Experimental Research On Mechnical Anchorage Property Of 600MPa Hot-ribbed Steel Bar

600MPa hot-ribbed steel bar is a new kind of structural high strength steel bar,which has been investigated and developed recently after 400 MPa and 500 MPa series of high strength reinforced bars.The universal application of 600 MPa steel bar is not only accord with the idea "a green four sections" requests,but also meets the development needs of construction industry in our country.Depending on the effective bond between reinforcement and concrete,high strength steel bar can play a performance advantage.Therefore,bond issue between high strength steel bar and concrete is a key problem for the application of high strength steel bar.However,the basic research work of 600 MPa steel bar is still at its preliminary stage in our country.Especially,the mechanical anchorage property research of 600 MPa steel bar has still not been started in our country.To solve the anchorage problem of 600 MPa steel bar for its application in concrete structural engineering,a systemic study on the mechanical anchorage property of 600 MPa steel bar is necessary.60 prism concrete specimens of 600 MPa steel bars with mechanical anchorage measure were investigated under pull-out test.Concrete strength,cover thickness,anchoring length and the stirrup for the mechanical anchorage performance impact of 600 MPa steel bars were analyzed.The mechanics mechanism,bond-slip relationship of mechanical anchorage between 600 MPa steel bar and concrete were investigated.At the same time,the ultimate strength calculating formula of mechanical anchorage between 600 MPa steel bars and concrete was given.By attaching strain gage at the surface of steel bar,the force bearing status of anchor head was obtained.The mechanics mechanism between 600 MPa steel bar and concrete was analyzed,and calculation formulas of characteristic strength and slip at internal crack point,split point,and limit point about mechanical anchoring between 600 MPa steel bar and concrete were derived,and τ-s basic relationship was introduced.Based on anchoring strength formula,anchor bar and anchor plate mechanical anchorage length of 600 MPa steel bar were presented by reliability calculation method.It is shown that both of anchor bar and anchor plate can decrease the anchorage length effectively and the mechanical anchor length of 600 MPa steel bar can still be designed by code for design of concrete structures(GB 50010-2010).