The impact of the rail welds geometry on the noise in urban zones

Abstract

This paper describes how, during many years of supervision of the construction and reconstruction of the tram tracks in Zagreb and Osijek (Croatia), it was noted that the damage caused by vehicles passing over uneven sections on the rail are large. Repair of the damage is expensive and in most of the cases requires suspension of the tram traffic that partially interferes with the road traffic as well, where the tram tracks are part of road construction. Existence of irregularity on rail running surface causes not only increased load on the track, but also reduces the effect of the rail fastening, deterioration of the track geometry, adverse impact on vehicles, reduce passengers’ comfort and especially increases noise levels. This paper studies the impact of the irregularities in the zones of rail welds as a noise-contributing factor. The measurements of the noise levels were performed in two phases. The first phase covered noise measurements for the tracks with irregularities in the welding zone. The geometry of the irregularities section was first recorded. The second phase covered measurements of noise levels at the same locations, but after the irregularities of the rail running surfaces were repaired. The measurements took into the account the tram types (seven types) and their speeds. That way it was possible to analyze the results to see to what extent the tram types and speeds do influence the increased noise levels. The analyses also took into the account the new low-floor tram type TMK 2200 produced in Zagreb and put into exploitation in June 2005. The research results helped to define the impact of the rails running surface geometry in the welding zone on the increased noise levels, and also to determine permissible tolerances for the geometry of welds on tram tracks in Zagreb.