Effects of mortar layers in the delamination of GFRP bonded to historic masonry

Externally bonded fiber reinforced polymers (FRPs) used as strengthening for shear historic masonry walls increase tensile capacity so as to support combined compression and high shear forces released during earthquakes. The local and global capacity of FRP strengthened shear walls depends on delamination. This paper deals with the anchorage strength of GFRP strips bonded to historic masonry by analysing results obtained in pull–push shear tests carried out on GFRP-to-historic-brick bonded joints. The experimental research also foresaw the analysis of effects deriving from the presence of mortar layers in actual historic brickwork masonry, simulated through the creation of grooves on the surface of mortar filled clay bricks. The experimental results indicated brittle failure of joints due to delamination; results were processed to evaluate failure load values, strain vs. anchorage length diagrams and shear stress vs. slip relationships experimentally. Finally, the anchorage of GFRP-to-historic-brick was theoretically studied to improve the classic solution by incorporating adherent shear deformation. Discussion on the experimental and theoretical data was developed.