Measurement methods and analysis tools for rail irregularities. A case study for urban tram track

Rail irregularities, in particular for urban railway infrastructures, are one of the main causes for the generation of noise and vibrations. In addition, repetitive loading may also lead to decay of the structural elements of the rolling stock. This further causes an increase in maintenance costs and reduction of service life. Monitoring these defects on a periodic basis enables the network rail managers to apply proactive measures to limit further damage. This paper discusses the measurement methods for rail corrugation with particular regard to the analysis tools for evaluating the thresholds of acceptability in relation to the tramway Italian transport system. Furthermore, a method of analysis has been proposed: an application of the methodology used for treating road profiles has been also utilized for the data processing of rail profilometric data

Rail roughness and rolling noise in tramways

Companies which manage railway networks have to cope continually with the problem of operating safety and maintenance intervention issues related to rail surface irregularities. A lot of experience has been gained in recent years in railway applications but the case of tramways is quite different; in this field there are no specific criteria to define any intervention on rail surface restoration. This paper shows measurements carried out on some stretches of a tram network with the CAT equipment (Corrugation Analysis Trolley) for the principal purpose of detecting different states of degradation of the rails and identifying a level of deterioration to be associated with the need for maintenance through rail grinding. The measured roughness is used as an input parameter into prediction models for both rolling noise and ground vibration to show the potential effect that high levels of roughness can have in urban environment. Rolling noise predictions are also compared with noise measurements to illustrate the applicability of the modelling approach. Particular attention is given to the way the contact filter needs to be modelled in the specific case of trams that generally operate at low speed. Finally an empirical approach to assess vibration levels in buildings is presented

Misura e valutazione dell'irregolarità delle rotaie nei sistemi ferroviari urbani

L’irregolarità del binario ed in particolare l’usura ondulatoria rappresenta attualmente, soprattutto per le infrastrutture ferroviarie che si sviluppano nei contesti urbani, la principale causa di generazione di rumore e vibrazioni. In aggiunta può determinare nel materiale rotabile il decadimento per fatica degli elementi strutturali con conseguente aggravio dei costi di manutenzione. Il monitoraggio continuo nel tempo e nello spazio di questa difettosità geometrica del binario permette al gestore dell’infrastruttura di mettere in campo le misure correttive per limitare queste problematiche. In questo articolo vengono presentate le metodologie di misura dell’irregolarità del binario attualmente in uso con particolare riguardo agli strumenti di analisi per valutare le soglie di accettabilità in relazione al sistema di trasporto tramviario

Soglie di accettabilità per le irregolarità delle rotaie tranviarie

La presenza di usura ondulatoria sulle rotaie ferroviarie determina notevoli problematiche di esercizio, ambientali e manutentive a cui il gestore deve far fronte in via preventiva. Esistono numerosi strumenti di monitoraggio che con-sentono di valutare lo stato di degrado superficiale delle rotaie con riferimento a diversi criteri di valutazione relativamente alle conseguenze generate. Dal punto di vista dei sistemi tranviari, dove questa problematica è più grave, esiste la difficoltà oggettiva di individuare dei limiti di accettabilità nei riguardi delle irregolarità in quanto queste sono generalmente, per questi sistemi, di entità maggiore rispetto ai sistemi ferroviari. Per questo motivo è stata condotta una campagna di misure su alcuni tratti della rete tranviaria del comune di Roma con attrezzatura CAT (Corrugation Analysis Trolley) per rilevare differenti stati di degrado con il fine di individuare vari livelli di degrado a cui associare altrettanti azioni manutentive. La valutazione delle irregolarità delle rotaie è stata effettuata con riferimento alla procedura descritta nella Norma UNI EN 15610:2009 ottenendo gli spettri in terze di ottava che identificano il contenuto in frequenza della forma d’onda. Tali spettri possono costituire il dato di partenza di modelli di simulazione per prevedere il livello di disturbo ambientale, in termini di rumore o vibrazione, nello spazio circostante al binario, e permettere quindi di stimare quali livelli di irregolarità rispetto alle condizioni di esercizio volute determinano le condizioni ambientali più critiche.The presence of rail corrugation on railway rails creates considerable operating, environmental and maintenance issues with which the manager has to cope in advance. There are many monitoring tools that allow you to evaluate the condition of the rail surface referring to several assessment criteria related to the effects produced. Regarding the tram systems, where this problem is more serious, there is objective difficulty of identifying the limits of acceptability for the irregularities since these are generally, for these systems, of greater magnitude than the railway systems’ ones. For this reason, a set of measurements was carried out on some sections of the tram network of the city of Rome with the CAT equipment (Corrugation Analysis Trolley) to detect different states of degradation the rails with the aim to identify different levels of wear to be associated with as many maintenance actions. The evaluation of rails irregularities was carried out with reference to the procedure described in the standard UNI EN 15610: 2009 obtaining the one-third octave band spectra that identify the waveform frequency components. These spectra can constitute the input of simulation models to predict the level of environmental disturbance, in terms of noise or vibration, in the area surrounding the track, and then allow to estimate what levels of irregularity, for the desired operating conditions, determine the most critical environmental conditions

Involving the private sector in tramway track network maintenance: case study of the City of Rome

A concern of several municipalities is to find the most economic way to keep their tramway track network at acceptable performance levels. This paper uses as a case study data from the City of Rome to estimate the annual cost for the municipality to carry out track network maintenance using the private sector through a form of public private partnership (PPP). Assuming that the private sector partner will be selected through a competitive bidding procedure, it is essential that the municipality carry out a preliminary study to estimate a reasonable level of annual payment required to compensate the private company for the services rendered during the concession life. This paper uses a recently developed financial model to simulate the project financing under several performance levels or standards, specified as the maximum allowed vertical displacement of the rail surface or in terms of the root mean square displacement, both related to a specified spatial wavelength. For each specified level of service, the minimum annual payment to the concessionaire is calculated using the model. The paper assumes that, in view of the relatively poor existing condition of the network, the concessionaire will be required to carry out a replacement of the existing track in the first year of the concession. Two different types of replacement will be investigated. Following the replacement, maintenance operations are carried out through different frequencies of rail grinding, defined as a function of the performance standard specified