| China’s urban rail transit(wheel-rail traffic)has experienced rapid development with the increase of urban population.This development effectively reduced the pressure on urban transport.However,many disadvantages(such as vibration and noise)along with it become more and more serious.Maglev traffic,with the advantages of slight vibration,low noise,good climbing ability and small space occupancy,is in great agreement with the current development of human society.As a representative of maglev traffic,low-to-medium speed maglev is very suitable for short-distance transport in city.Since the world’s first low-medium speed maglev commercial line(eastern Japan hilly line)was put into operation in 2005,South Korea and China have also successfully operated low-medium speed maglev lines.At present,following the Changsha maglev commercial line,Beijing low-to-medium speed Maglev line(S1)is about to put into operation.The development prospect of low-to-medium speed Maglev traffic is good.Different from the traditional wheel-rail train in structure,low-speed maglev train stably float near the rated levitation gap(8 ~ 10mm)through the electromagnetic levitation force.Therefore,in the elevated section,the forced form of track beam is greatly different from that of traditional wheel-rail beam.As with the wheel-rail traffic,when the maglev train acts on the rail beam,there is an obvious coupled maglev train-track beam vibration effect that affects the safe operation of the maglev train.Therefore,it is necessary to study the design and select appropriate section type of low-to-medium speed maglev track beam structure.There is a great practical significance to recognize the coupling vibration characteristics of low-to-medium speed maglev train-track beam system and put forward the key dynamic design parameters which can make the design and cost of the track beam become more reasonable.This paper,based on the multi-disciplines study,carried out research combining theory with experiment and analyzed the key design parameters of low-to-medium speed maglev track beam.The main work and achievements are as follows:(1)On the basis of reading relevant references both at home and abroad,this paper summarizes the development of maglev traffic and the research status of coupling vibration of maglev train-track beam system,summarizes the advantages and disadvantages of the current research methods and puts forward the research direction of this paper.(2)By studying the common structure types and span of simply supported track beam with maglev lines both at home and abroad,the paper chooses reasonable structure of simply supported track beam by comparative analysis under the requirements of using function,technical economy,beauty and maintenance.The static behavior of the track was analyzed by the structural design,which provided a reference for the static design of maglev track beam.(3)A coupled vibration model of 5 modules of train-track beam system was established and the software IMVB was independently developed.Then based on the field test of low-tomedium speed maglev line in Zhuzhou,the reliability of the system coupled vibration model and analysis software IMVB was verified.Finally,the coupling vibration characteristics of the 20 m simply supported track beam are analyzed in detail.The variation of the dynamic performance such as the dynamic deflection,acceleration,displacement,acceleration of the car body,the suspension frame,suspension clearance and so on are analyzed,which laid the foundation for the subsequent analysis.(4)According to the low-to-medium speed maglev test line in Zhuzhou and the low-tomedium speed maglev operation line in Changsha,20 m and 25 m simply supported track beams were selected for on-site dynamic test.The natural vibration characteristics of track beam,the dynamic characteristics,dynamic deflection,vertical and transverse amplitude,and vertical and lateral acceleration of the track beam under different speeds were analyzed from the perspective of the experiment,so as to provide experimental basis for subsequent theoretical analysis.(5)In this paper,the limit values of the dynamic coefficient,natural frequency,vertical stiffness,lateral stiffness and beam end angle of the rail beam are summarized in the domestic and foreign norms.Based on the theoretical analysis model,this paper analyzes the coupled vibration of many kinds of typical maglev track beams with 25 m span.The key design parameters(dynamic coefficient,natural frequency,vertical rigidity,lateral rigidity and beam end angle)suitable for medium-low speed maglev train track beam are put forward,which provides reference for improving relevant specifications of medium low speed maglev transportation. |
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