Study On The Shear Lag Thin-walled Box Girder

As the thin-walled box girder has good bending torsional performance, it is widelyused in bridge structures. Among them, continuous box girder and simple-supported boxgirder can be applied to overpass bridges which are across the river, bay or city. Withfurther development of prestress and the technologies of new materials, the prospect ofbox structure will be broader and broader.The shear lag effect of box girder is a complicated problem. Though, in the past30years, some experts and scholars have done some deep research in it and have obtainedsome achievements which have been applied in some projects, there are still someuncertain restrictions. Along with the development of traffic construction in china, newproblems of shearing force lag also continuously appear and need to be studied deeper.For the problems of shearing force lag, the main researches are as follows:①With the method of minimum potential energy principle calculus of variations,the author deduces the calculation formula of shearing force lag of box girder.Furthermore, the calculation formula of shearing force lag in terms of the differentforms of load and equal cross-sectional simple supported girger and cantilever beam.Calculus of differences of shearing force lag application is also analyzed for box girderwith different cross-section. Finally, the results of shearing force lag for different boxgirder deduced with the theoritical formula of calculus of differences are comparedand analyzed with the finite element software.②With the finite element software of MIDAS/FEA, the author analyzes thegeometric parameters which can influence the effect of shearing force lag of box girder,such as the ratio of width and span, the ratio of high and wide and the ratio of widthand thickness. Meanwhile, the author has given some advice for bridge design. And theresearch has some practical value.③The engineering background is Mianyang Yihao bridge. The author analyzesthe effect of shearing force lag for two stages with the software of MIDAS/FEA. Theeffect of shearing force lag at roof and floor of the box girder is also analyzed in twosituations: one is that there exists the axis force and the other is of no axis force.