Continuous Rigid Frame Bridge Shear Lag Analysis And Study

This paper takes Lucun Bridge which is in Dongguan City for engineering background. Based on Doctor Bridge analysis and finite element method, the shear lag effect of box girder bridges with variable cross sections is studied in the paper. It concentrated on calculating the shear lag coefficient and effective flange width coefficient of support section in different construction process conditions.And the test results and finite element analysis results were compared, the conclusions drawn.In the paper, is not only the causes of shear box girder is analyzed, but some sensitive factors such as width-length ratio,girder height ratio, loading arrangement and the section's location are also analyzed.The main content are:(1)Shear lag effect of box girder is reviewed in the paper.(2)The reason of shear lag effect of box girder is analyzed.(3)Flat-line analysis is a simplified analysis method, for which can not take the stress component of beam width direction into consideration; it can not fully consider the impact of shear lag effect. Especially to the large cantilever box-girder Bridge in which the shear lag effect is obvious. In order to ensure the security and stability of the structure, using finite element method to analyze the structure is very necessary.(4)The spatial FEM can relatively accurately reflect the stress of the practical structure. The shear lag effect of box girder bridges can't be neglected.(5)The shear lag effect is seriously affected by width-length ratio, girder height ratio, loading arrangement and the section's location. And the affect to shear lag effect by geometric parameters such as cross-section cantilever length, tilt degree of web section is not remarkable.(6)The shear lag remarkable than that of effect of the section under construction loads is more other sections. National Standard (JTJ023-85) is worth discussing further.