Impact of climate on multi-wythe stone masonry walls

The Hudson Bay Trading Company constructed the Prince of Wales Fort in the early eighteenth century with the goal of securing the fur trade in northern Canada. As a result of the fort's northern latitude the walls remained partially frozen throughout much of each year until recently. Warming in the climate has raised the average yearly temperature so freeze–thaw cycles have caused a breakdown of the mortar within the stone masonry, enabling washout from melting snow and rain. This has led to lateral deformation in some sections of the walls and collapse in others. Two-dimensional finite-element models have been formulated to represent the in situ conditions of a damaged wall section with varying strength mortar and bond conditions. The models were created in Abaqus and focus on the case of self-weight. Micro-modelling techniques were employed to model the stones and grout individually. Results indicate a significant reduction in either the strength or bonding capacity of the mortar will lead to instability in the wall sections studied. The research identifies a new general mechanism of failure for multi-wythe masonry walls and their susceptibility to environmental conditions, of which practising engineers should be aware when assessing heritage masonry structures.