Study On Effect Of Shear Lag Considering Longitudinal Stiffeners Of Single Box Twin-cell Steel Box Girder

With the development and progress of infrastructure undertakings in China,bridge engineering,as an important part of the highway,has developed rapidly,and the traffic flow has high requirements on bridge width increasingly.At the same time,with the advancement of engineering industrialization,thin-walled steel box girder is selected for most bridge projects.Compared with concrete box girder,it has good bearing capacity,good crossing performance and high quality reliability.When the single-box twin-cell steel box girder is subjected to external force,the web shear flow will be different from that of the single-box twin-cell steel box girder.In this paper,the shear lag problem of single-box twin-cell steel box girder with longitudinal stiffener structure is analyzed comprehensively by theoretical research and finite element numerical simulation..The main research contents and conclusions are as follows:(1)Based on the energy variational method,considering the equivalent conversion section,and longitudinal stiffeners of single-box twin-cell steel box girder considering shear lag warping of the differences between each wing,and combined with the cross section axial force from the equilibrium conditions,the quadratic displacement function is used as the shear hysteresis warping displacement function of each wing plate of the box girder,the differential equations governing the shear lag effect of a single twin-cell steel box girder with longitudinal stiffeners are established.This paper deduces the shear lag distribution of simply supported box girder and cantilever box girder under concentrated and uniformly distributed loads.(2)Based on ANSYS software,Shell63 element is used to simulate the steel box girder,and the stress is compared and analyzed.beam.It is concluded from this paper that,in the case of concentrated(uniformly distributed)load of 'simply supported beams,the errors at the edges and the middle webs were reduced by 21.82%(46.27%)and 19.7%(44.95%)respectively,under the concentrated(uniformly distributed)load of the cantilever beam,the errors at the edge and the middle web were reduced by 27.8%(25.5%)and 23.1%(26.13%)respectively.and therefore when considering the longitudinal stiffener influence after the resulting stress analytical solution is more close to the numerical solution.At the same time,the change of shear lag effect is not obvious,so it is an effective method to use single-box twin-cell steel box girder in practical engineering.(3)This paper establishes the finite element model of single-box twin-cell steel box girder,conducts simulated calculation for the settings of different forms of stiffener and steel box girder under different cases,and analyze the law of shear lag,It is concluded from this paper that,for the shear lag coefficient,when the distance and height reduce gradually,the shear lag coefficient curve variation increases,indicating that the shear lag effect ofsingle-box twin-cell steel box girder is more obvious.However,the shear lag effect is the most obvious when the load is only applied to the middle web.Based on the regularities of the research,the paper puts forward the structural measures and design points for the problems in the design and construction of single-box twin-cell steel box girderThe research in this paper has improved the analysis of the mechanical properties of the single-box twin-cell steel box girder with longitudinal stiffener structure,which provides a reference for the design and manufacture of steel box girder.