Micromechanical modelling of mortar joints and brick-mortar interfaces in masonry Structures: A review of recent developments

Suitable numerical models of masonry structures are very important in their response evaluation under various loading events. Masonry is a heterogeneous material, made of mortar and masonry units, and joined together by interfaces. Constitutive models of mortar joints and masonry-mortar interfaces play a crucial role in achieving high-fidelity numerical models for masonry structures. Hence, this review paper particularly collates the most commonly available constitutive models of mortar joints and brick-mortar interfaces in the literature. The previous experimental studies on mechanical characteristics of mortar joints and brick-mortar interfaces are first discussed in detail. The existing constitutive models developed based on theory of plasticity, fracture mechanics, and damage theory are then mathematically described, and their strengths and shortcomings are fully explained. It is found that the literature lacks reliable experimental calibration of the current constitutive models, and combined loading experiments are required for better understanding of nonlinear behaviour of mortar joints and brick-mortar interfaces. It is also seen that most current constitutive models are two dimensional, use many theoretical assumptions and hypotheses with no experimental verifications, and do not account for three dimensional irregular interface bonding, bonding degradation, and relevant post-yielding deformational pattern. Effects of unloading-reloading, dilatancy, surface asperities, and crack formations also need further investigations.