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The modelling method of the air spring and its additional pneumatic system has been studied more frequently in recent years. As for the railway field, the study of the secondary suspension system of the bogie is the most popular, while little focus is on the air spring of the pantograph. In this paper, the modelling method of the air spring on the pantograph is investigated and developed. Four thermodynamic models are derived step by step, which can roughly be separated into two types. The first two models are established to express the relationship between the inner pressure and the vertical displacement of the air spring, and the effect of a regulator is illustrated and discussed. The latter two models that are developed from the first two models are set up to express the relationship between the vertical force and the vertical displacement of the air spring, where the effect of air spring material is illustrated and discussed. All four models are validated by comparing the simulation results with experimental results for frequency characteristics. Finally, the characteristics of the four proposed models are illustrated and discussed. [ABSTRACT FROM AUTHOR]

The dynamical actions to which the catenary dropper is subjected during the pantograph passage can become very relevant for high speeds of railway vehicle. In some very rare and isolated cases, premature failure of the dropper positioned near the suspension and/or near the auto tensioning devices in catenaries for High Speed (HS) operation has been observed. In order to understand the phenomenon, an analysis developed in several activities was carried out, including numerical analyses and in line and in laboratory experimental activities. A final phase of the investigation was dedicated to the development of a prototype of a dropper specifically designed on the basis of the results obtained from this study with the aim of improving the dropper fatigue behaviour. The new dropper could be used in critical points of the overhead line, such as near the suspension and/or near the auto tensioning devices. [ABSTRACT FROM AUTHOR]

A conceptual design of an innovative test rig for endurance tests of ball screws is presented in this paper. The test rig layout is based on the power recirculating principle and it also allows to overtake the main critical issues of the ball screw endurance tests. Among these there are the high power required to make the test, the lengthy duration of the same and the high loads between the screw and the frame that holds it. The article describes the test rig designed scheme, the kinematic expedients to be adopted in order to obtain the required performance and functionality and the sizing procedure to choose the actuation system.

From an aerodynamic point of view, very large observation wheels are complex structures. Several parts are slender with bluff cross sections, and therefore wind–structure interaction effects can influence their dynamic behaviour. Vortex-induced vibrations (VIVs), wake-effects, galloping instability, wind–rain interactions and buffeting response must be considered and studied during the design of substructures such as the A-frames and spoke cables. Both wind-tunnel tests and numerical tools can be used to assess the expected vibration levels and eventually to design appropriate countermeasures. In this paper, the Ain Dubai observation wheel is taken as a test case to present a procedure that can be applied to verify and validate the design of such structures when considering the effects of natural wind. For the A-frame, which turned out to be prone to VIVs during wind-tunnel tests on a scaled model, tuned mass dampers are studied as mitigation devices; for the spoke cables, several parameters affecting their aerodynamics were investigated in a wind tunnel on a full-scale model: inclination angle, structural damping and LED equipment. The characterization of these effects allowed both the performance of the cable damping system to be assessed, and configurations that could not perform adequately to be discarded. [ABSTRACT FROM AUTHOR]

The tensioning forces applied to the contact wire in a railway catenary system influence the performance of the line. In this paper, a method to monitor the status of such tensioning forces is proposed based on the dependency that the waves that propagate through a tensioned wire have on the forces that pull the wire itself. A novel analytical formulation for the propagation of waves in a tensioned wire was proposed, and it was used to obtain the vertical acceleration of the wire when an external force acts as a concentrated input. The analysis of the acceleration with a moving standard deviation allowed a method to be defined for the generation of an index that describes the trend of the tensioning forces. The method was then tested on the wire accelerations obtained with laboratory tests and, afterwards, on the accelerations recorded on a contact wire of an electric railway regularly in operation and excited with the same kind of input. [ABSTRACT FROM AUTHOR]

A methodology to conduct the Response Gap Analysis (RGA) for offshore oil spill emergency activities was developed, able to identify, for a given area and a given time period, if the response, which depends on the combination of the environmental factors affecting the performance of the contingency actions, is favourable, impaired, or ineffective. The necessity for offshore oil and gas operators to perform a RGA derives from the provisions of the Directive 2013/30/EU on safety of offshore oil and gas operations. In this Directive, "oil spill response effectiveness" means the effectiveness of spill response systems in combating an oil spill, on the basis of the "analysis of the frequency, duration, and timing of environmental conditions that would preclude a response. Furthermore, the assessment of oil spill response effectiveness is to be expressed as a percentage of time that such conditions are not present and is to include a description of the operating limitations placed on the installations concerned as a result of that assessment". Firstly, a gap analysis was conducted, aimed at highlighting the state of the art of RGA. The various literature reports on RGA are based on different environmental factors, as well as on different response strategies. A detailed analysis of the available information allowed identifying 9 environmental factors to be included in RGA: the wind speed, the wave height, the air temperature, the wind chill, the superstructure icing, the daylight / darkness conditions, the horizontal visibility, the cloud ceiling, and the sea ice coverage. In addition, also the shoreline distance and the bathymetry, which are location specific factors, could impair the response. Thus, a total number of 11 "environmental factors" is taken into account in the new RGA methodology. The definition of threshold values to be applied to each environmental factor was also addressed. In literature, usually two limit values are adopted and three zones are identified: a green zone, where the factor is favourable to the response; a yellow zone, where it is marginal, and a red zone, where it is unfavourable. Technical reports were analysed in order to retrieve the limit values of the environmental factors mentioned. Thus, a set of threshold values was proposed for mechanical recovery, application of dispersants by vessel and by aircraft, and in-situ burning. As a further step, the criteria adopted to combine the environmental factors in order to evaluate the effectiveness of the response were investigated. All the most recent studies identify for the response a green zone for the favourable response, a yellow zone corresponding to the impaired response, and a red one, where the response is ineffective. This criterion is adopted in the RGA method developed in the present study. The RGA methodology was implemented in a software code, which was applied to a case study area, allowing the validation of the RGA procedure. [ABSTRACT FROM AUTHOR]

This paper deals with the design, development and testing of a novel force transducer based on fibre-optic technology, for the measurement of contact force between a pantograph and an overhead line. Due to the particular application, in which part of the measurement chain is at high voltage and part is at ground potential, fibre-optic technology has the advantage of making the set-up easier to install and to manage with respect to the adoption of classical electrical-based transducers. Fibre Bragg grating is used as detectors in strain-based force transducers developed for this purpose. Considering that the force transducers become part of the connection between each collector of the pan head and the suspension, a proper design matching many conflicting requirements, such as encumbrance, mass, static and fatigue strength and sensitivity, is necessary. Laboratory tests and in-line tests proved the suitability of the optical force transducers. In particular, tests demonstrated that optical transducers represent an alternative to the classical electrical-based transducers for pantograph–catenary force measurement, reducing the complexity of the complete measurement set-up. [ABSTRACT FROM AUTHOR]