Research On The Shear Lag Effect Of Sunflower-shaped Box Girder

Sunflower-shaped arch bridge is one of the most outstanding structural types in the large span arch bridges, which the main arch and the spandrel arch rings usually adopt box section. Affected by the web plate, box girder will produce shear lag effect when bearing longitudinal bending. In recent years, the research on box beam shear lag effect mainly about simply supported beam 、 continuous beam bridge and cantilever beam structure.Seldomly study on arch bridge, and the shear lag about sunflower-shaped arch bridge with less related research. This thesis take the Second Phoenix Bridge Guangzhou Nansha as the engineering background, study the shear lag effect of sunflower-shaped arch bridge. The main research works in this thesis as followed:(1) Used the finite element software ANSYS to establish the Second Phoenix Bridge of Guangzhou Nansha sunflower-shaped arch bridge finite element entity model of the whole bridge, this thesis make a loads calculation according to the design of each status. Analyzed the arch foot of spandrel arch and the midspan of spandrel under the dead load the most unfavorable load of the number 2 mian arch’s midspan 、 one quarter point and three eighths points section in the distribution regularity of the shear lag effect on the top plae and bottom plate.(2)Adopted the model test method and finite element method to study the distribution law of the shear lag effect of the number 62 spandrel arch in the Second Phoenix Bridge.Made the part of the Second Phoenix Bridge into 1:5 scale model.Through the experimental data,analyzing the shear lag effect distribution law of the model structure on corresponding section,and comparing the calculation results with the finite element software ANSYS.(3) Established box-shaped arch model in different parameters,analyzed the rise-span ratio、span- width ratio、load forms impact the shear lag effect influence law on the key sections and along the longitudinal distribution law. The results showed that the shear lag effect increasing with the rise-span ratio,however,decreasing withspan- width ratio.The positive shear lag coefficient gradually enlarged from the midspan to the arch foot,while the negative shear lag coefficient gradually decrease from the midspan to the arch foot. In addition,the load forms influcence the box-shaped arch section only on the positive shear lag.Compared with the uniform load,the stress distribution of the top plate in the box-shaped arch section under the concentrated load distributed more unevenly.