• Interaction and multiscale mechanics
• /
• v.3 no.4
• /
• pp.333-342
• /
• 2010

The Pseudo-Excitation Method (PEM) is applied to study the stochastic space vibration responses of train-bridge coupling system. Each vehicle is modeled as a four-wheel mass-spring-damper system with two layers of suspension system possessing 15 degrees-of- freedom. The bridge is modeled as a spatial beam element, and the track irregularity is assumed to be a uniform random process. The motion equations of the vehicle system are established based on the d'Alembertian principle, and the motion equations of the bridge system are established based on the Hamilton variational principle. Separate iteration is applied in the solution of equations. Comparisons with the Monte Carlo simulations show the effectiveness and satisfactory accuracy of the proposed method. The PSD of the 3-span simply-supported girder bridge responses, vehicle responses and wheel/rail forces are obtained. Based on the $3{\sigma}$ rule for Gaussian stochastic processes, the maximum responses of the coupling system are suggested.

• Proceedings of the KSR Conference
• /
• 1998.11a
• /
• pp.119-128
• /
• 1998

An electromagnets and a single-sided linear induction motor(SLIM) are used for suspension and propulsion equipment respectively. The electromagnets and SLIM are installed in the same frame, called a bogie, to reduce the volume under the vehicle floor and to raise the response charateristics to follow the track. Then the 3-dimensional forces(thrust force, normal force, side force) generated by SLIM direct]y affect the suspension system as the disturbance force. Moreover, in the running condition, the gap length variation in the electromagnets is the same as the SLIM. Therefore, the mutual interaction between the electromagnets and the SLIM is an important problem to realize the smaller gap length. In this paper, the dynamic interaction is analyzed and confir

• Wind and Structures
• /
• v.19 no.2
• /
• pp.145-167
• /
• 2014

Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.5
• /
• pp.435-444
• /
• 2017

The vehicle-track structure dynamic interaction analysis problem can be treated as sliding contact problem, and it is assumed that vehicle run at a constant speed over a rail modeled as beam elements. Unfortunately, Salome-Meca can not satisfy the compatibility condition for the beam master elements, which are consist of the elements with higher order polynomial shape function, in sliding contact problem. In this study, it is suggested to use more finer beam master element mesh as the remedy for incompatibility in sliding contact problem, and the accuracy of the solution is secured. For this, the effect of beam element mesh refinement consisting runway is analysed through simple examples, and the applicability to the dynamic interaction analysis is evaluated. Finally, the dynamic interaction analysis of railway skewed culvert transition problem is carried out to evaluate the effect of supporting stiffness due to backfill pattern changes and track irregularity due to uneven subgrade settlement.

• Structural Engineering and Mechanics
• /
• v.69 no.5
• /
• pp.499-509
• /
• 2019

While the wheel flat is an asymmetrical phenomenon in the railway, majority of researches have used two-dimensional models in the investigation of the effect of wheel flat on the wheel rail forces. This is due to the considerably low computational costs of two dimensional (2D) models although their reliability is questionable. This leaves us with the question of "what is the optimum modeling technique?". It is addressed in this research. For this purpose, two and three dimensional numerical models of railway vehicle/track interaction were developed. The three dimensional (3D) model was validated by comparisons of its results with those obtained from a comprehensive field tests carried out in this research and then, the results obtained from the 2D and 3D models were compared. The results obtained indicate that there are considerable differences between wheel/rail forces obtained from the 2D and 3D models in the conditions of medium to large wheel-flats. On the other hand, it was shown that the results of the 2D models are reliable for particular ranges of vehicle speed, railway track stiffness and wheel-fats lengths and depths. The results were used to draw a diagram, which presents the optimum modeling technique, compromising between the costs and accuracy of the obtained results.

• Journal of the Korean Society for Railway
• /
• v.18 no.2
• /
• pp.139-148
• /
• 2015

By increasing the vertical stiffness of the rail fastening system, the dynamic wheel load of the vehicle can be increased on the ballast track, though this increases the cost of track maintenance. On the other hand, the resistance acting on the wheel is decreased, which lowers the cost of the electric power to run the train. For this reason, the determination of the optimal fastener stiffness is important when attempting to minimize the economic costs associated with both track maintenance and energy to operate the train. In this study, a numerical method for evaluating the optimal vertical stiffness of the fasteners used on ballast track is presented on the basis of the process proposed by L$\acute{o}$pez-Pita et al. They used an approximation formula while calculating the dynamic wheel load. The evaluated fastener stiffness is mainly affected by the calculated dynamic wheel load. In this study, the dynamic wheel load is more precisely evaluated with an advanced vehicle-track interaction model. An appropriate range of the stiffness of the fastener applicable to the design of ballast track along domestic high-speed lines is proposed.

• Journal of the korean Society of Automotive Engineers
• /
• v.13 no.4
• /
• pp.76-84
• /
• 1991

The off-road tractive performance of tracked vehicles can be evaluated in terms of soil thrust, motion resistance and drawbar pull. The ability to predict accurately ground pressure distribution under track is of importance since the vehicle sinkage and motion resistance are closely related to it. While the formulation of the method for predicting ground pressure distribution follows closely in spirit the ideas outlined for the terrain with linear pressure- sinkage relation case by Garber and Wong, the analysis of various terrain stiffness is magnified by numerical implementation procedure. The effects of soil parameters on tractive forces can be introduced through the terrain-track interaction such as pressure-sinkage and shearing characteristics. It is illustrated by determining the drawber pull-slip relation and corresponding ground pressure distribution for the terrains typically chosen and by comparing the results with the conventional ones based on normal ground pressure. The factorial experiment method is finally adopted for checking the sensitivity of the values of soil parameters on the drawbar pull.

• Journal of Mechanical Science and Technology
• /
• v.19 no.spc1
• /
• pp.411-421
• /
• 2005

The development and implementation of an appropriate methodology for the accurate geometric description of track models is proposed in the framework of multibody dynamics and it includes the representation of the track spatial geometry and its irregularities. The wheel and rail surfaces are parameterized to represent any wheel and rail profiles obtained from direct measurements or design requirements. A fully generic methodology to determine, online during the dynamic simulation, the coordinates of the contact points, even when the most general three dimensional motion of the wheelset with respect to the rails is proposed. This methodology is applied to study specific issues in railway dynamics such as the flange contact problem and lead and lag contact configurations. A formulation for the description of the normal contact forces, which result from the wheel-rail interaction, is also presented. The tangential creep forces and moments that develop in the wheel-rail contact area are evaluated using : Kalker linear theory ; Heuristic force method ; Polach formulation. The methodology is implemented in a general multibody code. The discussion is supported through the application of the methodology to the railway vehicle ML95, used by the Lisbon metro company.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.678-684
• /
• 2011

In 2013, Korea will become the world's second country to operate the urban Maglev system with the inauguration of demonstration line at Incheon International Airport. A prototype Maglev is under the test at KIMM's(Korea Institute of Machinery & Materials, Daejeon) track. This Maglev is an EMS(Electromagnetic suspension)-type vehicle of controlled $8{\pm}3mm$ air gap. The air gap between electromagnet and the guiderail in an EMS-type Maglev must be maintained within an allowable deviation by controlling the magnet. The air gap response is strongly dependent on the structural characteristics of the elevated guideway. For this reason, the interaction between the vehicle with electromagnets and the elevated guideway must be understood to ensure safe running. The purpose of this paper is to compare vibration characteristics of the vehicle on the switching system and other sections when the full weight condition of urban maglev vehicle that 26.5 tons per car(empty car weight 19 tons + passenger condition 7.5 tons), is applied. Through such results, Maglev vehicles and switching system can be established and the levitation stability can be improved.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.10a
• /
• pp.444-451
• /
• 2003

In this study, a new three-dimensional finite element analysis model of high-speed railway bridges considering train-bridge interaction, in which various improved finite elements are used for modeling structural members, is proposed. The box-type bridge deck of a railway bridge is modeled by the NFS(Nonconforming Flat Shell) elements with 6 degrees of freedom. Track structures are idealized using the beam finite elements with the offset of beam nodes and those on Winkler foundation with two parameters. And, the vehicle model devised for a high-speed train is employed, which has an articulated bogie system. By Lagrange's equations of motion, the equations of motion of a bridge-train system can be formulated. Finally, by deriving the equations of the forces acting on a bridge considering bridge-train interaction the complete system matrices of total bridge-train system can be constructed. As numerical examples of this study, 2-span PC box-girder bridge is analyzed and results are compared with experimental results.