Study On Mechanical Behavior Of Square Concrete-filled Bimetallic Tubes Under Axial Compression

It is well know that concrete filled steel tube(CFST)is advanced in high strength,convenience of construction and economy.However,the application of CFST is limited due to bad corrosion resistance,durability deficiency and high maintenance costs.Stainless steel can be used in engineering structures as high performance steel owing to its good durability,corrosion resistance,ductility and toughness,excellent fire resistance and alluring appearance as well as low maintenance costs.But the application of stainless steel is limited due to its high costly to manufacture.Therefore,bimetallic steel can be used in structure because of its low production costs and maintenance costs.CFST encased in stainless tube could not only reducing the cost of building,but also improving the bearing capacity of CFST,improving durability of structure,which can used in the overhead pier,large diameter column,deep-sea platform and where may occur freezing,corrosion and other environmental effects in the field of civil engineering.In this paper,the axial compression performance of square CFBT is systematically studied by experimental result and finite element analysis by finite element software ABAQUS.Behavior and mechanism of concrete-filled bimetallic tubes(CFBT)were investigated.And based on the parametric analysis,simplified calculation methods of bearing capacities of CFBT subjected to compression were proposed.The following aspects are the main content:1)Experimental tests on twenty square concrete-filled bimetallic tubes(CFBT)were axially carried out,the main parameters were compressive strength of infilled concrete,tensile strength of carbon steel,type of stainless steel and wall thickness of outer stainless steel tube layer.The result show that: The CFBT columns behaved in a ductile manner.With fixing the other parameters,the axial compressive strength of a CFBT columns almost increases linearly with the increase of compressive strength of infilled concrete,tensile strength of carbon steel,type of stainless steel and wall thickness of outer stainless steel tube layer.2)Using ABAQUS to calculate the compressive performance of square concrete-filled bimetallic tube.the result shows that the load-deformation curve obtained by the test is agreed with the result obtained by the finite element analysis.And the bearing capacity of the test is agree well with the finite element analysis.3)Based on the validated FE model,the whole process of CFBT columns under axial load is analyzed.The stress distribution of each component under axial load is studied.The contact between the core concrete,carbon steel tube and stainless steel tube is analyzed.Finally,the working mechanism of the square CFBT columns under axial load is analyzed.4)Finally,based on the Eurocode 4 and DBJ/T13-51-2010,a simplified formula for the bearing capacity of square CFBT columns is obtained on the basis of experiment results and the finite element analysis..