Wave Attenuation in a Pre-tensioned String with Periodic Spring Supports

Abstract

The overhead catenary system is a crucial conductor for delivering steady electric power to the trains running on modern electrified railways. The propagation of vibration waves in the catenary system is of interest to railway engineers due to the pantograph-catenary interaction. To explore the wave transmission via the contact wires of a catenary system supported by hanging devices offered by the bracket structures, a simplified model composed of a pre-tensioned string periodically suspended by hanging springs is adopted. For a periodic structure with wider band gaps, also known as stop bands, a wider cluster of frequencies of waves propagating in the periodic structure can be attenuated (or filtered out). This will be beneficial to the maintenance of the catenary system. To take advantage of such a feature, a resonator is usually equipped on each of the hanging spring supports so as to widen band gaps for better attenuation of the waves transmitted in the pre-tensioned string. In this study, a unit cell conceived as a spring-resonator-string unit is adopted to formulate the closed-form dispersion equation, from which the key condition for widening the band gaps is derived. From the exemplar study, it was shown that the installation of adjustable resonators on a catenary system can increase the band gap width, serving as a wave filter for attenuating the pantograph-induced wave transmission in the contact wires of the pantograph-catenary system.