•Behaviour of closed tracks with inadequate drainage in presence of stray current.•Identification of the weakest points in fastening system for the onset of corrosion.•Localized stray current ...corrosion of the rail at the ends of the rail foot.•Degradation of the clip at the points with the highest stress concentrations.•Corrosion protection in urban track with a focus on the fasteners and the rail foot.
In urban railway tracks, the rails serve not only to guide the vehicle, but also as a return conductor for the current the vehicle needs to run. If the rails are not properly insulated, stray current will flow from the rail to the lower part of the track and cause corrosion damage to metal structures near the track. In this study, the damaging effect of stray current on track components (rail and fastening system) was analyzed. The experiment was performed on two identical samples of a rail fastened to the concrete base with a direct fastening system. Both samples were immersed in water, and one of the samples was also treated with a constant direct current from the laboratory power supply via a stainless steel electrode. After 168 days of testing, 3D scans of the rails and clips were made using the ATOS measuring system, comparing the corroded with the reference samples. Applied current caused severe localized corrosion on the rail and rail clips, creating sharp edges that can lead to significant stress concentration under load, accelerate cracking, and contribute to fatigue failure.
The Zagreb 2020 earthquake severely damaged the historic centre of the city. Most of the damage occurred on historic masonry residential buildings, many of which are situated very close to the tram ...track. Although traffic-induced vibrations generally do not affect surrounding buildings, they can be harmful to buildings damaged by a previous earthquake. Vibrations could contribute to the further propagation of existing cracks. The effect of vibrations depends on many factors, one of the most important being the distance between the track and the building. The vibrations are highest at the source, and the energy loss occurs due to transfer through the soil to the recipients. The impact of tram-induced vibrations on earthquake-damaged buildings in the city of Zagreb is investigated in this paper. The analysis is conducted on a tramway network scale to identify critical locations by performing continuous monitoring on the tramway network and risk analysis based on the distance of buildings from the track, vibration amplitude at source, and building damage. Further investigation is based on the level of buildings to evaluate the influence of vibrations on actual buildings damaged in the Zagreb earthquake. Based on detailed signal analysis, the vibration characterization is performed, and the influence on damaged masonry buildings is evaluated.
Urban railway tracks are the primary modes of transportation in many cities worldwide. Track vehicles mostly use DC from overhead lines, and rails are used as return conductors. Because it is ...challenging to fully insulate the rail and ensure high rail-to-ground resistance, current leaks from the rail to the lower part of the track. This current is referred to as stray current. To determine the detrimental effects of stray current on the rail and fastening system components, we performed a laboratory simulation of the stray current on four real-scale samples of the entire rail with all fastening components. The difference among these four samples was the type of fastening system used. Tests were performed under dry condition and at different water levels. After testing, the samples were visually inspected. Under dry conditions, corrosion occurred on the elements in contact with the concrete, and under immersed conditions, the current leaked from all components of the fastening system directly into the water, causing harmful local deterioration. The characteristics of the fastening systems are defined to satisfy other parameters, but not to prevent stray currents and ensure high rail-to-ground resistance. The aim of this study was to demonstrate the effects of stray current on the rail and fastening system and to prove the importance of providing adequate drainage of the track and using a fastening system that is insulated and does not allow the current to leak from the rail.
Despite the long-term experience in the application of noise walls, the uncertainty in wall panel service life efficiency is almost equal between panels built from established and new materials, ...which are—because of the desire to increase the sustainability of noise walls—developing at an ever-faster pace. The presented meta-analysis of data collected during a systematic review of concrete, metal, and wood panels’ acoustic and non-acoustic characteristics, long term performance, and cradle-to-gate sustainability aims to reduce this uncertainty and support the process of noise wall design and management by shifting the emphasis in decision making from construction costs to the long-term sustainability of the road traffic noise mitigation project. The multi-criterial analysis showed that when choosing a panel, preference should be given to those using lightweight concrete materials. A further comprehensive cradle-to-grave assessment of lightweight concrete panels with expanded clay and recycled tire rubber aggregates, which was performed to fill a knowledge gap observed in the literature and identify opportunities for the improvement of lightweight concrete sustainability, showed that the main environmental impacts of these panels are due to their production processes and that the way to reduce such impacts is to use panels made with aggregates from secondary raw materials.
Electrical resistance is among the characteristics that fastening systems must meet to ensure the proper functioning of signaling systems in railway infrastructure. The EN 13146-5:2012 standard ...specifies a laboratory testing method for determining the electrical resistance under wet conditions between running rails provided by a fastening system on steel or concrete sleepers. In urban railway tracks, the electrical resistance of fastening systems affects the stray current; however, there is no standardized electrical resistance measuring method. There is also no definition for the minimum value that the electrical resistance of fastening systems must satisfy to prevent stray currents. For this reason, this paper analysis the possibility of using the standard EN 13146-5:2012 for the measurement and analysis of the electrical resistance of fastening systems in urban railway tracks. In this study, the electrical resistance of different fastening systems used in urban railway tracks was measured. Based on the tests results, the modifications needed in the EN 13146-5 standard for it to be suitable for urban railway tracks were identified. The proposed modifications include the use of a DC current source. The test should be performed on a rail sample fastened to the concrete base, and the current circuit should be closed by the reference electrode installed in the base. Spraying water from nozzles is not applicable for this measurement. The test should be performed under dry conditions and at different water levels (water on the top of the concrete base and on the top of the levelling layer). Different water levels were used to simulate the most common conditions in urban railway tracks built as part of the road surface, where the track-drying process is very slow. The test should not be performed when the rails are immersed in water, because the current flows directly from the rail into the water in such case, and the fastening system has no influence on the measured electrical resistance value. In addition to describing the proposed changes, the calculation of the minimum electrical resistance value that fastening systems in urban railway tracks must satisfy is also presented.
In the track quality analysis, numerical values representing the relative condition of track geometry called track quality indices (TQIs) are calculated along a specific track segment. Segments are ...defined as linear track geometry datasets with the homogeneous characteristics of factors affecting geometry degradation. The 200m-long analytical segment is used most often on inter-city conventional and high-speed rail networks. However, in the case of the small urban rail networks, the homogeneity of track-geometry degradation influential factors is very low. This segment length is usually too long for efficient track maintenance or reconstruction with minimal disruption of the urban traffic. This paper explores the effect of reducing the analytical segment length in the condition assessment of the tram network in the City of Osijek, Croatia. The research had two main objectives: (1) to assess the narrow-gauge tram-track geometry quality through the application of the established synthesized TQIs, and (2) to analyze how a change in the analytical segment length affects this assessment. Two synthesized track quality indices—one based on a weighted value and the other on a standard deviation of measured track geometry parameters—were calculated for the 27.5 km of tracks on consecutive 200-, 100-, 50-, and 25 m long analytical segments. The comparative analysis of the TQIs’ calculation results showed that the reduction in the segment length increased the resolution of the track quality analysis in both cases, while the index based on a weighted value of geometry deviations proved less sensitive to this reduction. These results contribute to further segmentation process establishment and TQIs implementation on tram infrastructure.
Tram track system management is a complex, costly and interdisciplinary process. It involves construction, monitoring and maintenance of track infrastructure and rolling stock, and public transport ...organization. Track management cost reduction requires development of a modern management system that is based on integration and mutual complementarity of engineering and maintenance activities. The first step of its establishment is increasing the proportion of planned predictive-preventive track maintenance at the expense of corrective maintenance. This requires creation of a maintenance-planning model. Its basic prerequisite is the development of a mathematical model of tram track degradation during exploitation. The research presented in this paper describes the creation of mechanistic-empirical models for tram tracks (narrow) gauge degradation by adopting the modelling methodology used on the classic railway constructions. Two types of tram tracks are observed: tracks with indirect elastic rail fastening system and stiffer direct elastic rail fastening system. These models represent the first step towards establishing a predictive maintenance system on Zagreb tram tracks.
In line with current "green" transport initiatives, Croatia plans to build over the next investment period a high speed railway line which will connect central Croatia and its capital with coastal ...regions of the country. According to design documents, the track system will be built using ballastless concrete solutions. In the scope of the project "Concrete track system - ECOTRACK", researchers from the University of Zagreb - Faculty of Civil Engineering analysed a new material, i.e. the rubberized hybrid fibre reinforced concrete (RHFRC), in order to find out whether its properties are adequate for the proposed concrete track system. The RHFRC contains by-products from mechanical recycling of waste tyres (rubber and steel fibres). The study of fibre and rubber interaction and their contribution to mechanical properties of the fibre reinforced concrete is presented, as extensive research on positive interaction between industrial and recycled steel fibres has not as yet been made. The results show that the RHFRC is an innovative, sustainable and cost-effective concrete, which is fully compliant with criteria prescribed in relevant standards.
Tram system is a backbone of public transportation in the City of Zagreb. In the last decade, its fleet has been renewed by 142 new low-floor trams. Shortly after their introduction, it was observed ...that they have a negative impact on the exploitation behavior of tram infrastructure, primarily on the durability of rail fastening systems. Because of that, it was decided to modify existing rail fastening systems to the new track exploitation conditions. When the (re)construction of tram infrastructure is carried out by applying new systems and technologies, it is necessary to take into account their impact on the future propagation of noise and vibration in the environment. This paper gives a short overview of the characteristics of the two newly developed rail fastening systems for Zagreb tram tracks, their application in construction of experimental track section, and performance and comparison of noise and vibration measurements results. Measured data on track vibrations and noise occurring during passage of the tram vehicles is analyzed in terms of track decay rates and equivalent noise levels of passing referent vehicle. Vibroacoustic performance of new fastening systems is evaluated and compared to referent fastening system, in order to investigate their ability to absorb vibration energy induced by tram operation and to reduce noise emission.
The interim railway noise modelling method RMR, recommended by Directive 2002/49/EC, was developed with the aim of creating strategic noise maps for all major railways, as well as for tracks in urban ...areas, and harmonizing the parameters for noise level evaluation. Studies conducted in several European countries have shown that the interim method does not meet local conditions of these countries, and that noise levels determined by this method differ from noise levels obtained by field measurements. Traffic noise modelling in the vicinity of Ivanić Grad Railway Station, located near Croatia’s capital Zagreb, is described in this paper. Noise levels were determined by means of the RMR interim method, recommended by Directive, and Schall 03, German national method that is still widely used in Croatian noise protection practice. Furthermore, two different scenarios were considered so as to determine the impact of railway vehicle dynamics on noise levels. Vehicle acceleration and deceleration segments were defined in detail in the first scenario, while changes in vehicle moving speeds were neglected in the second scenario. Research results have shown that the noise levels determined by the RMR interim method are lower than those obtained by field measurements, and that the Schall 03 noise modelling method presents more accurate results, which points to the pressing need to develop a national railway noise modelling method in Croatia. Previous noise analyses, conducted on other railway stations in Croatia, have also pointed to this problem.
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