Research On The Ultimate Bearing Capacity And Structural Optimization Of The Steel Pylon For A Super-span Highway-railway Cable-stayed Bridge

Among many bridge systems,cable-stayed bridges are favored by more and more project builders because of their excellent spanning ability,excellent wind stability,lower cost and beautiful shape.As an important load-bearing member of the cable-stayed bridge force system,the bearing capacity of the bridge pylon is very important in the design of the cable-stayed bridge.Steel pylons have obvious advantages over concrete pylons in terms of mechanical performance,manufacturing and installation,cost and environmental protection.With the continuous development of our country’s economic strength,the demand for long-span bridges is also increasing,and steel pylons are more and more widely used.However,as the span of the cable-stayed bridge continues to increase,its pylons gradually develop along the trend of towering and thinning,which will undoubtedly reduce the rigidity of the steel pylon;in addition,with the increasingly diverse shapes of the steel pylon,the mechanical characteristics of the structure are also more complex,which makes the problem of bearing capacity of steel pylons become more and more prominent.In this paper,the ultimate bearing capacity of the middle steel pylon(global analysis)and cable-pylon anchorage structure(local analysis)of a super-span highway-railway cable-stayed bridge was studied.The main research work is as follows:(1)The development history,application status and research situation of steel pylons at home and abroad were analyzed and summarized.According to the structural form and stress characteristics of the steel pylon,the main research content of this paper was proposed,and the research methods were determined.The finite element analysis method of material nonlinearity,geometric nonlinearity and the finite element solution method of nonlinear equations in nonlinear buckling analysis were introduced in detail,and the evaluation indexes of the ultimate bearing capacity of the steel pylon were determined.(2)The spatial finite element models of the steel pylon and cable-pylon anchorage structure of the supporting project were established by using finite element software.The ultimate bearing capacity of the structures was calculated under different load modes considering material nonlinearity,geometric nonlinearity and initial geometric defects.The most unfavorable load mode to the bearing capacity of the structure,the failure mode,the cause of failure and the influence of nonlinear factors on the bearing capacity of the structures were clarified,and corresponding suggestions for the design of the structures were put forward.(3)The parameter analysis of the bearing capacity of the steel pylon and cable-pylon anchorage structure was carried out,and the influence of the main design parameters of the structure on the bearing capacity was clarified.A set of structural parameter optimization process based on influence coefficients was constructed to optimize the geometric size and spatial position distribution of steel pylon and cable-pylon anchorage structure’s components,and relatively optimal structural design parameter combinations were obtained.