| With the rapid development of steel structure building and steel smelting technology,high strength steel is more and more widely used in large steel structure building at home and abroad.Compared with ordinary steel,high-strength steel has higher yield strength,which can significantly reduce the section size of members under the same load conditions,reduce the self-weight of steel members,thus achieving the purpose of saving steel,expanding the building area,reducing the transport workload of components and the difficulty of lifting construction.At present,there are relatively many studies on the stability of high-strength steel members under axial and unidirectional eccentric compression at home and abroad.However,there are still relatively few studies on the local and overall stability of high-strength steel members under biaxial compression and bending,especially those with strength grade not less than 690 MPa.Therefore,the local-global buckling behavior of welded I-section bidirectional compression-bending members of Q690 steel is studied in detail.The main research contents and conclusions are as follows:(1)The finite element model under the influence of geometric nonlinearity,material nonlinearity and initial defects was established by ABAQUS finite element software.The calculation results of the model and the related experimental results were compared to verify the correctness of the finite element model.(2)The effects of web height-thickness ratio,flange width-thickness ratio,slenderness ratio,load relative eccentricity,residual stress and initial geometric imperfections on the local-global stability of Q690 steel I-section bi-directional compression-bending members were studied by parametric analysis.The research shows that with the increase of the aspect ratio of the web,the local buckling of the web is gradually increased,and the dimensionless ultimate bearing capacity of the member is decreased.As the width-to-thickness ratio of the flange increases,the restraining effect of the flange on the web becomes weak,the local buckling of the web is aggravated,and the dimensionless ultimate bearing capacity of the member decreases,but the decrease is very small.As the slenderness ratio increases,the dimensionless ultimate bearing capacity of the component decreases significantly.With the increase of the relative eccentricity of the load,the member gradually changes to the overall buckling with local buckling,and the dimensionless ultimate bearing capacity of the member gradually decreases.As the strength of the steel increases,the ultimate bearing capacity of the component increases gradually,but the dimensionless ultimate load decreases gradually.Residual stress and initial geometric imperfections will reduce the ultimate bearing capacity of members,and the degree of reduction is related to web height-thickness ratio,slenderness ratio of members and relative eccentricity of load.(3)Combined with the “steel structure design standard” and “European specification”,two calculation formulas for bearing capacity of effective section method are proposed;Combined with “steel structure design standard” and “North American specification”,the formula for calculating the bearing capacity of direct strength method is proposed.The results show that the three calculation formulas are all conservative,and the accuracy of the direct intensity method is relatively low.By correcting the calculation formula of direct strength method,the correcting formula for calculating the stability bearing capacity of Q690 high strength steel Isection bi-directional compression-bending members with web height-thickness ratio exceeding the limit is proposed.The calculation result of this formula is close to the finite element calculation result,and it is safe.It can accurately predict the stable bearing capacity of the local-to-overall buckling of the Q690 steel biaxial compressionbending component with the web height-thickness ratio exceeding the limit. |
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