Study On Mechanical Characteristics Of Curved Continuous Rigid Frame Bridge With Small-Radius And Long-Span

With the great development of road transportation, more and more curved bridges are widely used in route traffic. Curved bridges can better adapt to the constraints of ground objects and terrain, and also meet the requireents of aesthetics. Curved raliway bridges have mechanical characteristics of bending-torsional coupling effect and the uneven distribution of loading between inside beams and lateral beams under the external load, transverse internal force under the prestressed loads. Though there are many examples that the continuous bridges are successfully applied to curve, it is extremely rare about curved continuous rigid frame bridge with small-radius and long-span applied to railway bridges, and the research results are less.In this thesis, on the basis of introduction of research status and developmental trend about the domestic and foreign related fields, the study of the existing analysis theories and the basic differential equations on curved bridges are summarized. Xigu Yellow River Bridge, which is located on the intercity railroad from Lanzhou to Zhongchuan, is taken as an engineering example in this paper. The model is established by using finite element calculation software and its mechanical characteristics are comparatively analyzed. There are mainly three parts about comparative analysis:For the prestress losses, through the comparative analysis, the value of prestress losses of the prestressed tendons on the arrangement of curved horizontal bending is researched. In addition to the loss of shrinkage and creep in roof steel wires of the side-span and roof closure prestressed strands of the side-span, trends of other prestress losses are consistent between the straight bridge and the curved bridge. The overall trends of effective prestress are consistent, and remaining effective prestress in curved bridge is slightly greater than the straight bridge. Then the result shows that it is credible and safe to use the design of the straight line bridge to take the place of the design of the curved bridge.For the cantilever construction stage, through the comparative analysis, the stress characteristics at each construction stage are researched, including the deformation, internal force and stress. In each construction stage, there is no transverse deformation, torque and torsional stress in the straight bridge. The trends of other deformation, internal force and stress are consistent between the straight bridge and the curved bridge.For the finished stage and service stage, the stress characteristics of continuous bridge with long span and small radius curve under the dead load and live load through the comparative analysis are researched, including the distribution rule of internal force, deformation and especially the stress and deformation of beam under the influence of torque. Under dead load which namely is finished phase, the straight bridge has no lateral deformation, horizontal angle, torque and torsional stress. Under dead load and live load, the trends of other deformation, internal force and stress of the straight bridge and the curved bridge are consistent with each other.