Study On The Spectrum Characteristics Of CRTS ? Type Ballastless Track On Subgrade Under High-speed Condition

With the rapid development of high-speed railway in China,the ballastless track vibration has become more and more prominent.But the current researches on ballastless track dynamic response are mainly based on time-domain,the spectrum characteristics of ballastless track is not clear.However,as an important attribute of the ballastless track structure,the research of vibration spectrum is very important.From another aspect,the vibration spectrum will change when the ballastless track has defect.The frequency characteristics of track structure with typical damage can be obtained through the research of the spectrum,which can also be useful in the operation and maintenance of track structure.Based on the experiment and model,this article has studied the spectrum characteristics of CRTS ? type ballastless track structures on subgrade under different conditions.The main contents are as follows:1.Several experiments were carried out on the dynamic response of ballastless track on subgrade under high speed train dynamic load on Beijing-Tianjin intercity railway line.The vibration accelerations of each part of the track structure were analyzed,and the transmission rules of vibrations between the different parts are studied.The analysis results show that,from rail to subgrade surface,track structure vibration energy decayed sequentially.The vibration attenuation at high frequency decayed fast,and low frequency part decayed slowly.2.Aimed at CRTS ? ballastless track structure,the vehicle-track-subgrade coupling finite element model was established,and the spectrum characteristics were analyzed at various driving speed,train type,fastener stiffness and foundation sizes.The results show that,with the increase of train speed,the frequencies and amplitudes of accelerations spectrum curve of the track structure are increased.When trains of different types passing,the frequency of acceleration spectrum curve of the track structure is almost invariable,but the amplitude has a certain change.With the increase of stiffness of fastener,the frequencies of rail acceleration spectrum are basically unchanged,and also the track slab and supporting layer acceleration spectrum in high frequency,but the amplitudes are increased.The peak of accelerations spectrum curve of the track structure with foundations of different sizes is not obvious.The amplitudes of the track slab and the supporting layer reduced at the low frequency part under 50Hz.3.The vehicle-track-subgrade coupling finite element model with the crack defect between track slab and CA mortar was established,and the influence of crack on track structure spectral characteristics is analyzed.The results show that,when the track existing crack between track slab and CA mortar,the acceleration spectrum of track has an obvious peak in the low frequency part,and the amplitude is much greater than normal acceleration spectrum.With the increases of crack length,the vibration spectrum curves of the slab and supporting layer decrease firstly and then increase,while the amplitude increase first and then decrease.With the quantity of initial crack increasing,the main frequency of vibration spectrum of track structure is unchanged,but the amplitude at the low frequency part increase significantly.When the main frequency of track slab with crack defect is around 5Hz and its amplitude is greater than 2.12m/s2/Hz,the index of track structure safety exceeds the limit,which should be handled in time.