Study On The Torsional Behavior Of The Steel Truss Suspension Bridge With Double Orthotropic Decks

Because of its good ability to cross, beautiful structure design and clear structure force system, suspension bridge plays an increasingly important role in the field of large span bridge.The main study contents of this paper are the torsion behavior of steel truss stiffening girder.The main contents and conclusions are summarized as follows:1. For the stiffened girder of the double plate truss composite decks truss bridge, adopting the model experiment, selecting a segment, and the deformation behavior under the eccentric loads is studied. The finite element model consistent with the experimental model is established, simulating experiment, comparing with the experimental results. The results show that the cross section will not only appear a rigid twist under the eccentric load, but also occur a significant shear deformation.2. Response calculation method of plate truss composite deck truss bridge under torsional load is deduced. The truss girder is equalized into thin-walled box girder by the principle of stiffness equivalent. According to whether it occurs only rigid twist under the torsional load,it can be divided into two cases: the cross-section deformation and the non-deformation. For the case of rigid twist of the cross section under the torsional load, the Umansky constrained torsion theory of the closed section thin-walled bar is used, obtaining the differential equation for the cross section torsional deformation. For the torsion of the cross-section deformable,the deformation of the cross-section is regarded as the superposition of the rigid torsion and the shear deformation, and the torsional load is decomposed into pure torque load and the bidirectional anti couple load. Finally, the torsion and shear deformation differential equations are obtained. Taking the stiffened girder of Yangsigang Yangtze River Bridge as an example,the differential equations are solved and compared with the finite element method. This method works well.3. The calculation method of the torsion effect of the stiffened girder is extended to the calculation of the defonnation response of the suspension bridge under the vertical eccentric load. Based on the classical deflection theory, the differential equations of the torsion response of the stiffened girder are obtained under the eccentric load of the suspension beam. Taking a single-span suspension bridge as an example, the deflection theory and the finite element method are used to calculate the torsional deformation of the stiffened beam. The deflection theory agrees well with the finite element method.