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 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 Evaluation Method of the Vibration Reduction Effect Considering the Real Load- and Frequency-Dependent Stiffness of Slab-Track Mats

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 452
Author(s):  
Zeming Zhao ◽  
Kai Wei ◽  
Wenhao Ding ◽  
Fang Cheng ◽  
Ping Wang
Keyword(s):  
Frequency Dependence ◽  
Insertion Loss ◽  
Vibration Isolation ◽  
Evaluation Method ◽  
Vibration Reduction ◽  
Frequency Dependent ◽  
Tangent Stiffness ◽  
Slab Track ◽  
Secant Stiffness ◽  
Reduction Effect

The purpose of this research was to investigate and improve the accuracy of the existing slab-track mat (STM) specifications in the evaluation of the vibration reduction effect. The static nonlinearity and dynamic mechanical characteristics of three types of STMs were tested, and then a modified fractional derivative Poynting–Thomson (FDPT) model was used to characterize the preload and frequency dependence. A modified vehicle–floating slab track (FST) coupled dynamic model was established to analyze the actual insertion loss. The insertion loss error evaluated by the frequency-dependent tangent stiffness increased with the increase in STM nonlinearity, and the error obtained by the third preload tangent stiffness was usually greater than that of the second preload. Compared with the secant stiffness, the second preload frequency-dependent tangent stiffness was more suitable for evaluating STMs with high-static–low-dynamics (HSLD) stiffness. In order to reflect the frequency dependence effect and facilitate engineering applications, it is recommended that second preload tangent stiffness corresponding to the natural frequency of the FST be used for evaluation. Furthermore, the insertion loss of the STMs with monotonically increased stiffness decreased as the axle load increased, and the opposite was true for the STMs with monotonically decreased stiffness. The vibration isolation efficiency of the STMs with HSLD stiffness was both stable and better than that of the STMs with monotonic stiffness.

Vibration Reduction Analysis of an Old Residential District under Vehicle Load

2014 ◽  
Vol 522-524 ◽  
pp. 1697-1702
Author(s):  
Bo Huang ◽  
Tang Dai Xia ◽  
Peng Fei He
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Vibration Reduction ◽  
Seismic Load ◽  
Far Field ◽  
Vehicle Load ◽  
Residential District ◽  
Bored Piles ◽  
Reduction Effect

Vibration phenomena on buildings in old residential district under non-seismic load are increasing. Given the vibration phenomenon on buildings in an typical old residential district under vehicle load, cast-in-situ bored piles in rows are suggested to reduce the vibration through analysis. Finite element method (FEM) is used to simulate vibration reduction effect of piles with different lengths. Considering analysis of the isolation of Rayleigh wave from far field and the result of FEM, 40 meter is the reasonable length of the vibration reduction piles. A vibration reduction solution is presented.

An experimental study of vibration reduction of a ballasted ladder track

2016 ◽  
Vol 231 (9) ◽  
pp. 1035-1047 ◽  
Author(s):  
Meng Ma ◽  
Weining Liu ◽  
Yulu Li ◽  
Weifeng Liu
Keyword(s):  
Laboratory Test ◽  
Vibration Reduction ◽  
Potential Effect ◽  
In Situ Experiment ◽  
Low Frequencies ◽  
Environmental Vibration ◽  
New Type ◽  
Reduction Effect ◽  
The Time Domain

The ballasted ladder track is a new type of longitudinal track. In this paper, to investigate its vibration reduction effect, both a laboratory test and in situ experiment were conducted. As the vibration sources, a newly designed drop weight impulse setup was employed in the laboratory test, and moving metro trains were employed in the in situ measurement. The vibration reduction effects of the ballasted track with ladder sleepers and regular concrete sleepers were compared. The results show that the ballasted ladder track can effectively decrease the peak value in the time domain and has the potential effect to control the environmental vibration in low frequencies. The shape of the sleeper can induce changes in the vibration field of the ballast.

Minimizing noise from metro viaduct railway lines by means of elastic mats and fully closed noise barriers

2018 ◽  
Vol 232 (6) ◽  
pp. 1828-1836 ◽  
Author(s):  
Caiyou Zhao ◽  
Wang Ping
Keyword(s):  
Noise Reduction ◽  
Vibration Energy ◽  
Rail Transit ◽  
In Situ Experiment ◽  
Noise Barriers ◽  
Transit Systems ◽  
Slab Track ◽  
Noise Barrier ◽  
Reduction Effect

An adverse effect of urban elevated rail transit systems is the associated noise, which has become a source of environmental complaints. In order to effectively address this problem, an in situ experiment has been conducted on the elevated sections of Hangzhou Metro Line 1 involving three cases: a 2.2 m vertical noise barrier with integrated bed track, a 2.2 m vertical noise barrier with an elastic mat floating slab track, and a 5.1 m fully enclosed noise barrier with an elastic mat floating slab track. The noise reduction effects of the elastic mats and the two kinds of noise barriers for metro viaduct railway lines were evaluated, and the mechanisms of these countermeasures were analysed. The results show that elastic mats can effectively reduce the transmission of wheel–rail vibration energy into the bridge, thus decreasing bridge-borne noise; meanwhile, the elastic mats could lead to an increase in wheel–rail noise. An excellent noise reduction effect was achieved in the area below and near the bottom of the bridge, while an increased noise effect was observed close to the area above and near the rail surface. The fully enclosed noise barrier controlled the propagation of wheel–rail noise more effectively than the vertical noise barriers, but no difference was found between these two kinds of noise barriers in controlling bridge-borne noise.

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

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