Research On The Local-Distortional Interaction Buckling Performance Of Stainless Steel Beams With Lipped C-Section

Stainless steel used in building structure can solve the problem of corrosion from from the material level,and stainless steel structure has the advantages of beautiful appearance,easy maintenance and low life cycle cost,which is in line with the concept of green sustainable development.Stainless steel structure has increasingly become the preferred scheme of building structure in harsh environment.Lipped C-section stainless steel member is one of the typical stainless steel members with light weight,high strength,good ductility and high utilization efficiency.However,due to its large width thickness ratio,this kind of member is prone to global,local and distortional single mode buckling failure,or complex buckling failure under multiple mode coupling in the bending state.At present,there is little research on the buckling performance of lipped C-section stainless steel beams at home and abroad,and the corresponding design theory is not perfect,especially for the local-distortional interaction buckling performance of stainless steel beams.Based on the above background,this thesis carried out experimental research and finite element numerical simulation analysis on the localdistortion related buckling mechanical properties of C-section stainless steel beams with rolled edges,and proposed the calculation formula of local-distortional interaction buckling capacity of lipped C-section stainless steel beams based on the direct strength method.Based on the domestic austenitic S30408 stainless steel,the mechanical properties tests were carried out on stainless steel plate specimens,and obtained the stress-strain curve and mechanical properties of stainless steel.On this basis,the local-distortional interaction buckling capacity tests were carried out on 10 lipped C-section stainless steel beams,and the relationship curves of mid span vertical displacement,loading point vertical displacement,bearing angle,flange deformation and strain of each measuring point with load were obtained,as well as the ultimate bearing capacity of each specimen.The development process and failure mechanism of the local-distortional interaction buckling of stainless steel beams were revealed.The test results show that all specimens first appear local buckling,then distortional buckling,and finally local-distortional buckling failure occurs.Each specimen has a certain post-buckling strength.Near the ultimate load,each specimen experienced a long loading process and showed good ductility.The larger the section height and crimp width of the specimen,the greater the local-distortional interaction buckling capacity.The refined numerical analysis model of lipped C-section stainless steel beam was established by ABAQUS finite element software.The constitutive model of stainless steel material adopted the modified two-stage R-O model proposed by Rasmussen.The localdistortional interaction buckling failure process of each test specimen was numerically simulated and analyzed.The numerical analysis results were in good agreement with the test results,which verified the accuracy of the refined numerical analysis model.On this basis,the refined numerical analysis model was reasonably simplified to obtain a simplified numerical analysis model with fast calculation speed and reliable analysis results.Based on the simplified numerical analysis model,parametric analysis was carried out on the influencing factors of local-distortional interaction buckling bearing capacity of lipped Csection stainless steel beams.The analysis results show that: The amplitude of initial geometric imperfection,the increase of material strength in the corner region,and the buckling slenderness ratio of section have significant indigenous effects on the local-distortional interaction buckling bearing capacity of lipped C-section stainless steel beams;The local-distortional interaction buckling bearing capacity of members decreases with the increase of the initial geometric imperfection amplitude;The larger the proportion of the cross-sectional area of the corner area,the more obvious the improvement of the material strength in the corner area will improve the local-distortional interaction buckling bearing capacity of the member;The ratio of localdistortional interaction buckling capacity to local buckling capacity has a strong correlation with the slenderness ratio of local-distortional interaction buckling;The ratio of localdistortional interaction buckling capacity to edge yield moment is also strongly correlated with the local buckling slenderness ratio(or distortion buckling slenderness ratio).The existing formula of direct strength method were used to calculate the ultimate bearing capacity of the test specimens in this thesis,and the calculated results were compared with the test results.The results show that: The existing local-distortional interaction buckling bearing capacity formulas of low carbon steel or high strength steel bending members and the bearing capacity formulas of stainless steel bending members under single buckling mode are not suitable for the calculation of local-distortional interaction buckling bearing capacity of stainless steel members.Therefore,based on the results of 107 finite element numerical simulation analysis,the direct strength method formulas suitable for the calculation of localdistortional interaction buckling bearing capacity of lipped C-section stainless steel beam are obtained.By comparing the experimental results of the ultimate bearing capacity of the specimen with the calculation results of the formulas,it is verified that the fitting formulas can better predict the local-distortional interaction buckling bearing capacity of lipped C-section stainless steel beam.