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Fibre Reinforced Polymer (FRP) confinement represents an effective tool for retrofitting masonry piers or columns enhancing their structural performance. This technique has been widely studied in the literature mainly with reference to short columns, while no extensive information is available on the influence of second order effects on its efficacy in case of slender members. Within this framework, the presented study concerns a simplified method able to assess the effects of FRP confinement on the compressive behaviour of slender masonry columns. A proper constitutive law of FRP confined masonry in compression is adopted for performing a sectional analysis, in which also considerations are made on the increase of ultimate moment and curvature depending on the role of some key parameters. The effect of column slenderness is evaluated using a simple analytical iterative procedure, making it possible to calculate the allowable slenderness ratios as function of the maximum drift, taking into account both strength and stability. The effect of slenderness on eccentrically loaded columns is finally examined through a finite element model used for validating the results of the proposed analytical procedure, allowing also to draw safety domains useful for design/verification purposes. It is shown as the column’s slenderness affects the efficiency of confinement, being the latter negligible for values of normalized length greater than 20.

In the present study a numerical model is proposed for the response of out-of-plane loaded calcarenite masonry walls strengthened with vertical CFRP strips applied on the substrate by means of epoxy resin. A simplified structural scheme is considered consisting in a beam fixed at one end, subjected to constant axial load and out-of-plane lateral force monotonically increasing. Two different constraint conditions are taken into account: in the first one, the panel is assumed free to rotate at the top end while, in the second one, the rotation is restrained. Three-dimensional finite elements are used for the calcarenite parts and an equivalent constitutive law available in the literature is considered for the compressive behavior of the system ashlar-mortar. Conversely, shell elements are used for modeling the CFRP strips and linear elastic behavior is assumed for the composite while cohesive contact properties are introduced at the FRP-calcarenite interface. The model is validated using both experimental results available in the literature and simplified analytical formulations recently presented by the authors in a previous paper.