Unreinforced masonry walls under two-way out-of-plane bending: Comparison of FE model predictions with analytical models

Abstract

Four existing design guidelines based on the virtual work method have been compared to predict the out-of-plane (OOP) bending capacities of unreinforced masonry (URM) walls to one-way and two-way actions. The two-way OOP bending design equation as per the Australian masonry standard (AS 3700) and the three subsequent models developed by other researchers are based on specific wall geometries, support conditions, dimensions and strengths of masonry units and mortar. Due to limited experimental data available on URM walls under two-way bending, it is difficult to carry out a detailed investigation of the performance of these two-way design models against all the design parameters. This paper applies the finite element (FE) modelling technique to generate data and extensively investigate the influence of support conditions, pre-compression and aspect ratio on the two-way OOP bending capacity of URM walls. An explicit FE model previously developed by the authors where masonry is macroscopically modelled as an anisotropic composite material, is used for this purpose. Performances of three key parameters (i.e., moment capacity under horizontal bending and diagonal bending and torsional shear strength of masonry) that differentiate the four design models are investigated against varying levels of vertical pre-compression and flexural tensile strength of masonry. The OOP bending capacity predicted by the FE model is compared with the predictions of the design models. Results show that three out of four design models generally overpredict the two-way OOP bending capacities of square and taller walls. Further refinement to the AS 3700 design equation has been proposed in a modified model. The outcomes of this research will help to improve the design of masonry walls under OOP bending.