Analysis Of Ultimate Load-Bearing Capacity Of Long-Span Steel-Box Handle Basket Arc Bridge Based On Multi-Scale Finite Element Method

Arch bridge is a kind of compression-bending structure system.With the increase of the span of arch bridge,the slenderness ratio of arch rib is increasing;the development of domestic economy greatly improves the traffic volume,and correspondingly aggravates the aging and damage of the bridge.These changes highlight the stability of the arch bridge,and the ultimate bearing capacity of the bridge in service is increasingly concerned.The stability bearing capacity of long-span bridge is for the whole structure.However,the bridge usually suffers from local damage first,and there is a process of damage accumulation,which eventually leads to serious damage and even failure of the whole bridge.It is a complex nonlinear dynamic process,involving the small scale of local component materials to the macro scale of the whole bridge.It has multi-scale response,and its essence is also the local-global related buckling problem.In order to balance the calculation amount and calculation accuracy with the local and overall mechanical response of different scales in the process of long-span bridge failure,this paper uses the multi-scale finite element method to study the ultimate bearing capacity of a large-span steel box basket high-speed railway arch bridge in China,and makes the following work:(1)The structural characteristics and bearing forms of long-span steel arch bridges are summarized.The research status of ultimate bearing capacity of steel arch bridges and the achievements of the stability theory and research methods of long-span steel arch bridges have been reviewed.The concept of multi-scale method has been introduced,and the multi-scale research methods of large-scale civil structures at home and abroad have been reviewed.Combined with the related research of stability and multi-scale analysis,the overall stability theory and local component stability theory of the structure are introduced in detail,and then the technical route of limit bearing capacity analysis in this paper is determined.(2)The ABAQUS finite element software is used to model a large-span steel box basket arch bridge in China,and the multi-scale finite element analysis is carried out by using the multi-point constraint method: firstly,the relevant calculation examples are established to verify the technical methods adopted;the single-scale member system model of the wholebridge is established,and then the multi-scale modeling parts are determined to complete the multi-scale modeling.(3)The self vibration characteristics of the whole bridge are analyzed,and the reliability of the model is verified by comparison;five load cases are set to analyze the linear elastic stability of the whole bridge;the parameters of the influence of the in-plane and out of plane stiffness of the arch rib on the structural stability are analyzed according to the buckling mode of the linear elastic analysis.According to the nonlinear factors of long-span steel arch bridge,the ultimate bearing capacity of three working conditions is analyzed,and the influence degree of nonlinear factors on the ultimate bearing capacity of long-span steel arch bridge is discussed.(4)This paper studies the influence of live load distribution on the ultimate bearing capacity of long-span steel box basket arch bridge,and analyzes the buckling failure process of local components by three multi-scale models: arch crown,1/4 arch rib and main longitudinal beam at Auxiliary Pier location.The local-overall buckling of the whole bridge and the nature of progressive failure of large civil structure are studied.