Unusual vibrations were observed in the live conductor rail on the northern railway line near the Danube bridge at Handelskai. These occurred independently of the train traffic, but at the same time as noticeable crosswinds. Initial assumptions indicated that certain combinations of wind speed, wind direction and aerodynamic flow could have triggered resonance effects.
This represents a risk which, in extreme cases, can lead to material fatigue or even breakage of the conductor rail. The Austrian Federal Railway (ÖBB) therefore decided to systematically investigate the phenomenon and technically verify possible causes. The BERNARD Gruppe was commissioned to carry out comprehensive vibration monitoring to provide a sound assessment of the structural integrity. As direct measurements on the conductor rail are not permitted for safety reasons, two precise laser sensors were used to record the vibration amplitudes without contact. In addition, acceleration sensors were mounted on the mounting rail to determine relative movements and to be able to comprehensibly evaluate the dynamics of the overall system. This interaction of different sensors enables high measuring accuracy, even under real operating conditions. An additionally installed weather station provided meteorological parameters such as wind direction and wind speed. This allowed external influences to be clearly assigned. The entire system was operated continuously over a period of three months. The evaluation included frequency analyses, peak value observations and detailed investigations of prominent weather situations. Overall, the dynamic behaviour of the conductor rail was precisely recorded and potentially critical resonance areas were reliably identified. The results form the basis for the long-term safe operation of the system.
César Martínez, BERNARD Gruppe
