Theoretic Analysis and Experimental Research about Shear Lag Effect of Variable Cross-section Continuous Box Girder Bridge
|School||Wuhan University of Technology|
|Keywords||Shear lag 3-bar simulation method Finite element method ANSYS|
The box girders have been widely used in the bridge engineering beeause their beautiful extemal shapes, good behaviors and structural fucnetions, but they show the shear lag ornegative shear lag effete when symmetry bending loads act longitudinally. If the effect of shear lag is negleeted, high risks up to collapse of bridges may take place.This article take the soap city river especially big bridge as the object of study, with 3-bar simulation method, the scene empirical datum and the finite element method the bracket length increases a stage correspondence to the construction in the box Liang root to assign the section every time to cut stagnates the coefficient the distributed rule to carry on the analysis and the contrast research. First, elaborated the thin wall box beam shearing force lagging effect’s concept and the present solution shearing force stagnate the question three kind of main theories and the method: The analytic theory solution, the numerical solution, the model experiment, and have discussed these theories and the method serviceability and the limitation. Then, analyzed has bent under the load combined action the box Liang shearing force to stagnate the effect 3-bar simulation method governing equation, and boundary condition. Then, through on-site testing of experimental data plane finite element bridge structural design software GQJS9.6 on the primary beam theory of stress. Utilized general finite element analysis software ANSYS, the solid bridge’s characteristic which union this article used had determined the ANSYS model’s establishment and the analysis method, used in analyzing assign on the section the stress distribution.Through the above analysis, has drawn the following conclusion:(1)Selects arm’s box beam regarding the belt length, cuts stagnates the effect the influence to be not allow to neglect, carries on the bridge structure the spatial analysis is very essential.(2)In actual project, obtains the measured data receives many factors the influences, must avoid and reduce these factors the influence, guarantees the measured data real reliable.(3)Cuts looking from each construction stage stagnates the coefficient distribution map, also along with construction progress’s increase, after the abdomen, the roof intersection point cuts stagnates the coefficient changes first small, has increases, namely bracket box Liang is only exerting in the longitudinal pre-stressed muscle’s situation, increases after the bracket length cuts stagnates the effect to weaken first achieves a small value starts changes is getting more and more obvious.(4)In exerts the pre-stressed to the bracket structure in the situation, the box Liang root assigns on the cross section to cut stagnates the coefficient to lengthen along with the bracket displays already is not unceasingly obvious is cutting stagnates the effect, is also not obvious negative cuts stagnates the effect.(5)3-bar simulation method avoided the troublesome mathematics inferential reasoning, the computation load have been relatively few, the result was reliable, might take in the preliminary design the computational method, if further studied, might cause it to become the bridge standard the computational method.