Experimental Investigation and Numerical Modeling of Peak Shear Stress of Brick Masonry Mortar Joint under Compression

This paper presents a study on the shear load-displacement behavior of horizontal joints in unreinforced brick masonry subjected to constant compression. In general, under static shear loading masonry joints show a peak shear stress followed by a residual shear strength. To investigate these aspects in greater detail, triplet tests were conducted on masonry specimens using different types of mortar. The results found in this study and previous tests show that normal compressive stresses acting on the interface and the interface mortar strength affect the peak shear stress and the residual strength in a rather similar way. The cohesion and the internal friction angle, i.e., the two parameters required by the Mohr-Coulomb criterion, are then derived from a linear regression of the test results. The pre-peak and post-peak response of a masonry bed joint can best be represented by simple equations, and their shear stiffness depends on material properties and the magnitude of the normal compression. Computational modeling strategies are then presented considering the shear slip at the brick-mortar interface. The comparison of the model prediction with the results found in this study and previous tests shows the reliability of the proposed model for bed joint behavior. (C) 2014 American Society of Civil Engineers.