Experimental Research On Bond Strength Of Concrete Filled Steel Tube Columns

In recent years, the CFST as a combination of material is more and more widely used inengineering with its good mechanical performance and economic rationality. Its goodmechanical performance is based on the bond strength between the steel and concrete. Someresearch work has been carried out on the bond carrying capacity of CFST. In order to ensurethat these two materials can work together, interfacial adhesion of steel and concrete ishighlighted. The mainly factors impacted on the interface bonding are steel and core concrete.The interface between steel and concrete will have the inevitable initial imperfections, whenunder external loads, these initial defects continue to accumulate and develop, resulting ininterface bonding performance degradation, bond stress reduction, structural capacity decline.Therefore, we must explore the initial damage of the impact on material properties, identifyways to reduce and prevent the occurrence and the development of the initial defects.The research work is summarized as follows:1. The width-thickness ratio and water-cement ratio are considered as the two basicparameters, The push-out test is designed nine CFST columns presented by using theorthogonal experimental method. the role of interfacial adhesion were been discussed, Obtainthe law of interface bonding strength changes with the width to thickness ratio andwater-cement ratio. The statistic regression analysis has reflected the deformation rule of thebond strength.2. To explore the mechanical properties affected by the pipe polished and ribbed, the testthat11specimens designed with the parameters was carried out, examining CFST interfacebond performance.3. Put fly ash、expansion agent and polyacrylonitrile fiber into the concrete. To probe themechanical properties affected by the change of concrete character, the test that4specimensdesigned with the parameters of fiber content was carried out, examining CFST interfacebond performance.4. Based on the test result, the working mechanism about CFST push-out test wasrevealed deeply. At first, the CFST interface states were described, the basic concepts aboutultimate bond strength and the average bond strength were defined clearly. The load-strainrelationships for all the specimens were obtained. Then, we investigate the composition of thebond strength, deduce the size of the bond strength, obtaining the relationship between bondstrength and these factors considered in this test.