Study On The Reasonable Arch Axis Of Long-span Concrete-filled Steel Tubular Arch Bridge

The selection of the reasonable arch axis of the Long-span CFST Arch Bridge plays an important role in its structure bearing capacity,especially for the Long-span CFST Arch Bridge with a span of over 500 m.The deviation between arch axis and pressure line will greatly affect the stress state of the Long-span CFST Arch bridge.Therefore,this paper takes the main span 530 m long span CFST Arch bridge-Bosideng Yangtze River Bridge as the engineering support,mainly from the following aspects:(1)Briefly introduces the development of CFST Arch Bridge and the research status of reasonable arch axis.Deduce several common arch axis mathematical models,such as Arc line,parabola,catenary and spline curve and introduces several optimization methods for arch axis of Long-span CFST Arch Bridge.(2)In order to quantitatively analyze the applicability of the axes optimization method of each arch in CFST Arch Bridge,this paper proposes an index of evaluating the stress state of CFST Arch Bridge--arch Axis Shape Evaluation Index.From the angle of the strength,stiffness and stability of CFST Arch bridge and the operational complexity of arch axis optimization method,the applicability of each arch axis optimization method in CFST Arch bridge is accurately evaluated.(3)According to the shortcoming of the existing arch axis optimization method and the essence of the arch axis optimization of the CFST Arch Bridge--to ensure the optimal stress state of each major member of Arch Rib,this paper presents an optimal method for the arch axis of Long-span CFST Arch Bridge--the minimum eccentric distance method,puts forward a kind of optimization method which can judge the applicability evaluation index.Based on the engineering background of the Bosideng Yangtze River Bridge,the paper calculates the optimal arch axis shape of parabola,catenary and other traditional arch axis optimizing the minimum method of bending energy,the minimum section eccentricity,and the minimum method.The superiority of the minimum eccentric distance method is analyzed by the arch Axis Shape Evaluation Index,which is better than that of the existing arch axis.(4)It is necessary to adjust the arch axis parameters continuously in the calculation of the optimal arch axis of the parabola and catenary line.Based on the engineering background of the Changjiang River Bridge,in order to facilitate the calculation of arch axis shape optimization,the paper puts forward a theory of parametric modeling for the main arch rib element of CFST Arch Bridge--the parametric calculation method of truss section main arch coordinate,and compiles the MATLAB calculation program.(5)Considering parabola,catenary and other existing arch axes of single variable to determine the arch axis of the defect and the Director of the minimum eccentricity method in the arch axis optimization method of superiority,put forward the charge of eccentric distance iterative method to determine the arch axis of CFST Arch bridge.The calculation of eccentric distance of CFST arch bridge and the optimization of three spline interpolation function of CFST Arch bridge are mainly used in this article.The first is to reduce the bending moment value of each supervisor by the principal eccentric distance iterative method,then a smooth and guiding arch axis is obtained according to the theory of three spline interpolation function.(6)The eccentric-distance iterative method with three-spline interpolation function optimization are proposed to the engineering example of the Bosideng Yangtze River Bridge.In addition,the internal force comparison and the arch axis shape evaluation index are compared between the optimized arch axis and the traditional arch axis,verifying the feasibility of the optimization theory of arch axis of concrete-filled steel tube arch bridge.