Study On Stability Of 700m-span Concrete Filled Steel Tubular Arch Bridge

With the acceleration of urbanization and the increasing demand for transportation,the application of concrete-filled steel tubular arch bridges with long spans is becoming more and more widespread,and the span of bridge construction is increasing day by day.By the end of 2020,the third Pingnan Bridge in Guangxi with a span of 575m had been completed and opened to traffic,and the construction of a 700m span concrete-filled steel tubular arch bridge is imminent.However,as the span of concrete-filled steel tubular arch bridges continues to increase,the problem of structural stability becomes more and more prominent due to the further reduction of the bridge width-to-span ratio.Based on the results of the trial design of a 700m span concrete-filled steel tubular arch bridge by the research group,this paper uses a combination of theoretical analysis and numerical simulation to study the stability of the 700m span concrete-filled steel tubular arch bridge.The main research work includes:(1)The influence of inclined rib angle on the stability of a 700m span concrete-filled steel tubular arch bridge is studied in this article.A parallel rib scheme with a distance of31.6m between two ribs(the same as the bridge width)is designed.In addition,five different inclined rib arrangements are designed by changing the rib spacing at the top of the arch while maintaining a constant distance of 40m between the ribs at the foot of the arch.A full-bridge model is established using Midas/Civil finite element software to analyze the effects of different rib angles on the stability of the arch bridge.The most favorable range of inclined rib angles for the 700m span concrete-filled steel tubular arch bridge in this article is proposed.(2)The influence of transverse bracing arrangement on the stability of a 700m span concrete-filled steel tubular arch bridge is studied in this article.Based on the critical axial force formula of the double-rib arch surface,the influence of transverse bracing spacing and different transverse bracing stiffness on the stability of the 700m span concrete-filled steel tubular arch bridge is analyzed for the lattice truss type transverse bracing,and the suitable transverse bracing stiffness and maximum spacing are obtained.By comparing the stability of the arch bridge using the"米"shaped transverse bracing,the influence of the lattice truss type transverse bracing on the stability of the arch bridge with different arch rib inclination arrangements is analyzed,and a reasonable form of transverse bracing arrangement for the 700m span concrete-filled steel tubular arch bridge is proposed.(3)The influence of initial stress in steel tubes on the stable bearing capacity of a700m span concrete-filled steel tubular arch bridge is studied in this article.An ANSYS finite element analysis model is established,considering material and geometric nonlinearity.By applying different initial stress coefficientsβof steel tubes,the stable bearing capacity of the 700m span concrete-filled steel tubular arch bridge is calculated under different initial stress coefficientsβand different cross-sectional steel contents,and the influence coefficient k_p of stable bearing capacity under different initial stress coefficientsβand cross-sectional steel contents is given.(4)The influence of initial deviation of arch rib on the stable bearing capacity of a700m span concrete-filled steel tubular arch bridge is studied in this article.For the overall initial axial deviation of the arch rib surface and the overall initial elevation deviation in the plane of the arch rib,different sinusoidal functions with different periods are selected to simulate different initial deviation forms of the arch rib.By selecting different peak values of arch rib initial deviation,namely 0.05m,L/3000,L/2000 and L/1000,the influence of different forms and peak values of arch rib initial deviation on the stable bearing capacity of the 700m span concrete-filled steel tubular arch bridge is analyzed.