This paper deals with the fluid-structure interaction related to the transit of railway vehicles in proximity to noise-reduction barriers. During train transit a pressure wave is generated and consequently, due to the barrier's large surface area, non-negligible loads on the support elements arise. This problem applies in particular to high-speed railway lines and becomes critical when the train-barrier gap is small. Moreover, the presence of lateral wind can increase the loads acting on the structures, influencing the design of the support uprights. The problem has been numerically and experimentally evaluated. A preliminary study consisted of Computational Fluid Dynamics (CFD) simulations, reproducing the train and barriers geometries and the relative motion with the "sliding mesh" technique. The conditions of both the absence and presence of lateral wind were investigated. The pressure distribution along the barriers was analysed for different conditions. Then, experimental tests were performed in the wind tunnel at the Politecnico di Milano. Different wind speeds and exposure angles were considered in order to define lateral wind contributions. The pressure on the barriers was calculated at several points by means of pressure taps. Finally, the results obtained were compared with the data collected during an experimental campaign performed on the Rome-Naples high-speed railway line.
Among the topics related to the interaction between the contact wire of the overhead line and the collector strip, the wear that takes place at the contact interface, depending on both electrical and mechanical quantities, represents an important aspect of maintenance costs, affecting the mean lifetime of collectors, in terms of travelled kilometers (in terms of tenth of thousands), and contact line duration, in terms of years (between 15 and 40). Due to its importance in the global maintenance of both rolling stock and infrastructure, this topic deserved the attention of several regulations in the last decade.In order to investigate the effects of electro-mechanical wear on both contact wire and contact strip, a new test equipment has been designed and installed at Politecnico di Milano. A series of tests have been performed, involving different kinds of collector strip materials and contact conditions, tested at varying speeds and current intensities. This investigation concerned different collector strip configurations intended for 3 kV D.C. lines. The combination of different contents of copper and metallised carbon in the collector has been found to influence the wear rate of both collector strip and contact wire. Differences in wear up to four times for the former and up to six times for the latter have been found depending on the composition of the collector.
Subject of the paper is a particular configuration of overhead line, in which noise barrier structure is used as supports of the catenary instead of standard poles. This configuration is foreseen in case the noise barrier position is in conflict with the poles location. If the catenary is supported by the noise barrier, the motion that the latter undergo due to wave pressure associated to train transit is transmitted to the overhead line, so that potentially it influences the interaction between the catenary itself and the pantograph of the passing train. The paper focuses on the influence of such peculiar configuration on the quality of the current collection of high speed pantograph, for single and double current collection. The study has been carried out first with an experimental investigation on the pressure distribution on noise barrier, both in wind tunnel and with in-field tests. Subsequently a numerical analysis of the dynamics of the barrier subjected to the wave pressure due to train transit has been carried out, and the output of such analysis has been used as input data for the simulation of the pantograph-dynamic interaction at different speeds and with front or rear pantograph in operation. Consideration of structural modifications was then highlighted, in order to reduce the influence on the contact loss percentage.
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