| With the development of ‘the Belt and Road’ construction,China’s stainless steel and other building materials industry have entered a new stage of economic growth.Cold-formed thin-walled steel is one of the widely used components in stainless steel structure.Cold-formed thin-walled steel has the advantages of light weight,high intensity and good ductility performance,which makes cold-formed thin-walled steel be hotspot and have a great application perspective.However,the cold-formed thin-walled steel member is easily affected by multiple buckling modes because of thin wall,large width-thickness ratio of the plate and mostly open cross-section.So far,the design specifications and relevant researches for cold-formed stainless steel members with open sections still need to be supplemented and the corresponding design codes urgently need theoretical basis and technical support.Therefore experimental study and numerical analysis have been carried out on lipped C-section stainless steel axial compression column in this thesis to invesgate the overall-local interaction buckling behavior and parametric finite element analysis on the key factors which may affect the overall-local interaction buckling bearing capacity of lipped C-section stainless steel axial compression column was performed.Then the calculation formula for the overall-local interaction buckling bearing capacity of lipped C-section stainless steel axial compression column was finally proposed on the basis of the direct strength method.At first,overall induction and analysis of the existing strength design method(including effective width and direct strength method)for local buckling,overall buckling and overalllocal interaction buckling were given.Then,based on the domestic austenitic S30408 stainless steel,the mechanical property tests were conducted on 8 flat coupons and failure tests were carried out on 20 lipped C-section stainless steel axial compression specimens.Flat coupons were divided into two different thicknesses: 1.5 mm and 2.0 mm.The strain hardening coefficient,the initial elastic modulus and nominal yield strength of the stainless steel material can be obtained through the material property tests.Through the failure tests of lipped C-section stainless steel axial compression specimens,the development process of local buckling waves was revealed and the overall-local interaction buckling bearing capacity,the load-axial displacement curves,the load-lateral displacement curves,the load-rotation curves and the load-strain variation curves of measuring points were obtained.In the experiments,All specimens occured the overall-local interaction buckling and most of the specimens firstly experienced local buckling and then the global buckling.Numerical simulation analysis has been conducted on the lipped C-section stainless steel specimens by using finite software ABAQUS.The finite element models were verified against the experiments and good agreement was obtained.Based on the refined finite element models,parametric finite element analysis on the key factors which may affect the overall-local interaction buckling bearing capacity of lipped C-section stainless steel axial compression columns was performed,including the mechanical properties of stainless steel,the enhancement of the strength of corner region,the initial geometric imperfection,the slenderness ratio,the ratio of height and width and the slenderness for interaction buckling.The results imply that in a certain range,the strain hardening coefficient of stainless steel material and the enhancement of the strength of corner region have little effect on the overall-local interaction buckling bearing capacity of lipped C-section stainless steel axial compression columns and nominal yield strength of stainless steel material,the initial geometric imperfection,the slenderness ratio and the ratio of height and width have certain influences on the overall-local interaction buckling bearing capacity.There is also a strong correlation between the slenderness for interaction buckling and the overall-local interaction buckling bearing capacity and the slenderness for interaction buckling is the key parameter to calculate the overall-local interaction buckling bearing capacity.At last,the finite strip program CUFSM was employed to study the elastic local buckling stress of lipped C-section columns and the simplified calculaton formula of the local buckling stress for the C-section stainless steel columns was fitted.The bearing capacities of the specimens were calculated by using the existing direct strength formulas of overall-local interaction buckling and the calculation results were compared with the test results.The results showed that calculations of the direct strength formula in <North American Cold-Formed Steel Specification for the Design of Cold-Formed Steel Structural Members> and the direct strength formula modified by Becque were slightly conservative,so the existing direct strength formulas are not suitable to calculate the overall-local interaction buckling bearing capacity of lipped C-section stainless steel axial compression columns.Then the finite element analysis were conducted on 138 specimens undergoing overall-local interaction buckling.Based on the analysis results,the direct strength equation for lipped C-section stainless steel axial compression columns undergoing overall-local interaction buckling was given in the paper.The fitting equation was testified against the test results and good agreement was obtained.At last,the reliability analysis was proposed and the reliability indexes were larger than 3.2,proving the reliability of the fitting formula. |
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