INTERNATIONAL RAILWAY TRANSPORTATION CONFERENCE AND RAILWAY INDUSTRY EXHIBITION | Year:2006 | دوره:8 |Papers Count:3

In this paper operational modal analysis technique is employed in model identification of a railway car body structure which uses recorded responses of the structure for identification of modal parameters of the body. Since excitation of the railway car body with conventional shakers is difficult due to the large mass of the structure, the classical modal analysis techniques are not commonly used for mode identification of these structures. To overcome this problem a different technique known as Operational Modal Analysis (OMA) which uses responses of the structure during its working conditions is used. Two sets of operational measurements were performed on the structure and results are used to extract mode shapes and natural frequencies of the structure. Validation of obtained modes is performed by comparing the modes obtained from the two sets of measurements.

The railway structure is the mechanical system compounded of both vehicles and track and its foundation. The track itself is constituted not only of the rails and sleepers, but also of the various available supporting structures (slabs, bridges. The scope of the present study is more particularly dedicated to the dynamical behaviour of the track and its foundation. An original numerical method, including a proper modeling of track geometry irregularities, has been built to compute the movements of the structure under progressing loads. Applications presented here are restricted to some cases in the field of track component like comparison of sleeper types or influence of foundation constitution on ground vibration spreading. This theory and the associated program are still being developed. The final aim is to offer research or project engineer a specific tool to evaluate more easily influence of key design parameter (masses, inertias, stiffness, depth of foundation layers) for a satisfactory static and dynamic behaviour.

Progressive Increase in urban and rural traffic in the modern world, demands for more efficient transportation systems especially in terms of speed, safety and capacity. This as well as the improving tendency towards economically feasible transport system, has lead to worldwide introduction of new rail-based transportation systems such as urban (LRT, MRT, regional metros, commuter lines, tramways, monorails and etc.), intercity passenger and cargo (heavy haul, high axle loads, etc.) and newly developed HSL (such as ICE, TGV, IPA, Shinkansen and etc.). This development requires innovative solutions in infrastructure especially track engineering. In this paper, the applicability of elastic PU materials in railway track structures for increasing the track bedding modulus and vibration damping is discussed. Several track layout alternative as well as application of different types of PU materials is investigated. The key elements in designing the track systems using elastic materials (also called MSS) such as dynamic modulus of elasticity, natural frequency, vibration damping and specific dead load is discussed. A practical case study in Isfehan railway line is also presented.