In-plane shear strengthening of masonry panels using pultruded FRP rebars

Existing masonry buildings often suffer significant earthquake-induced damage, due to the activation of both out-of-plane and in-plane mechanisms. Various retrofitting methods, particularly those using composite materials, can be applied to enhance the capacity of these structures against horizontal loads. This study introduces a novel strengthening approach for masonry panels made of solid and hollow clay bricks, that involves inserting Carbon Fiber Reinforced Polymer (CFRP) rebars into vertical grooves within the masonry, secured with cementitious mortar, and applying CFRP sheets to the outer surfaces of the walls. This method is especially beneficial when retrofitting must be done externally, allowing ongoing indoor activities without disruption. To evaluate the effectiveness of this technique in enhancing the in-plane shear behaviour of masonry structural elements, direct shear tests and diagonal compression tests were conducted on both unreinforced and retrofitted samples. A total of 32 direct shear tests and 16 diagonal compression tests were performed on two different types of masonry, considering both single- and double-wythe panels. The findings indicated that the proposed retrofitting solution is able to improve both the shear sliding and the diagonal cracking resistance, providing valuable information about the shear failure mechanisms of the strengthened elements. The execution of direct shear tests allowed to evaluate the reinforcement contribution at the local level. The strength increments obtained in diagonal compression tests ranged between 29 % and 90 % depending on the masonry typologies and reinforcement ratio.