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- Ground vibration (12)
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- Track-soil interaction (6)
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- Slab track (5)
- Train passage (5)
- Vehicle-track interaction (5)
- Force transfer (3)
- Hammer impact (3)
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Organisationseinheit der BAM
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Die diskrete Stützung der Schiene auf Schwellen in regelmäßigem Abstand ergibt für den fahrenden Zug eine Parametererregung. Die Berechnung der parametererregten Schwingungen und der zugehörigen dynamischen Radlasten erfordert die Analyse des Gesamtsystems Fahrzeug-Fahrweg-Untergrund. Es wird eine Substrukturmethode vorgestellt, bei der Fahrzeug, Fahrweg und Untergrund jeweils mit geeigneten Methoden (Mehrkörperdynamik, Finite Elemente, Randelemente) berechnet werden. Das Verfahren wird auf eine Situation angewandt, die auch mehrfach experimentell untersucht wurde, die Hochgeschwindigkeitsversuchsfahrten des Intercity Experimental (ICE) auf der Neubaustrecke bei Würzburg. Es werden die Ergebnisse der Teilsysteme und des Gesamtsystems und schließlich die dynamische Radlast für verschiedene Fahrgeschwindigkeiten dargestellt. Die dynamische Radlast nimmt bei Steigerung der Fahrgeschwindigkeit bis 200 km/h zu, bleibt bei höheren Fahrgeschwindigkeiten jedoch ungefähr konstant. Eine ähnliche Tendenz wird bei den Erschütterungen in der Umgebung bemerkt. Mit den berechneten Radlasten werden die ICE-Vorbeifahrten sehr detailliert simuliert und die berechneten Erschütterungen mit den gemessenen verglichen. Es zeigt sich eine gute Übereinstimmung, so daß der wichtige Fahrgeschwindigkeitseffekt als theoretisch und experimentell abgesichert angesehen werden kann.
A method is presented which allows to calculate the wave-field in a homogeneous or layered soil in case of a dynamic interior load. The wave propagation along the surface, the distribution of the response over the depth, the horizontal propagation at different depths and the vertical downward propagation are shown and compared with the simpler surface solution of the half-space and the interior solution of the full-space. The complete wave-field (Green's function) is applied to the dynamic behaviour of piles and pile groups by use of a boundary element formulation. The stiffness, damping and – typically for piles – mass of different groups of piles are presented. Different group effects occur for lines, circles, grids, parallels and crosses of piles, which can be regarded as oscillations around average values. Moreover, the piles and pile groups behave almost like a damper for most of the frequencies. A building on a pile group that is excited by ground vibration due to surface or interior loads shows a reduction of the wave-field due to kinematic and inertial soil–building interaction effects. The results presented lead to simplified descriptions of the wave-field due to interior loads and of the soil–pile–building interaction which can be used for the prediction of technically induced vibration.
The vibrations of soil and foundations are demonstrated for different types of loading. Train-induced ground vibrations are studied in a measurement campaign where a test train has run with regularly varied speeds. The measured train-induced soil vibration at 2 to 100 m distance from the track is compared with the wave propagation due to hammer excitation and with the theoretical wave field. The strong influence of the soil and the train speed on the amplitudes and frequencies of the vibration has been analysed for passages of the locomotive and the carriages. - The generation of ground vibration by strong explosions has been studied on a large testing area with sandy soil. The propagating waves were measured in a regular grid of measuring points in 10 to 1000 m. Therefore, the dominance of certain waves at certain distances and the changes of compressional waves and Rayleigh waves could clearly be observed. The results are compared with impulse hammer measurements in the range of 5 to 50 m. - A drop test facility has been built on the testing area of the Federal Institute of Materials Research and Testing (BAM). Heavy masses (containers) of up to 200 t can be dropped from 10 m height on a big reinforced concrete foundation. The foundation was instrumented by accelerometers, strain gauges and pressure cells to give information about the loading condition and by geophones to measure the vibration of the surrounding soil and building. Both excitation processes, the release of the mass and the impact, produce high vibration amplitudes. On a smaller drop foundation, the influence of the drop height and the target stiffness has been studied more systematically.
This article deals with two topics of vehicle-track-soil interaction, the mitigation of railway induced ground vibration by soft track elements, and the identification of track damage. Theoretical results have been achieved by a combined finite-element boundary-element method (FEBEM). The theoretical results are confronted with measurements at four sites. Improved mitigation effects have been found for soft rail pads under heavy sleepers. The insertion loss, however, can be too optimistic if a strong vehicle track resonance occurs for the un-isolated reference track. Two measurement sites show this strong vehicle-track resonance at about 80 Hz, which has been approximated by using the results of a wide parameter study including the rail pad, ballast, and soil stiffness, as well as the ballast model and the soil layering. – The detection of slab track damage is mainly based on the differences of the receptance or compliance functions. Theoretical results have been confirmed by measurements at one site where a loss of contact between track plate and base layer was visible. Measurements at a second site with a hidden damage have been compared with the theoretical results of a loose sleeper. The differences between intact (or repaired) and damaged tracks are strong enough to encourage the further development of this method for the identification of track damages.
Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results.
The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.
Ground vibrations near railway lines are generated by the forces that are acting between wheel and rail. It seems to be a straight forward assumption that the vehicle dynamics are important for the level and the frequencies of the excitation forces. Different vehicle dynamics phenomena are analysed for their role in the excitation of ground vibrations: rigid body modes of the bogies, elastic (bending) modes of the car body, and elastic modes of the wheelset. The theoretical analyses use rigid body models, simplified elastic models, and detailed elastic models. Some of these problems are vehicle–track interaction problems where 3D finite‑element boundary‑element models have been used for the track and soil. It is shown that the rigid or flexible vehicle modes are well in the frequency range of ground vibrations (4 to 100 Hz). They have an influence on the excitation force but the additional forces are rather small and can be neglected in ground vibration prediction. The theoretical results are checked by experimental results of a simultaneous measurement of vehicle,
track, and ground vibrations.