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- ja (14) (entfernen)
Schlagworte
- Train passage (4)
- Hammer impact (3)
- Slab track (3)
- Axle impulses (2)
- Axle sequence (2)
- Ground vibration (2)
- Irregular soil (2)
- Static axle loads (2)
- Train-induced ground vibration (2)
- Vehicle–track interaction (2)
- Achsfolgespektren (1)
- Attenuation (1)
- Ballast track (1)
- Bauteile (1)
- Bauwerke (1)
- Boundary element (1)
- Bridge (1)
- Bridge resonance (1)
- Bridge vibration (1)
- Brücken (1)
- Cancellation (1)
- Compliance function (1)
- Continuous soil (1)
- Continuously inhomogeneous soils (1)
- Dynamic axle loads (1)
- Elastische Gebäudelagerung (1)
- Fequency domain (1)
- Filter effects (1)
- Finite element (1)
- Finite-element boundary-element method (1)
- Geometric vehicle and track irregularities (1)
- Irregular ballast (1)
- Layered soil (1)
- Layered soils (1)
- Mitigation (1)
- Modal analysis (1)
- Modalanalyse (1)
- Multi-beam track model (1)
- Obstacles (1)
- Pile bending stiffness (1)
- Pile foundation (1)
- Quasi-static response; (1)
- Rail roughness (1)
- Railway (1)
- Railway bridge (1)
- Random dynamics and vibrations (1)
- Random stiffness variation (1)
- Randomly heterogeneous soil (1)
- Rechenmodelle (1)
- Resonance (1)
- Scattered axle impulses (1)
- Scattering (1)
- Soil forces (1)
- Soil stiffness (1)
- Stiffness variation (1)
- Track deflection (1)
- Track displacements (1)
- Track filter (1)
- Track filtering (1)
- Track-soil interaction (1)
- Train-induced vibration (1)
- Trench (1)
- Tunnel (1)
- Tunnel-to-surface reduction (1)
- Vehicle-track interaction (1)
- Wavenumber domain (1)
- Wheelset (1)
- Wind energy tower (1)
- layered soil (1)
Organisationseinheit der BAM
- 7.2 Ingenieurbau (14) (entfernen)
Die Grundidee einer Schwingungsminderung ist es eine tiefe Eigenfrequenz der Struktur zu erreichen, so dass höhere Frequenzen abgemindert werden. Das gilt für die Minderung an der Quelle, zum Beispiel einem Eisenbahngleis, und für die Minderung am Empfänger, dem Gebäude. Die Eigenfrequenz ermittelt man aus dem Verhältnis der Auflagersteifigkeit und der Masse. Wie ist die Masse bei einem Gebäude zu wählen? Und wie ist die Untergrundsteifigkeit zu berücksichtigen? Als Referenzsituation ohne Minderungsmaßnahme? Der Beitrag bringt Rechenergebnisse zu abgefederten Gebäuden mit einfachen und komplexen (FE-) Modellen, Mess- und Rechenergebnisse zur Schwingungsübertragung von unabgefederten Gebäuden. Es wird der Einfluss der Abstimmfrequenz, der Bodensteifigkeit und der „starren“ Gebäudemasse untersucht. Die komplexen Gebäudemodelle erlauben, neben der Berechnung einer elastischen Gebäudelagerung, auch die Variation von Gebäudeparametern zur Reduktion der Deckenschwingungen. Den Ergebnissen bei der Erschütterungs-übertragung in Gebäude werden zwei ähnliche Beispiele zur elastischen Maschinenlagerung und zur elastischen Gleislagerung gegenübergestellt.
The vehicle–track interaction generates forces and consequently vibrations in the environment. The interaction has been analysed by the simultaneous measurements of vehicle, track and ground vibrations during test runs with varied train speeds. The special effects of the passage over a bridge and through a tunnel are studied and compared with the measurements on a conventional ballasted surface line. The maximum amplitudes, narrow band and one-third octave band spectra are presented for the axle-box accelerations and for the track, bridge and ground vibrations. The different frequencies and frequency bands are related to wheel out-of-roundness, track alignment errors, the sleeper passage and the wheelset–track resonance. An axle impulse component has been observed at the track, at the near-field soil and as a scattered version in the far field. Specific results can be found for the bridge track, where clearly speed-dependent bridge resonances occur due to the axle sequence of the train, and for the tunnel track where soft rail pads are responsible for a strong amplification around the wheelset–track resonance. On the other hand, the axle impulses are strongly reduced by the tunnel track, and the scattered axle impulse component is not as relevant as for the surface track. As a consequence, a strong mid-frequency amplitude reduction of the tunnel compared to the surface line has been measured for low and high train speeds by the Federal Institute of Material Research and Testing (BAM) and by other institutes.
Train-induced ground vibrations are all generated by the vehicle, by static or dynamic vehicle loads. The most important and most accepted excitation are the dynamic wheel loads from the passage over track irregularities. Dynamic wheel loads will be compared from parallel axle-box and ground vibration measurements at more than seven sites. Some low-frequency excitation of ground vibrations, typically between 10 and 30 Hz, cannot be found in the axle-box measurements. Therefore, other vehicle modes, such as rigid bogie modes, flexible carriage modes, rigid and flexible wheelset modes, have been analysed for additional excitation forces. These vehicle dynamics analyses give an explanation for higher axle-box results at high frequencies, but not for the excitation of the higher low-frequency ground-vibration component. Finally, the effect of the moving static train loads will be analysed. For a regular track and soil, the moving static train loads yield the quasi-static response which exists only in the low-frequency nearfield of the track. If the support stiffness is randomly varying along the track, the pulses on the track generate an additional low-frequency component which is called the irregular pulse responses.
This component will be demonstrated by numerical analysis where all axle pulses are superposed in frequency domain.
Many measurements of train induced ground vibrations show high amplitudes for a certain mid-frequency range. This ground vibration component cannot be well explained by dynamic loads of the train. Many characteristics indicate that the axle impulses, which are scattered by an irregular soil, are the excitation. This new understanding of railway-induced ground vibration is verified by numerical analysis. The response of the regular homogeneous and irregular inhomogeneous soils has been calculated by the finite-element method in frequency domain. A specific superposition of the impulse responses has been invented including time shift, axle sequence, track filter and hanning filter. The superposition yields the quasi-static component of the ground vibration which is restricted to very low frequencies and to the close near-field of the track. In case of an irregular soil of which the stiffness varies randomly in space, the superposition yields a mid-frequency ground vibration component from the scattering of the axle impulses. The existence and the importance of this component can thus be demonstrated by the calculations. Some rules of the influence of distance, train speed, soil stiffness, strength and width of the stiffness variation have been derived from the calculations. Many measurements show the unique explanation of the mid-frequency ground vibration component by the scattered axle impulses.