| According to the commonly used methods for design of steel girders,the plates of girders are not allowed to show up with local buckling.However,in the reality,the steel girders can still withhold relatively large shear forces after the buckling of certain plates.Although the Code for Design of Steel Structures in China(GB50017-2003)is consisted of design methods for I-girders allowing for the post-buckling strength,the methods have some disadvantages.Thus,proper revisions of them are needed.The main work and conclusions of this thesis are as follows:(1)Methods aiming to calculate the resistance of I-girders in shear are summarized.Then,comparison was made between the results derived from methods just mentioned and 49 relating test results.According to the comparison,owing to the failure in considering the effects of flanges on the shear resistance of I-girders,all the methods summarized in this study cannot provide accurate results.(2)Nonlinear buckling analysis of I-girder models was performed via the ANSYS finite element software,to analyze the effects of end-post situations,initial geometrical imperfections,thickness and spacing of stiffeners and stiffness of flanges on ultimate shear resistance,Results show that end-post situations,initial geometrical imperfections,stiffeners,thickness of stiffeners have little influence on the resistance of I-girders in shear,while the stiffness of flanges and spacing of stiffeners exert comparatively large influence on it.(3)In order to consider effects of flanges on the resistance of I-girders in shear,the ratio of the stiffness of flanges to the stiffness of webs was introduced to the expression in the Code for Design of Steel Structures in China(GB50017-2003).Then the results of the finite element analysis were fit with the new expression.On the basis of this,new formula,which allows for the effect of the flanges and matches well with test results in references,was proposed. |
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