Ultra-fine Grain Steel Bonded Anchor Performance

Ultra-fine grain steel bar is a new kind of close grain hot-ribbed bar which is made by controlling the temperature of rolling.It has many kinds of characteristics such as high strength and good ductility .In this paper , we carried out the research about the mechanical capability(including 400 MPa and 500 MPa steel bar), especially the bond-anchorage property in concrete of ultra-fine grain steel bar steel bar to solve the problem on the anchorage design of this new kind of steel bar in concrete structures.In addition,we carried out the research about the bond-anchorage property of symmetric-ribbed bar and asymmetric-ribbed bar .The mechanical capability test proves that the strength and the elongation of ultra-fine grain steel bar not only satisfy the requirements in Chinese standard , but also achieve the demands in Eurocode . So it can be used in seismic design structures. And in the design of concrete structure , the values of characteristic tensile yield strength f_yk can be set as 500 MPa , the value of modulus of elasticity E_s can be set as 2.1×10⁵ N/mm².According to 48 pullout tests of ultra-grain steel bars and 18 pullout tests of the symmetric-ribbed bar and asymmetric-ribbed bar ,the effects of concrete strength , thickness of concrete cover , anchorage length , and stirrup ralio etc . for the bond -anchorage property have been analysed. By way of experimental statistical regression ,the calculating formula of ultimate bond-anchoring strength has been established . The result is in good agreement with what comes from the formula of crescent hot-ribbed bar proposed by the special bond-anchorage research group of Chinese code for design of concrete structure.The design of anchoring length through reliability analysis has been proposed , the result shows that the anchoring length for ultra-fine grain steel bar can be designed by the formula in existing code for design of concrete structures (GB50010-2002) .