Probabilistic assessment of historical masonry walls retrofitted with through-The-Thickness confinement devices

A very popular and efficient technique for structural retrofit of historical masonry buildings is represented by Jacketing techniques coupled with Through-The-Thickness (TTJ) ties since the triaxial stress state induced by confinement increases structural ductility and strength. In this respect, the authors have recently developed an Equivalent Single Layer (ESL) Firstorder Shear Deformation (FSDT) shell theory capable of modeling the TTJ interaction at the global structural level by a computationally less expensive 2D continuum layered formulation. The present contribution investigates the sensitivity of the TTJ formulation, used in conjunction with MITC finite elements, with respect to the constitutive uncertainties of an existing masonry panel. To this end, constitutive parameters of the existing structure are characterized by means of random variables which take into account masonry nonhomogeneities as well as the state of knowledge of structural parameters. All remaining mechanical and loading parameters are treated herein as deterministic variables and dimensioned according to common design practices of Italian and European code regulations. Therefore, a Monte Carlo simulation is performed in order to get the probability distributions of the structural responses. A subsequent reliability analysis aims to investigate the influence of TTJ confinement devices on the ultimate limit state of plane elements. Moreover, comparisons are made between the results obtained by the investigated methodology and simpler and more empirical estimates of the strength increment based on the Italian building code recommendations.