Stjepan Lakusic

POSITIVE INTERACTION OF INDUSTRIAL AND RECYCLED STEEL FIBRES IN FIBRE REINFORCED CONCRETE

AbstractIn 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 ...

Testing the shear strength of soft rock at different stages of laboratory simulated weathering

U radu je opisano određivanje promjene cvrstoce temeljeno na simuliranju procesa rastrosbe u laboratorijskim uvjetima, koristeci uzorke lapora iz flisne formacije s podrucja Dalmacije. Na temelju provedenih ispitivanja zakljuceno je da je predloženi postupak simuliranja rastrosbe u laboratoriju provediv unutar prihvatljivih vremenskih okvira. Zbog uocene promjene parametara posmicne cvrstoce na vrijednosti koje odgovaraju cvrstoci materijala koji se opisuje kao tlo, ponekad je potrebno, zbog raspona velicine opterecenja koje se nanosi u pojedinom tipu uređaja, koristiti i uređaje za tlo.U radu je opisano određivanje promjene čvrstoće temeljeno na simuliranju procesa rastrošbe u laboratorijskim uvjetima, koristeći uzorke lapora iz flišne formacije s područja Dalmacije. Na temelju provedenih ispitivanja zaključeno je da je predloženi postupak simuliranja rastrošbe u laboratoriju provediv unutar prihvatljivih vremenskih okvira. Zbog uočene promjene parametara posmične čvrstoće na vrijednosti koje odgovaraju čvrstoći materijala koji se opisuje kao tlo, ponekad je potrebno, zbog raspona veličine opterećenja koje se nanosi u pojedinom tipu uređaja, koristiti i uređaje za tlo.

Analize stabilnosti pokosa metodama granične ravnoteže i smanjenja parametara čvrstoće tla

This paper presents results of comparative slope stability analyses conducted by limit equilibrium and strength reduction methods. Several slopes, taken either from geotechnical practice or literature review, are considered. The influence of tension, distributed load, finite element size and model parameters is analysed in relation to the location, shape of the critical failure surface and the corresponding value of the factor of safety. Both methods provide similar results if they are correctly applied using appropriate software programs.

Toward Noise Modelling in Urban Areas

Noise field measurements are the only precise method of estimating environment pollution. They are long-term and expensive and are not applicable in case of prediction of conditions caused by the new intervention in space. Independent of the bases of available data, which are sometimes very limited, and of the choice of calculation method for reliable prediction of environmental conditions, making the calculation model is an important segment. In that process it is necessary to consider specific features of the location as well as of the model of behavior of all elements in the process of noise emergence (vehicle, traffic surface, machines, devices), significantly influenced by socioeconomic and economic conditions in the country. This paper provides the calculation model for the prediction of environmental noise for three relevant locations in business and residential areas of Zagreb (Croatia) and their verification was done with regard to field measurements.

Proposal for the value of permitted tolerance on width of grooved rails

This paper describes a research in geometry of grooved rails (type Ri 60/R10). The research was carried out in the last seven years (from 1994 to 2001). The measuring of rails geometry was done before building-in of the rails in to the tramway track or during the supervision grooved rails of production in the factory. Special attention was given to the width guide of grooved rails because the technical specifications for grooved rails (VDV OBERBAU Richtlinien) have not defined permitted tolerance for a guide width of grooved rails. Therefore, some difficulties arise from this fact, during production and supervision of grooved rails in the factory. The results of research can serve as a recommendation for the value of permitted tolerance of the guide width of grooved rails. The results can also be applied as a proposal in the setting of European Standard for grooved rails.

Optimisation of railway track maintenance and renewal works by genetic algorithms

This paper describes a new approach to optimisation of railway track maintenance and renewal works via genetic algorithms. Decision support systems and genetic algorithms are used in this study to optimise railway track maintenance and renewal activities. The results obtained in the scope of this study show that planned maintenance and renewal management systems can be developed and successfully used instead of resorting to corrective maintenance activities.

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.

Tram track maintenance-planning by gauge degradation modelling

AbstractTram 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 fa...

Ponašanje slojevito mikroarmiranih betonskih greda izloženih cikličkom opterećenju

Over the past decade, the functional grading has been applied as a new method for the manufacturing of reinforced-concrete elements. The objective of this investigation is to evaluate performance of the functionally graded reinforcedconcrete beams exposed to cyclic loading. The steel and polypropylene fibres are used for the preparation of samples. Concrete beams with full composite action are strengthened with 0.5 to 2 % of steel fibres, and functionally graded RC beams contain 1.3 % of steel fibres. The use of the functionally graded method to reinforce concrete increases the dissipated energy due to the applied cyclic loading.

The Effect Of Tram Track Permanent Way Closure System On The Level Of Noise

The paper deals with the analyses results of the noise level measurements carried out on the five different types of tram track permanent way closure while varying the following key parameters: load, speed and the type of the tram vehicle. The study involves the performance of the tram vehicles that are operating in the city of Zagreb. Measurement results were used for the choice of the system of the tram track permanent way closure. In addition to the noise level, the criteria included the economy of the performance and maintenance as well. The choice refers to the tram track closure system that is not separated from the road traffic, which means that the same traffic surface is shared by the road and tram vehicles. The next closure system proved to be optimal for the tram tracks in a separated lane.