| RPC-Filled Steel Tube has higher strength,ductility and toughness than Concrete-Filled Steel Tube,which is full of reactive powder concrete(RPC)with high performance cement matrix composites in the steel tube.The role of RPC interfacial interaction is an important factor in the combined effect of steel pipe RPC.In recent years,more and more applications of steel pipe RPC,but in addition to compression performance,the steel tube RPC static performance research is not enough depth.In order to improve the mechanical performance theory of steel pipe RPC and promote the engineering application,this paper studies the bond-slip performance between steel pipe and RPC interface.A total of 27 test specimens in the direct push-out test of RPC-Filled Steel Tube,including different Sectional Steel Ratio(4.73%,6.89%,8.65%,10.43%,12.22%,Changing the thickness of the steel pipe),steel fiber volume fractions(0%,1%,2%,3%)and different curing temperatures(20?,90?)in this test parameters.The main achievements are summarized in detail as follows:1.In the experiment,the curves of N-s was obtained.The experimental results show that the N-s of RPC-Filled Steel Tube is similar to that of concrete-Filled Steel Tube.The curves of N-s is including three phases:Initial sliding segment;Wearing sliding segment;Stationary sliding segment.The interaction of the initial sliding segment is composed of chemical cementing force,mechanical bite force and friction;the interaction of Wearing sliding segment is composed mainly of friction and mechanical bite,this phase of N-s curve produces fluctuates up and down;the interaction of Stationary sliding segment is composed of friction and the mechanical bite of the new boundary.2.The distribution curve of the longitudinal and lateral strain of steel pipe outer surface along the load direction are obtained.Test results showed that longitudinal strain of steel tube is triangular distribution patterns along the axis of the specimens,lateral strain showed convex curve.Strain in the middle of steel tube is greater than at the end of the specimens,RPC has passive constraints from steel tube.3.The influence is different to initial bonding strength and ultimate bonding strength of RPC-Filled Steel Tube by the curing temperature the steel ratio and volume of steel fiber.Curing temperature has the greatest impact on the initial bond strength,the sectional steel ratio has the least influence on the initial bonding strength.The sectional steel ratio has the greatest impact on the ultimate bond strength,the volume of steel fiber has the least influence on the ultimate bonding strength.Specifically,the influence of the three parameters are as follows:(1)Curing temperature is helpful to promote the chemical composition in the RPC fully reflected,the hydrated calcium silicate in the products is easier to bonding closely with steel pipe surface,the temperature can effectively improve the chemical cementation force of the RPC-Filled Steel Tube,which is one of the main influencing parameters of the bonding strength.Compared with 20 curing conditions,the initial bonding strength and ultimate bonding strength of the specimens under 90 curing conditions are increased by 36%and 11%.(2)The radial deformation of the RPC under the force from constraint of the steel pipe,the greater the steel ratio,the greater the constraint effect,the greater the friction of the RPC-Filled Steel Tube.The effect of the sectional steel ratio is increased with the increase of load.When the load is small,the radial deformation of the RPC is small,the influence of the sectional steel ratio is small.The effect of the steel ratio to the initial bond strength is not obvious;When the load increases to ultimate load,the radial deformation of the RPC is large,the influence of sectional steel ratio increases,the friction of RPC-Filled Steel Tube increases significantly.Ultimate bond strengths sectional steel ratio increases linearly with the sectional steel ratio.(3)The effect of steel fiber on the ultimate bonding strength is not obvious.Influence of steel fiber content on the initial bonding strength is greater than the effect of the ultimate bonding strength,relationship is very complicated between the degree of influence and the amount of volume of Steel fiber.Content of Steel fiber is increased from 0%to 1%,the initial bonding strength decreased by 3%,while steel fiber content is increase from 1%to 3%,the initial bonding strength improved by 92%. |
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