Nonlinear response of Masonry panels strengthened with FRP

Recent codes extended the use of displacement-based design methodologies, such as the pushover analysis, to the case of masonry buildings. On the base of this procedure, the seismic demand of buildings depends not only on the value of the peak load but also on their post-peak behaviour. In the case of FRP-strengthened masonry structures, the post-peak behaviour is both influenced by the softening behaviour of the masonry material and by the brittle delamination phenomenon that can affect the FRP-reinforcement. Therefore, in a modelling process of FRP-strengthened structures it is very important to account for both the softening behaviour of masonry material and the delamination phenomenon of FRP reinforcement. Moreover, the arrangement of FRP reinforcement and the anchorage of the FRP strips play an important role in the efficiency of strengthening techniques. In this paper analytical models have been proposed to evaluate the nonlinear response of some un-strengthened and FRP-strengthened masonry panels. Particular regard has been addressed to the modelling approach of FRP reinforcement taking into account both the delamination phenomenon and the anchorage of the strip on the panel. In the first part of paper, comparisons between the analytical and experimental responses of some examined panels are shown; considerations on the effectiveness of the strengthening and on the structural failure modes are pointed out for simple panels, emphasizing the ability of the proposed models to reproduce the experimental behaviour of masonry elements. In the second part, the seismic performance of a masonry facade of a three-story building is evaluated according to the Italian seismic code [OPCM3431-2005] adopting different FRP strengthening solutions. The effect of FRP reinforcement in terms of ductility level and ultimate behaviour is discussed.