The Research On The Torsional Properties Of Steel Box Girder Of Cable-stayed Bridge With Single Cable Plane

Thin-walled box girder is widely used in modern bridge due to its superior mechanicalperformance, but the restrained torsion situation of box girder is rather complicated,especially in the single cable plane cable cable-stayed bridge system, whose cables do littlecontribution to resist torsion of the main beam. This paper takes the Daxie Second Bridge asresearch background, using the method that combining experimental study with finiteelement theory model to research the mechanical characteristics of the steel box when thebridge twist under the partial load. The main work of this article:As the theoretical basis for this article, based on The Umansky second theory,Torsional stress due to beam torsion can be derived when thin-walled box girder takes freetorsion and restrained torsion situation, the restrained torsion governing differentialequations can be derived and the general solution can be get.Using the finite element model method to analyze the torsional performance of mainbeam under the stage of completed bridge and the largest single cantilever of The DaxieSecond Bridge. The results show that there is a great imbalance of vertical displacement andreaction force of the main beam between upstream and downstream when withstandingpartially live load. In the design load single deck loaded condition studied in this paper, theside which reaction force is smaller is in tension; Torsional and distorted stress generated bythe twisting action of the main beam takes a large proportion of the total of the normal stress,the ratio of between torsional and distorted stress with bending normal stress reach up to295.2%in the most unfavorable cross-section, despite the values of torsional and distortedstress is very small, the effects of torsion and distortion can’t be ignored.And the torsionalperformance of Daxie Second Bridge under the stage of completed bridge and the largestsingle cantilever under wind loads were calculated and analyzed, The results show that themain beam torsion effect caused by the wind loads is obvious, supports also appeared at thetensile force,but the torsional and distorted stress of the main beam caused by wind load isvery small.For the complexity under torsion of The Daxie Second Bridge, the load experimentalstudy was carried out to text the deflection and stress of the key sections under the most unfavorable load case, and the measured results were compared with finite element modelresults, the results show that Test data and the finite element model results are in goodagreement, therefore, based on the experimental research, further analysis of the finiteelement model can be conducted to the bridge. In order to get the factors that affecting mainbeam torsion, series of systematic parametric analysis was carried out to the steel boxgirder.