Research On Torsional Performance Of Cable-stayed Bridge With Single Cable Plane Girder

Single cable-stayed cable-stayed bridge has the advantages of wide vision,simple and elegant driving.The bridge tower arranged in the center of the carriageway and the cable anchored directly in the midline of the beam save the amount of material used.For cable fatigue problems,it is advantageous to use a single cable surface arrangement.Based on the above advantages,single cablestayed cable-stayed bridges are commonly used in the engineering sector.However,a single cable surface arrangement does not provide additional torsional stiffness for the main beam.Therefore,the main beam generally adopts a box section with a relatively high torsional stiffness.When the thin-walled steel box girder is used,its torsional distortion effect under eccentric loading is worth exploring.In this paper,the torsional distortion effect of the cable-stayed bridge with single cable plane steel box girder under eccentric load is studied.Firstly,the analytical method based on Umanski's second theory for analyzing the rigid torsion of box girders is reviewed,and the simulation method of elastic foundation beam for analyzing the distortion effect of box girders is presented.The rigid torsional response of steel box girders was calculated by analytical method,rod-based finite element method and plate shell finite element method.Based on the comprehensive analysis,the spatial stress distribution of steel box girder under eccentric load of steel box girder is obtained.Comparing the results of the analytical method and the plate shell finite element method,it was found that the constrained torsion ratio was 1 and the analytical stress calculation results were conservative.It reveals the limitations of classical theory.From the aspects of torsion angle,torsional stress,main beam form,support arrangement and so on,the limit values of cable-stayed bridges with single cable-faced steel box girder are discussed and several design suggestions are put forward.The distortion effect of the box girder is calculated by using the elastic foundation beam comparison method and the plate and shell element method.The reliability of the distortion calculation of the elastic foundation beam method was examined.Explain the mechanical mechanism of the distortion behavior of wide box girders.The distortion effect of the steel box girder along the cross-section and the longitudinal distribution of the bridge are clearly defined.According to the stress calculation results and laws,it is pointed out that the stress of the outer web of the box girder under twisting conditions is the most unfavorable.For the outer web,different stress amplification coefficients corresponding to different regions in the longitudinal direction of the bridge are given to achieve the purpose of approximately considering the torsional stress.It is clear that the stable design load conditions of the outer web are controlled along the longitudinal bridge to different sections.For webs that take into account torsional stress,a reasonable placement of longitudinal stiffeners is given.Finally,the secondary effect of the torsion under the action of the axial force is analyzed.The bending and twisting normal stress considering the secondary effect is only increased by 0.6 MPa at the most,and it is not necessary to pay too much attention to the design calculation.