In Situ Tests Procedures for the Evaluation of Masonry Mechanical Parameters

The evaluation of seismic vulnerability of existing masonry building is a first fundamental step for the preservation of historical buildings in seismic prone area. However, the definition of masonry’s mechanical behavior, which is characterized by a complex, nonhomogeneous, anisotropic, non-linear behavior, is still a critical issue that significantly influences the structural analysis and the evaluation of seismic risk index. Different test procedures have been proposed in the past such as double flat jack, diagonal compression and shear compression tests to characterize the masonry behavior; but their outcomes are often contradictory and can differ significantly for the same class of masonry or even for the same wall. In the paper, a new test procedure for the characterization of masonry mechanical parameters and especially the shear behavior of masonry walls is presented together with the experimental test results obtained for a stone masonry wall and a brick masonry wall. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is done to derive the normal compressive stress acting on the wall, then a double flat jack test is carried out to estimate the elastic modulus and finally a shear test is performed to directly assess the capacity curve and estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors show the capability of the proposed methodology that allows a complete assessment of masonry mechanical parameters reducing the uncertainty in the estimation of shear behavior and consequently on the evaluation of seismic vulnerability of the investigated buildings.