Model Updating Of Medium And Low Speed Maglev Track Beam Based On Python-ABAQUS

In recent years,the first medium and low speed maglev line from Changsha South Station to Huanghua Airport in Hunan Province has been constructed and operated.However,due to its unique mode of operation,the structure of magnetic levitation track beam is different from that of the wheel-rail traffic bridge and highway traffic bridge.The beam span and cross-section forms are determined on the basis of the research of ordinary railways and highway bridges,and meet special structural requirements and operational safety and comfort.The requirements for various indicators of the track structure are more stringent,and more stringent requirements are imposed on the stiffness of the track beams.In general,the finite element model of the track beam is established according to the dimensions and material parameters given in the design drawings,and it is difficult to reflect the actual working status of the track beam structure due to construction error and environment and other factors.Therefore,this article relies on the major science and technology projects of Hunan Province named "Medium and low speed maglev train set technology engineering and high reliability operation demonstration",with the background of the(25+35+25)m double-track continuous track beam of the Changsha low-speed maglev transportation project,uses the dynamic test results of the track beam under environmental excitation conditions,and updates the main design parameters affecting the dynamic characteristics of the track beam with the methods of the combination of simulated annealing algorithm and secondary development of ABAQUS by writing Python scripts.The main research content of this article is as follows:(1)This paper discusses the domestic and international development of medium and low speed magnetic levitation track beams,and expounds the research status of the finite element model revision and the theoretical basis for the secondary development of ABAQUS based on Python script language.(2)The test method for dynamic characteristics test of double-track continuous track beam based on the mobile measurement method was proposed and successfully applied to the modal test of(25+35+25)m double-track continuous track beam.The results showed that thevertical stiffness of the track beam structure is less than the transverse stiffness,and the vertical vibration frequency increases more than the transverse vibration frequency.(3)The influence of the K value of the support pier and bearing stiffness on the dynamic characteristics of the track beam is studied.The results show that the bridge pier significantly increases the lateral stiffness of the track beam,and has a significant influence on the lateral natural frequency,while the natural vibration frequency and the displacement of the vibration mode of the same order mode of the beam are proportional to the bearing support stiffness,but the change of the natural frequency becomes insignificant with the increase of the order.(4)The refined model of the track beam with complex track structures considered in different forms of mass and stiffness is established.The results show that the impact of the bearing platform and the H-shaped steel sleeper on the free vibration frequency of the track beam is relatively small,and the rate of change is ±2%.In the interior,the F-rail has a relatively small influence on the first three-order lateral characteristic frequency,and has a greater influence on the first three-order vertical characteristic frequency.Among them,the vertical frequency increase is most obvious when only the F-rail stiffness is considered,and the rate of change reaches 17.77%.and the first order vertical vibration mode is delayed,which means that in the fine modeling process,we can not only consider the influence of stiffness,and the influence of quality can not be ignored.(5)Selecting five main design parameters of mass density and elastic modulus of box girder and bridge pier,and elastic modulus of F rail based on the combination of empirical method and ABAQUS DSA and taking the sum of the squares of the relative error of the calculated frequency and the measured frequency as the objective function.A modified method for the second development of ABAQUS and the simulated annealing optimization algorithm was written,which successfully modified the initial finite element model of the(25+35+25)m orbital beam.The largest change in design parameters is the elastic modulus of the box girder,which is an increase of 15.2%from the initial parameter value.