• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.867-878
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• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using three-dimensional Euler equations. Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. Numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, length and the existence of a tunnel on the crossing event. Unsteady aerodynamic loads-a side force and a drag force-acting on the train during the crossing are numerically predicted and analyzed. The side force mainly depends on the nose-shape, and the drag force depends on tunnel existence. Also. a push-pull (i.e.impluse force) force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary to evaluate the stability of high speed multi-car trains. The results also indicate the effectiveness of the present numerical method for simulating the unsteady flow fields induced by bodies in relative motion.

• Structural Engineering and Mechanics
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• v.46 no.5
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• pp.713-734
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• 2013

Bridges are vital components of the railroads. High speed of travel, the periodic and oscillatory nature of the loads and the comparable vehicle bridge weight ratio distinguish the railway bridges from the road bridges. The close proximity between estimations by some numerical methods and the measured data for the bridge-vehicle dynamic response under the moving load conditions has boosted the confidence in the numerical analyses. However, there is hardly any report regarding the responses of the railway bridges under the effect of the trains entering from the opposite directions while running at unequal speed and having dissimilar geometries. It is the purpose of this article to present an analytical method for the dynamic analysis of the railway bridges under the influence of two opposing series of moving loads. The bridge structural damping and many modes of vibrations are included. The concept of modal superposition is used to solve for the system motion equations. The method of solution is indeed a computer assisted analytical solution. It solves for the system motion equations and gives output in terms of the bridge deflection. Some case studies are also considered for the validation of the proposed method. Furthermore, the effects of varying some parameters such as the distance between the bogies, and the bogie wheelset distance are studied. Also, the conditions of resonance and cancellation in the dynamic response for a variety of vehicle-bridge specifications are investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.138-141
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• 2008

The screen doors installed in the station of subway are subject to the train-wind pressure caused by the operation of trains. The train-wind pressure has to be correctly estimated for the design of safe structure of screen doors. As three-dimensional numerical flow analysis technology has been significantly developed, the analysis on the train-wind pressure with diverse variables such as train specifications, train speed, tunnel and station configurations, and blockage ratio can be effectively carried out with three-dimensional numerical method. In this study, computational analysis of train-induced wind in a subway tunnel employing the screen doors are carried out by using the three-dimensional numerical method with the model of the moving boundary for the run of trains. While the numerical analysis of train-wind pressure was applied on the one island-type station in the Seoul Subway Line 2, maximum pressure of 494 Pa was estimated on the screen door when two trains pass each other at the speed of 80km/h in the platform.

• Smart Structures and Systems
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• v.20 no.2
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• pp.197-205
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• 2017

The dynamic performance of railway bridges under high-speed trains draws the attention of bridge engineers. The vibration issue for long-span bridges under high-speed trains is still not well understood due to lack of validations through structural health monitoring (SHM) data. This paper investigates the correlation between bridge acceleration and train speed based on structural dynamics theory and SHM system from three foci. Firstly, the calculated formula of acceleration response under a series of moving load is deduced for the situation that train length is near the length of the bridge span, the correlation between train speed and acceleration amplitude is analyzed. Secondly, the correlation scatterplots of the speed-acceleration is presented and discussed based on the transverse and vertical acceleration response data of Dashengguan Yangtze River Bridge SHM system. Thirdly, the warning indexes of the bridge performance for correlation scatterplots of speed-acceleration are established. The main conclusions are: (1) The resonance between trains and the bridge is unlikely to happen for long-span bridge, but a multimodal correlation curve between train speed and acceleration amplitude exists after the resonance speed; (2) Based on SHM data, multimodal correlation scatterplots of speed-acceleration exist and they have similar trends with the calculated formula; (3) An envelope line of polylines can be used as early warning indicators of the changes of bridge performance due to the changes of slope of envelope line and peak speed of amplitude. This work also gives several suggestions which lay a foundation for the better design, maintenance and long-term monitoring of a long-span high-speed bridge.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.289-291
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• 2003

Railway takes an important role of transporting massive passenger and freight. Accidents which occur related to trains have a risk of serious loss of lives, so those accidents need to be controlled urgently Therefore moving picture transmission system is required which transmits exact information of moving picture of accident status to CTC and also communication line is also required with it. By using WTB line as a wayside transmission line, railway telephones, fax and train service information are provided to local offices. As transmission line improving project, optical cabling work is being processed by phases. Therefore optical fiber line is more effective way for a communicating way between stations than coaxial transmission line. This Paper considers connecting method when optical fibers is used for moving picture data transmission of train accidents and its problems.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.64-71
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• 2002

Recently, mechanical systems such as a high-speed vehicles and railway trains moving on flexible beam structures have become a very important issue to consider. Using the general approach proposed in the first part of this paper, it is possible to predict motion of the constrained mechanical system and the elastic structure, with various kinds of foundation supporting conditions. Combined differential-algebraic equation of motion derived from both multibody dynamics theory and finite element method can be analyzed numerically using a generalized coordinate partitioning algorithm. To verify the validity of this approach, results from the simply supported elastic beam subjected to a moving load are compared with the exact solution from a reference. Finally, parametric study is conducted for a moving vehicle model on a simply supported 3-span bridge.

• Proceedings of the KIEE Conference
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• summer
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• pp.1412-1414
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• 2004

Railway takes an important role of transporting massive passenger and freight. Accidents which occur related to trains have a risk of serious loss of lives, so those accidents need to be controlled urgently. Therefore moving picture transmission system is required which transmits exact information of moving picture of accident status to CTC and also communication line is also required with it. By using WTB line as a wayside transmission line, railway telephones, fax and train service information are provided to local offices. As transmission line improving project, optical cabling work is being processed by phases. Therefore optical fiber line is more effective way for a communicating way between stations than coaxial transmission line. This paper consider's connecting method when optical fibers is used for moving picture data transmission of train accidents and its problems.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.757-769
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• 2016

Rail support modulus is an important parameter for analysis and design of ballasted railway tracks. One of the challenges in track stiffness assessment is its dynamic nature under the moving trains which differs it from the case of standing trains. So the present study is allocated to establish a relation between the dynamic and static stiffness of ballasted tracks via field measurements. In this regard, two different sites of ballasted tracks with wooden and concrete sleepers were selected and the static and dynamic stiffness were measured based on Talbot - Wasiutynski method. In this matter, the selected tracks were loaded by two heavy and light car bodies for standing and moving conditions and consequently the deflection basins were evaluated in both sites. Knowing the deflection basins respect to light and heavy loading conditions, both of static and dynamic stiffness values were extracted. Finally two definite relations were obtained for ballasted tracks with wooded and concrete sleepers.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.27-34
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• 2010

Recently, high-speed railway systems have gained increased interest as a means of environmental friendly transportation, and numerous bridges for high-speed railways have been constructed accordingly. However, bridge design for high-speed railways requires more consideration than conventional railway design because fast-moving trains will lead to significant impact on bridge structures. Thus, this research proposes a revised design considering both bridge-rail longitudinal interaction and dynamic effect of trains to ensure stability of fast travelling trains. To validate the proposed design algorithm, numerical analyses are performed and compared using a constructed 250 m long bridge with 5 spans for a high-speed railway. From the numerical results, the proposed optimum design of high-speed railway bridges exhibits the most economic life-cycle-cost (LCC) when compared with several existing design approaches.

• Geomechanics and Engineering
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• v.19 no.3
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• pp.241-254
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• 2019

A finite element approach is presented to examine ground vibration characteristics under various moving loads in a homogeneous half-space. Four loading modes including single load, double load, four-load, and twenty-load were simulated in a finite element analysis to observe their influence on ground vibrations. Four load moving speeds of 60, 80, 100, and 120 m/s were adopted to investigate the influence of train speed to the ground vibrations. The results demonstrated that the loading mode in a finite element analysis is reliable for train-induced vibration simulations. Additionally, a three-dimensional finite element model (3D FEM) was developed to investigate the dynamic responses of a track-ballast-embankment-ground system subjected to moving loads induced by high-speed trains. Results showed that vibration attenuations and breaks exist in the simulated wave fronts transiting through different medium materials. These tendencies are a result of the difference in the Rayleigh wave speeds of the medium materials relative to the speed of the moving train. The vibration waves induced by train loading were greatly influenced by the weakening effect of sloping surfaces on the ballast and embankment. Moreover, these tendencies were significant when the vibration waves are at medium and high frequency levels. The vibration waves reflected by the sloping surface were trapped and dissipated within the track-ballast-embankment-ground system. Thus, the vibration amplitude outside the embankment was significantly reduced.