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Aim of the present paper is to numerically study the bond behavior of curved masonry specimens externally strengthened by Carbon Fiber Reinforced Polymer systems (CFRP). A simple 1D-modeling approach is presented to this aim, where the coupled behavior between shear and normal stresses developing at the reinforcement/masonry interface level is specifically introduced to properly account for the role played by the curvature radius. The model is indeed enriched by the introduction of shear stress-slip laws able to account for the beneficial friction effect, when compression normal stresses develop at the interface level and the reduction of the slip strength corresponding to the de-cohesion in presence of normal stresses in tension. Considering some case studies derived from the current literature, consisting of shear-lap bond tests of curved masonry specimens characterized by different curvatures of the bonded surface and different strengthening configurations, the validation of the proposed approach is carried out. In particular, two modeling strategies are considered and critically compared: the first one, denoted as approach (A), where the presence of the mortar joints is neglected, and the second one, denoted as approach (B), where mortar joints are specifically introduced in the model. Finally, the results obtained by using the proposed simple approach are compared with those obtained from both sophisticated FE numerical models and theoretical formulas deduced from the current literature. [ABSTRACT FROM AUTHOR]

The present paper aims at developing a simple but effective numerical model for the study of the bond behavior of Fiber Reinforced Strengthening systems (FRP) externally applied on curved masonry substrates. The main peculiarities of the proposed model are its simplicity and the possibility to straightforwardly introduce at the interface level coupled cohesive laws for accounting a mixed mode debonding mechanism. Indeed, the model relies on a discretization based on in-series and in-parallel springs for modeling the substrate, the reinforcement and the reinforcement/substrate interface layer. In particular, while both the substrate and the reinforcement springs are assumed linear-elastic, nonlinear constitutive laws are accounted for the interface springs where, in addition, a coupled behavior between normal and shear springs is assumed considering the Mohr-Coulomb failure domain. The proposed numerical model is used in the paper as a tool for the assessment of formulas specifically devoted to the evaluation of the bond resistance of curved masonry samples strengthened with FRPs. In particular, both formulas derived from the closed form solution of equilibrium equations and a formula derived by approximating the closed form solution through an exponential law are here presented. With the main purpose to validate the proposed model, numerical analyses are preliminary presented in the paper with reference to experimental bond tests on masonry samples with concave and convex substrate configurations strengthened by glass FRP strips. Then, further numerical analyses developed by considering different values of the geometry curvature and mechanical properties of the interface, are subsequently developed with the main goal to check the reliability of the proposed formulas. [ABSTRACT FROM AUTHOR]