Experimental and numerical study on the impact of geometrical and mechanical properties of joints on the out-of-plane behaviour of masonry walls

Masonry walls are common in residential and public buildings worldwide. Masonry walls are usually considered non-bearing, non-constructive components and are often not considered in the structural analysis. However, these walls significantly impact the building's response during extreme events such as earthquakes or failure of a load-bearing element. They may detach from the surrounding frame, fail, and injure people inside and outside the building. Therefore, it is necessary to understand their behavior under out-of-plane deformation. The present research includes investigating the behavior of hollow concrete blocks with a moderate interlocking geometry combined with adhesive material between the blocks. In this case, two factors affect the behavior: the geometric factor, which originates from the shape of the block, and the material factor, which depends on the properties of the adhesive material. The present paper investigates the effect of these two parameters through an experimental investigation, which included 24 wall specimens with different combinations of joint material and block geometries. The walls were subjected to loads applied either perpendicular or parallel to the bed joints. The wall's response was further investigated using a finite element micro-model, validated through both analytical method and experimental results. A mesoscale approach was adopted to ensure computational efficiency while capturing critical behaviors, such as block and interface failures. The model accurately predicted key failure mechanisms, including plastic hinge formation and damage in both blocks and bed joints, while efficiently managing complex nonlinear behavior using an explicit solver. The results show that the adhesive material significantly affects the response. The flexural strength of the wall built with adhesive is almost double that of the typically used cement-based mortar when referring to smooth-edge blocks subjected to loads parallel to the bed joints. The interlocking block showed a significant increase in strength only in walls with cement-based bed joints and when the load is parallel to the joints. In contrast, the interlocking blocks have a minor effect when combined with adhesive or when the load is perpendicular to the bed joints.