Study On Mechaniccal Analysis Of Long-Span Railway Concrete-Filled Steel Tube Tied Arch

As a newly-developing bridge style, concrete filled steel tubular (CFST) arch bridge has been widely applied and rapidly developed in our country, for its own merits and can make agreement with the factual situation of bridge engineering in China. Because a large number of CFST arch bridge have been or under constructed in our country, the span of arch become larger and the bridge tends to have lighter andthinner structures. So engineers pay more attention to the static character, dynamic character and Anti-seismic character.Gechougou extra-large bridge is a railway concrete-filled steel tubular (CFST) tied arch bridge with maximum span in China. The currency finity software Midas is applied. First of all, the software model is set up, the static character of concrete-filled steel tubular (CFST) tied arch bridge under action of railway load is analysed. The axis force of arch ribs is changed almost equally, every section of arch ribs is pressed.The bending moment of arch ribs is changed unequally, the bending moment which is in the arch footsie is largest, the picture of bending moment which is in the arch ribs is symmetric in the middle of the arch bridge. The shearing force of the arch ribs is largest in the arch footsie, the shearing force which is in the place of suspenders is different from others. the picture of shearing force which is in the arch ribs is different from the bending moment.The axis force of the longitudinal tied beams is changed almost equally, it is largest in the place of arch footsie, every section of the longitudinal tied beams is pressed because of the prestress, the bending moment of the longitudinal tied beams is not changed almost equally, the bending moment number is the largest of positive number in the middle of the longitudinal tied beams, and the number is the largest of negative number in the arch footsie.the picture of bending moment which is in the longitudinal tied beams is symmetric in the middle of the arch bridge, the shearing force of the longitudinal tied beams is largest in the arch footsie, the axis force of the suspenders is symmetric in the middle of the suspenders, as well as the displacement. Basing on the result of the calculation, assuming some suspenders were damaged, the damages of suspenders play a dominant role in distributing static tensile forces of the system of suspenders, and once a suspender is deactivated, its adjacent suspenders' static tensile forces will substantially increase meanwhile; the damages of suspenders slightly influence the axial forces of arch ribs and longitudinal tied beams whereas evidently influence their bending moments;the vertical displacements in the position removing the damaged suspenders are relatively larger. The reasonable early axial force which is in every construction phase is calculated with the method of inverse removing.To meet the bending moment of rigid bearing girder when the bridge is complete, the axial force of the suspenders is calculated.which makes the bending force of the arch ribs and the longitudinal tied beams be disposed properly under the dead force, at the same time, theoretic evidence is supplied for the safe construction and the convenient operation. Next, the dynamic character is calculated, The through CFST tied arch bridge's vibrations mainly involve three types of vibrations, the arch ribs' vibrations out of plane, the vertical vibrations of the whole bridge and torsional vibrations. The bridge deck system has a larger stiffness in plane. No vibration or deformation in plane appears in the first 15 sets of modes of vibration basically. The bridge deck system has a smaller stiffness in plane.However, the bridge deck system is connected with the CFST arch ribs by the suspenders and the vertical vibrations of the bridge deck system appear to be the through CFST tied arch bridge's vertical vibrations of the whole bridge system. As suspenders are set between arch ribs and tied beams, the deck and arch ribs present the characteristics of synchronous vibrations.the damaged suspenders effects great on the arch bridge's vibrations, with the damaged suspenders increasing, the arch bridge's vibrations fell quickly. Last, applying the anti-seismic theory, the anti-seismic capability of steel box tied arch bridge is analyzed by response spectrum analysis.The data is analysed by lengthways seismic input, horizontal seismic input, lengthways seismic input+vertical seismic input, horizontal seismic input+vertical seismic input, the worst distortion and distortion place is confirmed.The most dangerous section of the bridge is in the arch footsie, which is in the fourth condition.