Study Of Dividing Rings And Pouring Length Method Of Outer-Wrapped Concrete For Long-span Stiff Skeleton Arch Bridge

Long-span rigid skeleton concrete arch bridges have strong competitive advantages in railway and high-speed construction of bridges in mountainous areas due to their advantages such as high structural stiffness,strong bearing capacity,and good mechanical property.In recent years,which have gradually become a preferred structural form in the construction of long span bridges in mountainous areas.The calculated span of the Tian’e Longtan Bridge in Guangxi,which is currently under construction,has reached 600 m.The rationality of the outer-wrapped concrete segmentation directly affects the stress level of the rigid skeleton arch and the outer-wrapped concrete.How to quickly and reasonably find out the segmental points and their lengths of outer-wrapped concrete working surface is the core problem to control the force of the stiff skeleton arch and the alignment of the bridge.In this thesis,based on the key research project of Chongqing Municipal Education Commission,"Key Technology for Design and Construction of 300 m Cantilever Casting Reinforced Concrete Arch Bridge"(KJZD-K201900705),the Xining River Bridge is used as the research object to carry out study of dividing rings and pouring length method for outer-wrapped concrete of large-span stiff skeleton arch bridge.The main research content is as follows:(1)In view of the current status of the research on outer-wrapped concrete casting for large-span stiff skeleton arch bridges,combining the existing outer-wrapped concrete casting methods and calculation theories,analyzing the advantages and disadvantages of the multi-working surface balanced casting method and the buckling cable transfer method by using the finite element method around the force characteristics of the stiff skeleton concrete arch bridges,and giving the former suitable for the outer-wrapped concrete casting scheme for larger span stiff skeleton concrete arch bridges.(2)Based on the stress and deformation influence lines of the control section,a deformation/stress curve calculation method is proposed.This formula can accurately predict the deformation/stress trend and development law of the outer-wrapped concrete of arch ribs during the whole process of casting.The mathematical model of outsourced concrete segmentation was constructed by analyzing the basic stress theory and principles of the stiff skeleton and determining the optimization objectives and constraints of the outsourced concrete from the mechanical point of view.(3)The deformation and stress changes of the main arch ring under different methods of placing outer-wrapped concrete sections are investigated.The results of dividing the segmental length of outer-wrapped concrete by the calculation method of this thesis and the traditional equal arc length method are analyzed and compared.The research results show that,compared with the traditional equal arc length method,the concrete casting scheme derived from the calculation method of this thesis makes the whole strong skeleton arch deformation uniform,the control section stress can be improved to different degrees,and the maximum stress reduction of the main chord steel pipe is 9%,through the reasonable setting of the working surface and the location and length of the working section,the casting of the outer-wrapped concrete plays a role in equalizing the stress of the main arch ring;and put forward the strong skeleton arch bridge Arch ring optimization suggestion: adopt the design method of different thicknesses of top and bottom slabs to strengthen the overall stiffness of outer-wrapped concrete bottom slab and reduce the stress gap of arch circle section of top and bottom slabs.