-plane strength and failure mode. An extensive numerical investigation employing three-dimensional finite element (FE) analysis was also undertaken to better understand the influence of pre-compression, wall height to length ratio, and aspect ratio of masonry units on the in-plane force capacity of the masonry walls. First, a cyclic quasi-static test was utilized to validate the numerical model. The results from the numerical analysis were in good agreement with the experimental findings in terms of load vs drift curve and damage pattern. Following that, the numerical model was used to implement a parametric investigation. According to the findings, in-plane strength decreases as the aspect ratio of the wall increases. Pre-compression also influences the in-plane strength of the masonry wall and the brittleness of the failure. In-plane strength of the shear-controlled walls was higher than that of flexure-controlled walls. Failure mechanisms of walls were also extensively studied and a combination of failure mechanisms was observed. Also, the aspect ratio of masonry units was found to influence the failure mechanism of the wall. The comparison of the estimated strength and failure mode of the walls using the code formulations with those obtained from the numerical study indicates that in some cases (particularly the squat walls and shear-controlled walls) the codes did not predict the behaviour of the wall panels satisfactorily. This may be attributed to the multiple governing modes of failure in real cases, while the code formulations only consider a particular failure mode. The findings presented here highlight the need for updated design codes.