Computational Modeling of Damage Progression in Unreinforced Masonry Walls via DEM

Abstract

Unreinforced masonry (URM) walls are the common load-bearing elements for old masonry buildings and heritage structures. As witnessed from the past and recent earthquakes, URM walls may demonstrate various collapse mechanisms along with different crack patterns influenced by the wall aspect ratio, vertical pre-compression load, opening size and ratio, among many other factors. Typically, the mortar joints and unit-mortar interfaces are the weak planes where we expect to observe most failures, such as sliding, cracking and joint opening. However, it is not a straightforward task to simulate the structural behaviour and the failure mechanism of URM walls, including the crack localizations and propagation through the mortar joints, using the standard continuum-based computational models given the composite and highly nonlinear nature of the material. In this context, the present research offers a discontinuum-based approach to simulate the damage progression in URM walls subjected to combined shear-compression loading using the discrete element method (DEM). The masonry walls are represented via distinct elastic blocks interacting through point contacts to their surroundings. It is aimed to present the effect of the local fracture mechanism on the macro response of the masonry walls via validated DEM-based numerical models that can address all possible fracture mechanisms occurring at the unit-mortar interfaces. An innovative damage monitoring technique relying on the stress state at the point contacts is implemented and utilized to explore the associated damage progression in URM walls. The results show the great potential of the adopted modelling strategy to better understand the mechanics of URM walls and indicate the effect of strength properties of masonry constituents on the overall in-plane capacity of the load-bearing walls.