Research On The Overall Stability Of Compression-flexure Member With Closed L-shaped Section

The wide-flange H-shaped steel or box-shaped section steel columns used in traditional steel-frame structure have the problem of convex angles,which brings lots of inconvenience for the layout of buildings and is also one of the reasons why steel-frame structure cannot be widely applied to civil building area.If heteromorphic closed section steel columns matching with the wall thickness are introduced into new steel structure dwelling system,the problem can be settled effectively.Compared with concrete structure area,there are few researches on heteromorphic section steel columns.The shapes of heteromorphic closed section include T-shaped,L-shaped and cross-shaped.The thesis conducts theoretical study and finite element analysis of the overall stability of L-shaped closed section steel columns under the simultaneous effect of stress and bending moment.If the length and the finess are big,usually it is stability damage not strength damage occurring to the member.Therefore,the research of L-shaped closed section steel columns is of great significance for their application in practical engineering.At first,the article uses energy method to deduce the flexural-torsional buckling balance equation of the compression-flexure member,and derives the general formula of the critical load of its flexural-torsional buckling according to the cross-section characteristics of L-shaped closed section.Then it explores flexural-torsional buckling utility design formula of the compression-flexure member with L-shaped closed section by combination of corresponding standards.Under the guidance of theoretical derivation,use ANSYS software to establish L-shaped closed section steel column model and analyze the elastic buckling;compare the theoretical resolution and the analysis result to verify the correctness of the modeling approach.At last conduct nonlinear buckling analysis with respect to that kind of steel columns and mainly consider the influences of nonlinearity,geometric nonlinearity and residual stress of materials;analyze the influence law of each factor on the ultimate bearing capacity of L-shaped columns,and verify and improve the flexural-torsional buckling utility design formula by combination of the analysis result.