Investigation On Distortional Buckling And Interacted Buckling Behaviors Of Thin-walled Irregular-shaped Aluminum Alloy Columns Under Axial Compression

Aluminum alloy has high strength-to-weight ratio,excellent corrosion resistance and good workability and has been widely applied in practical structures globally.Aluminum alloy members can be manufactured by extrusion into flexible cross sections.Aluminum alloy extrusion members with complicated cross section can be easily produced and has very small initial geometric imperfection.Aluminum alloy extrusion members are widely used in bridge structures and spatial structures since it can meet both structural and integration requirements of all kinds of building structures.This paper studied buckling behaviors and design method of thin-walled irregular-shaped aluminum alloy columns which were used in the sun-house with the method of test and finite element analysis.The studied columns have complicated cross section shape with many thin-walled plates,resulting in various buckling modes and complex failure mechanism.Initial geometric imperfection and material properties have big influences on column buckling behaviors and ultimate strength.Initial geometric imperfections of six thin-walled irregular-shaped aluminum alloy columns were measured prior to axial compression test.Stress-strain curves of 6063-T5 aluminum alloy were obtained from tensile couple tests.Six.thin-walled irregular-shaped aluminum alloy columns were tested under axial compression.Ultimate strength,failure mode,out-of-plane displacement and strain evolution were measured during the tests to study distortional buckling behaviors and strength of test specimen.A finite element model(FEM)for axial-loaded aluminum alloy columns were developed in this paper and verified by 36 test specimen.The verified FEM was subsequently used to study the influences of plate thickness on column distortional buckling behaviors and ultimate strength.Current calculation method for distortional buckling stress of C-section steel members were modified on the basis of finite element analysis results to be suitable for thin-walled irregular-shaped aluminum alloy columns.The modified calculation method was compared with FEM results.Thin-walled irregular-shaped aluminum alloy columns could undergo local,distortional and global buckling and their interactions,which makes various failure modes and complex failure mechanism of the columns.Finite element analysis was employed in this paper to study six interacted buckling failure modes of the aluminum alloy columns.Occurrence mechanism of the interacted buckling failure modes was revealed and their impact on column strength and deformation were studied.Thin-walled aluminum alloy columns were sensitive to initial geometric imperfection,which is random for real members.Thin-walled irregular-shaped aluminum alloy columns with different initial geometric imperfections were numerically studied to reveal the detrimental effects of initial imperfections on column ultimate strength and failure mode.Current aluminum alloy design codes generally applied effective section method to consider the effects of local buckling on axial-loaded aluminum alloy columns.However,current design codes do not take the influences of distortional buckling and interaction of different buckling modes into consideration.The design codes had been proved to be suitable for regular-shaped aluminum alloy columns,such as H-section and box-section columns.In order to evaluate the application of current design codes to irregular-shaped aluminum alloy columns,ultimate strength of 174 thin-walled irregular-shaped aluminum alloy columns were calculated by finite element model and current design methods were compared.