Developing a New Vibration Analysis Calculative Method for Esfahan Subway Train and Railways Design, Manufacturing and Construction
The simulated mass and spring evaluation for subway or railways construction and installation have wide applications in rail industries. This kind of design should be optimize all related parameters to reduce the amount of vibration in cities, residential areas, historical zones and other critical locations. Finite element method used too much to analyze such applications with an excellent accuracy but developing some simple, fast and user friendly evaluation always was required in subway industry. In addition, process parameter optimization required in railways to achieve optimal railways design with maximum safety, reliability and performance. The simple but useful simulated mass and spring evaluation system developed for Esfahan subway construction. This method discussed in this paper. Esfahan subway construction has a historical zone. Historical buildings should protect from harmful vibrations. Polyurethane layer used to reduce vibrations. This layer completely covered by concrete layers in all directions. It is worthy to know that, all the operation criteria like displacement and stress could be adapted with all vibration criteria like natural frequency, operation frequency and damping. Adaptation performed by changing in polyurethane layer thickness. The results showed that if 25-millimeter thickness polyurethane layer covered completely by two concrete layers with 12 millimeter thickness, the amounts of vibrations reduce considerably. In addition, it strongly recommended increasing the polyurethane layer up to 37 millimeter in historical zone to prevent potential harmful effects. The results confirmed by other commercial methods. The calculative method successfully performed. Furthermore, it is important to reduce maintenance costs in any potential design. The process parameter like rail ways dimension, rail ways material, cabins loading, cabins quality, cabins dimension and polyurethane layer thickness properly designed to keep the subway natural frequency around 18 Hz ( less than allowable 20 Hz). Numerical design results will protect all historical buildings, palaces paintings and old bridges in future subway operation times. In addition, some interesting patent and innovation in rail industry like Suspension mass tuned vibration reducer, short sleeper vibration-attenuation fastener and airtight track vibration noise reducing fastener discussed in this paper.
ON VERTICAL ANALYSIS OF RAILWAY TRACK VIBRATIONS
The paper herein presents a vertical vibration analysis of the ballasted track using a new model of the periodic support of the rail that improves the prediction of the rail response for both low and high frequencies. The model of the periodic support consists of two three-directional Kelvin-Voigt systems for the rail pad and the ballast, and a mixed Kelvin-Voigt/Maxwell system for the subgrade. Also, the inertia of the sleeper and the ballast block are introduced. The rail response due to a stationary and moving harmonic load is analyzed by applying the Green’s functions method. The influence of the rail pad stiffness and of the Doppler effect on railkway track vibrations are presented.
Green's functions for analysis of dynamic response of wheel/rail to vertical excitation
Abstract An analytical model to simulate wheel/rail interaction using the Green's functions method is proposed in this paper. The model consists of a moving wheel on a discretely supported rail. Particularly for this model of rail, the bending and the longitudinal displacement are coupled due to the rail pad and a complex model of the rail pad is adopted. An efficient method for solving a time-domain analysis for wheel/rail interaction is presented. The method is based on the properties of the rail's Green functions and starting to these functions, a track's Green matrix is assembled for the numerical simulations of wheel/rail response due to three kinds of vertical excitations: the steady-state interaction, the rail corrugation and the wheel flat. The study points to influence of the worn rail—rigid contact—on variation in the wheel/rail contact force. The concept of pinned–pinned inhibitive rail pad is also presented.