Assessment of Design Formulas for In-Plane FRP Strengthening of Masonry Walls

Masonry structures have demonstrated their seismic vulnerability during recent world seismic events. This paper investigates in-plane seismic performance of unreinforced masonry (URM) walls before and after they are retrofit using fiber-reinforced polymer (FRP) materials. An assessment of available design formulas for evaluating both the in-plane performance of URM walls and the contribution of FRP strengthening systems was performed. Walls with two configurations of the FRP reinforcement have been analyzed: one based on FRP strips installed parallel to the mortar joints, the other characterized by FRP strips arranged along the diagonals of the wall. Based on shear–compression tests carried out on FRP-strengthened masonry walls available in the literature, a comparison between theoretical and experimental data is performed. A discussion about the FRP strains at failure of the walls is provided and values of effective FRP strains to be used for design purposes are proposed.