Research On The Size Effect Of Stainless Steel Tube Concrete Short Columns Under Axial Compressio

In recent years,concrete-filled stainless steel tube(CFSST)have attracted more and more researchers’ study interest.Concrete-filled stainless steel tubular combine the advantages of stainless steel materials and concrete-filled steel tube(CFST)components.Therefore,compared to CFST components,CFSST has a wide range of applications in marine environments and other scenarios that require high durability and corrosion resistance.However,current research on large size CFSST components is limited,and there is no systematic study on the size effect of concrete-filled stainless steel tubular.This paper conducts the analysis of the size effect of concrete-filled stainless steel tubular short columns under axial compression.The main research contents are as follows:(1)Based on the relatively mature finite element theoretical model of concrete-filled stainless steel tubular,A total of 42 concrete-filled stainless steel tubular short columns was established using the finite element software ABAQUS.The finite element analysis results of axially compressed short columns are compared with the experimental results.The accuracy of the numerical analysis results is verified by the vertical load-displacement curve and failure mode of the finite element model.(2)The size effect of circular CFSST members under axial compression was studied.A total of 30 circular CFSST members,including different steel ratios(3.7%≤α≤10.3%),diameter(500 mm ≤D ≤900 mm),and concrete strength(fcu=40 MPa,50 MPa).The size effects of peak axial stress,peak axial strain,and combined elastic modulus of circular CFSST members were studied.The results show that the peak axial stress and peak axial strain of the component increase with the increase in diameter.As the diameter increases,the combined elastic modulus basically remains unchanged,indicating that there is no significant size effect on the combined elastic modulus in circular CFSST members.The size effects of peak axial stress and peak axial strain are influenced by the steel ratio.Increasing the steel ratio helps to reduce the size effect of circular CFSST components.The calculation method of ultimate bearing capacity in current codes GB50936-2014 and EN1994-1-1 has been improved,and the improved formula can more accurately predict the ultimate bearing capacity of concrete filled circular stainless steel tubular members.(3)A total of 40 square CFSST members under axial compression was studied,including different steel ratios(4%≤α≤10%),width(500 mm ≤B ≤900 mm)and concrete strength(fcu=40 MPa,50 MPa).The size effect on peak axial stress,peak axial strain,combined elastic modulus and ductility coefficient were studied.The data were then analyzed using two-way analysis of variance(ANOVA).The results show that the peak axial strain,combined elastic modulus,and ductility coefficient have the size effect,but the size effect of the peak axial stress in square CFSST members is not significant.It is found that the steel ratio also affects the size effect of square concrete-filled stainless steel tubular members,and the size effect decreases with the increase of the steel ratio.By introducing a size effect coefficient,the formula method for calculating the ultimate bearing capacity in the current code has been improved.The improved ultimate bearing capacity calculation formula based on the specifications can more accurately predict the ultimate bearing capacity of square concrete-filled stainless steel tubular members.