| Thin-walled box girder is the structure often used in bridge engineering project. However,thin-walled box girder shall create shear lag effect during longitudinal bending. Regardingshear lag phenomenon, scholars both here and abroad have carried on the research anddiscussion, and have made some achievements, but still many existing problems needed forfurther research. In this paper, the variation method of energy principle is taken analyse theshear lag issues of thin-walled box beam. this conducted the following jobs:(1) the existing theory of the shear lag effect theory, the research status at home andabroad and all kinds of advantages and disadvantages of theory solution, and summarizes somecommon problems existing in the theory.(2) select four parabola as the longitudinal displacement functions, using the energyvariation method deduced the formula of the shear lag effect at cross section between simplysupported beam and cantilever beam under uniformly distributed load the relevant, and validatethe adaptability and correctness of the formula.(3) analyze the causes of negative shear lag phenomenon, combining with calculationexample analysis the distribution rule of the negative shear lag effect under different forms ofload effect, and discusses the factors of influencing of negative shear lag effect of cantileveredbox girder.(4) the energy variation method is used to calculate influence on cantilever box beam shearlag caused by width-length ratio, width-height ratio, the flange length, thickness of top plate,bottom plate thickness, web plate thickness and the ratio of G/E.(5) the energy variation method is used to calculate the shear lag coefficient differentflange width thin-walled box beam, compared the results by finite element method, withanalyzed the difference, and discussed shear lag adaptability of box girder calculated by energyvariation method.within this paper, hope to provide reference to the design of thin-walled box girder bridge. |
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