| The Compact Reinforced Composite（CRC）is poured into steel pipe to form CRC-filled Steel tube.Not only can it improve bearing capacity of structure,but it also reduce the use of CRC.The basic problem in steel-concrete composite structures is bond-slip problem between steel tube and core concrete.However,there are relatively few studies about the bond-slip performance of CRC-filled steel tube in the current domestic and foreign.Therefore,this paper uses a combination of experimental research and theoretical analysis to study the bond-slip performance of CRC-filled Steel tube,to provide a reference for the design and construction.Mainly the following:The bond-slip performance of CRC-filled steel tube is studied by push-out test.In this test,a total of 32 CRC-filled steel tube specimens were designed and made with the section type of steel tube,the ratio of width（diameter）to thickness and the content of steel fiber as variable parameters.The test results show that there are two main failure modes of specimens,which are material failure and interfacial bond slip failure,and the Nuof the circle steel tube specimen is much larger than that of square steel tube when t=6mm,and the growth rate is about 50%,when t=4mm is used,which is about 1.0-1.4 times higher than that of square steel tube specimen.The bond failure load value Nuof all specimens increases with the decrease of diameter-thickness ratio;with the increase of steel fiber content,the bond failure load value Nuincreases continuously,but the increase decreases continuously.From the point of view of safety and economy,this paper suggests that the steel fiber content of 3%is the most reasonable.Based on the test results,starting with the influence of a single parameter on the interfacial bond properties of CRC-filled steel tubes,and comprehensively considering the influence of various factors,the formulas for calculating the interfacial bond strength of square and circular steel tubes CRC are established by using the mathematical program First stopt,respectively.Starting with two typicalτ-s curves,the simplifiedτ-s constitutive model of CRC-filled steel tube is obtained,and the interface bond-slip constitutive models of square and circular CRC-filled steel tube are proposed respectively by fitting the mathematical program First stopt.According to the force balance equation,the function expression of interface bond stress of steel tube is obtained.The function expression of longitudinal strainis obtained by using mathematical program First stopt.The position function of interfacial bond stress of CRC-filled steel tube is put forward. |
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