Enhancement in in-plane shear capacity of unreinforced masonry (URM) walls strengthened with fiber reinforced polymer composites

Experimental study was performed to evaluate the enhancement in in-plane shear capacity of unreinforced masonry (URM) walls externally retrofitted and/or rehabilitated with fiber reinforced polymer (FRP) composites. Six identical wall specimens of size 1.83m×1.83m were used; four of them were externally retrofitted using different composite retrofitting schemes and one was repaired with composite laminates after having diagonal cracks on wall faces. All specimens were tested under in-plane cyclic shear in presence of constant gravity load. Wall response with the gradual increase in lateral loading was recorded in the form of hysteretic load deflection curves from which wall ductility under cyclic loading is computed. During experiment, the damage progression in wall specimens and their ultimate failure modes were recorded. From these observations, the enhancement in ultimate in-plane shear capacity and wall ductility are calculated by comparing the response of retrofitted and non-retrofitted walls. A significant enhancement in wall ultimate capacity is observed due to the application of fiber reinforced polymer composite laminates. Experiment showed that the ultimate failure modes of the walls shifted from brittle to ductile nature when they were externally retrofitted with fiber reinforced polymer composites. Furthermore, the in-plane shear capacities of the same wall specimens are calculated using currently available code-based and research-based analytical models. Four such analytical models are used according to their applicability for different retrofitting schemes. The comparison of analytical result with experimental observations indicated that analytical models are very case specific and their applications are very restrictive. Thus further study is required to develop analytical models that will be generally applicable to a higher population of concrete masonry walls externally retrofitted with different combinations of composite materials and lamination schemes.