Cfst Arch Bridges Of Large Span Asymmetric Force Characteristics

Geological and topographical conditions of Yichang-Wanzhou Railway are extremely complicated. It is the most complicated mountain railway in China so far. Yesan River Bridge is located in deep river vally, where the topography is steep and height difference between two sides of the bridge is considerable.Combining with the topographic characteristics, Yesan River Bridge is designed as an unsymmetrical large-span half-through and through concrete-filled steel tubular arch bridge. The main span is 124m and height difference between two arch springs is 15.85m. Lattice-type floating system with longitudinal and lateral beams is adopted on bridge deck and the span assembly of main girders is 3 X 9.75+11.25+10×9.75 (the total length is 138m) .The adopted type of this bridge is first applied in railway bridge construction at home and abroad. It's a new type with high technical content.Mechanical behavior of Yesan River Bridge was analyzed by finite element method. The major tasks are summarized as follows:1. Structure features, mechanical behavior and application scope of unsymmetrical arch bridges were studied. The results show that, unsymmetrical arch bridges built in such places is reasonable and ecnomical, whereas the geological and topographical conditions are complicated and height difference between two sides of the bridge is considerable.2. Rational arch axis curve and rigidity ranges of beams, arch ribs, and vertical columns on arch of Yesan River Bridge were determined. The results show that, if m_z = 1.9 , m_y = 1.7 , the arch axis curve is rational; rational rigidity ranges of beams and vertical columns on arch is 75 % to 125% of the adopted rigidity in design, and the designed rigidity of arch ribs is rational.3. Mechanical behavior of the bridge under main loads was studied. The results show that, stiffness of the bridge is large enough; the tuber and concrete of arch ribs in most areas are in compress condition, and stresses are low; stresses of the middle longitudinal beam are lower than the others; forces in hangers are much less than its strength; influence of geometry non- linear effect is small.4. Mechanical behavior of the bridge under lateral swaying force, braking force, temperature, shrinkage and creep of concrete was studied. The results show that, influence of internal force and deformation under lateral swaying and braking loads is small; influence of internal force and deformation on arch ribs is large under temperature, shrinkage and creep of concrete, influence on the others is small.The research results in this paper provide reference for the design of Yesan River Bridge, the basic ideas and methods can provide references for the design and mechanical behavior analysis of other arch bridges and concrete-filled steel tube structures.