Axial Compression Performance Of Twin-wall Lace-barred Latticed Column Combined By Cold-formed G-section Steel

In order to study the stability of cold-formed thin-walled steel members under axial load,a series of investigation has been performed in recent time.Since the performed studies mainly focused on solid-web members and simple combined members,investigation about stability of latticed members is insufficient.Accuracy of recent design rules in ultimate load prediction of twin-wall lace-barred latticed column combined by cold-formed steel with complicated lips is not verified,as the DSM equations in current code are adequate only in solid-web members,not including latticed members.For the investigation of stability of twin-wall lace-barred latticed column combined by cold-formed steel with complicated lips under axial load,a study which includes test and numerical analysis of FE-models was performed.In the study,a total of 18 twin-wall lace-barred latticed specimens combined by cold-formed steel with complicated lips were tested to research their stable ability under axial loads.The failure modes,deformations and ultimate loads of specimens were recorded.The test results indicate that the main failure modes of specimens are coordinated failure of global buckling and local buckling,and global buckling.In the specimens with larger slenderness ratio,global buckling were main failure mode,and in other specimens,coordinated failure of global buckling and local buckling was in dominate position.FE-models based on test specimens were built and calculated.The ultimate loads,failure modes and deformations of FE-models and test specimens were compared,and validity of FE-models was testified according to its results.A series of twin-wall lace-barred latticed column FE models with different combination of parameters were built and performed in numerical analysis,to investigate the effect of different parameters,including slenderness ratio,width to thickness ratio of web and inter-node length,on ultimate load of twin-wall lace-barred latticed columns.As the results revealed,the increase of slenderness ratio result in decline of ultimate loads.Since the slenderness ratio of specimens were the same,higher width to thickness ratio of web leads to smaller ultimate loads.Meanwhile,the influence of inter-node length is limited in these specimens.By comparing tests and numical analysis results and results of EWM equations in Technical Criterion on Cold-formed Thin-wall Steel Structure(GB-50018-2002),DSM equations in North American Specification for the Design of Cold-Formed Steel Structural Members(AISI S100-16),it was revealed that two equations were not safe enough in high slenderness ratio area when it is used in twin-wall lace-barred latticed column combined by cold-formed steel with complicated lips under axial loads.On the base of current design codes,including EWM and DSM equations,new design equations aimed at twin-wall lace-barred latticed column combined by cold-formed steel with complicated lips under axial loads were put forward.