232
A. Andersson
5 Conclusion
In this paper experimental testing of a railway bridge was presented, comprising both
forced vibration tests at resonance and passing trains. A preliminary numerical model
was presented that is able to describe the main dynamic characteristic of the bridge. The
following is concluded.
– The forced vibration tests show that increased load amplitude results in slightly
reduced natural frequencies but a significant increase in damping.
– Based on the free vibration after train passages, the estimated natural frequencies and
damping corresponds to those from the forced vibration tests at low load amplitudes.
– The experimental estimate of the damping for the first mode is less than proposed by
EN 1991–2, even from the forced vibration test with high load amplitude.
– The numerical model is able to accurately describe both the natural frequencies and
mode shapes, by introducing a vertical spring at the tip of the over-sail.
– When simulating passing trains on the model, best agreement with the experimental
results is obtained if the load is not applied to the over-sail. This indicates that this
region of the model may need to be improved.
It should be pointed out that the presented numerical model does not describe the
origin of damping. This can be accounted for either by introducing dashpots and more
elaborate boundary conditions, e.g. as in [2], or by more accurate models of the subgrade
system, e.g. as in [4, 5].
References
1. Andersson, A., Ülker-Kaustell, M., Borg, R., Dymén, O., Carolin, A., Karoumi, R. Pilot testing
of a hydraulic bridge exciter. EVACES’15, Dübendorf, Switzerland, 19–21 October (2015)
2. Andersson, A., Östlund, J., Ülker-Kaustell, M., Battini, J-M., Karoumi, R.: Full-scale dynamic
testing of a railway bridge using a hydraulic exciter. EVACES 2017, San Diego, United States
(2017)
3. Zangeneh, A., Svedholm, C., Andersson, A., Pacoste, C., Karoumi, R.: Identification of soilstructure interaction effect in a portal frame railway bridge through full-scale dynamic testing.
Eng. Struct. 159, 299–309 (2018)
4. Lind Östlund, J., Andersson, A., Ülker-Kaustell, M., Battini, J.-M.: The influence of model
assumptions on the dynamic impedance functions of shallow foundations. Int. J. Civil Eng. 18,
1315–1326 (2020)
5. Lind Östlund, J., Andersson, A., Ülker-Kaustell, M, Battini, J-M.: On the influence of the
dynamic soil-structure interaction on simply supported high-speed railway bridges founded on
shallow soil strata. Int. J. of Rail Transportation (in press) (2020)
A. Andersson
5 Conclusion
In this paper experimental testing of a railway bridge was presented, comprising both
forced vibration tests at resonance and passing trains. A preliminary numerical model
was presented that is able to describe the main dynamic characteristic of the bridge. The
following is concluded.
– The forced vibration tests show that increased load amplitude results in slightly
reduced natural frequencies but a significant increase in damping.
– Based on the free vibration after train passages, the estimated natural frequencies and
damping corresponds to those from the forced vibration tests at low load amplitudes.
– The experimental estimate of the damping for the first mode is less than proposed by
EN 1991–2, even from the forced vibration test with high load amplitude.
– The numerical model is able to accurately describe both the natural frequencies and
mode shapes, by introducing a vertical spring at the tip of the over-sail.
– When simulating passing trains on the model, best agreement with the experimental
results is obtained if the load is not applied to the over-sail. This indicates that this
region of the model may need to be improved.
It should be pointed out that the presented numerical model does not describe the
origin of damping. This can be accounted for either by introducing dashpots and more
elaborate boundary conditions, e.g. as in [2], or by more accurate models of the subgrade
system, e.g. as in [4, 5].
References
1. Andersson, A., Ülker-Kaustell, M., Borg, R., Dymén, O., Carolin, A., Karoumi, R. Pilot testing
of a hydraulic bridge exciter. EVACES’15, Dübendorf, Switzerland, 19–21 October (2015)
2. Andersson, A., Östlund, J., Ülker-Kaustell, M., Battini, J-M., Karoumi, R.: Full-scale dynamic
testing of a railway bridge using a hydraulic exciter. EVACES 2017, San Diego, United States
(2017)
3. Zangeneh, A., Svedholm, C., Andersson, A., Pacoste, C., Karoumi, R.: Identification of soilstructure interaction effect in a portal frame railway bridge through full-scale dynamic testing.
Eng. Struct. 159, 299–309 (2018)
4. Lind Östlund, J., Andersson, A., Ülker-Kaustell, M., Battini, J.-M.: The influence of model
assumptions on the dynamic impedance functions of shallow foundations. Int. J. Civil Eng. 18,
1315–1326 (2020)
5. Lind Östlund, J., Andersson, A., Ülker-Kaustell, M, Battini, J-M.: On the influence of the
dynamic soil-structure interaction on simply supported high-speed railway bridges founded on
shallow soil strata. Int. J. of Rail Transportation (in press) (2020)