Some Vital Issues Of Fiber Reinforced Polymer Strengthening Concrete

In recent years, the inspection, evaluation, maintenance and strengthening of existing buildings, bridges and roadways have turned into the main body of investment, research and development of Civil Engineering. In the strengthening and modification works, the most popular method is using one kind of fiber reinforce polymer (FRP), such as carbon fiber (CF) or glass fiber (GF), to strengthen concrete. Because of apparent merits and demerits of single FRP, the strengthening efficiency was not high. Under this background and the existing research information, the thesis performed a detailed comparative experiment study of tensile properties of a hybrid fiber reinforced polymer (HFRP) composed of CF and high strength glass fiber (SGF). Both the influence of the mix ratio between CF and SGF and the specimen size on behavior of FRP were studied. It is emphasized especially that only large specimens can display the "plastic" property of HFRP.Based on the tension comparative experiment study of HFRP, the reasonable matching of HFRP was chosen to strengthen concrete columns. The mechanical properties and working mechanism of HFRP-strengthened columns under axial pressure were studied through experiments. It was shown that, the HFRP strengthening method may significantly enable the strengthened column higher ductility and deformability, and decrease strengthening cost greatly.Then, Via bonding mechanism, the importance of exerting pressure to the bonding interface between FRP and concrete was indicated. Experimental study showed that the request of bonding strength can be satisfied by exerting contact pressure, and a rational contact pressure was suggested.At last, the thesis enumerate some cases to illustrate how to apply HFRP and how to exert contact pressure in strengthening concrete structures.