Dynamic Performance Optimization Of Steel Truss Bridge Based On H? Norm

Due to its structural simplicity,high bearing capacity,high longitudinal and lateral stiffness,and short construction period,the steel truss bridge plays an important role in the development of modern bridge science.In the first half of the 20th century,standardized steel truss bridges and large-span continuous truss bridges emerged.With the gradual popularization of steel structural material bridges,in the construction of long-span steel structure bridges,the design of steel trusses is often used.Therefore,steel truss bridges are widely used in the construction of transportation lines.With the development of society,the urban population density will also increase.As a lifeline project of transportation,bridge failure will not only cause serious economic losses during the' earthquake,but also hinder the subsequent rescue work.However,with the development of bridge science,the structure of modern bridges tends to be light and soft,which also tests the structural response of steel truss bridge structures subjected to earthquakes,train loads and other dynamic effects.Therefore,the H? norm is introduced as the control parameter for dynamic performance optimization,and the genetic algorithm is used to optimize the dynamic performance of steel truss bridge.The specific work content is as follows:(1)The dynamic performance index of steel truss bridge is proposed.The H? norm characterizes the maximum gain of the transfer function of the system.For steel truss bridge systems,the H? norm represents the ratio of the output energy of the structure to the input energy of the dynamic action under dynamic action.Therefore,the H? norm can be used as an indicator to measure the dynamic performance of steel truss bridges.In order to calculate the H? norm of the structure,it is necessary to calculate the stiffness and mass matrix of the steel truss bridge structure.The finite element model of steel truss bridge is established by using MATLAB software.The stiffness and mass matrix of steel truss bridge structure are calculated and optimized and optimized.For the steel truss bridge model established by MATLAB software,the accuracy of the model established by MATLAB software is verified by comparing the displacement of the nodes under the vertical unit force.(2)Introducing genetic algorithm to realize optimization of steel truss bridge based on H?norm.The steel truss bridge is optimized mainly for the section size optimization,and the optimization method is genetic algorithm.Taking the H? norm as the optimization performance index,the inverse of the H? norm is taken as the fitness of the genetic algorithm,and the genetic algorithm program is constructed.The static working conditions of the main truss section of the steel truss bridge are checked,and the overall quality comparison of the structure before and after optimization is incorporated into the penalty function program.The optimized section of the steel truss bridge is selected by running the genetic algorithm optimization program.(3)Perform optimization result verification.The numerical simulation method is used to verify the optimization results.The finite element model of steel truss bridge before and after optimization is established respectively.The dynamic load is applied to the steel truss bridge model before and after optimization.The dynamic response of the model before and after optimization is compared to verify the optimization effect.The dynamic loads used in the verification include the dynamic loads of the earthquake and the dynamic loads generated by the train.(4)Propose a parameterized construction drawing method for optimization results.Use MATLAB software to write the program and output the required parameterized drawing data:graphic point coordinates,positioning coordinates of the comment content,the content of the comment text,and the contents of the node comment.The program is written in AutoLISP language,and the parametric drawing data generated by MATLAB is read.When the program is run,the target design drawing can be drawn only by simple operation instructions to achieve the purpose of parametric drawing.The results that can be output include:structure outlines,dimensions,node comments,and text comments.The length size information table can also be drawn by means of parameterized drawing.