Syudy On Shear Lag Effect Of Steel-concrete Composite Double Box Beam

The steel-concrete composite box girder bridge is a combined structural form that connects the steel box girder and the concrete slab as a whole through shear connectors.the composite girder bridge has been widely used in bridge engineering in The composite beam cross-section wing plate and bottom plate have the same shear deformation as the ordinary concrete cross section,so that the phenomenon of shear lag effect occurs.If the influence of the shear lag effect on the composite beam bridge is ignored during the design process,the safety and performance of the bridge structure may be threatened.Therefore,studying the influence of shear lag effect on the stress distribution of composite beam concrete roof and steel box girder bottom is of great significance to bridge engineering.A large amount of research result has been achieved with the effort of scholars home and abroad concerning the shear lag effect of composite beams in the past decades,which laid a solid foundation for further in-depth study of the shear lag effect of composite beams.However,these studies are mainly carried out in relatively simple steel beam sections such as T-shaped steel beams and single-box single-chamber steel beam composite beams.Nowadays,the cross-sections of composite beams used in bridge engineering are becoming more and more complicated.It is urgent to study the shear lag effect of composite beams with complex cross-sections.The steel-concrete composite double box girder with complex structural form is selected as the research object.With the energy variation principle,the quadratic parabolic shear lag warping displacement function is selected to establish the shear lag control differential equation considering the interface slip.Based on this differential equation,the analytical solution of the shear lag effect of the double-box composite beam subjected to concentrated load and uniform load under the simply supported and cantilever boundaries is derived.Through the ANSYS finite element analysis,several examples were analyzed,and the normal stress,shear lag coefficient and deflection of the mid-span of each example were solved separately.The results of which is compared with the value calculated by the analytical solution in this paper to verify the rationality and correctness of the analytical solution in this paper.Further more,the influence of the cross-sectional parameters and the stiffness of the shear connector on the shear lag effect of the composite beam was studied,obtained with different geometric parameters and the stiffness of the connecting member to establish the influence of the shear lag effect of bis composite beam on this basis.Finally,The shear lag effects of The chadian bridge during the construction and operating phases are analyzed with ABAQUS and Midas Civil,and relevant suggestions for design reference are given finally in the thesis,which shows certain practical significance.