Numerical Investigation on the Influence of FRP Retrofit Layout and Geometry on the In-Plane Behavior of Masonry Walls

Unreinforced masonry (URM) structures have shown their vulnerability to major events like as earthquakes, severe wind, blast, and impact. The present work started from experimental programs available in scientific literature related to masonry walls made of clay or natural stone units. The finite-element method (FEM) was used to describe the global behavior of tested specimens in terms of shear/displacement curves, shear capacity, and cracking pattern. FEM, and particularly detailed micromodeling, was adopted as a numerical simulation tool for masonry walls. International design codes underline that some fiber reinforced polymers (FRP) dimensions (e.g., width, thickness, and spacing of FRP strips applied as external strengthening of URM walls made of different brickworks) may influence the global behavior of strengthened masonry. The present work, starting from experimental programs by other research groups, related to walls made of solid and hollow clay units as well as natural tuff units subjected to compression/shear loading aims at identifying the actual influence of those dimensions. Diagonal and horizontal strips were investigated. Different brickwork panels having the same FRP strengthening (quantity and geometry) showed different behaviors. Present outcomes highlighted that the influence of some FRP strengthening parameters (e.g., strip spacing) is not so meaningful if compared to FRP total amount even if the code formulations predict significant differences.