Extended applications of track irregularity probabilistic model and vehicle–slab track coupled model on dynamics of railway systems

2017 ◽  
Vol 55 (11) ◽  
pp. 1686-1706 ◽  
Author(s):  
Lei Xu ◽  
Wanming Zhai ◽  
Jianmin Gao
Keyword(s):  
Probabilistic Model ◽  
Coupled Model ◽  
Slab Track ◽  
Railway Systems ◽  
Track Irregularity

scholarly journals Numerical Analysis of Vibration Responses in High-Speed Railways considering Mud Pumping Defect

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Ting Li ◽  
Qian Su ◽  
Kang Shao ◽  
Jie Liu
Keyword(s):  
High Speed ◽  
Coupled Model ◽  
Test Results ◽  
External Excitation ◽  
Slab Track ◽  
Vibration Responses ◽  
Track Irregularity ◽  
Mud Pumping ◽  
Element Theory ◽  
Good Agreement

As a newly appeared defect under slab tracks in high-speed railways, mud pumping weakens the support ability of the subgrade to slab track, bringing about deviations on the vibration responses of the vehicle, slab track, and subgrade. Therefore, this paper proposes a vehicle-slab track-subgrade coupled model based on the multibody simulation principle and the finite element theory to highlight the influences of mud pumping defect. As an external excitation to this model, random track irregularity is considered. In order to simulate the mud pumping defect, the contact between the concrete base and subgrade is described as a spring-damper system. This model is validated by field test results and other simulation results, and a very good agreement is found. The vibration responses of the vehicle, slab track, and subgrade under different mud pumping lengths and train speeds are studied firstly. The deviations of vibration responses in high-speed railways induced by mud pumping are then obtained, and the limited mud pumping length is put forward finally to provide a recommendation for maintenance works of high-speed railways in practice.

scholarly journals The Influence of an Integration Time Step on Dynamic Calculation of a Vehicle-Track-Bridge under High-Speed Railway

Mathematics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 431
Author(s):  
Junjie Ye ◽  
Hao Sun
Keyword(s):  
High Speed ◽  
Coupled Model ◽  
Short Wave ◽  
Integration Time ◽  
Vertical Acceleration ◽  
Dynamic Calculation ◽  
Time Step ◽  
High Speed Railway ◽  
Track Irregularity ◽  
Track Bridge

In order to study the influence of an integration time step on dynamic calculation of a vehicle-track-bridge under high-speed railway, a vehicle-track-bridge (VTB) coupled model is established. The influence of the integration time step on calculation accuracy and calculation stability under different speeds or different track regularity states is studied. The influence of the track irregularity on the integration time step is further analyzed by using the spectral characteristic of sensitive wavelength. According to the results, the disparity among the effect of the integration time step on the calculation accuracy of the VTB coupled model at different speeds is very small. Higher speed requires a smaller integration time step to keep the calculation results stable. The effect of the integration time step on the calculation stability of the maximum vertical acceleration of each component at different speeds is somewhat different, and the mechanism of the effect of the integration time step on the calculation stability of the vehicle-track-bridge coupled system is that corresponding displacement at the integration time step is different. The calculation deviation of the maximum vertical acceleration of the car body, wheel-sets and bridge under the track short wave irregularity state are greatly increased compared with that without track irregularity. The maximum vertical acceleration of wheel-sets, rails, track slabs and the bridge under the track short wave irregularity state all show a significant declining trend. The larger the vibration frequency is, the smaller the range of integration time step is for dynamic calculation.

scholarly journals Deformation Law and Control Limit of CRTSIII Slab Track under Subgrade Frost Heave

2021 ◽  
Vol 11 (8) ◽  
pp. 3520
Author(s):  
Xiaopei Cai ◽  
Qian Zhang ◽  
Yanrong Zhang ◽  
Qihao Wang ◽  
Bicheng Luo ◽  
...  
Keyword(s):  
High Speed ◽  
Base Plate ◽  
Element Model ◽  
Middle Part ◽  
Railway Track ◽  
Frost Heave ◽  
Track Structure ◽  
Slab Track ◽  
Plastic Damage ◽  
Track Irregularity

In order to find out the influence of subgrade frost heave on the deformation of track structure and track irregularity of high-speed railways, a nonlinear damage finite element model for China Railway Track System III (CRTSIII) slab track subgrade was established based on the constitutive theory of concrete plastic damage. The analysis of track structure deformation under different subgrade frost heave conditions was focused on, and amplitude the limit of subgrade frost heave was put forward according to the characteristics of interlayer seams. This work is expected to provide guidance for design and construction. Subgrade frost heave was found to cause cosine-type irregularities of rails and the interlayer seams in the track structure, and the displacement in lower foundation mapping to rail surfaces increased. When frost heave occured in the middle part of the track slab, it caused the greatest amount of track irregularity, resulting in a longer and higher seam. Along with the increase in frost heave amplitude, the length of the seam increased linearly whilst its height increased nonlinearly. When the frost heave amplitude reached 35 mm, cracks appeared along the transverse direction of the upper concrete surface on the base plate due to plastic damage; consequently, the base plate started to bend, which reduced interlayer seams. Based on the critical value of track structures’ interlayer seams under different frost heave conditions, four control limits of subgrade frost heave at different levels of frost heave amplitude/wavelength were obtained.

An advanced vehicle–slab track interaction model considering rail random irregularities

2017 ◽  
Vol 24 (19) ◽  
pp. 4592-4603 ◽  
Author(s):  
Lei Xu ◽  
Zhaowei Chen ◽  
Wanming Zhai
Keyword(s):  
Dynamic Model ◽  
Calculation Method ◽  
Three Dimensional ◽  
Interaction Model ◽  
Dynamic Responses ◽  
Computational Time ◽  
Infinite Length ◽  
Slab Track ◽  
Rail Irregularity ◽  
Track Irregularity

This paper investigates a more advanced vertical vehicle–slab track interaction model (VTIM) by considering the discontinuity of track slabs, besides, it can be degenerated to the traditional two-dimensional model conveniently. Moreover, a cyclic calculation method (CCM) is further developed to solve infinite length calculations. On this basis, the proposed dynamic model and CCM are validated by comparing with the more comprehensive three-dimensional train–track model and fixed-point excitation method. Then, from aspects of probability statistics and frequency analysis, an illustrative example is particularly conducted to comprehensively characterize the dynamic responses of vehicle–slab track systems, in which the representative and realistic rail irregularity sets simulated by the track irregularity probabilistic model are used as the loading inputs. Results show that, with a low consumption of computational time and computer memory, the dynamic results derived from VTIM and CCM have a high accuracy, which indicates that the proposed dynamic model and calculation method can be efficiently and accurately used to analyze train–slab track interactions.

Dynamic characteristic difference of steel-spring floating slab track between single-carriage and multi-carriage models

2021 ◽  
pp. 095745652199986
Author(s):  
Wenhao Chang ◽  
Xiaopei Cai ◽  
Qihao Wang
Keyword(s):  
Coupling Effect ◽  
Three Dimensional ◽  
Coupled Model ◽  
Measured Data ◽  
Dynamic Responses ◽  
Theoretical Research ◽  
Maximum Displacement ◽  
Steel Spring ◽  
Slab Track ◽  
Computation Efficiency

The steel-spring floating slab track (SSFST) is a low-stiffness structure, sensitive to the vehicle loads. Due to the coupling effect of the superposition of adjacent bogies, it is difficult for conventional single-carriage models to meet the simulation requirements. To find a balance between computation efficiency and authenticity of analytical model results, the influence of carriage number on SSFST should be studied. Based on the finite element method and multi-body dynamics, a refined three-dimensional coupled model of multi-carriage-SSFST-tunnel was established. The difference in the dynamic response of the SSFST between single-carriage and multi-carriage models was analyzed and compared with the measured data. The field test results show that structural displacements and accelerations under the two-carriage model are much closer to the measured data. The dynamic model analysis results show that the maximum displacement of the rail and SSFST in the midspan of the slab increase by 0.48 mm and 0.34 mm under the multi-carriage model, and the vibration reduction effectiveness increases by 1.4–2.0 dB. Dynamic responses of the rail and SSFST show minor differences under the two-carriage and three-carriage models. The article is expected to provide a reference for the theoretical research, design, and layout optimization of subway SSFST.

scholarly journals Sustainable Disaster Response Management Related to Large Technical Systems

2020 ◽  
Vol 12 (24) ◽  
pp. 10290
Author(s):  
Sergey Kinzhikeyev ◽  
József Rohács ◽  
Dániel Rohács ◽  
Anita Boros
Keyword(s):  
Probabilistic Model ◽  
Disaster Response ◽  
Process Management ◽  
Management Decision ◽  
Management Approach ◽  
Management Support ◽  
Railway Systems ◽  
Management Procedures ◽  
Markov Decision ◽  
Technical Systems

Numerous investigations assess the technical, technological, and managerial aspects of disaster response related to large technical systems. This paper deals with the possibility of synthesizing these aspects in a disaster response methodology, thus combining the technical, technological methods, tools, and software with the art of management. Its objective is to develop a preliminary methodology that supports the response management decision making processes related to earthquake-damaged large technical systems. The introduced methodology is demonstrated with the example of railway systems. It utilizes a combination of (i) a probabilistic model of railway system damage caused by earthquakes, (ii) a Markov model related to the damage and recovery phases, (iii) a probabilistic model of aftershocks, (iv) a statistical model of secondary effects, (v) impact models of management support actions, and (vi) response process management supported by a Markov Decision Process. The simulation results validate the concept. Based on these research results, the authors recommend that the described preliminary response management approach be further specified and implemented in disaster management procedures.

Influence of static preload on vibration reduction effect of floating slab tracks

2018 ◽  
Vol 25 (6) ◽  
pp. 1148-1163 ◽  
Author(s):  
Minghang Li ◽  
Meng Ma ◽  
Weining Liu ◽  
Bolong Jiang
Keyword(s):  
Vibration Reduction ◽  
Coupled Model ◽  
Mitigation Measures ◽  
Vehicle Body ◽  
Reference Case ◽  
Slab Track ◽  
Vibration Responses ◽  
Reduction Effect ◽  
Impact Vibration

To effectively reduce the railway vibration and its environmental impact, vibration mitigation measures are increasingly used. The vibration reduction effect of railway tracks is described quantitatively by insertion loss (IL). ILs obtained from in situ measurements under moving train loads and laboratory tests under artificial excitation differ significantly due to the different track loading state between these two methods. The differences of track loading state are induced by the moving effect of train passages and the preloads effect of vehicle masses, the latter of which is a significant factor to discuss in this paper. In order to study the static preload by vehicle masses influence on the vibration reduction effect in isolated tracks, the steel spring floating slab track and regular slab track, as a reference case, were compared. First, a theoretical simplified model was constructed, following which a finite–infinite element coupled model was built, which was calibrated by experimental test results. Impact loads were applied to both tracks with preloads using unsprung wheelsets or sprung vehicle-body masses, with the total mass varying from 0 t to 30 t. The results demonstrate that the increase in preload of unsprung mass makes the natural frequencies further reduced, and the peak IL value increased from 39 dB to 48 dB. The increase in preload has a significant effect on vibration responses below 5 Hz, and the application of the preload has different effects on the reduction effect in different frequency ranges.

scholarly journals Analysis of Influencing Mechanism of Subgrade Frost Heave on Vehicle-Track Dynamic System

2020 ◽  
Vol 10 (22) ◽  
pp. 8097
Author(s):  
Liang Gao ◽  
Wenqiang Zhao ◽  
Bowen Hou ◽  
Yanglong Zhong
Keyword(s):  
Dynamic System ◽  
High Speed ◽  
Frost Heave ◽  
Leverage Effect ◽  
Cold Regions ◽  
Severe Problem ◽  
Slab Track ◽  
Influencing Mechanism ◽  
Track System ◽  
Track Irregularity

Uneven subgrade frost heave has been a severe problem for the operation of high-speed railways in cold regions. In order to reveal the influencing mechanism of frost heave on the vehicle-track system, a novel FEM (finite element method) model based on an explicit algorithm was proposed. In the novel model, the existence of the leverage effect in slab track, which was caused by frost heave, was realistically reproduced at first, and then the vehicle model started running for evaluating the influence of the frost heave on the whole dynamic system. Results show that the leverage effect plays a key role in analyzing the influence of frost heave on the vehicle-track system, besides for track irregularity and contact loss. Specifically, the leverage effect decreases the stability of the slab track and causes an increase in dynamic irregularity. The roles of the track irregularity and the contact loss in the influencing mechanism were also revealed. With the ratio of wavelength to amplitude increasing, the track irregularity is gradually dominant in the influence mechanism of frost heave on the vehicle-track system. The research could provide a reference for the management and maintenance of the slab track in cold regions.

The Exploration and Research of CRTS I Slab Ballastless Track Used in the Freight Lines

2012 ◽  
Vol 253-255 ◽  
pp. 2031-2034
Author(s):  
Dong Hui Peng ◽  
Zi Sen Wei ◽  
Jue Fei Liu
Keyword(s):  
Coupled Model ◽  
Vertical Displacement ◽  
Track Structure ◽  
Vertical Force ◽  
Interference Spectrum ◽  
Ballastless Track ◽  
Track Dynamics ◽  
Track Irregularity

The CRTSⅠslab ballastless track structure was the research object of this thesis and the truck vehicle-track dynamics coupled model had established in this thesis. Germany track interference spectrum was used as the track irregularity. The study analyzed the force conditions of the CRTSⅠslab ballastless track under the action of heavy freight trains in 110km/h, as well as the wheel-rail vertical force, vertical displacement and acceleration of the rail and rail board changes with time. The results show that the CRTSⅠslab ballastless track can meet the basic requirements of freight line.

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