Distortional Buckling Of Welded I-section Continuous Beam

Steel structure in the modern building engineering is widely used in various fields,such as high-rise steel structure buildings,large-span industrial factory buildings,large stadiums,large span viaducts and so on.Stability is always the importance problem in design of steel structure.And the stability of steel beam is an important problem in engineering application.In order to fully utilize the bending capacity of steel beam and increase the bending stiffness in the working plane,the narrow and high cross-section beam is better in design,and the most commonly used is I-section.The buckling modes of I-section beam include lateral distortional buckling,lateral torsional buckling and local buckling and distortional buckling is a failure mode between lateral torsional buckling and local buckling modes.Scholars at home and abroad have carried on the theoretical and experimental research of the distortional buckling of I-section girder.Due to the instability mechanism of distortional buckling is more complicated than lateral torsional buckling buckling and local buckling,the influence of major parameters to the distortional buckling of I-section beam has not yet been summarized.And the method of ultimate bearing capacity of distortional buckling still needs further research.This paper carries out the elastic and elastic-plastic performance analysis of distortional buckling of double span continuous beam with single axisymmetric I-section.First,The elastic and elastoplastic analysis of double span continuous beams with single axisymmetric I-section were carried out by changing the parameters,such as section dimension,section asymmetry coefficient and the span of beam.According to the deformation of cross section,the instability mode of I-section beam was judged.The influence range of major parameter was summarized by compared the results judged above and the results of theoretical analysis:Under uniformly distributed load L/hw>2.4 and K3??>1.92;Under concentrated load L/hw>2.8 and K3??>1.74.Then,within the scope of the main parameters,the influence of each parameter to ultimate bearing capacity of distortional buckling was studied.Through the analysis found that distortional buckling mode of I-section continuous beam is relatively complex,A1t10-.-d500 series for example,L/hw within the range of 2.4?3.2,web local stress is larger,beam distortional buckling mode is given priority to with local-related buckling distortion;L/hw within the range of 3.2?6,flange stress is larger.Third,According to the result of parameter analysis,based on the existing research and the method of bearing capacity of lateral torsional buckling,this paper introduced distortional stability coefficient and the design method of bearing capacity of distortional buckling was established.Finally,The paper analyzed the effect of welding residual stress on the bearing capacity of the distortional buckling.In the processes of finite element analysis,the ultimate load considering the residual stress is significantly higher than regardless the residual stress.On the basis of the method of bearing capacity regardless the residual stress,the design method of the bearing capacity of continuous beam distortional buckling considering the influence of residual stress was established in this paper.