| With the development of economy,the concept of energy conservation,emission reduction and green energy conservation is becoming more and more obvious in China.At present,many super large reinforced concrete structures are involved in the engineering field.Roll rebars and ordinary concrete can not meet the needs of the actual project,so that more and more rebars and concrete with higher strength and performance are needed in the engineering design of our country to meet the design requirements.The application of high-strength steel bars will improve the safety performance of the structure,reduce the use of steel bars,reduce energy consumption and air pollution.At present,there are few experimental researches on high-strength steel bars in our country,which slows down the pace of its use in infrastructure construction.In order to make the reinforced concrete structure specifications conform to the international standards,it is necessary to study the bond performance between high-performance steel bars and concrete as soon as possible.When designing the bearing capacity of members,the bond between the rebar and concrete should be considered.Many academic researchers have studied the bond behavior of reinforced concrete members,and put forward various constitutive relations.However,due to the advanced influence of technology and theory,there is no accepted common theory for the relationship between bond and slip.It can be seen from the previous related thesis that the influence of diameter on the bond performance is analyzed by taking the size of protective layer as the constant value and the diameter of rebars as the research sample.In this thesis,the ratio of the perimeter of rebars to the size of test piece is taken as the constant value.The main research contents are as follows:(1)HRB500 high-strength ribbed steel bar with tensile strength of 525N/mm~2 and concrete mixed with fly ash are used as research materials in the test.The corresponding data and characteristic values of different types of steel bars are obtained through the test.(2)In the process of concrete pouring,the strength and size of the test pieces will affect the calculation of the test results,so in this thesis,Bayesian estimation method is used to correct the characteristic values obtained from the test,so as to eliminate the influence of the strength and size of the test pieces on the test results.(3)The characteristic value of stress obtained by Bayesian estimation method is checked and analyzed with the test value,and the comparison result proves the correctness of this method.The formula of ultimate bond strength considering the front angle of rib and the constitutive relation of bond slip under different rebar diameters are established by numerical regression analysis.Then the theoretical bond slip curve is compared with the experimental bond slip curve,the theoretical and experimental results are in good agreement.(4)When the bond stress between the rebars and the concrete reaches the maximum,the maximum tensile stress of the rebars is calculated by using the European code,and compared with the tensile stress based on the Chinese code.Through the comparative calculation,the anchorage length of the rebars is optimized,so that the reinforced concrete members can save more rebars in the design and production process,material budget is more economical.(5)The stress diagram of each group of test specimens under load is obtained by using the finite element software,and the bond slip curve obtained by ANSYS software is compared with that obtained by the test bond slip curve.The results show that the proposed constitutive relation is correct. |
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