Ivo Haladin

The Effect of Rail Fastening System Modifications on Tram Traffic Noise and Vibration

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.

Mjerenje stupnja prigušenja vibracija na klasičnim kolosiječnim konstrukcijama

U radu se ocjenjuje stupanj prigusenja vibracija na kolosijecima, jednog od kljucnih svojstava pri određivanju utjecaja kolosijeka u ukupnim razinama buke i vibracija od prometovanja tracnickih vozila. Prikazan je i detaljan pregled znanstvenih istraživanja na temu dinamickih svojstava kolosijeka, a navedene metode uspoređene su na dvije ispitne lokacije. Nadalje, u analizi rezultata mjerenja razmatra se metoda obrade podataka, razlicite pozicije akcelerometara i razliciti tipovi modalnih cekica kao izvora pobude. Rezultati dobiveni razlicitim analizama međusobno su uspoređeni u svrhu sto preciznijeg određivanja stupnja prigusenja vibracija.

Application of Osijek’s tram tracks geometry analysis results in their reconstruction strategy development

Tram system in Osijek consists of 30 km narrow-gauge tracks served by 26 trams. This backbone of urban public transport is characterized by old age of both system components - vehicles have an average age of about 50 years, and the average period from the last major track section reconstruction is 15 years. In order to ensure safe, accessible and efficient future public transport, network manager GPP Osijek has foreseen the modernization of the fleet via purchase of new low-floor trams. Of course, such investments should be made with great responsibility to the users of public transport, but also to all Osijek’s citizens. It was soon concluded that the renewal of the fleet would not be able to meet the demands of modern public transport in the long run, but that the introduction of new, heavier and faster vehicles would require imminent tracks reconstruction. Due to the high cost of both system components modernization, it became of utmost importance for manager to establish the tenable strategy i.e. the dynamics of the phased approach to tramway network reconstruction. Since track geometry is one of the most important factors for ensuring a safe and comfortable ride, effective planning of phased tracks reconstruction is impossible without the knowledge of its condition and quality across the entire network. This paper describes the procedure and results of the measurement and analysis of the narrow-gauge tram tracks geometry in Osijek, carried out to determine the required investment dynamics in their reconstruction.

Vibro-acoustic performance of newly designed tram track structures

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, its benefits compared to standard method of track decay rate measurements and method evaluation based on noise measurements of the vehicle pass by.

CROATIAN EXPERIENCE IN ROAD TRAFFIC NOISE MANAGEMENT - CONCRETE NOISE BARRIERS

Abstract 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.

Measuring and Simulation of Road Traffic Noise on Rijeka Zagreb Highway

This paper focuses on noise pollution problems of a small town Cavle (suburbs of Rijeka), located near highway Rijeka - Zagreb. Namely, during the construction work of the highway, no noise barriers were planned within the project on this location. Today, 12 years after the construction, traffic load are much higher and so are the noise levels which have exceeded the limits defined by the law. The local population has written petitions to the ARZ Company, which is responsible for the highway maintenance, asking them to find a solution to the problem. In order to meet these demands, the noise levels have been measured and a traffic noise prediction model has been developed. The model incorporates all significant variables, such as traffic load and topographic characteristics of the area. After calibration based on the noise measured and the verification, model has been used in making a solution proposal for noise protection.