Study On Bond Properties Of GFRP Bars And Fiber Concrete

Traditional reinforced concrete structures are prone to corrosion damage under corrosive environment.In order to improve the durability of RC structures and reduce the damage caused by steel corrosion,the researchers use fiber reinforced polymer bar(FRP bar)instead of steel bars as stress bars.However,the surface shape and mechanical properties of FRP bars are quite different from those of ordinary steel bars.The application of FRP bars in concrete structures will lead to the problem of insufficient bond strength.Fiber can improve the bond strength between FRP bars and concrete.Hybrid Fiber Concrete(HFC)is formed by adding two or more fibers into concrete,which can give full play to the advantages of each fiber.At the same time,compared with single fiber,it can play a positive hybrid effect,better restrict the development of internal cracks in concrete,and enhance the bond between concrete and FRP bars.On the basis of previous studies,a series of studies have been carried out on the bonding properties of carbon,polypropylene,aramid HFC and GFRP bars with relatively good properties in this paper.The main contents are as follows:(1)The effects of hybrid fibers,carbon fibers,aramid fibers,polypropylene fibers,diameter of GFRP bars,surface form and anchorage length on the bonding properties of GFRP bars to concrete were studied through the central pull-out tests of 36 150 mm×150 mm×150 mm cubic concrete blocks.It is considered that hybrid fibers,carbon fibers,aramid fibers and polypropylene fibers can improve the bond strength and ductility of GFRP bars to concrete to a certain extent.With the increase of polypropylene fiber content,the bond performance is improved more significantly,while aramid fiber is difficult to disperse,and the effect of increasing the content of aramid fiber on the bond performance is not significant.Hybrid fiber has a good positive hybrid effect on improving the bond performance.(2)The variation of bond stress along anchorage length of GFRP tendons is studied through the central pull-out test of strain gauges attached to the GFRP bars,and the measured bond-slip curves of each anchorage length of each test block are given.(3)Based on the pull-out test results of GFRP bars and concrete,the ?-s constitutive model of specimens is established,which is in good agreement with the ?-s test curve,and the recommended formula for the basic anchorage length of GFRP bars and HFC is given.