Spatial Correlation of Flexural Tensile Bond Strength in Unreinforced Masonry Walls

The flexural tensile bond strength of the unit-mortar interface is an important material property in defining the load-carrying capacity of unreinforced masonry (URM) walls. This property often governs the response of URM walls subject to in-plane and out-of-plane flexure. Masonry is an inherently variability building material, with properties such as the flexural tensile bond strength having been observed to vary considerably when comparing adjacent mortar joints. This spatial variability influences the performance of URM structures and is an important consideration when performing stochastic assessments of masonry behaviour. This study describes an experimental investigation in which an URM wall was sequentially deconstructed utilising a bond wrench, and the bending stress to failure of each individual mortar joint was recorded. The bending capacity of each of these joints allows for an assessment of the spatial correlation of joint strengths within a masonry wall. Furthermore, 15 additional mortar joints, constructed in piers under identical conditions, and using the same unit type and the same mortar batch, as the examined wall, have been tested using a bond wrench. These supplemental tests are a standard form of estimating the strength of mortar joints within an URM structure. Examination of these specimens, therefore, provides insight into how accurately such tests estimate the true strength of joints within a wall.