| In comparison with the costs and the efforts of “destroying and rebuilding new buildings”,strengthening can be a better option for extending the life spans of existing structures.As such,it is worthwhile to conduct a systematic comparative study to provide guidance on selecting the strengthening method in engineering practice.In this study,the performances of reinforced concrete(RC)beams flexurally strengthened with Externally bonded(EB)CFRP sheets,Near-surface-mounted(NSM)FRP bars,Prestressed steel wire ropes(P-SWRs)as well as various combinations from two of the mentioned three strengthening techniques were investigated and analyzed by experimental studies and theoretical analyses.The experimental work included testing of nine reinforced concrete beams,one of which stayed un-strengthened as a baseline for comparison.In the first stage,four beams strengthened by an individual method(i.e.with EB CFRP sheets or NSM FRP bars or P-SWRs)were tested.In the second stage of the experiment,the other four beams strengthened by various hybrid methods(i.e.,combining two different strengthening methods)were tested.The test variables included the technique of strengthening(NSM,EB,and P-SWRs)and the type of FRP bar in the NSM strengthening technique.Among all the beams which were strengthened by an individual technique,the P-SWR reinforced beam delivers the most satisfactory flexural performance,especially for crack width control.Also,it was observed that,among the hybrid strengthening cases,the adoption of P-SWR is favorable to improve the flexural performances.More specifically,the P-SWR strengthening technique results in a better improvement of the flexural capacity,the cracking control,and the ductility,especially in cases where the strengthened beams have yielded.When P-SWRs were combined with EB CFRP sheets or NSM CFRP bars for strengthening,the advantage of the latter can be amplified,and the disadvantages of the latter can be suppressed. |
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