| The overhead contact system(OCS)is one of the most important systems in the electrified railway system.Cantilever structure is the main support structure of overhead contact system.Its main function is locating the contact line and messenger wire,bearing mechanical load and electric load.The service state is coupled to each other in cantilever structure and over head contact system,so it is significant to improve the service state of cantilever structure.Up to now,most researchers used beam elements to substitute cantilever structures in the study of the static and dynamic characteristics of cantilever structures.There are few studies have been devoted to systemic analysis about influence of cantilever structure’s parameters on the its static characteristics,mechanical properties of representative cantilever structures,the effect of pre-stress on the dynamic characteristics of cantilever structure and so on.Therefore,it is significantly necessary to analyze and optimize cantilever structures and its key components,which can provide important engineering guidance for design,optimization and installation of the cantilever structure of electrified railway.In this work,four typical cantilevers models have been built,based on actual dimensions.Firstly,four cantilever structures and two types of steady arms(limit/non-limit steady arm)of overhead contact system were analyzed under maximum working load by using finite element software(ABAQUS).Secondly,the dynamic characteristics of the German steel cantilever structure under different pre-stress working conditions are calculated.Thirdly,Particle Swarm Optimization Algorithm(PSOA)and Genetic Algorithm(GA),based on MATLAB and ABAQUS are used to solve steel cantilever structure shape and sizing optimization under maximum working load.Finally,according to the above analysis,an integrated steel cantilever structure was designed.The main conclusions can be drawn as following:1.According to the analysis of four types of cantilever structures,it is showed that steel cantilever structures are less displacement and more strength than aluminum alloy cantilever structures under maximum working load.Japanese steel cantilever structure performance is best in four structures.The performance of German aluminum alloy cantilever structure is equalization,so it is a desired cantilever structure.There is a better performance on limit steady arm than non-limit steady arm on structure stiffness,high stress of limit steady arm concentrates on the contact position of steady arm and steady arm supporter,which may consequently cause the unwanted material wear and damage generated in this area during working process.2.The first ten natural frequencies and their corresponding modes under multiple pre-stress working conditions are calculated.Furthermore,the resonance frequency is obtained by using the harmonic response method,to evaluate the stability of the cantilever structure.Results show that the lower-order model frequencies show significant variation when the cantilever structures applied different pre-stress.Moreover,results obtained from the harmonic response method indicates that the existence of the pre-stress can significantly suppress the vibration of cantilever structure along the railway line(Y)direction.3.Mass optimization on shape and sizing with maximum displacement and maximum stress constraints problems of steel cantilever structure of overhead contact system were built.PSO and GA,based on MATLAB and ABAQUS were used to solve steel cantilever structure shape and sizing optimization under maximum working load.The result of particle swarm optimization showed that mass of the steel pipe in cantilever structure decreased to 28.7 kg from 40.23 kg after optimization with reduction of 28.7%.The deformation decrease little.The station-keeping ability of steel cantilever structure remains as before.The result of genetic algorithm showed that mass of the steel pipe in cantilever structure decreased to 31.65 kg from 40.23 kg after optimization with reduction of 21.1%.Compared results of PSO and GA,PSO had a better performance on the problem of steel cantilever structure shape and sizing optimization.Furthermore,when pipe cross-section dimensions remains unchanged and the positions of support arms are as after PSO optimization,the maximum deformation of registration arm decreased to 2.026 mm from 2.789 mm after optimization with reduction of 27.4%.The maximum displacement of steady arm supporter decreased to 1.906 mm from 2.730 mm after optimization with reduction of 30.2%.4.Based on the analysis of four types cantilever structures,an new integrated steel cantilever structure was designed.New structure is less three joints than German steel cantilever structure,which have improved its stability and reliability.New integrated steel cantilever structure choose acute triangle structural type,which simplify its installation and make it’s easy to adjustment.Furthermore,parameters and mounting holes positions of new cantilever structure have been designed.Finally,new cantilever structure have been proved safe and reliable,using finite element analysis. |
