| Reactive Powder Concrete(RPC)is an ultra-high performance concrete,which has super high strength and excellent durability,can effectively reduce the weight of the structure,improve economic efficiency,has a broad application prospects.but similar to other high-strength concrete,Its ductility is relatively poor and its destruction is abrupt.The RPC is poured into the steel tube to form a reactive composite concrete structure of the steel tube.Through the constraint of the steel tube,the weak point of brittleness of the material can be effectively overcome,and the application space of the RPC is expanded.The axial pressure behavior of RPC filled steel tubes is the basis for the mechanical properties of compression,bending,shearing,and twisting.The loads on the the bottom bearing columns of high-rise and super-high-rise structures are very large,and the form must to be the short columns with relatively large cross-section,therefore,it is of great theoretical and practical significance to study the pressure behavior of the RPC filled steel tube.Under this background,this paper studies the axial pressure behavior and bearing capacity calculation of short steel tubes filled with RPC by means of experimental research,numerical simulation and theoretical analysis,and mainly includes the following aspects:1)Experimental study on the axis behavior of the short column of RPC filled steel tubes.Using the axial loading test of 20 short column specimens,the axial compression failure mode,bearing capacity,load-displacement curve of the speciments were studied,the force mechanism of the test piece and the ratio of diameter to thickness,RPC strength,curing method,loading method,etc.were analyzed.By analyzing the variation law of the stress and strain states of the steel tube and the core RPC in the loadingprocess,the understanding of the restraining mechanism of the steel tube is strengthened.2)Research on constitutive model of constrained RPC.The stripping analysis of steel tubes and concrete was carried out.Using the test data,the stress-strain curves of the steel tubes at different stages were respectively launched.Combined with the theory of internal force balance,the stress-strain curve of the RPC under the constraint of the steel tube was deduced,and the RPC under the constraint of the steel tube was proposed.The elastic modulus,compressive strength,and ultimate strain establish a constitutive model of constrained RPC.3)Numerical simulation analysis of RPC filled steel tube.Based on the ABAQUS analysis platform,using the proposed constitutive model of constrained RPC,a numerical simulation analysis model of the test piece was established,and the mechanical capacity under the axial compression was analyzed,and the calculated load-displacement curve,cloud image of destructed specimen were compared.The two are in good agreement;on this basis,the stress-strain curve of steel tube and RPC in the whole process is analyzed,and the influence of RPC strength and steel strength on the mechanical properties of the component is analyzed.4)Analysis of axial compression bearing capacity of RPC filled steel tubes.According to the research results of this article,and referring to the classic strength theory,the ultimate bearing capacity calculation model and calculation formula for the full-section loaded and core-loaded steel tubular RPC short columns were deduced,and the simplify the calculation model and calculation formula of residual bearing capacity was established..After verification,it shows that the formula calculation is in good agreement with the experimental and simulation results,and the proposed formula is reasonable. |
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