Masonry columns strengthened with FRCM system: Numerical and experimental evaluation

The present paper deals with the structural behavior of masonry columns strengthened by a system made up of composite fiber grids embedded in cementitious matrix; in particular, the problem has been investigated both numerically and by performing experimental tests. Starting from the Spoelstra-Monti's iterative approach for FRP-confined concrete columns, an analytical approach for FRCM-reinforced masonry columns has been proposed. In particular, critical equations have been improved or modified in order to properly taken into account masonry behaviour and its interaction with the composite reinforcement. A 3D numerical description of the problem has been also considered, by using the commercial code MIDAS FEA, based on a macro-model approach; masonry and the reinforcement system have been considered as homogeneous materials with non-linear constitutive behaviour. The two models have been compared in order to understand the capabilities and limitations of the 1D model. To calibrate the models, some tests on plain masonry columns and composite specimens have been carried out at the University of Bologna and described. Other tests on strengthened columns, coming from the same experimental campaign, have been used to validate the capability of the models. Different types of reinforcement have been considered. Further validation has been obtained by considering also experimental results coming from literature data. The comparison of the numerical models with the experimental outcomes shows a good matching both in terms of mode of failure and quantitative behavior.