Vibration Measurements for the Control of Damaged and Repaired Railway Tracks
The damage detection and repair control have become important tasks for ballast and slab tracks. Measurements which compare the damaged and the repaired status of the same track section at different times, or which compare a damaged and an intact track se
- PDF / 1,124,142 Bytes
- 18 Pages / 439.37 x 666.142 pts Page_size
- 45 Downloads / 160 Views
Introduction, Experimental Methods of Multi-sensor Vibration Measurements This contribution presents experimental methods to detect track damage. At BAM (Federal Institute of Material Research and Testing), a measuring car with a measuring system of 72 channels, geophones, mountings, cables, harmonic and impulsive exciters is used for dynamic measurements of the track, the soil and buildings (Fig. 1). An instrumented hammer allows force measurements and to evaluate transfer functions of the track, and the soil. Wave measurements are used to identify the soil characteristics [1, 2]. Train passages are measured at the track [3] and for the train induced ground vibrations [4, 5]. In addition to these in situ options, tests of tracks or track elements can be performed in a large laboratory [6, 7].
Calculations by the Three-Dimensional Finite-Element Boundary-Element Method The track-soil systems are calculated in full detail by the combined finite-element boundary-element method [3, 8]. The track including the rails (beam elements), the rail pads (truss elements), sleepers, ballast or plate (volume elements) is modelled by the finite element method (Fig. 2) whereas the homogeneous or layered soil is L. Auersch (&) S. Said Federal Institute of Material Research and Testing BAM, 12200 Berlin, Germany e-mail: [email protected] S. Said e-mail: [email protected] © Springer Nature Singapore Pte. Ltd. and Zhejiang University Press 2018 X. Bian et al. (eds.), Environmental Vibrations and Transportation Geodynamics, DOI 10.1007/978-981-10-4508-0_2
13
14
L. Auersch and S. Said
Fig. 1 Measuring system (left) in the measuring car (right)
calculated by the boundary element method. The dynamic stiffness matrix of the soil is established by using the Green’s functions of an elastic layered half-space [9]. All calculations (Green’s functions, boundary matrix and dynamic finite element matrices) are performed in frequency domain. The track is excited by a dynamic axle load (a pair of vertical forces, which acts on the rails above the central sleeper), and the frequency dependent displacements (compliances) are calculated. It is worth to notice that the important base of the finite-element boundary-element method, the point load solution for the layered soil, is established in wavenumber domain just as in the simplified method of the next section.
Calculations by the Simplified Two-Dimensional Wavenumber Domain Method The slab tracks can also be modelled as multiple-beam systems: The first beam represents the two rails, and the second beam represents the track plate including the sleepers and the base layer. Additional beams have to be modelled if elastic elements lie between sleepers and track plate or between track plate and base plate. Each beam is described by the bending stiffness EIj and the mass per length mj′ which are assembled in a diagonal stiffness matrix EI and a diagonal mass matrix m′. The global stiffness matrix K′ is a nxn matrix assembled from the 2 2 dynamic stiffness matrices of each support section.
Data Loading...
