Analysis On The Load Effect Of Single Cable Plane (Shear Lag Effect) Of Xiamen Maxin Bridge

The main span which is steel box girder of the single cable surface cable-stayed bridge of Ma Xin bridge in Xiamen is a closed thin-walled single-box girder with multi-cell,its top deck is wide and 23 pairs of cables are arranged in the central isolation belt of the main girder.For the convenience of anchoring,the space between the webs of the steel box girder is very small,and the effect of the shear deformation on the top and bottom plates is serious.In the meantime,the pier,tower and beam of this beidge are consolidated together and its mainspan steel box girder is also in the elastic support by cable,so the uneven stress distribution in its mainspan section is more prominent,also called the remarkable shear lag effect.For the simply supported beam with a section of mainspan steel box girder of Ma Xin bridge,the author of this paper,respectively,using the lever analogy method,the energy variational method,the orthotropic plate method and spatial finite element method(fem)to analy and calculate its stress distribution in mid-span section,and evaluate the applicability and accuracy of these calculation method by comparing these calculation methods of shear lag.In the meantime,the model of bar systems and spatial model of Ma Xin cable-stayed bridge was respectively established by the finite element software Midas/Civil and Ansys to calculate and analyse the rule of the stress distribution of top and bottom flange of key sections of mainspan steel box girder under dead load and live load,and the factors of shear lag effect were analyzed.The shear lag coefficient and the effective distribution width of section are respectively used to evaluate the shear lag effect under dead load and live load.Under the dead load,if the action of the constraints on a cross section is stronger,the shear lag coefficient on the top and bottom deck is larger,the shear lag effect on this cross section is stronger.And if a cross section away from these constraint,deformation capacity of the top and bottom deck is bigger,the shear lag effect diminishes quickly.Under the live load,the overall effective distribution width of top and bottom deck of a cross section near tower pier consolidation area is relatively large.With the help of single cable plane axial compression effect on cross section and section stiffness effect near the steel-concrete composite beam area,stress non-uniform degree on these sections is suppressed,so the shear lag effect is relatively weak.Through the experiment and research on Maxin bridge which is called single cable plane cable-stayed bridge,selecting a cross section of mainspan on which the bending moment is maximum as the strain test section,the consistency of rule of stress distribution on bottom deck under test load condition and finite element calculation is contrasted to verify the correct and the rationality of the calculation and analysis for distribution regularity of shear lag on mainspan key cross sections of steel box girder in this paper.