For today's railways, the continuous welded rail, which enhances driving dynamics and comfort for passengers, is often the construction method of choice. However, bridges and viaducts, which can be seen as singularities in the railway substructure, still pose a few unsolved problems; the bridge structure deforms under the impacts of thermal variation, creep, shrinkage, train passage and braking. The track-bridge interaction is an important parameter in railway bridge design. Measurement campaigns and research projects have been performed to investigate the interaction process and learn how to predict longitudinal forces in the rail and the concrete slab track. For the construction of long bridges on high-speed railway lines, new computational tools, monitoring systems and enhanced verification methods for tolerable rail stresses on bridges had to be developed. In order to take the modified stiffness conditions and recent findings on rail resistance into account, the verification schemes and safety concepts based on monitoring data have to be revised and performancebased methods need to be developed. The target of this article is to present monitoring-and reliability-based assessment methods for the concrete structure-rail interaction using monitoring and non-linear analysis techniques.
Heavy tamping is a deep dynamic compaction technique and has been increasingly used since the beginning of the 1970s. The present paper reports on in situ measurements and theoretical investigations referring to the decay of free soil vibrations caused by the falling weight after each impact. This behaviour is significant for the respective soil—falling mass interaction and enables a site-specific optimisation of the heavy tamping technique. The field tests comprised acceleration measurements of the falling mass and the soil whereby the falling height was changed repeatedly. The decay of the amplitudes of free vibrations provided a damping coefficient and a damped natural frequency, which are used to determine the Poisson's ratio and the E-modulus of the ground after each impact from numerical calculations. The scope of the research project was to gain a reliable indicator for the degree of compaction of the soil immediately after each impact, and hence obtain a method for compaction control and documentation. Le pilonnage lourd est une technique de compactage dynamique en profondeur, utilisée de plus en plus depuis le début des années 1970. La présente communication rend compte de mesures in situ et de recherches théoriques portant sur la dégradation des vibrations propres dans le sol, causées par la retombée du poids après chaque impact. Ce comportement est significatif pour l'interaction entre le sol et la masse tombante, et permet d'optimiser la technique du pilonnage lourd spécifiquement pour chaque lieu d'utilisation. Les essais sur place comprenaient des mesures de l'accélération de la masse tombante et du sol, et comportait le changement répété de la hauteur de chute. Le décroissement de l'amplitude des vibrations libres permettait d'obtenir un coefficient d'amortissement et une fréquence amortie naturelle, qui sont utilisés pour déterminer le coefficient de Poisson et le module E du sol après chaque impact, au moyen de calculs numériques. L'objet de ce projet de recherche était d'obtenir une méthode pour le contrô le et la documentation du compactage.
Vibratory rollers are mainly used for the near-surface compaction of granular media for a wide variety of construction tasks. In addition to the pronounced depth effect, vibratory rollers have offered the possibility of work-integrated compaction control (intelligent compaction) for decades. State-of-the-art measurement values for intelligent compaction (ICMVs) only take into account, if at all, a constant geometry of the contact area between the drum and soil. Therefore, this paper introduces a comparatively simple mechanical model, which describes the dynamic interaction between the vibrating drum and the underlying soil during compaction to investigate the influence of the changing geometry of the contact area on the motion behavior of the vibrating drum. The model is tested on realistic soil and machine parameters, and the results of the simulation with varying drum contact geometry are compared to a conventional simulation with a fixed contact geometry. The analysis shows that only a consideration of the varying drum contact geometry can map the dynamic interaction between the vibrating drum and soil sufficiently and provide a motion behavior of the drum that is in good accordance with the field measurements.
In this paper, the static load plate test and the dynamic load plate test by means of the light falling weight device are assessed utilizing numerical simulations. Simplified computational models of the tested subsoil and of the testing devices are developed, which capture the main effects of both the static and the dynamic load plate test. In extensive parametric studies, the impact of various subsoil conditions on the test results and several sources of error are evaluated and discussed. Computational test results of the static load plate test and of the dynamic load plate test are set in contrast to an effort to demonstrate the differences and the common features of the outcomes.
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