Batkhuyag Baasanjargal

Evaluation of shear carrying-capacity of steel girder

Takeshi Miyashita

  
�@In 2017, the design rules for road bridges in Japan shifted to a limit state design method that is more rational than before and enables a detailed design of the safety factor. At present, the specifications for highway bridges, which are technical standards for bridges and elevated highways in Japan, require the conditions of limit setting which requires proper evaluation of load bearing capacity. There is a Basler equation as a previous study on the evaluation of shear load capacity. The Basler equation is expressed as the sum of elastic buckling and post buckling.
�@The purpose of this study is to clarify the prerequisites for the Basler equation to be established by performing parameter analysis using the nonlinear finite element method. Through this research, the contribution of each member is clarified, and it is expected that useful back data will be given not only for setting the limit state of the new bridge but also for repairing and reinforcing the existing bridge.
�@US design provisions (AASHTO) allow the designer to include the contribution of tension-field action after web buckling in calculating the ultimate shear strength of interior panels, but not exterior panels, because it is believed that no effective anchor mechanism exists to resist the horizontal component of the tension-field force. On the other hand, in this study, we performed FEM analysis on the web panel at the end of the girder and the inner panel and confirmed that the Basler equation was effective in any case.
�@The results of this parameter analysis show that the abdominal plate is unable to support the post-buckling strength due to the absence of the oblique tension field effect, which is the cause of the decrease in the shear load capacity. When the stiffness of the upper flange decreases, the abdominal plate does not have post-buckling strength, which indicates that the shear load capacity is greatly affected. The next largest effect is on the stiffener on the fulcrum. The effect of the lower flange and the stiffener at the loading point on the shear load capacity is small. Despite lowering the stiffness of the lower flange, an oblique tension field action occurs.