Study On Main Arch Structure Of 700m-level Concrete-filled Steel Tube Arch Bridge

By the end of 2020,the main span of the third Pingnan Bridge in Guangxi has reached 575 m.Academician Zheng Jielian has carried out a feasibility study on the design and construction of a 700m-level concrete-filled steel tube arch bridge based on the construction of Hejiang Yangtze River Bridge in Sichuan,and believes that there is no great technical obstacle to the construction of a 700m-level concrete-filled steel tube arch bridge.So far,there is no research literature on structural design of 700m-level concretefilled steel tube arch bridge.Therefore,this paper studies the structure of main arch ring of 700m-level concrete-filled steel tube arch bridge.The main contents include:(1)Study on main arch ring structure and arch axis shape of 700m-level concretefilled steel tube arch bridge.According to the development and application of engineering materials and the structural parameters of concrete-filled steel tube arch bridge over 300 m in China,the basic structural parameters of main arch ring of 700m-level concrete-filled steel tube arch bridge are proposed.The axis shape of the arch was selected by considering the eccentricity of the section,eccentricity of the section,eccentricity of the single tube section and the force of the chord pipe at the foot of the arch.(2)Study on in-plane and out-plane stability of 700m-level concrete-filled steel tubular arch bridge.Based on the deflection differential equations of beam,the deflection and Angle expressions of two different types of transverse braces,meter brace and K-type braces,were deduced.The influence of different types of transverse bracing,stiffness of transverse bracing and spacing of transverse bracing on the stability of 700m-level concrete filled steel tube arch bridge is analyzed,and on this basis,the suggestion of transverse bracing arrangement is put forward.(3)Study on variable section height of arch rib of 700m-level concrete-filled steel tube arch bridge.On the basis of the traditional Ritter formula,a generalized Ritter formula was proposed,which changed the arch thickness coefficient from the arch 1 to the arch foot n from a linear variation to a beta parabola variation.The influence of different parabola times on the stress,stability,dynamic performance and main arch stiffness of the main tube of 700m-level concrete-filled steel tube arch bridge is analyzed,and the reasonable suggestion of β value is given.(4)Study on stress regularity of web member of 700m-level concrete-filled steel tube arch bridge.Based on structural mechanics,the simplified calculation formula of internal force of the vaulted web member was derived,and the influence of the horizontal dip Angle of the oblique web member on the internal force and stability of the ventral tube was analyzed.The formula for calculating the internal forces of the vaulted web member was extended to the general formula for calculating the internal forces of the web member,and the critical condition for the change of the tensile and compressive law of the web member near the arch foot was analyzed.The parametric model of the hinged shaft area of the arch foot was established by using the finite element software ANSYS,and the influence of the structural parameters of the hinged shaft on the stress of the arch foot segment was analyzed.