Study On The The Local Buckling Behavior Of High Strength Steel Welded Box Section Beams Under Bending

Compared with ordinary steel,the yield strength of high-strength steel components is higher,and the reasonable use of high-strength steel in engineering construction can reduce the cross-sectional size and self-weight of components and increase the span and height of the structure.However,as the yield strength of steel increases,the problem of steel structure stability becomes more prominent,and the high-strength steel structure may suffer from overall instability or local instability damage before the load reaches the ultimate strength.At present,domestic and international research on the local stability of high-strength steel is mainly focused on the axial compression members and welded Ibeam section bending members,and little research has been done on welded box-section beams.In this study,the local stability mechanical properties of the webs of welded boxsection bent members of high-strength steels were mainly studied,and the main research content and conclusions are as follows.(1)By using the general-purpose finite element software ANSYS to build a model,a fine-grained finite element model of the shell unit considering the strength level,initial geometric defects,residual stresses,and material nonlinearity of the steel was established.In this study,the modeling process and analytical solution process of the finite element model were described in detail,and numerical simulations were performed on the existing specimens,and the results of the finite element calculations were compared and analyzed with the relevant test results in the literature to verify the scientific validity and effectiveness of the adopted finite element model.(2)By selecting reasonable component parameters,the effects of changes in flange width-thickness ratio,web height-thickness ratio,steel strength grade,steel ultimate strain,steel elastic modulus,yield ratio,residual stress and initial geometric defects on the local stable force performance of welded box girder members were analyzed and studied.(3)The results of the finite element analysis were compared with four domestic and international codes(Chinese "Steel Structure Design Standard" GB50017-2017,European Code Eurocode 3,American Code ANSI/AISC 360-16,and Japanese Code AIJ LSD 2010).The results show that the calculation results of GB50017-2017 and Eurocode3 are close to each other;the cross-sectional classification of the first three codes are based on the classification of the slab class according to the width-to-thickness ratio less than the limit value,and then on the maximum class of the slab.The Japanese code takes into account the effect of the flange and web aspect ratio on the bending performance of the member.On the basis of finite element analysis,based on the four types of crosssectional classification criteria of the European code,and taking into account the load capacity and rotational deformation capacity of welded box girders,a limit value formula for the cross-sectional classification of welded box members of high-strength steel in bending,taking into account the flange width-to-thickness ratio and web height-tothickness ratio,was proposed.(4)Based on the steel structure design standards and finite element parameter analysis results,the proposed formula was further proposed to modify the ultimate load capacity after considering the flexural strength of the plate under pure bending load.The calculated values of the formula for the ultimate load were compared with the FEM simulation values,and it is found that the two agree well.