The Research On The Shear Lag Effect Of Single-crosslope Thin-walled Box Girder

The effects of bridge deck cross slope were ignored in the former research on shear lag effect of box girder bridges. However, the cross slope is actually existence. So studying the effects of cross slope on shear lag effect can help us know it better. This thesis depends on arithmetic solution and theory, trying to find the relation between single-crossslope and shear lag effect of box girder. Finally the analytic solution and conclusion were proved to be correct by the model experiment. The main researchs are as follows. 1) Using numerical calculation investigated the relationship between single-crossslope of box girder and shear center offset. The results show that the more slope, the more difference of longitudinal stress between bridge deck of low web and high web is. Then the mechanisms of these phenomena were approached and a method of additional twist moment of shear lag effect was presented to solve this problem. 2) On the basis of classical theory of shear lag effect, displacement pattern of shear lag effect of box girder was updated. A series of corresponding theoretic calculation formula can be obtained with considering the effect of single-crossslope on shear lag effect. 3) the Qingyuang's North River No3 Bridge is selected as an example to analyze shear lag, Ansys8.0 is taking in to consideration the bridge's final and construction state with single-crossslope, and the effects of single-crossslope were calculated and contrasted. Then some conclusions can be draw: shear lag effect occurs during construction and the final state; the changes of shear lag effect results from single-crossslope of bridge deck are corresponding with the above regular. 4) Base on principle of bridge model design, two acryl glass models (one with single-crossslope, the other one without single-crossslope) were made to verify the above conclusions. The theoretical value of the thesis is warranted by its improvement, in terms of formulas and conclusions, upon the earlier theories concerning bending box girder.