| The span of the high-speed railway suspension bridge continues to increase,and now it has developed to the kilometer level.The stiffness of stiffening girder is one of the important control indexes in structural design,which is directly related to smoothness of line and safety of traffic.At present,the vertical stiffness and transverse stiffness of stiffening girder have been clearly specified,but there is no clear control index for torsional stiffness.Based on a long-span high-speed railway suspension bridge to be built,this thesis studies the calculation method and influencing factors of torsional deformation of the new plate truss stiffening girder.The main work and achievements are as follows:(1)According to the equivalence of shear stiffness or shear strain energy,considering the axial deformation of inclined web members of main truss,the eccentric connection of main truss joints,joint stiffness and shear deformation of U-rib,a continuous equivalent model of new plate truss stiffening girder is constructed.(2)Based on the rigid perimeter assumption and considering the longitudinal restraint of the chord,the calculation method of torsional deformation of new plate truss stiffening girder is proposed,the calculation formula of torsional angle of stiffening girder is obtained,and the influence of inclination of the inclined web member on the torsional stiffness of new plate truss stiffening girder is discussed.The results show that the influence of longitudinal restraint of the chord on the torsional deformation of the new plate truss stiffening girder can’t be ignored,and its influence decreases with the augment of span;The torsional stiffness of stiffening girder increases with the increase of inclination angle of the diagonal web member.(3)The continuous equivalent model of the new plate truss stiffening girder considering the shear deformation of section is constructed,the analytical expression of the section shear deformation of the new plate truss stiffening girder is proposed,and the influence of the joint transverse frame structure on the section shear deformation of the new plate truss stiffening girder is discussed.The accuracy of the analytical formula is verified by an example;The shear stiffness of the joint transverse frame has a significant restraint effect on the shear deformation of the new plate truss stiffening girder section.(4)Considering the coupling effects of restrained torsion,distortion and warpage of section,a new continuous equivalent model of plate truss stiffening girder based on generalized coordinate method is constructed,and the calculation method of torsional deformation of stiffening girder is obtained.The example shows that the accuracy of torsional angle of stiffening girder calculated by this method is improved by 3.8% and the maximum error of distortion deformation is reduced from 17.4% to 8%.(5)According to the project supported in this thesis,the spatial refined finite element model and simplified model based on single beam are established respectively;Considering the torsional deformation and section distortion of the stiffening girder,an analytical simplified calculation method of torsional deformation of stiffening girder is proposed.The results show that the simplified model based on single beam in this thesis is applicable for the preliminary design stage of suspension bridge,but the analytical simplified calculation method has higher accuracy,and can be used for the preliminary design and optimization of torsional stiffness of new plate truss stiffening girder for suspension bridge.This thesis is a part of the project "Research on torsional instability mechanism of steel truss stiffening girder for the suspension bridge with a span of kilometers" of China Railway Group Limited.It will provide basic reserves for the research on torsional stiffness control of high-speed railway suspension bridges with spans in kilometers. |
