Study On Behaviour Of Steel Tube-Wood-Concrete Short Columns Under Axial Compression

Wood is a kind of biomaterial with a long history.It has the advantages of light weight,high strength and easy processing.In recent years,the emergence of new engineering wood products and the state’s advocacy of green building stimulate the exploration of more extensive application of wood.Therefore,based on the original theory of CFST column,considering the properties of CFST structure and wood structure,this paper proposes a composite column of CFST wood concrete,and studies its mechanical properties under axial compression.This new combination form is to put wood into concrete-filled steel tube,through the synergistic action of square steel tube,concrete and wood,to improve the bearing capacity of the structure,improve the ductility of the structure and reduce the self weight of the structure.In this paper,the development,application and research status of concrete-filled square steel tube structure and timber composite structure at home and abroad are summarized.The nonlinear finite element analysis of nearly 40 steel tube timber concrete short columns under axial compression is carried out by using the large-scale general finite element software ABAQUS.The load displacement curve of typical members and the stress working mechanism of composite columns are analyzed,and the square steel in each loading stage is studied At the same time,the distribution of stress and strain in the section of each component is analyzed.In addition,the influences of steel tube yield strength,concrete strength,steel tube wall thickness,wood section form and section size on the mechanical properties of composite columns are analyzed.Finally,based on the unified theory,the simplified calculation formula of the bearing capacity of the steel tube wood concrete short columns is deduced,and the comparison between the calculation results of the formula and the simulation results provides a reference for the later calculation of the bearing capacity of the steel tube wood concrete short columns.According to the calculation results,adding wood to the ordinary CFST columns can improve the bearing capacity and the ductility of the structure.With the increase of steel pipe strength,the bearing capacity increases gradually,but the growth rate decreases.The higher the concrete strength is,the more obvious the ultimate bearing capacity is,but the influence of the increase of concrete strength to a certain extent on the ultimate bearing capacity of members is weakened.The larger the wall thickness of the steel tube is,the more obvious the bearing capacity of the member is,and the ductility tends to increase.With the increase of wood section size,the ductility of the members will be improved,and the strengthening phenomenon of the load displacement curve of the members will be more and more obvious,but the influence on the bearing capacity of the members will be less.When the size of wood is small,the influence of the cross-section form of wood on the members is weak;when the cross-section size is large,the ductility of square wood core members is better than that of round wood core members,and the mechanical performance of square wood core members is better than that of round wood core members as a whole.Finally,based on the unified theory,the calculation results of the simplified formula of bearing capacity of square steel tube wood concrete short columns are in good agreement with the simulation results.The results of this paper can provide reference for the further study of this new type of composite column.