Experiment Study On Steel Bar Bonded To High Performance Steel Fiber Concrete

The bond action between steel bar and concrete is the premise to bear load together for the reinforced concrete structure.Concrete matrix tensile strength is improved because steel fiber is mixed with concrete mixture,which makes bond performance between steel bar and concrete different from that of ordinary concrete.It is greatly significant to deeply carry out experimental research on steel bar bonded to high performance steel fiber concrete for relevant design theory and concrete engineering practice.The bond behavior is studied between ordinary steel bar and large fluidity and high performance steel fiber concrete by the central pull out test in the paper.Relevant researchs about steel bar bonded to concrete is summarized at home and abroad.The 20 bond specimens are tested by central drawing test.The change law of bond property of steel bar and high performance steel fiber concrete is systematically studied due to variation of steel fiber contents(0,0.8%,1.2%,1.6%,2.0%)and steel bar diameters(16mm,20mm).The main research contents are as follows:(1)Bond specimens which contain steel fiber volume rates(0,0.8%,1.2%,1.6%,2.0%)and steel bar diametrs(16mm,20mm)are tested through the central drawing tests.The influence law of steel bar bonded to steel fiber concrete are acquired according to the change of steel fiber content and steel bar diameter.According to the obtained test results,the conclusion is received that bond strength between steel bar and steel fiber concrete does not change obviously with the increase of steel fiber content and grows with the rise of steel bar diameter.(2)The damage forms of bond specimens are oberserved.The test phenomenonsoccurring in the process of bonding test are described.The failure mechanism of bond specimens is analysed.The experimental results are indicated.The destroyed form of bond specimens is drawing failure.There is no obvious transformation on the surface of bond specimens.The tearing sound of steel fiber arises in the drawing process.Cohesive force is mainly determined by mechanical interaction between ribbed steel bar and concrete.(3)Description,comparison and analysis are presented on the gained bond slip cures.Test conclusions are received.The bond slip cures consist of ascending section,stable section and degressive section.Steel fiber enlarges the covered area of bond slip cures and makes bond slip cures more gentle.(4)The characteristic values of bond strength and the respectively corresponding relative slips between steel bar and concrete are achieved through bond tests.Test results show that the evident change rule of the ultimate bond strength does not appear along with raise of steel fiber content.However,the respectively corresponding relative slippage of the ultimate bond strength is increased in the wake of increase of steel fiber content.(5)The constitutive relation expression of stress slippage curve suitable for steel bar and high performance steel fiber concrete is obtained according to stress slippage cure got from bonding tests.The experimental data is analyzed.According to the constitutive relation of ordinary reinforced concrete,the constitutive relation expreesion fit for high performance steel fiber concrete is received.