Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 A. Cunha, E. Caetano, P. Ribeiro, G. Müller (eds.) ISSN: 2311-9020; ISBN: 978-972-752-165-4
Automatic train type identification in railway bridge monitoring
H. Bigelow1, B. Hoffmeister1, M. Feldmann1, F.Weil1 1RWTH Aachen University, Institute of Steel Construction, Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany email: [email protected], [email protected], [email protected], [email protected]
ABSTRACT: When studying dynamic behaviour of railway bridges subjected to (high-speed) trains, monitoring of these bridges is a very useful tool. Reactions to different train types at different crossing velocities can be investigated as well as subsequent free decay processes. Nevertheless a certain amount of work is required to analyse the recorded data. Especially long term monitoring of frequently crossed bridges can lead to a large number of recorded reactions of train passages. In any case the respective train type and its crossing velocity have to be known to be associated with a certain reaction of the bridge, e.g. resonance phenomena. Using the example of a monitored German filler beam bridge, it is shown how this information can be derived directly from the measured data. At this bridge longitudinal strain and tri-directional acceleration measurements were performed at measuring points placed underneath the bridge. The strain measurements were used to identify the respective train type and its crossing velocity. Crucial for the identification of the train type and respective velocity is the knowledge of the carriage formation (number and order of engines, passenger coaches, etc.) and the length over buffers of each component. In the paper the methods used are presented and examples of the automatically identified train types are given by illustrations of measurements.
KEY WORDS: Railway bridge, Long term monitoring, Train induced vibrations, Filler beam bridge.
1 INTRODUCTION Three options for the identification of a train type are Permanent or long term monitoring systems of railway provided. At least one of them has to be defined to enable the bridges are installed for various reasons, e.g. surveillance of automatic train identification. critical structural members or research of dynamic behaviour of bridges subjected to crossing train loads. Certain bridge 1. Determination of total number of local maxima. reactions, e.g. resonance phenomena are of special interest. 2. Definition of system reaction. These have to be associated with crossing train types and 3. Comparison of the measured train passage characteristic crossing velocities. If train type and velocity can be directly to a reference characteristic. derived from the measured bridge reaction, no additional measurements of the velocity and comparison of time tables to The first method was already part of [3]. As can be easily seen identify the train type are required. when comparing the characteristics of passenger trains to the As presented in [1] a long term monitoring system was characteristics of freight trains in the following sections, installed on German filler beam twin bridge Erfttalstraße as method 1 is only valid for freight trains. These trains consist part of a European research project [2]. The single span bridge of higher numbers of carriages and thus cause a higher consists of two decks separated by a longitudinal gap but with number of local maxima. Passenger train types usually have a continuous ballast layer. The monitoring system consists of lower numbers of carriages similar to each other. On the other four measuring rows with eleven measuring points each, hand comparison to a reference characteristic cannot be used placed underneath the two bridge decks. Each deck carries for the identification of freight trains as they differ very much one track. Longitudinal strain and tri-directional acceleration in their carriage configurations. measurements were carried out. An analysis routine [3] was The second method requires a definition of the train developed which included the algorithm given in [1] to configuration. Each train consists of a defined number of calculate bridge deformations from strain measurements. The carriages, each with specific carriage “length over buffers” routine was expanded [4] and now includes amongst other (Figure 1), which are arranged in a certain order. In [4] four functions an automated train type identification which is carriage types were defined: presented in this paper. r engine 2 METHODS b end vehicle c centre coach The routine [4] uses strain measurements obtained during v centre coach with speed determination train crossings (in the diagrams in section 3 depicted in red) for the train type identification. The subsequent free decay Several carriages of one type in a row can be combined in one process and ambient oscillations before and after the command. The definition of a centre coach with speed excitation are illustrated in blue.
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determination is as follows, the definition of the other carriage high-speed trains passing over the bridge. Maximum speeds types can be carried out analogously. are limited to 250 km/h. Furthermore there is local traffic and freight transportation as well as individual engines. v[
Table 1. ICE 1 configuration
r [1] (19.78) {0.9} c [1] (26.4) {0.85} v [5] (26.4) {0.75} b [1] (24.9) {0.7}
Figure 2. Illustration of train type definition [4] Of the six centre coaches the latter five are suited for the The number of local maxima strongly depends on the speed estimation; the resulting six local maxima used by the crossing velocity. A higher velocity leads to a smaller number routine [4] are numbered in the diagrams. of local maxima (minimum n + 1). At a low speed the system can respond to single axle loads while at higher velocities one local maximum combines the reactions to several axle loads. This circumstance also affects method 3. There reference characteristics are defined. Measured reactions caused by known train types are stored at a database and new measurements can be compared with them. The reference reaction with the smallest difference defines the most probable train type. The routine [4] has a graphical user interface where the results obtained can be checked by the user. At this point the user can control and if necessary adjust automatically Figure 3. Measured strains due to an ICE 1 train crossing [4] determined indexes, e.g. the points defining beginning and end of the train crossing. In the strain diagrams in section 3 these are the red dots. Furthermore falsely determined train types can be revised before further analyses or eliminated from the overall assessment. Not all measured data are suited for further evaluation, e.g. sometimes both decks are crossed at the same time by trains with opposite direction of travel. Reactions cannot be assigned to one crossing train as both decks influence each other.
3 CONSIDERED TRAINS Figure 4. Measured strains due to an ICE 1 train crossing [4] The bridge Erfttalstraße is located between Cologne and Aachen and thus part of the European railway network Comparison of Figure 3 and Figure 4 shows that ICE 1 connecting Germany e.g. with Brussels, Paris or London. trains are used with the engine in front as well as at the end of Currently Inter-City-Express ICE and Thalys are the only the train (pull/push operation). The defined routines always
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check both directions. The durations of the train crossings and thus the crossing velocities differ slightly (Figure 3: v = 46.65 m/s = 168k km/h; Figure 4: v = 41.8 m/s = 150.6 km/h; Figure 5: v =28.5 m/s = 103 km/h). All figures show the respective reaction on the loaded deck; in case of Figure 3 this is the south bridge deck, while the other two show reactions on the north deck.
Figure 7. Measured strains due to an ICE 3 train crossing [4]
Figure 5. Measured strains due to an ICE 1 train crossing [4] 3.2 ICE 3 ICE 3 trains basically can be put to many different coach configurations. It is also usual to couple two trains. The latter Figure 8. Measured strains due to an ICE 3 train crossing [4] enables decoupling of the two trains after covering part of the railway line together. Each train then terminates for a different Figure 6 to Figure 8 show phenomena related to the destination. Possible maximum speeds in Germany are interaction of bridge and train characteristics. The diagrams in 300 km/h. Figure 6 and Figure 8 have very distinct free decay curves; the The biggest difference between ICE 3 and ICE 1 (or ICE 2 one in Figure 7 does not. This is usually called “cancellation respectively) is that in the ICE 3 does not have a dedicated phenomena” [7]. It occurs when at the end of the train engine car. It is driven by powered bogies distributed along crossing the two components of the oscillation -forced and the train. The ICE 3 configuration used between Aachen and free vibration- cancel each other. This can be related to the Cologne can be characterised as follows: crossing velocity; a “cancellation velocity” can be defined as:
2 vcancel = ⋅ n0 ⋅ LS j = 1, 2,.... (1) Table 2. ICE 3 configuration 2 j + 1
The equation considers fundamental frequency n and span b [1] (21.605) {0.65} 0 LS of the bridge. In case of the Erfttalstraße those are 3.5 Hz v [6] (24.775) {0.9} and 24.6 m, respectively [1]. Table 3 summarises the first b [1] (21.605) {0.7} three values for vcancel.
The “length over buffers” of the centre coaches is the one also given in [6]; the end lengths of the end coaches differ Table 3. Cancelation velocities Erfttalstraße slightly. The configuration given in [6] describes the j 1 2 3 maximum possible number of 16 coaches. v [m/s] 57.4 34.4 24.6 cancel vcancel [km/h] 206.6 124.0 88.6
Comparison of the crossing velocities of the presented ICE 3 train crossings (Figure 6: v = 71.2 m/s = 256 km/h; Figure 7: v = 59 m/s = 212 km/h; Figure 8: v = 70.0 m/s = 251 km/h) shows that crossing velocity and cancelation velocity are close together in Figure 7 which already shows the cancelation effect. Damping also influences the cancelation effect; strictly speaking formula (1) applies only to undamped systems. Therefore even train crossings at the exact cancellation velocity are followed by a small decay Figure 6. Measured strains due to an ICE 3 train crossing [4] process. Again examples obtained from both decks are presented; Figure 6 shows a reaction of the loaded south deck, while the other two diagrams show reactions on the loaded north deck.
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3.3 Thalys cancellation effect in Figure 9. The first two diagrams were The Thalys train traveling between Aachen and Cologne obtained on the north deck, the one in Figure 11 on the south (Thalys PBKA) can be defined as follows: deck. 3.4 Local trains Table 4. Thalys configuration The bridge Erfttaltraße is frequently crossed by local trains. Respective train configurations, especially the number of centre coaches depend on the expected number of passengers. r [1] (17.145) {0.7} Between Aachen and Cologne there are local trains with three, c [1] (21.845) {0.7} four or five centre coaches; they can respectively be defined v [6] (18.7) {0.6} as follows: c [1] (21.845) {0.7} r [1] (17.145) {0.7} Table 5. Local train configuration with three centre coaches The four outer coaches differ slightly from the six centre coaches. The configuration given above differs from the one b [1] (23.4) {0.6} given in [6] for design purposes. v [1] (26.8) {0.7} The centre coaches have significantly smaller “lengths over c [1] (26.8) {0.7} buffers” than ICE trains and a different arrangement of r [1] (14.65) {0.95} bogies, which support commonly two coaches. This leads to higher excitation frequencies at the same speed level. Table 6. Local train configuration with four centre coaches
b [1] (23.4) {0.6} v [2] (26.8) {0.7} c [1] (26.8) {0.7} r [1] (14.65) {0.95}
Table 7. Local train configuration with five centre coaches
Figure 9. Measured strains due to a Thalys train crossing [4] b [1] (23.4) {0.6} v [3] (26.8) {0.7} c [1] (26.8) {0.7} r [1] (14.65) {0.95}
The local trains are either pushed by an engine (Figure 12, v = 39.8 m/s = 143 km/h, obtained on the north deck) or pulled (Figure 13 v =38.0 m/s = 137 km/h; obtained on the south deck).
Figure 10. Measured strains due to a Thalys train crossing [4]
Figure 12. Measured strains due to a local train RE crossing [4]
Figure 11. Measured strains due to a Thalys train crossing [4]
Comparison of the three curves (Figure 9: v = 57.5 m/s = 207 km/h; Figure 10: v = 57.8 m/s = 208 km/h; Figure 11: v = 25.7 m/s = 93 km/h) again shows the occurrence of the
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effects. The reaction to the heavy engine exceeds the reactions to the coaches.
Figure 13. Measured strains due to a local train RE crossing [4]
3.5 Freight train Figure 17. Measured strains due to a freight train crossing [4] Freight train configurations differ very much from each other as do the bridge reactions to their crossings. Different lengths In [4] no estimation of the crossing velocities of freight of coaches often lead only to a partially periodic excitation trains is provided. Not only because the freight train and response of the bridge during the train crossing. There are configurations differ so much but also because the respective very long trains with identical coach lengths, so called block “lengths over buffers” were unknown. trains. These train characteristic has led to a discussion if 3.6 Engine resonance phenomena have to be considered in the design Individual engines sometimes cross the bridge, being sent loads of freight trains. from one operation to another. In their case the estimation of
the crossing velocity is not implemented in [4]. It would be possible to include lengths of certain engine models to the programme and expand the train type identification to a more differentiated engine type identification. As the routine was developed to analyse dynamic behaviour and especially resonance phenomena due to train crossings with regular axis- centre distances, the implementation of engines was not scope of the development.
Figure 14. Measured strains due to a freight train crossing [4]
Figure 18. Measured strains due to an engine crossing [4]
Figure 15. Measured strains due to a freight train crossing [4]
Figure 19. Measured strains due to an engine crossing [4]
4 CONCLUSION Figure 16. Measured strains due to a freight train crossing [4] The correct identification of train types is an important part of research of bridge reactions to train crossings. This paper The presented case in Figure 15 shows a periodic behaviour shows examples how this information can be derived from during the passage of the centre coaches without resonance measured train reactions.
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ACKNOWLEDGMENTS The bridge monitoring was supported by the European research Fund for Coal and Steel (RFCS) within the research project DETAILS [2] which is gratefully acknowledged. Subsequent work on the enhancement of the analysis routine has been performed during the German national research Project P941 [5] supported by Forschungsvereinigung Stahlanwendung e. V. (FOSTA).
REFERENCES [1] Rauert, T., Feldmann, M., He, L., De Roek, G.: Calculation of bridge deformations due to train passages by the use of strain and acceleration measurements from bridge monitoring supported by experimental tests, Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011. [2] RFCS-project DETAILS: Design for optimal life cycle costs (LCC) of high-speed railway bridges by enhanced monitoring systems, RFSRCT- 2006-00032, Duration 2006-2009. [3] Weil, F., Rauert, T.: FOX 1.40 - Auswertungsroutine Monitoring EÜ Erfttalstraße, Institute of Steel Construction, RWTH Aachen University, 2010. [4] Weil, F.: Auswertung von Monitoring-Ergebnissen einer WiB- Eisenbahnverbundbrücke, Bachelor thesis, Institute of Steel Construction, RWTH Aachen University, unpublished, 2012. [5] FOSTA P941 – Dynamische Auslegung von Eisenbahn-Verbundbrücken mit kleinen und mittleren Spannweiten für den Hochgeschwindigkeitsverkehr, 2011-2013. [6] DB Netz AG: Richtlinie 804 - Eisenbahnbrücken (und sonstige Ingenieurbauwerke) planen, bauen und instand halten, 2013. [7] Rauert, T.: Zum Einfluss baulicher Randbedingungen auf das dynamische Verhalten von WiB-Eisenbahnbrücken, Dissertation RWTH Aachen University, ISBN 978-3-8440-0360-4, 2011.
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