Retrofitting damaged unreinforced masonry using external shear strengthening techniques

The in-plane shear behavior of unreinforced masonry panels retrofitted with three different techniques was investigated, and in particular the effectiveness of reinforcing methods to restrain the diagonal cracking failure mode was studied. Fifteen standard sized panels of 1.2 x 1.2 x 0.25 m were subjected to diagonal compression testing and then repaired using polypropylene fiber reinforced mortar, ferrocement jacketing, or carbon fiber reinforced polymer (CFRP) wraps applied externally on both sides. The panels were made of two different types of mortar; type N representing modern masonry buildings and type O mortars for older buildings of the 1950s and earlier. Several parameters such as mode of failure, shear stress-strain behavior, shear strength, shear modulus, elastic modulus, and ultimate drift were determined. At the end of 30 diagonal compression tests, plain panels exhibited sudden brittle failure mainly characterized by step-like cracks along the diagonal, whereas retrofitted panels had a more ductile behavior, with an increment of shear strength by 161-454% and of ultimate drift by 863-1486%.