Research Of A Railway Emergency Repair Beam With Integral Deployable Main Truss

China is a vast country with frequent natural disasters.Railway bridges are easy to be damaged by natural disasters such as earthquakes,landslides and debris flows,and they are also the key targets of enemies in wartime.Whether the damaged bridge can be repaired on time becomes the key to the smooth transport of materials to the disaster area or war zone by railway.With the progress of railway technology,Chinese railways are developing towards the direction of "high speed and heavy load".The existing railway beam repair equipment is mostly designed and developed in the 1960 s and 1970 s according to the economic and technological conditions at that time,which has the disadvantages of difficult storage and transportation,slow assembly speed,low bearing capacity and slow traffic speed.It cannot fully adapt to the needs of modern railway beam repair.In order to solve the existing problems of railway emergency repair beams,based on the characteristics of developable structure,this thesis puts forward the structural form and deployable scheme of deployable railway emergency repair beams,and through the comparison and selection of schemes,the technical scheme of the deployable railway emergency repair beam was determined;Using the APDL language of ANSYS software,the rapid parametric modeling program of the developable emergency repair beam was compiled,and the static analysis and modal analysis of the emergency repair beam were carried out,and the appropriate number of the main truss of the emergency repair beam under different spans and different load types was judged;The multi-body dynamics model of railway vehicle was established by using the multibody dynamics software UM,and the vehicle-bridge interaction model of the deployable emergency repair beam was established by importing the emergency repair beam into UM;Based on the vehicle-bridge interaction model of the deployable emergency repair beam,the vehicle-bridge dynamic response of the emergency repair beam was studied when different types of railway vehicles pass through,and the maximum safe traffic speed of the emergency repair beam was evaluated.The main conclusions are as follows:(1)In this thesis,the characteristics of deployable structure are applied to the design and research of railway emergency repair beam,and a technical scheme of railway emergency repair girder with integral deployable main truss is put forward.The design idea of the deployable emergency repair beam is modular.In addition to the end frame,the other components can be replaced with each other.The vertical and horizontal assembling of the main truss frame with different numbers and different expansion states can adapt to the emergency repair of railway bridges with different spans,different beam heights and different load types,so as to meet the different emergency repair conditions.The railway emergency repair beam with integral deployable main truss solves the problem that "storage and transportation performance and assembly speed" cannot be taken into account in the existing emergency repair equipment of the railway beam section.(2)The emergency repair beam is composed of the same structure of the component elements,and the different number of force elements along the vertical and horizontal bridge directions can adapt to different emergency repair conditions.Therefore,for the standard bridge repair equipment,the finite element model modeling program can be prepared according to its characteristics.Input the required span,the number of main truss pieces,and the height of the beam in the program,and then the different number of stress elements can be assembled,so as to realize the rapid modeling and analysis of the emergency repair beam.(3)The static analysis shows that the mid-span chord bar,beam end oblique belly bar and beam end steel pin of the main truss can control the safety of the beam.When the span of the emergency repair beam,the number of main truss pieces and the height of the beam are the same,the ZKH load is the most unfavorable to the strength,height and stability of the emergency repair beam,followed by the ZK load and the DF4 load.Under the recommended span-speed-number scheme,the strength,stiffness and stability of the common span and the number of main truss pieces meet the limit requirements of the code.(4)The vehicle-bridge interaction analysis shows that the response of the emergency repair beam is greatly affected by the different assembly state,and the change tends to be unfavorable with the increase of the span and the decrease of the number of the main truss.The derailment coefficient,wheel load reduction rate and wheelset lateral force are greatly affected by the speed and the span of the beam,but are less affected by the number of main truss pieces.This indicates that the impact of the vibration of the emergency repair beam on the safety of the vehicle is far less than the impact of the uneven track on the safety of the vehicle.When the lateral natural vibration frequency of the emergency repair beam is close to the lateral force frequency of the train wheelset,the transverse resonance interaction between the emergency repair beam and the train will occur,which will seriously affect the safety of the emergency repair beam and the vehicle on the beam.(5)By comparing the response of the emergency repair beam and the vehicle response obtained from the vehicle-bridge interaction analysis with the code,the maximum traffic speed of the emergency repair beam can be obtained.The maximum safe traffic speed of the emergency repair beam increases with the decrease of the span of the emergency repair beam and the increase of the number of the main truss.The method of judging the maximum speed of high-speed train and freight train when they pass through the emergency repair beam is the same.Compared with the freight train,the maximum speed of the high-speed train is higher than that of the freight train,because the overall mass of the high-speed train is smaller and the design parameters of the first and second suspension are better than that of the freight train.