Size dependence of strength and fracture properties of brick masonry walls

The problem of size dependence of the fracture properties in brick masonry structures is addressed. The constitutive heterogeneity of the material seems to be responsible for this effect, which provides multiscale cooperation as fracture develops. Three-point bending tests have been carried out on notched masonry walls with five different sizes, and the nominal ultimate strength and fracture energies have been computed according to conventional theories. It is shown that the multifractal hypothesis for the composite mesostructure of the masonry allows for the proper determination of the scaling regimes of these physical quantities. By means of two multifractal scaling laws, for strength and toughness, respectively, the asymptotic values of these quantities, valid for real-sized structures, and the threshold scale between the disordered regime and the homogeneous one can be determined.