| The stainless steel shares a highly praised reputation for its preeminent corrosion resistance,glossy and clean appearance,high recovery ratio.Its fine fire resistance,durability and toughness obviously superior to these of carbon steel,as well as some stainless steel grades possess special peculiarities such as nonmagnetic,etc.Accordingly,all of these excellent characteristics promote the application of stainless steel structures over recent years.Meanwhile,high material cost has made it the biggest dilemma for the widespread application of stainless steel structures.Thin-walled cold-formed members bear a higher level of strength-to-weight ratio and rigidity-to-weight ratio,they also possess a high level of cold-working ability and material utilization.These characteristics especially suitable for the high cost material of stainless steel structures.However,the buckling behavior of cold-formed stainless steel members tends towards complexity due to the versatility of the thin-walled sections forms and the nonlinear constitutive relation of the material.Accordingly,the buckling performance and design method of stainless steel structures are expected a further investigation.Moreover,for the design and checking calculation of beam-columns,all current design specifications employ unified,simplified linear interaction expression based on combining isolated axial and bending strength responses.This method always tends to be conservative,and fails to embody the bearing performance of various sections with different buckling characteristics.It will help to achieve a more economical design solution by investigating and putting forward a more accurate beam-column interaction design expression of stainless steel members,and it possesses a significant theoretical and practical values.This paper aims to systematically explore the sectional buckling behavior,sectional capacity and influence parameters of cold-formed lipped-channel stainless steel stubs under axial compression as well as combined compressive axial load and bending through experimental investigation,numerical simulation and theoretical study.The sectional capacity formula which suits the members mentioned above are put forward based on the form of current Direct Strength Method(DSM).(1)Experimental investigation of stainless steel lipped-C stub beam-columns24 stub beam-column tests,which reflect reasonable arrangements,such as the selection of member sections,the design of loading devices and loading parameters,the arrangement of data acquisition system,etc,are systematically designed and carried out.A series of results which reflect the member failure behavior of distortional buckling or local buckling are obtained.These results,as well as the practical measured data,such as coupon tests and the measurement of initial geometric imperfection,may lay a solid foundation for the following verification of the finite element model and the mechanism & law analysis of the buckling behavior.(2)Numerical simulation and parameter analysisThe refined finite element(FE)model of stub beam-columns is established through ABAQUS,with the consideration of geometric nonlinearity,material nonlinearity,actual boundary conditions,etc.The accuracy and validity of the FE models are verified by the comparison of the key responses between the results a nd FE analysis.Some key parameters are verified through sensitive analysis to see their effects on the ultimate bearing capacity of the member.The parameter analysis is conducted based on calibrated models and sensitive analysis.The parameter analysis includes 2 buckling modes,2 materials,4 section thickness,4 section slenderness and 5 eccentric conditions.(3)The sectional capacity of lipped-C stainless steel stub beam-columnsThe current Direct Strength Method has been compared and tested based on the results of the members obtained from the tests and numerical simulations.The formula of sectional capacity which suits axial compressive and lipped-C stainless steel stub beam-columns are put forward based on the form of current Direct Strength Method. |
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