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Keywords: dynamics, railway bridges, design curves, acceleration, conceptual design, ballast instability.

Summary

Swedish authorities have begun investigating the consequence of upgrading three of their major railway lines from 200 km/h to 250 km/h. The total track length is more than 1200 km and covers over 1000 bridges. Obviously, it is only possible to perform finite element analysis for a limited number of bridges for which the dynamic effects are considered to be a problem. Thus, as a consequence of the large number of bridges, a more efficient assessment approach has to be developed. The project initiated exemplifies the way in which a simple model may be used to identify bridges that need to be further analysed, strengthened or replaced.

This paper describes a methodology for the preliminary dynamic assessment of bridges along an existing railway line, with the focus on serviceability conditions. Design curves are developed based on a parametric study of 72,000 bridges. A semi-analytical model was developed which enabled the simulation of such a large number of bridges [1]. The model provides the ability to consider; sectional variations, multiple spans and elastic springs as support.

Two case studies are presented to validate the design curves and to show possible applications. From the design curves, the following conclusions can be drawn:

A normal two-span bridge has 10% to 60% lower bridge deck acceleration compared with a similar simply supported bridge.
For a certain span length, the acceleration could vary with up to ten times, depending on whether the fundamental frequency is close to the upper or lower recommended value given in EN1991-2 [2].

Moreover, the importance of fundamental frequency, span length and damping are highlighted. From the results is it also possible to discuss which bridge type is more suitable for a high-speed line.

References

1: C. Johansson, R. Karoumi, C. Pacoste, "Vibration of continuous bridges under moving load with focus on high-speed trains", 2012. (submitted)
2: European Committee for Standardization (CEN), "Eurocode 1: actions on structures-part 2: traffic loads on bridges", Final draft prEN 1991-2, 2002.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 98 PROCEEDINGS OF THE FIRST INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 3 Preliminary Dynamic Assessment of Railway Bridges subject to Higher Speeds C. Johansson^1,2, C. Pacoste^1,2 and R. Karoumi¹ ¹KTH Royal Institute of Technology, Stockholm, Sweden ²ELU Konsult AB, Stockholm, Sweden doi:10.4203/ccp.98.3 purchase the full-text of this paper Full Bibliographic Reference for this paper C. Johansson, C. Pacoste, R. Karoumi, "Preliminary Dynamic Assessment of Railway Bridges subject to Higher Speeds", in J. Pombo, (Editor), "Proceedings of the First International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 3, 2012. doi:10.4203/ccp.98.3 Keywords: dynamics, railway bridges, design curves, acceleration, conceptual design, ballast instability. Summary Swedish authorities have begun investigating the consequence of upgrading three of their major railway lines from 200 km/h to 250 km/h. The total track length is more than 1200 km and covers over 1000 bridges. Obviously, it is only possible to perform finite element analysis for a limited number of bridges for which the dynamic effects are considered to be a problem. Thus, as a consequence of the large number of bridges, a more efficient assessment approach has to be developed. The project initiated exemplifies the way in which a simple model may be used to identify bridges that need to be further analysed, strengthened or replaced. This paper describes a methodology for the preliminary dynamic assessment of bridges along an existing railway line, with the focus on serviceability conditions. Design curves are developed based on a parametric study of 72,000 bridges. A semi-analytical model was developed which enabled the simulation of such a large number of bridges [1]. The model provides the ability to consider; sectional variations, multiple spans and elastic springs as support. Two case studies are presented to validate the design curves and to show possible applications. From the design curves, the following conclusions can be drawn: A normal two-span bridge has 10% to 60% lower bridge deck acceleration compared with a similar simply supported bridge. For a certain span length, the acceleration could vary with up to ten times, depending on whether the fundamental frequency is close to the upper or lower recommended value given in EN1991-2 [2]. Moreover, the importance of fundamental frequency, span length and damping are highlighted. From the results is it also possible to discuss which bridge type is more suitable for a high-speed line. References 1 C. Johansson, R. Karoumi, C. Pacoste, "Vibration of continuous bridges under moving load with focus on high-speed trains", 2012. (submitted) 2 European Committee for Standardization (CEN), "Eurocode 1: actions on structures-part 2: traffic loads on bridges", Final draft prEN 1991-2, 2002. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £110 +P&P)
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