Optimization Design Of U-shaped Beam For Rail Transit

Recently,U-shaped beam is the most innovative kind of viaduct bridge In urban rail transit.And U-shaped beam is using more and more widely in other countries.as a new type of prestressed concrete bridge,U-shaped beam belong to the concrete-filled bridge and composed of floor,web and beams.As is known to us,U-shaped beam has the characteristics of saving investment,beautiful appearance,low standard of rail surface and short construction period.What's more,Web can also achieve the purpose of noise reduction.Many factors restrict the use of U-shaped beam.such as,U-shaped beam cross-section of the thin-walled section,the torsional stiffness is relatively poor,and the traditional U-shaped beam has been the more complex force,making more cumbersome,and difficult construction.Moreover,the study of U-shaped beam is limited and the research of U-shaped beam optimization cross-section at home and abroad.It is important for the research of U-shaped beam optimization cross-section to make U-shaped beam be better applied to urban rail transit.it is necessary to optimize the U-shaped beam performance,so that U-shaped beam more affordable.The basic principles of bridge structural design are safety,application and economy.Optimization design can make full use of the material's performance so that every unit to get the best coordination,with a standardized degree of security.Of course,optimization design can make reasonable decision for the overall design of the program and achieve the ultimate goal of design-safe an,economical and effective.At present,the most extensive mathematical method of section optimization is Genetic Algorithm.It is a parallel and efficient global search method based on biological evolution theory and biological genetic theory.It has many advantages such as wide application range and accurate optimization result.In this paper,the U-shaped beam bridge in a rail transit is used as the engineering background in Shanghai.The finite element analysis software MIDAS CIVIL andmathematical model calculation software MATLAB are used to optimize the U-shaped beam section by genetic algorithm,and the beam element method is used to establish the model.The mechanical properties of U-beams with different cross sections are studied and compared,and the optimized section satisfying the stress conditions is obtained.The main contents include:(1)Determine the main cross-section parameters that affect the structural performance of the structure.The main parameters affecting the mechanical properties of U-shaped beam structures are beam height,web thickness,floor thickness and prestressed reinforcement area,different cross-section parameters determine the cross-sectional shape of the U-shaped beam and have different effects on the structural forces.(2)According to the genetic algorithm and the specific circumstances of the project to determine the design variables,the objective function,constraints.According to the relevant information,in this paper,the cost of prestressed U-shaped beam is taken as the objective function and the requirement structure,the normal section strength,the stress of the construction stage and so on.Based on the beam height,beam thickness,floor thickness and prestressed reinforcement area of U-shaped beam section,the genetic algorithm is used to calculate the structure of different cross-section.(3)According to the above data,by using MIDAS CIVIL finite element analysis software to build the model before the optimization of the cross-sectional structure.Comparison of the mechanical properties of the cross section under different parameters.Finally,analysis of the optimal cross-section and economic analysis.