Flexural strengthening of reinforced concrete beams with mechanically fastened fiber reinforced polymer strips

The purpose of this research was to study a new method of flexurally strengthening reinforced concrete beams. The proposed method uses multiple mechanical fasteners unlike current practice, where a fiber reinforced polymer (FRP) strip is attached to the beam with an adhesive.; In order to study the method of strengthening beams by mechanically attaching FRP strips, construction engineering, material engineering, and structural engineering research areas were addressed. Coupon tests were performed on the material components. Custom FRP strips were designed specifically for use with mechanical fasteners. Behavior of connections with single and multiple fasteners were examined experimentally, and small-scale beam tests were conducted to examine the feasibility of the overall method and to further identify factors affecting the structural behavior of the strengthened beam. Large-scale experiments were conducted in order to examine the behavior of larger beams with the custom strips. Parameters such as fastener spacing, pre drilling pilot holes and edge distance were examined in these tests. To further increase the understanding of the method, an analytical model was developed and predictions obtained by analysis were compared to the experimental results.; Small-scale beams strengthened using this method showed increases in yield and ultimate moment capacities of 34.2 and 24.8 percent over the unstrengthened control beams, while the large-scale beams achieved increases of 21.6 and 20.1 percent in the yield and ultimate moments. Large-scale beams not only achieved levels of strengthening comparable to the adhesively bonded method, but the fastened method resulted in strengthened beams with a gradual failure mode, as opposed to the sudden failure mode of the adhesively bonded beams. The FRP strip attachment with mechanical fasteners was completed in less time than it took to attach the FRP strips with an adhesive.; Analytical and experimental investigations have shown that reinforced concrete beams can be flexurally strengthened by mechanically attaching custom FRP strips.