| With the improvement of the theory of large-span design,the application of highstrength materials,and the mature application of cable-stayed cable-stayed cantilever assembly,large-span CFST arch bridges are becoming more and more popular,reentering the large-span bridge comparison scheme,the domestic Scholars also studied the feasibility of design and construction of 700m-class CFST arch bridges.However,no matter how the theory and construction technology are developed,the span is difficult to grow endlessly.The span of the CFST arch bridge is no longer included in the plan comparison,which is a concern of bridge designers.This paper aims to study the ultimate span of CFST arch bridges by finite element analysis method,analyze the main factors restricting the development of ultimate span of CFST arch bridges,and establish the calculation formulas of ultimate span and diameter,height and wall thickness.The specific research is as follows:(1)Through the investigation and analysis of the structure and structural form of the long-span CFST arch bridge,and the qualitative analysis of the factors restricting the growth of the span,based on the existing design theory,the level of processing and manufacturing,and the formulation principle of the construction method,the limit span research process is determined.The structure and structure,the research variables and the range of reasonable variables are adopted,and the constraints such as structural strength,stiffness,stability and construction feasibility are drawn up.(2)The selection of the reasonable arch axis shape of the arch bridge plays an important role in the internal force distribution and size,structural bearing capacity and stability of the main arch section.Therefore,a reasonable arch axis should be selected for the ultimate span research process.Through the investigation and qualitative analysis of the arch axis of the long-span CFST arch bridge,the arch axis selected by the ultimate span research process is determined,and the reasonable arch axis coefficient optimization method is described.The applicability of the long-span CFST arch bridge is analyzed.The reasonable arch axis coefficient optimization method for the subsequent research process is obtained.(3)For the modeling complexity of multi-span concrete-filled CFST arch bridges,the iterative process of multi-parameter variation limit span is cumbersome.A parameterized modeling procedure of concrete-filled CFST arch bridge controlled by several structural parameters is proposed.The combination of MATLAB program and MCT commands in Midas/CIVIL enables variable parametric modeling to effectively improve research efficiency.(4)Based on the limited indexes of structural strength,stiffness and stability,the influence trend of pipe diameter,wall thickness and truss height on the corresponding ultimate span is studied.The ultimate span values and the optimal arch axis coefficients corresponding to each group of parameters are calculated by finite element analysis.Some sample points are provided for the following establishment of the ultimate span response surface model,and then the variables are increased according to the proposed step size.The variation trend of the research variables and the ultimate span was obtained.(5)Aiming at the problem of large workload and long iteration time for the ultimate span search of CFST arch bridges,a method of solving the ultimate span based on response surface method is proposed.The response surface model is used to replace the complex finite element model.The experimental design,response surface model and optimization algorithm are used to establish the ultimate span optimization model based on response surface method.The results show that the proposed method can effectively improve the efficiency of optimization problems and is suitable for complex engineering problems. |
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