Identification of Bending Modes of Vibration in Rails by a Laser Doppler Vibrometer on a Moving Platform
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RESEARCH PAPER
Identification of Bending Modes of Vibration in Rails by a Laser Doppler Vibrometer on a Moving Platform K. Kaynardag 1 & G. Battaglia 2 & A. Ebrahimkhanlou 1 & A. Pirrotta 2 & S. Salamone 1 Received: 27 January 2020 / Accepted: 3 September 2020 # The Society for Experimental Mechanics, Inc 2020
Abstract This paper introduces a method to identify the bending modes of vibration of railway tracks by using a laser Doppler vibrometer (LDV) mounted on a moving platform. Two sets of experiments were conducted at Transportation Technology Center Inc. (TTCI) in Pueblo Colorado, in order to validate the proposed method. First, the bending vibration modes were identified using the signals collected from a rail span (rail section between two consecutive sleepers) by accelerometers under moving car excitation. Then, vibration measurements from rail spans were obtained by using an LDV mounted on the moving railcar. All tests were carried out at four different rail car speeds: 8 km/h (5 mph), 16 km/h (10 mph), 35 km/h (22 mph), and 45 km/h (28 mph). To find LDV signal segments corresponding to rail spans, a novel approach based on the sleeper passing frequency is introduced. Comparison of the results from both sets of tests demonstrated good agreement for all speeds. Keywords Moving laser Doppler vibrometer . Rail . System identification . Vibration modes . Sleeper passing frequency
Introduction The increase in axle loads and speeds applied to the aging and deteriorating railway tracks, the desire to reduce downtime associated with regular maintenance operations have all sparked interests and researches into better understanding vibrations induced by passing trains in both the track and its components. In general, railway tracks are one of the most
* S. Salamone [email protected] K. Kaynardag [email protected] G. Battaglia [email protected] A. Ebrahimkhanlou [email protected] A. Pirrotta [email protected] 1
Department of Civil, Environmental and Architecture, The University of Texas at Austin, 10100 Burnet Road, Building 24, Austin, TX 78758, USA
2
Dipartimento di Ingegneria, Università degli Studi di Palermo, viale delle Scienze Ed. 8, 90128 Palermo, Italy
complex dynamic systems in engineering; many vibration modes can be observed including vertical and lateral bending, torsional, longitudinal and the coupled forms of these modes [1]. This paper focuses on the vertical bending modes. Various theoretical models (analytical and numerical) and experimental works, have been proposed over the years to study the vertical dynamics in the railway tracks induced by moving loads [2–11]. The level of detail required depends on the frequency range of interest. The theoretical models are usually derived from the Euler-Bernoulli or Timoshenko beam theories. Both continuous or discretely supported rails have been investigated; however, conventional railway tracks are supported discretely by the fasteners and sleepers, therefore discretely supported models are usually more appropriate.
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