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.
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.
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.
Overhead line system is a vital element of any electrified railway infrastructure. Its performance reflects to all vital parameters such as traction, reliability, availability and safety of railway ...infrastructure. Operator GPP Osijek runs a 27.5 km long tramway network which plays a key role in transit system of the city of Osijek, Croatia. In 2016 GPP Osijek applied to a tender for acquisition of new rolling stock with 85% EU investment. Mayor requirement prior to rolling stock acquisition was to document, analyse and upgrade current infrastructure (including track structure, electric substations and catenary) to an optimal level. Task of measurement and evaluation of tram track structure and catenary has been appointed to University of Zagreb Faculty of Civil Engineering. Overhead line analysis comprised from several measuring procedures, including supporting columns evaluation, catenary stagger, height, shocks and wear. Such extensive analysis included GPS positioning and on-site evaluation of 1214 supporting columns of overhead line, as well as overhead line measurements using an instrumented tram vehicle on 18 km of track. For conducting overhead catenary wire measurements, a tram pantograph has been fitted with equipment for measuring catenary height, accelerometers for shock measurement, camera, ruler and GPS for stagger measurement. Catenary wire wear was checked manually from catenary inspection vehicle. To conduct measurements, power had to be switched off on all electric substation along the route and tram vehicle had to be towed by a catenary inspection vehicle. All the data has been analysed and presented to end user in a user-friendly and intuitive GIS environment capable of further updates and detailed analyses. Evaluation of overhead line based on direct measurement results pointed out all the defects and weak spots on the system. It resulted in a series of recommendations for reconstruction and upgrade of the catenary system to fit the need of existing state and further development of tramway network.
The paper gives an overview of concrete noise barrier application in several EU countries and in Croatia. It describes a process of introducing different noise protection solutions on Croatian market ...in the phase of intensive motorway construction in recent years. Namely, an extensive motorway network has been constructed in Croatia in the last 10 years. Following the process of motorway construction, noise protection walls have also been erected. Usage of different building materials and installation processes as well as variations in building expenditures has led to a comparative analysis of several types of noise protection solutions (expanded clay, wood fibre) including a new eco-innovative product RUCONBAR, which incorporates rubber granules from recycled waste tyres to form a porous noise absorptive layer.
In the case o seismic impact on rail infrastructure, even small deformations or damage to track structure can compromise safe operation of rail traffic. Damage can affect track substructure or ...permanent way of the track, but also the electrification system and safety-signalling devices. Ballast prism will suffer damage in case of greater intensity earthquakes, resulting in the reduction of lateral and longitudinal resistance of track structure. Earthquake action may also cause derailment of moving rail vehicles. Operation of rail vehicles also causes certain levels of vibrations, and so an analysis of subsequent effects of rail traffic.
An overview of methods for evaluating comfort on tram tracks is given in this paper. Tramway systems differ in many aspects from standard railway tracks and, therefore, standards developed for ...standard rail lines have to be analysed and evaluated. Equivalent level of vibrations, Sperling ride index, and several methods proposed in EN 12299 are described, and these methods are compared on two trial tram sections 21 km in total length. Conclusions and recommendations for measuring ride comfort on tram tracks are presented.
Rail corrugation is an irregularity that often occurs on a railhead running surface and can cause an increase in the noise and vibration levels as well as faster track deterioration. The ...possibilities of direct and indirect rail corrugation measurements are described in this paper as well as direct rail corrugation measurement that was carried out on a tramway track network in the city of Zagreb. Railhead corrugation was measured on several locations on the tramway track and the values were analysed with respect to the exploitation period of the tramway sections and the type of horizontal alignment. Analysis has shown that rail corrugation occurs more often in the curves than in the straight track and that the wavelength and amplitude of rail corrugation are higher on tramway track that has longer exploitation period. The conclusions of this paper are as expected, but as a next step towards automating the rail corrugation data analysis, the indirect measurements model is tested with the purpose of application on the whole tram track network using tramway vehicle monitoring. Keywords: tramway vehicle; track; rail corrugation; measurement; rail irregularities
Rail vehicles in interaction with a railway structure induce vibrations that are propagating to surrounding structures and cause noise disturbance in the surrounding areas. Since tram tracks in urban ...areas often share the running surface with road vehicles one of top priorities is to achieve low maintenance and long lasting structure. Research conducted in scope of this paper gives an overview of newly designed tram track structures designated for use on Zagreb tram network and their performance in terms of noise and vibration mitigation. Research has been conducted on a 150 m long test section consisted of three tram track types: standard tram track structure commonly used on tram lines in Zagreb, optimized tram structure for better noise and vibration mitigation and a slab track with double sleepers embedded in a concrete slab, which presents an entirely new approach of tram track construction in Zagreb. Track has been instrumented with acceleration sensors, strain gauges and revision shafts for inspection. Relative deformations give an insight into track structure dynamic load distribution through the exploitation period. Further the paper describes vibro-acoustic measurements conducted at the test site. To evaluate the track performance from the vibro-acoustical standpoint, detailed analysis of track decay rate has been analysed. Opposed to measurement technique using impact hammer for track decay rate measurements, newly developed measuring technique using vehicle pass by vibrations as a source of excitation has been proposed and analysed. Paper gives overview of the method, it's benefits compared to standard method of track decay rate measurements and method evaluation based on noise measurements of the vehicle pass by.
The rail-track vibration damping level, as one of key properties for determining proportion of rail track influence in the total rail traffic noise and vibration levels, is estimated in the paper. A ...detailed overview of research conducted so far on dynamic properties of rail tracks is given, and the methods presented are compared on two test sections. The data processing method, various accelerometer positons, and various types of modal hammers as excitation sources, are also considered in the analysis of measurement results. The results obtained by various analyses are compared to each other so as to increase accuracy in the determination of the vibration damping level.
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