Experimental compressive and shear behaviour of clay brick masonry with degraded joints

Historical masonry constructions can be affected by degradation phenomena, which may produce significant effects on structural behaviour, strength and safety. Nonetheless, a few studies investigated the influence of ageing and deterioration on mechanical properties and nonlinear behaviour of degraded masonry. In this study, the results of a research project carried out on brick masonry wallets with degradation in masonry joints are presented. Simple (uniaxial) and diagonal compression tests were respectively performed on single- and double-leaf specimens made of clay bricks and natural hydraulic lime mortar. The latter masonry constituent is usually affected by progressive deterioration over time, so degraded specimens were fabricated by lumping degradation in mortar joints through reduced width. Experimental tests allowed the characterization of both Young's and shear moduli as well as compressive and shear strengths, comparing experimental values to those predicted in accordance with different standards. Local-global data sets were used to develop linear regression models that allow a quick prediction of mean masonry properties given mortar joint loss used as degradation measure, to be included in finite element models for structural safety assessment of historical masonry structures.