Experimental Shear Performance of Old Masonry Walls Typical of Eastern Canada

Abstract

Eastern Canada’s unreinforced masonry (URM) buildings are amongst the most seismically vulnerable structures in North America, contributing to the high earthquake risk characterizing St. Lawrence River valley. However, the seismic performance of their URM walls is still mostly unknown, preventing the informed design of rational repair and retrofit interventions. Of particular interest are the URM components built with clay bricks and lime mortar in the 19th century, featuring common bond pattern and timber inclusions in unique multi-wythe arrangements. Adapted to local climate and resources by European settlers, these vernacular systems are largely widespread in populous urban centres. This paper is the first to present a comprehensive experimental study on the in-plane (IP) diagonal strength of mixed URM-timber walls typical of Eastern Canada, as well as to determine the mechanical characteristics of their components. To this end, four full-scale URM walls extracted from an existing building in Montréal (QC, Canada) were tested under diagonal compression. Through the combined use of Digital Image Correlation (DIC) and a modified ASTM E519 setup tailored to accommodate fragile specimens, and by testing original walls with timber inclusions at different heights, this research provides valuable insights on the influence of typical construction methods on the structural performance of local URM walls under lateral loading, while also unprecedently deriving shear strength and drift capacity parameters required for code-based seismic evaluation. Comparison against past experimental data also highlights the peculiar seismic response to be expected from Eastern Canada’s old URM, something critical that could not be quantified before.

Keywords: unreinforced masonry, wall, in-plane, diagonal compression, shear strength, timber inclusions, Eastern Canada