Stability Analysis Of Welded Q460Ⅰ-section Columns With Slender Web Under Biaxial Bending

In the design of high-strength steel (Yield strength≥460MPa) welded I-sectionbeams-columns，the web width-thickness ratio in the code for design of steel structures(GB50017-2003) is so restrictive that the capacity of high-strength steel member can not befully developed. In the present design method, thin and high webs are adopted,which leadsto the local buckling of the web. But this doesn’t means the loss of overall bearing capacity.So broadening the web width-thickness ratio appropriately and forming I-section memberswith slender web can give full play to the effective use of the post buckling strength ofplate.Firstly, the finite element model of Q460I-section columns with slender web underbiaxial bending are established and the stability capacity is analyzed by finite method.Secondly, the effects of the web depth-to-thickness ratio, flange width-to-thickness ratio,slenderness ratio and eccentricity ratio on the stability capacity were investigated carefully.What’s more, the stability capacity of Q460members and Q235members are contrasted andanalyzed. Lastly, combined with the Code (GB50017-2003) and North AmericanSpecification (AISI2004), the design formulas used for high-strength steel welded I-sectioncolumns under biaxial bending is proposed by direct strength method. Meanwhile, therelevant parameters in the formula is corrected by the finite element results.By analyzing, we can see that similar to the ordinary welded I-section columns withslender web web, local buckling lowers the stability capacity of the member greatly whenaxial loading dominates, while the detrimental effect is less significant when bendingmoments prevail. The detrimental effect is directly related to slenderness ratio, the webdepth-to-thickness ratio, the flange width-to-thickness ratio and eccentricity ratio.Compared with that of equivalent Q235members, the stability capacity of Q460members is improved,which is also related to the web depth-to-thickness ratio,slenderness ratio, the flangewidth-to-thickness ratio and eccentricity ratio. Comparison of FE results with those of thecurrent code (Code for design of steel structures (GB50017-2003) and Technicalspecification for steel structure of light-weight buildings with gabled frames(CECS102:2002))method shows that the later too conservatively predicts stabilitycapacities of such members, while the proposed modified DSM method possesses rathergood accuracy and is safe.