K.F. HANSEN Danish Building Research Institute


Tensile flexural strength and ductility are important properties of masonry walls. In this paper these properties are investigated by means of deformation controlled tests with bending of masonry walls, and shear tests with a single bed joint between 2 bricks. The bending tests showed that a weak mortar produces tensile flexural strengths, equal to, and sometimes higher, than those produced by a strong mortar They also showed that, in most cases, masonry walls possess some ductility in bending, recognizable by a post peak tensile flexural strength of about 40-70% of the peak tensile flexural strength.
Especially in the case of bending about an axis parallel to the bed joints this observed ductility was greater than expected, A possible source of this ductility, which was not observable in tests with a single bed joint, is given.
When perforated bricks were used in combination with a weak mortar, an unusually low coefficient of variation (0.05) of the tensile flexural strength corresponding to bending about an axis normal to the bed joints was found An explanation for this is given, based on results (mode I! fracture energy) from the deformation controlled tests with a single bed joint in shear. The explanation involves subtle geometrical features of the surface of the wire cut perforated bricks and leads to a proposal for optimising the geometry of the perforations with respect to the mode II fracture energy of a bed joint in shear.