Externally bonded grids as strengthening and seismic retrofitting materials of masonry panels

Externally bonded grids are used in this study as a means of increasing the load-carrying and deformation capacity of unreinforced masonry (URM) walls subjected to cyclic loading. The experimental investigation was carried out on two groups of medium-scale, single-wythe wallettes consisting of either perforated fired clay bricks, or solid stone blocks. The specimens were subjected to cyclic loading which induced in-plane flexure combined with axial force, out-of-plane flexure and in-plane shear with axial force. The parameters considered were the number of strengthening layers (one or two layers, applied on both sides), the type of grid (open mesh structures comprising carbon, glass or basalt fibers and polypropylene or polyester), the type of bonding agent (mortars of different compositions or epoxy resin) and the compressive stress level applied to specimens undergoing in-plane loading. Based on the findings of this work the use of externally bonded grids comprises a promising solution for the structural upgrade of existing masonry structures.