Study On Bearing Capacity Of Hollow FRP-concrete-steel Tubes Composite Long Columns Subjected To Eccentric Compression

Hollow FRP-Concrete-Steel tubular composite column(DSTC)is a new type of composite column proposed by Professor J.G.Teng of Hong Kong University of Technology.This kind of composite column is composed of FRP tube on the outside,steel tube on the inside and plain concrete placed between the two tubes.FRP pipe can not only provide protection for concrete and steel pipe,but also provide strong restraint for concrete,so that the ductility of composite column is greatly improved,and the gap in steel pipe can also be filled with concrete when it is necessary.This new type of composite column is not only convenient for construction in practical engineering,but also has outstanding seismic resistance and durability.Although there are many researches on the mechanical properties of composite columns at present,the finite element analysis of the eccentric compression performance of hollow FRP-Concrete-Steel tubular composite columns is less,and the calculation formula of the eccentric compression bearing capacity of such columns based on a large number of parameter analysis has not been reported.Based on this,this subject takes the actual project as the research object,establishes the finite element model of hollow FRP-Concrete-Steel tube composite long column by combining the large-scale finite element software ABAQUS,and determines the non-linear constitutive model suitable for DSTC composite column by comparing and verifying the constitutive model.Through the extended parameter analysis,the static deflection performance of the composite column is studied,the load displacement curve of the composite column is obtained,and the deflection bearing capacity of the specimen is extracted.The main research works and conclusions are as follows:1.Several common constitutive models of confined concrete at home and abroad are summarized,and according to the actual situation,the concrete constitutive model that conforms to the stress characteristics of composite columns is selected,which lays the foundation for further finite element analysis of composite columns.2.The finite element software ABAQUS is used to simulate and analyze the existing tests,obtain the load displacement curve of the test piece,extract the bias bearing capacity of the test piece,and compare with the test results,the two are in good agreement,which verifies the rationality of the finite element modeling method in this paper.3.The effects of the slenderness ratio,FRP pipe,steel pipe thickness,concrete strength and eccentricity on the mechanical properties of DSTC composite columns were investigated by analyzing the expansion parameters of 33 specimens.With the increase of FRP pipe,steel pipe thickness and concrete strength,the eccentric load-carrying capacity of the specimens increases gradually,but with the increase of slenderness ratio and eccentricity,the eccentric load-carrying capacity of the specimens decreases gradually,and all the specimens show good load-carrying capacity.4.Based on the Empirical coefficient method,the caculation formula of bearing capacity of composite columns is deduced.Using the calculation formula to verify the bearing capacity of composite columns.The result show that the calculation accuracy is high,which can be used for reference in practical engineering design.At the same time,it lays a foundation for the further elastic-plastic analysis of the frame with this kind of columns.