Experimental Study On Bond Slip Properties Between Steel Reinforcement And Concrete At High Strain Rates

A large plastic deformation of the reinforced concrete joints and other structural members could be generated under the impact load,which will lead to the bond slip between the steel reinforcement and concrete.As a result it will further reduce the load bearing capacity of the structural members.Thus,it is very important to study the failure mechanism and dynamic characteristics of the bond slip properties between the steel reinforcement and concrete for reinforced concrete structures.In this thesis,the quasi-static testing machine CRIMS? YNS-Y3000 and the high strain rates testing machine INSTRON? VHS 160/100-20 available in the Key Laboratory of Coast Civil Structure Safety of China Ministry of Education in Tianjin University are used to carry out the quasi-static and dynamic tests on the bond slip properties between steel reinforcement and concrete.The bond stress-slip relationship is also studied based on the test results.The main research work is as following.(1)The current loading device are modified and improved to fulfill the needs of the quasi-static and dynamic tests.The push-in tests are selected to study the bond slip properties between steel reinforcement and concrete,and a standard test procedure is put forward.(2)Four main parameters such as cover thickness,anchoring length,concrete strength and bar diameter are considered to study their influence on the test results,therefore,four groups of the specimen,namely A,B,C and D are designed and made for the push-in tests.Nine strain rates from 0.001 1/s to 150 1/s are chosen in the dynamic tests to study the bond slip properties between steel reinforcement and concrete at high strain rates.Therefore totally 132 specimens are made,including 44 groups(3 specimens in each group).Thus,132 test data could be derived.The test results show that the bond slip properties are obviously influenced by the strain rate.The adhesive anchorage strength increases almost linearly when strain rate increases in the strain rate scope from 0.001 1/s to 150 1/s.The dynamic increase factor of bond strength at medium and high strain rates are influenced by parameters such as strain rate,cover thickness,anchoring length,concrete strength and bar diameter.Strain rate and cover thickness are of great importance,while the influence of anchoring length,concrete strength and bar diameter are insignificant,which can be neglected.(3)Based on the test results,the failure mode of specimens under quasi-static load,medium and high strain rates are observed and summarized.The influence of strain rate on bond slip properties is investigated,and the empirical formulae to predict the maximum bond strength between steel reinforcement and concrete at different strain rates are put forward.