Structural behavior of strengthening masonry in-filled frames subjected to lateral load using bonded and un-bonded CFRP

Lateral loads annually destroy many reinforced concrete structures in different countries. However, there is a necessary need to retrofit masonry infill walls to utilize them as lateral load resisting elements. For this purpose, an experimental program has been carried out on half scale specimens to characterize the behavior of single story brick masonry in-filled frames under the effect of lateral loads. The effectiveness of different strengthening techniques is investigated using Carbon-fiber Reinforcement Polymer (CFRP). The steel reinforcement at the beam-columns joints of all specimens was detailed as hinged connection. FRP sheets and FRP strips were used as strengthening agents for the tested specimens. They were utilized in two different cases, bonded or unbonded to the masonry wall. In addition, the FRP anchor technique was used to increase the efficiency of bonding the strengthening agents with the frames and the walls. The load-displacement behavior, FRP strain, crack pattern, steel strain, and mode of failure of the tested specimens were investigated. The results showed that the used strengthening methods are effective, with high increase in strength and ductility. In addition, an analytical model was presented and solved. Based on this model, simplified empirical equation to design the required amount of FRP needed to resist lateral loads was proposed. The equation showed a good agreement with both the experimental result and finite element output.