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CONTENTS

Dr Veselin Batalović, Dr Dušan Danilović, Dr Marija Živković 237 - 242 MODEL OF OIL AND GAS PIPELINE RINSING USING THE FLUID FLOW

Mr Olivera Medar, Mr Aleksandar Manojlović INTERNATIONAL ROAD HAULAGE INDUSTRY IN SERBIA: 243 - 252 CRITICAL ISSUES ANALYSIS

Mr Marko Nikolić VISITORS’ CENTERS AT ARCHEOLOGICAL SITES IN SERBIA 253 - 258 AS AN IMPUT FOR SUSTAINABLE DEVELOPMENT OF THE COUNTRY

Dr Gradimir Danon, Dr Branko Vasić, Bojan Jokić, Žikica Simović, Marko Marjanović COMPARATIVE ANALYSIS OF CHARACTERISTICS 259 - 266 OF PASSENGER CAR TIRES IN SERBIA

Mr Saša Mitić, Dr Branislav Rakićević, Dragan Stamenković, Dr Vladimir Popović ADVANCED THEORETICAL - EXPERIMENTAL METHOD FOR OPTIMIZATION 267 - 275 OF DYNAMIC BEHAVIOUR OF FIREFIGHTING VEHICLE MODULAR SUPERSTRUCTURES Dr Radoljub Tomić, Dr Predrag Petrović, Dr Tomislav Jovanović CONTRIBUTION TO REVIEW OF THE EFFECTS LEKHNITSKII INFLUENCE TO 276 - 280 DYNAMIC PARAMETERS OF COMPOSITE STRUCTURES

ANNOUNCEMENT OF EVENTS

281

BOOK RECOMMENDATION

285

INSTRUCTIONS FOR AUTHORS

286

EDITORIAL AND ABSTRACTS IN SERBIAN LANGUAGE

288

Institute for research and design in commerce & industry, Belgrade. All rights reserved

Journal of Applied Engineering Science 9(2011)1


IMPRESSUM Naučno-stručni časopis ISTRAŽIVANJA I PROJEKTOVANJA ZA PRIVREDU Journal of APPLIED ENGINEERING SCIENCE The journal publishes original and review articles covering the concept of technical science, energy and environment, industrial engineering, quality management and other realted sciencies. The Journal follows new trends and progress proven practice in listed fields, thus creating a unique forum for interdisciplinary or multidisciplinary dialogue. All published articles are indexed throught international abstract base, Elsevier Bibliographic Databases that includes EMBASE, Compendex, GEOBASE, EMBiology, Elsevier BIOBASE, FLUIDEX i SCOPUS. Ministry of Science and technology development of Republic of Serbia admitted the Journal Research and design for commerce and industry in a list of reference journals.

Publisher Institute for Research and Design in Commerce and Industry www.iipp.rs For publisher: Prof. dr Branko Vasić

Copublisher Faculty of Transport and Traffic Engineering – Belgrade University www.sf.bg.ac.rs

International Editorial Board Prof. dr Robert Bjeković, Germany; Prof. dr Jozef Aronov, Russia; Dr Jezdimir Knežević, England; Dr Nebojša Kovačević, England; Adam Zielinski, Poland; Doc. dr Miloš Knežević, Montenegro; Dr Vladimir Buljak, Italy; MSc Siniša Vidović, USA.

For copublisher: Prof. dr Slobodan Gvozdenović

Publishing Council Editor in Chief Prof. dr Jovan Todorović Assistant Editor Dr Predrag Uskoković

Editorial Board Prof. dr Jovan Todorović, Faculty of Mechanical Engineering, Belgrade; Dr Predrag Uskoković, Belgrade Waterworks and Sewerage, Belgrade; Prof. dr Gradimir Danon, Faculty of Forestry, Belgrade; Doc. dr Dušan Milutinović, Institute for Transport and Traffic CIP, Belgrade; Mr Đorđe Milosavljević, CPI - Process Engineering Center, Belgrade; Prof. dr Miodrag Zec, Faculty of Philosophy, Belgrade; Prof. dr Nenad Đajić, Mining and Geology Faculty, Belgrade; Prof. dr Vlastimir Dedović, Faculty of Transport and Traffic Engeneering, Belgrade; Dr Dejan Curović, Faculty of Mechanical Engineering, Belgrade; Doc. dr Vladimir Popović, Faculty of Mechanical Engineering, Belgrade. ISSN 1451-4117 UDC 33 Papers are indexed by SCOPUS Journal Istraživanja i projektovanja za privredu (Applied Engineering Science) is also available on www.engineeringscience.rs

Nebojša Divljan, Delta Generali, Belgrade; Prof. dr Miloš Nedeljković, Faculty of Mechanical Engineering, Belgrade; Milutin Ignjatović, Institute for Transport and Traffic CIP, Belgrade; Dragan Belić, Transport Company “Lasta”, Belgrade; Dr Miljko Kokić, Zastava, Kragujevac; Dr Zdravko Milovanović, Faculty of Mechanical Engineering, Banja Luka; Dr Drago Šerović, Adriatic Shipyard, Bijela; Vladimir Taušanović, Belgrade Waterworks and Sewerage, Belgrade; Nenad Jankov, Power Plant Kostolac B, Kostolac; Ljubiša Vuletić, National Bank of Serbia, Belgrade; Dušan Đurašević, Euro Sumar, Belgrade.

Editorial Office Nada Stanojević, Aleksandra Stevanić, Miloš Vasić, Miloš Dimitrijević, Institute IIPP, Belgrade; Bojan Mančić, Ivana Spasojević, Faculty of Mechanical Engineering, Belgrade. Printed by: R - print, Beograd Design and prepress: IIPP Journal of Applied Engineering Science 9(2011)1


EDITORIAL Journal of Applied Engineering Science

Prof. dr Jovan Todorović

The Journal IIPP (Research and design for commerce and industry) enters its ninth year of publishing. In the previous 30 issues nearly 190 papers are published. The authors are from universities, scientific institutes, industrial companies, small, medium and large enterprises, from Serbia and several other countries. In spite of a very various subjects, all papers published in the Journal are characterized by direct or indirect connections with economy. It is in a line with main scope and target of the Journal, accepted by its beginning. The published papers deal with development and application of new technologies, new products and production systems, with new management and control methods, in different sectors of economy and commerce.

Having in mind the actual situation in Serbian economy, the intention is to pay a particular attention to the production sector in Serbia, to domestic industrial and other manufacturing units. The Publisher and Editorial board are completely conscious of the fact that only by significantly enlarged and quality improved products in all production’s sectors, especially in industry, in energetic complex, in agriculture and all others, real and necessary conditions for healthy and efficient economy and country progress may be achieved. The corresponding improvements in resources management and environment protection are necessary conditions for a effective and sustainable development of the country. It is linked to the spatial planning and regional development, as well as to corresponding improvements in all important social sectors, science, education, health, culture and arts. It is very broad field of activities, which require serious thinking, large sensibility and persistence and a lot of ambitions. To achieve successes in these undertakings a full engagement of all available intellectual capacities, all scientists, engineers and professionals from all economy sectors is necessary. Their knowledge has to be further improved, in line with the extreme and rapid improvements in today’s technology world. And finally, and may be the most important, it is necessary that all roads of our development shall be interconnected with the corresponding movements in the world, enabling an interchange of ideas and results with engineers, scientists and other professionals from other countries, from developed and those which are in similar transition periods as our country. These assignments of the Publisher and the Editorial board, being accepted from the very beginning, are in a good way demonstrated in the fact that the Journal from the last issue is published in English (with a broad summaries in Serbian). Our wish is to present to international public what we know and what we can, in belief that it is worthy, and to improve communication of our authors with corresponding experts in other countries. At the same time, in such a way, our professionals are motivated to improve practical knowledge of English language, which is a leading language in today’s world of science, technology and economy. In line with that, our Journal IIPP from this issue has a new title in English - „Journal of Applied Engineering Science“. The focus is on all engineering activities, such as development, production, operation, maintenance, management and others.

Prof. dr Jovan Todorović

Institute for research and design in commerce & industry, Belgrade. All rights reserved

Journal of Applied Engineering Science 9(2011)1


Paper number: 9(2011)1,189, 237- 242

MODEL OF OIL AND GAS PIPELINE RINSING USING THE FLUID FLOW Dr Veselin Batalović* Faculty of Mining and Geology, University of Belgrade Dr Dušan Danilović Faculty of Mining and Geology, University of Belgrade Dr Marija Živković Faculty of Mining and Geology, University of Belgrade Pipes and channels, of devices for oil and gas transport are often exposed to impurities (sowdust, soot, grease, products of oil oxidation, crust of oil or scale, etc) that remain after poor quality filtration or are accumulated from the fluid that is being transported. The accumulated impurities reduce the flow cross section and increase pressure loos. The consequences are as following: low efficiency, frequent break downs, increased expenses etc. By rinsing the sediment, a more reliable operation of the hydraulic devices is achieved. The aim of this paper is to consider and present the rinsing procedure and to establish criteria for choosing the most suitable cleaning regime (optimal flow parameters and rinsing time). Key words: Model, Gas, Pipeline, Rinsing, Flow. INTRODUCTION Rinsing of the pipes and channels of hydraulic devices, by fluid flow, is a procedure that has been used for a long time in technical practice. Pipelines of hydraulic installation on: mines, construction works, traffic machines, water supply, fluid supply in industries, gas lines, etc., are rinsed. Numerous procedures (mechanical, chemical, hydraulic, etc.) are used for these operations [2], [10], [11],[13]. Talking of the hydraulic rinsing, which is the topic of this paper, three procedures are used [14], [9]: stationary flow of clean fluid; unsteady flow of clean fluid; mixture flow-clean fluid - gas. For these procedures, the following phases of the rinsing development process, are common [1], [10]: • Removing the remaining particle from the wall of the pipe (channel); • Levitation of the removed particle and drawing it into the flow; • Transport of the removed particle The question, which is of special importance for the technical practice, remains: how and based

on what criteria do we decide on the choice of the rinsing procedure, ie. on the choice of the flow velocity and the time necessary for the rinsing procedure? Unfortunately, there is no specifically defined answer to this question. This paper will attempt to provide an answer, anaylising the rinsing of pipe, using the stationary fluid flow. The answer should be simple so as to enable quick decision that would further provide an efficient solution. REMOVING THE PARTICLE FROM THE WALL OF THE PIPE The condition for removing the solid particle from the wall of the pipe (channels) is defined by the following equation: (1) Calculating the forces: Fo,and Fa is a complex process and the acquired results are inaccurate. Knowing that the resistance force Fo is proportional to the shear stress (the coefficient B depends on the shape of the particle) as a criteria, for defining the force used to remove the

* Faculty of Mining and Geology, Djusina 7, Belgrade, Serbia; batalovic@rgf.bg.ac.rs

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Dr Veselin Batalović and etc. - Model of oil and gas pipeline rinsing using the fluid flow

particle from the wall pipe (channels), we can use the size of the shear stress , Pa.

during the fluid flow of the same characteristics (density, viscosity):

(2)

(4)

Rinsing, using the turbulent flow of the clean fluid, is a procedure very often used in practice.

Two phase fuild flow rinsing (liquid-gas) is more and more often applied due to its efficiency and lower expenses. This procedure typically requires specific equipment for forming and introducing mixtures into the device that is being rinsed. The rinsing efficiency is defined as following:

The fact that this procedure does not involve additional equipment makes it acceptable for most of the hydraulic devices. Practice has shown that shear stress, on the walls pipes (channels) is essential for the quality of particle removal. The value of the sheer stress depends on the stream velocity, and the stream velocity is one of the significant values. The time of rinsing also significantly influences the quality, but the rinsing expenses as well. Since fluids of the same or weaker characteristics than of the working fluids are used for rinsing, the influence of viscosity should be considered as well. Hydralically efficient and shorter process of rinsing is achieved by using the pulsing fluid flow. The accelerated impurity removal from the wall of the pipe (channel) is developed on behalf of the amplitude energy of the shear stress of the pulsing fluid flow [14]: (3)

(5) DRAWING THE REMOVED PARTICLES INTO THE FLUID FLOW The removal process of the solid particles from the pipe wall does not draw the particles into the fluid flow. This process depends on the values of vertical puslations of the turbulent flow. According to the statistical theory of turbulence, the local speed c of the fluid flow can be presented as following: (6) The vertical component of this speed is: (7)

0

- stationary flow shear stress, Pa; - shear stress amplitude, Pa; - Reynold’s number.

These equations can be applied to for laminar flow ie. flow.

for turbulent

The pulsations are produced artificially, by installing a special device in the installation rinsing device (pulsator: piston, valve or some other). The pulsator forms impact waves, in the fluid flow, which remove the particles quicker. In order to compare the rinsing efficiency of the pipe (channel) using the stationary and pulsing flow, it is best to establish a relationship of shear stresses

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The frequency f of pulsation in the turbulent flow, in a pipeline of diameter d is defined by formula: (8) Experiments show that the speed of floating particles co [3] is a variable value dependent of the particle size and that it has a probability characteristic. The probability of floating particles is defined as following: (9) - the velocity of particle (diameter, ds) sedimentations, m/s; - sedimentation time (the particle is increased for the value of its diameter ds). Journal of Applied Engineering Science 9(2011)1, 189


Dr Veselin Batalović and etc. - Model of oil and gas pipeline rinsing using the fluid flow

Therefore, the active force, that brings the particle into a floating state, is the result of the pulsing fluid volume having an impact on the particle of the same volume. The particle movement equation is as following:

(13) Or, considering formula 7: (14)

(10) - particle’s resistance to movement (Stock’s law); - the gravity force. In the moment t=0 csy=0. Having in mind the sedimentation velocity cs the particle velocity, vertically, is: (11) The vertical component of the pulsing velocity csy from formula (11) must provide the following condition: csy>cs. The maximum speed t→∞ is defined by the following equation:

Where is the tablular value of the Gauss distribution. For: s= 7850kg/m3 (sowdust); oil density =850kg/m3; particle diameter ds=100 ; pipeline diameter d=25mm; pipeline length L=2m; resistance coefficient =0,02, the values of probabilities, of bringing the particle into floating state, is in Table 1. TRANSPORT OF FLOATING PARTICLE Particles separated from the pipe’s wall and brought to the fluid flow, need to be transported to the filtration point. Maximum horizontal velocity is [3]: (15)

(12)

The particle trajectory is defined by horizontal cx,max. and vertical sedimentation velocity cs.

The boarder values, of probability changes, of bringing into floating state assuming that the component of the pulsing velocity acts according to the Gauss distribution, can be defined by the following equation

The probability of particle transport is defined by the equation: (16)

Table 1. The separation, transport probability and rinsing time of the 25mm pipeline

Journal of Applied Engineering Science 9(2011)1, 189

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The transportation and the sedimentation time are defined by the equations: (17)

defined by equation: (20) The number of particles that remain: Nio-Ni., at a length L of the pipline is: (21)

- Stok’s number By the analogy with the previous procedure we derive the following function:

From the eqation: (22) We derive:

(18) (23) For the above mentioned conditions, the probability values for transportation are given in Table 1. For successful rinsing, it is necessary to fulfill both of the conditions, ie. it is necessary to separate and transport the impurity particle. Therefore, the probability of simultaneous separation and transport is:

The optimal rinsing time is calculated based on the assumption that only 5% of registered particles is contained in the pipline. This is achieved when the exponent in the equation (23) is equal to 7. If it is adopted that ls=20ds,than from the equation (23) we derive the following:

(19)

(24)

The particle transport is most commonly done in leap of particles, lengths of leap is ls., For the period of time dt, the number of particles included in the separation and transportation process is

The rinsing efficiency, the most favourable regime is best seen in the equation for specific energy consumption, Table 2.

Table 2. Specific energy consumption

LABORATORY RESEARCH OF THE PIPELINE RINSING PROCESS By monitoring the state of the pipeline installation, it is the technologist’s task to predict such a regime of cleaning the pipeline which would provide maintenance of the desired purity class. Based on the shear stress of the rinsing surface, the technologist needs to define the optimal rinsing fluid speed and the time necessary for rinsing, all with an aim to acquire the desired quality of the pipeline purity. In order to achieve this connection, apart from theoretical considerations, it is also necessary to conduct a great number of experiments. For that purpose, a laboratory test facility has been set up, Fig. 1. In the middle part of the rinsing pipeline (1) an implant (2) has been

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installed with artificially imposed impurities. The shear strees gauge (3) measures stress on the pipe’s walls according to the procedure that is similar to the procedure presented in the article [4]. Fluid flow is provided by the gear pump, and the flow is measured by the flow gauge (8). In this phase of research the stationary fluid flow has been used, although the laboratory facility has been set up to operate with unsteady flow as well. The impurities (sowdust) have been imposed on the implant by the process of gluing and drying (acetone). Using acetone for gluing, gives the most realistic connection force (athesia) between the particles and the pipe’s walls. Journal of Applied Engineering Science 9(2011)1, 189


Dr Veselin Batalović and etc. - Model of oil and gas pipeline rinsing using the fluid flow

1. Rinsing pipeline 2. Implant with artificially imposed impurities 3. Measuring the shear stress 4. Oscilograph 5. Charging source 6. Pulsator 7. Gas battery 8. Flow gauge 9. Valve Figure 1. Test device scheme

The roughness of the point where impurities have been imposed is similar to the size of the roughness of new iron seamless pipes ( =0,02). Rinsing of the pipeline is done by the oil flow of

SAE 10 gradation. The number of particles is calculated by the use of microscope. Upon processing the measurment data, the output values are given in Table 3.

Table 3. Shear stress dependency for the oil purity class

DISCUSSION AND CONCLUSIONS

Upon realizing the set tasks, one can conclude:

The problem of rinsing the pipeline of the hydraulic pipes and channels is constantly present in the process of servicing and maintaining in: mining, oil and gas production, construction works, traffic, hydraulic transportation of solids, etc. Using theoretical analysis and experiments we have tried to find valid criteria for the choice of the rinsing parameters (the flow velocity c and rinsing time t) which would provide optimal cleaning regime. The laboratory facility that we had avaliable during this research could not enable a greater speed range, and we therefore had to limit ourselves to operate with speeds up to 20m/ s. Still, we feel, that for industrial conditions, this range can be accepted as realistic. Any speed increase, for real facilities would most often exceed the posibilities of power devices (pumps), and rinsing would therefore entail the introduction of additional equipment, which would further lead to the increase of expenses.

By monitoring the removal and transport process of the solid particles, as the probable value, enables us to choose the most favourable flow velocity, based on the desired quality of solid particle removal.

That the specific energy consumption grows with the speed increase up to a certain limit (10m/s), after which it would soon start to subside, Table 2. This points to the fact that the optimal flow speed should be in the range of 10-20m/s.

By comparing the data acquired on the laboratory facility with the data recommended for the desired cleaning quality values, Table 3, one can conclude that rinsing done using the fluid flow can achieve the class 3 quality, Table 3, which is for a great majority of technical devices acceptable.

Journal of Applied Engineering Science 9(2011)1, 189

For finer rinsing, much greater speeds should

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Dr Veselin Batalović and etc. - Model of oil and gas pipeline rinsing using the fluid flow

be used and longer operation time, which significantly raised the expenses. In the end, we can say that by applying the procedure, that has been presented in this paper, we can easily and quickly acquire technological rinsing parameters that provide us with a desirable rinsing quality, involving minimal expenses.

ACKNOWLEDGEMENTS This paper is the result of the project (Project No 33001) financed by the Ministry of Science and Technological Development in Serbia. We give many thanks to the Ministry of Science for the support that they have provided during this project.

Nomenklature:

REFERENCES 1) Batalović V. (1995), One aspect on a critical velocity definition during hydraulic transportsation of pulp. Proc. 6th Balcan Confrerence on Mineral Processing, Macedonia, pp, 278-281; 2) Batalović, V. (2009) Separacija mešavina gasovito–tečno–čvrsto, Istraživanja i projektovanja za privredu, Vol.7, broj 4 3) Chemical Cleaning and Lube Oil Flushing (2005) Handbook, BJ Services Company 4) Condolios E., Chapus E. (1960) Designig Solids Handling Pipelines, Chemical Engineering, pp. 98-106 5) Etebari A. (2008) Recent Innovations in Wall Shear Stres Sensor Technolgies Naval SurfCE Warfare Center, pp. 22-28 6) Flow of Fluids, (1988) Engineering Department, Crane Valves, Crane Co, USA. 7) Fuels and lubricants (2000) Handbook, (Serbian). 8) Gopal M. (2005) Ash Handling System in Thermal Power Plants, TCE World pp. 1-6; 9) Hil R.A. Et al. (1999) Hydraulic transport of solids, 10) Hiromoto U. Et al. (2001) Rheology and pipeline transportation of dense fly ash-wa-

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ter slurry, Korea-Australian Rheology Journal, pp. 47-54 11) Hutchins G. (1993) Method for cleaning water pipe, US Patent 5178648. 12) Munson B.R. Young D.F. Okiishi T.H. (2002) Fundamentals of Fluid Mechanics, 4th Ed. John Wiley &Sons, USA. 13) Slatter P.T. (2004) The hydraulic transportation of thickened sludges, Water S.A. Vol30, No5 (Special edition), pp.66-68; 14) Svirdov A.N. Vaganov V.M (1985) Pipes cleaning, Vestnik Masinostroenia No11, Moskva pp. 19-21; pp. 33-36 (Russian) 15) Svirdov A.N. (1981) Pipe cleaning by unstable flow, efficiency ana quality, Vestnik Masinostroenia No 10 pp. 33-36 (Russian); 16) http//www.freepatentsonline.com/5178684. html; Paper sent to revision: 01.02.2011. Paper ready for publication: 14.03.2011.

Journal of Applied Engineering Science 9(2011)1, 189


Paper number: 9(2011)1,190, 243 - 252

INTERNATIONAL ROAD HAULAGE INDUSTRY IN SERBIA: CRITICAL ISSUES ANALYSIS Mr Olivera Medar* Faculty of Transport and Traffic Engineering, University of Belgrade Mr Aleksandar Manojlović Faculty of Transport and Traffic Engineering, University of Belgrade The first stage of a transport policy analysis for Serbia’s international road haulage sector is presented in the paper. The objective of the research was to define issues, priorities and possible policy instruments, or their combinations, having the most favourable effect, considering the opinion of the main stakeholders – haulage operators. The determination of key issues in the industry, their ranking and prioritizing by the main group of stakeholders are the base for definition of the objectives, policies and instruments that can guide government action in the sector. Relying on the available data sources and haulier survey results, the basic segments of the industry and their characteristics have been described. Key issue identification, selection and ranking methodology are presented, as well as the results of the study. The critical issues for the industry are also identified and described. Finally, the paper explains issues’ causes and effects, as well the government actions suggested to eliminate or mitigate their negative impact. Key words: Policy analysis, International road transport, Hauliers, Survey INTRODUCTION The road haulage industry is facing many challenges that might undermine its productivity, efficiency and the quality of transport service. Clearly, market fluctuations and declining transport system performances can make road haulage operations very difficult. A full spectre of challenges would also include not only the regulatory instruments covering safety and environmental protection [7], which are likely to create a potential source of significant costs and disrupt the service delivery process, but also unnecessary administrative burdens, procedural issues and undefined responsibilities. Noteworthy, too, are the challenges specific for countries in transition, such as limited access to the market. Road transport is of vital importance for economy and these challenges clearly demand the attention of the public sector and measures to remove or alleviate their effects. The study presented in this paper is a part of the research that defines the methodology behind decision-making in the process of development and implementation of transport policy elements relevant to long distance haulage (international road haulage). The methodology based on a

participatory policy analysis is to enable the creators, actors and decision makers to develop options for formal decision making and approval, and to ensure participation by all interested parties in the regulatory processes. This approach will ensure more significant participation of all stakeholders from the start of the process (i.e. the initiative) [15, 5]. Using this framework for transport policy analysis and instruments for its implementation, will ensure the involvement of all stakeholders and make it possible for fundamental challenges, needs and key issues to be taken into consideration. The objective is to define critical issues, priorities and possible policy instruments or their combinations, having the most favourable effects in view of all stakeholders. The paper presents the characteristics of the international road haulage sector and its segments in Serbia (Title: Industry overview), offering the following statistics: the number of hauliers in Serbia, their share in the total international transport of goods by road, number of vehicles and the structure of vehicle fleet size. Chapter 3 describes the methodology and results of the study, covering, more specifically, the identification of key issues, the consideration of critical issues and the synopsis of strategies for further

* Faculty of Transport and Traffic Engineering, Vojvode Stepe 305, Beograd; a.manojlovic@sf.bg.ac.rsbg.ac.rs

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analysis. Finally, Title Conclusions is offering the concluding remarks. INDUSTRY OVERVIEW Road freight transport is a dominant mode of transport in Serbia. According to the 2006 report by the Statistical Office of the Republic of Serbia, the international transport of goods by road (transit excluded) was twice as large as transport by railway and inland waterways measured in transported tonnes [10]. Serbian road hauliers are the most active in international road freight transport, representing just over one half of total performance (in tonnes) [11, 12, 13] (Figure 1). Of foreign hauliers, companies from Bosnia and Herzegovina, Croatia, Montenegro and Slovenia dominate the sector [10]. The Bosnian hauliers aside, those from the states that are involved in a large-scale external trade (Italy and Germany for instance) do not have an adequate share in Serbia’s international road transport market. This market is not very attractive to them; there are too many obstacles for the transportation process to develop smoothly.

decided that there is an irrelevant number of other hauliers, whose involvement in international road transport is sporadic, and mostly for their own account, or in a limited market only. According to the Annual Permit Distribution Plan, 746 hauliers operated in Serbia at the end of 2010 [9]. In the 2001-2008 period, the number of hauliers more that doubled (Figure 2), but dropped in the following years as the consequence of the global economic crisis; some have left the sector, some have been temporarily blocked. During the same period, similar trends have been noted for a number of drawing vehicles (lorries and road tractors).

Figure 2. Number of hauliers and drawing vehicles Indexes (2001=100), 2001-2010

Figure 1. Share in total international road freight transport by the haulier’s nationality (based on tonnes) [%], 2005-2009

For the purposes of this paper, Serbian hauliers involved in international road transport of goods (hereinafter: hauliers) include the hauliers that have met the conditions for admission to the occupation of road haulage operator, as defined by the national legislation and perform the activity continually over the year; these include the hauliers that participate in the annual distribution of foreign permits (Annual Permit Distribution Plan), which grant them access to the international road haulage market. The authors have

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Apart from the increase of vehicles in numbers, the fleet structure changed in favour of environmentally friendly vehicles, satisfying Euro III, Euro IV and Euro V standards (Figure 3). While in 2001 the vehicle fleet was largely composed of vehicles that did not meet Euro standards (75%), it is the other way round in 2010 – nearly 80% of vehicles meet Euro III, Euro IV or Euro V standards. The procurement of vehicles meeting the latest standards was largely motivated by the prospect of overcoming severe market access barriers (quotas of bilateral and ECMT multilateral permits). Any addition to the existing quotas was only possible by reshaping fleet structure in favour of environmentally friendly vehicles. The 2007 research (see Chapter 3) showed that the permits motivated 69.2% hauliers to buy better vehicles. The other motives include the company’s policy and image (12%), reliability and safety (6.3%), costs (5.7%) and users’ requests (3.1%). Even though the size of vehicle fleet varies, Figure 4 shows that those with more than 20 vehicles account for quite a small share, whereas the Journal of Applied Engineering Science 9(2011)1, 190


Mr Olivera Medar and etc. - International road haulage industry in Serbia: critical issues analysis

Figure 4. Vehicle fleet size [%], 2000–2010

Figure 3. Fleet structure by environmental class [%], 2001–2010

number of vehicle fleets of less than six vehicles is rising again, after a short decline. The average vehicle fleet size increased over the years to 9.8 in 2009. In a 2007 survey (titele: Study methodology and results), the hauliers gave the following reasons for expanding the vehicle fleet: a rise in their permanent customers operations (65%); expansion to new markets (12%); positive business results (10%); the fear of losing a market share (9%). In 2010, as the share of “small” vehicle fleet grew, the average vehicle fleet size fell to nine. In close to 95 percent, these include vehicle combination (articulated vehicle or road train), indicating the prevalence of heavy goods vehicles. Articulated vehicles cover over 80%, whereas the payload of more than 95% semitrailers exceeds 20 tons. Over 80 percent of all Serbian hauliers are engaged in road transport for hire or reward, less than five percent for their own account; the others are involved in both types of hauling. Most of them are performing international operations only and for nearly 50% of them hauling is the sole business activity. According to the data recorded by the Serbian Business Registries Agency, carriage of goods by road is a dominant business activity for nearly 70 percent of hauliers, followed by different trade operations (17%) and production (7.5%). Based on the transport operations, i.e. international transport services, Serbian hauliers reported a total turnover of 35 billion dinars from October 1, 2009 to September 30, 2010. The average turnover per haulier amounts to 45 million dinars, and the average turnover per vehicle close to four million dinars [9]. Journal of Applied Engineering Science 9(2011)1, 190

STUDY METHODOLOGY AND RESULTS Key issues identification The screening process was used to identify key issues. A comprehensive list of all issues was based on a review of similar studies and industry trade publications [1, 2, 3, 4, 6, 14], and discussions with industry and university experts. The criteria for assessing the importance of each issue and their respective suitability for the study were identified as follows: • • • •

the issue has potentially significant effects on hauliers’ productivity and quality of service, the issue has an impact on Serbian hauliers’ competitiveness, the issue is an existing issue, expected to grow in importance in the future, there are opportunities for a public sector reaction to the issue, as well as private sector solutions, where a government role in supporting them is possible, and the issue warrants additional study.

A list of potential issues was presented to the industry experts during a workshop organised in December 2006 at the Faculty of Transport and Traffic Engineering in Belgrade. Industry experts (primarily haulage operators’ executives) were asked to discuss the issues in terms of importance, and to identify additional issues that were not listed. Then a pilot survey was carried out (March 2007) and 41 hauliers were interviewed. A group of questions was designed to cover key issues.

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The workshop debate and pilot survey results served as a basis for the final list of issues prepared for ranking. The 47 issues were arranged in eight groups as shown in Table 1. Time losses include all waiting times and delays caused by traffic bans on heavy goods vehicles, the capacity and condition of infrastructure, administrative actions and the way they are enforced, and bad working practices at loading/unloading facilities. Consequently, delivery times increase and delivery reliability drops. This in turn leads to productivity declines, underexploited available driving hours, reduced fuel efficiency, and more frequent maintenance interventions; additionally, drivers’ turn-over is going up, because time losses diminish their satisfaction and have a direct impact on driver retention. The chain reaction that occurs when one time loss leads to another is a source of additional problems. Some time losses are predictable, allowing for the transport operations to be planned and adjusted accordingly, but some are impossible to predict. In that case, either the risks are taken into account in the planning phase, or the unforeseen loss is covered in the process, usually by disobeying traffic safety regulations (speed, driving hours, rest periods). The costs attached to prolonged waiting times and delays are considerable and unlikely to be transferred to the service user. Cost increases include the increase and instability of fuel prices, rising insurance premiums, the introduction of new taxes and fees and the increase of the existing ones, drivers’ and other costs, which combined constitute an ever-increasing burden on small profit margins in the transportation of goods by road. The cost jumps caused by growing fuel prices, tolls and insurance fall within a global trend the sources of which are unlikely to change in the foreseeable future. A traffic safety policy (prescribing reduced driving times, for instance), charges for the use of infrastructure or a tax policy may also account for these increases, as well as some taxes and charges enforced to compensate for deficiencies in other funding areas. Quite often the fees (i.e. tolls) are too high for the quality of the specific service. Complicated administrative actions keep increasing the costs, and it’s not infrequent that different taxes and fees are imposed unexpectedly and for “virtual” services, often discriminating against certain categories of hauliers.

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Not only can this create direct cost increases, but also the impression of uncertainty and the lack of confidence in the regulatory framework. Another boost to cost inflation is that the quality of certain products, notably fuel, oil and spare parts, is insufficiently or inadequately regulated and/or controlled. Part of the problem is that the costs are both considerable and unpredictable; the frequent cost increases, often unexpected, makes it very difficult to carry out proper cost planning. Many hauliers do not possess mechanisms to absorb quick cost fluctuations, especially fuel price jumps. Secondly, in a sector as highly competitive as this one, it is impossible to transfer the costs to the user by increasing the price of transport service. This particularly refers to unpredictable costs. Acutely prone to this are the haulers whose services are based on long-term contracts, because they are unable to adjust their prices quickly enough to cover the difference. Finally, there is a specific sensitivity to the costs that do not have equal effect on the competition, be they the consequence of different national fiscal and tax policies or discrimination. Unfair competition includes breeches of the regulations covering traffic safety, vehicle dimension and mass, driving hours and rest periods or access to the market. It also refers to transport service price cuts based on insufficient knowledge of the costs and the way they are determined, as well as any attempt to create an opportunity to make a profit based on illegal actions; even though these are criminal actions per se, they are rather treated as actions to create unfair advantage in the market. Hauliers can sometimes use this to survive in the market, either because they have been pushed by both the user and the competition, or because they are unable to use their resources to the full advantage. Likewise, in this way they can cover up for the costs they are unable to manage or transfer to the user. What makes matters worse is the lack of knowledge and awareness of the risks and consequences for traffic safety, company business and the reputation of the haulage industry. Working outside the legal framework is often facilitated by complicated regulations, difficult to implement and control, while poor supervision and inappropriate sanctions only add to the problem. User payment collection covers bad debt, partially collected accounts, delayed payments, Journal of Applied Engineering Science 9(2011)1, 190


Mr Olivera Medar and etc. - International road haulage industry in Serbia: critical issues analysis

Table 1. Final list of issues for ranking Issue

Staff

Legislation

Status

Market access

Payment collection

Unfair competition

Cost increases

Time losses

Group 1.

Congestion

2.

Traffic bans

3.

Border-crossing delays

4.

Inner customs delays

5.

Customers’ working time limitations

6.

Features of loading/unloading points

7.

Waiting due to incomplete documentation

8.

Idle time during visa issuing procedure

9.

Fuel price

10.

Fuel quality

11.

Insurance

12.

Wages

13.

Road charges and tolls

14.

Various taxes and charges

15.

Visas

16.

Vehicle purchasing costs

17.

Hauliers operating without authorisation

18.

Working hours violation

19.

Permits usage violation

20.

Masses and dimensions violation

21.

Criminal intentions

22.

Insufficient cost structure knowledge

23.

Bad debt loss

24.

Payment period extension

25.

Imprecise contract details

26.

Contract negligence

27.

Late payment costs

28.

Insufficient quotas for access and transit

29.

Market narrowed by shortage of permits

30.

Third country limitations

31.

Critical permits allocation

32.

Uncritical permits operational limitations

33.

Hauliers’ status and treatment by government, local authorities, and customers

34.

Dangerous goods transport

35.

Weights and dimensions

36.

Drivers hours and rest periods

37.

Lack of prompt information

38.

Short implementation periods

39.

Implementation issues

40.

Excess of powers and competencies

41.

Enforcement and control methods

42.

Insufficient foreign operators control

43.

Liability of customers, shippers, agents

44.

Lack of skilled drivers

45.

Lack of skilled dispatchers

46.

Lack of skilled sales specialists

47.

Lack of skilled mechanics

Journal of Applied Engineering Science 9(2011)1, 190

extended due dates and breach of contract; the lack of room to define the terms of covering the losses generated by a breach of contract and the costs arising from the process can limit the development of the sector and threaten hauliers directly. The existing legal and institutional framework is the immediate source of this group of problems – the hauliers, in fear of losing the job, are forced to accept the risks of collection, hardly ever suing their debtors. Market access has been reduced by a series of obstacles arising from the existing permit quotas for bilateral, transit and cross-trade transport operations. The transport permits make it very difficult, if not impossible, to operate in certain markets, they complicate the organization of transport processes, reduce work efficiency and create additional costs for the hauliers and users alike. The permit quotas include CEMT permits issued to the Serbia within the multilateral system of quotas, and bilateral permits exchanged between the Republic of Serbia and other states. The number of permits available to Serbian hauliers, which are distributed by the competent authority, does not correspond to their needs. The insufficient quotas are the result of many things, including a very restrictive approach the other states have taken to protect national hauliers or the environment; a focus of interest in another field; poor negotiations or even the total lack of engagement by national authorities in this respect. More often than not the status and needs of the market change too rapidly for the national authorities to react. There is also a number of problems lying in the prescribed national criteria for the allocation of permits to individual hauliers, the way these criteria are actually implemented and the amendment procedure. Status and treatment of hauliers by different levels of the executive authorities, the community and clients are far from satisfying. The executive authorities treat the businesspeople in this sector superficially, casually, largely disrespecting their opinions and views. Even though the average haulier operates with the funds worth close to half a million euros, reports a RSD 45 million turnover based on international transport operations and employs more than 15 people, hardly anyone would treat them as professionals or respected businessmen. On the other hand, what created this attitude is the fact that some hauliers do operate in an unprofessional manner, breaking the rules and destroying the repu-

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tation of the majority never behaving like that. Besides, the national hauliers do not have a shared platform with clear goals to send a common message to the government and represent their interests successfully. Regulations cover the issues of harmonization, implementation, enforcement and supervision, which are all of vital importance to hauliers. There is a flood of regulations in Serbia’s road transportation, ranging from those defining conditions for the performance of the business to those covering daily operations, such as allowed driving hours. Discrepancies between national laws in certain areas, i.e., the transport of dangerous goods, create many impediments in everyday business: it is necessary to conform to both national and international regulations, which, predictably, increases the costs. There are also situations when this is entirely impossible, and a breach is inevitable. As a result, confusion surrounds both transport operations and supervision by inspectors. Apart from the harmonization of regulations that have not been transposed into national legislation, the national laws are also to be harmonized with acquis communitaire, which, in itself, is not a problem for the haulier community as it strives to make business conditions equal for all. The problem however lies in the very preparation of regulations – the process allows for little involvement by the public and clearly disregards the impact analysis of certain solutions. The public usually learns about the changes only after a draft has been sent for adoption or after the adoption, so there is not enough time for adjustment. Moreover, implementation is often inconsistent, which intricate administrative actions and corruption only complicate further. Controls and supervision are ill-organised, often sporadic. In addition, it happens that supervisors are neither properly trained nor committed. Even though regulated by myriad complex rules, there are several areas in the industry that are clearly under-regulated. This has proven to be instrumental in defining the responsibility for the losses occurred due to bad working practice by the user, or a breach by the haulier which is the result of the fault or intention of the user/distributor (i.e. overloaded vehicle). The lack of professional and trained staff: Declining career interest in the sector and the increasing turn-over of drivers and other staff

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are two ever-increasing problems that will gain in importance in the future. This is a very complex issue resulting from the growing needs of the sector. The growing external trade of goods and more stringent requirements for drivers’ working and driving hours directly increase the number of drivers needed. The economic environment has generally improved and produced more employment alternatives, which, coupled with hard working conditions, diminished the interest of potential employees and raised the number of drivers abandoning the sector. The possibility of higher earnings with EU hauliers has additionally cut the number of available drivers, professionals and well-trained staff in particular. The training system for drivers is unsatisfactory and obsolete, and training facilities covering special skills far below the existing needs. Facing the decreasing numbers, the hauliers tend to employ undertrained and undereducated staff, training them as they go and taking the risk of the consequences that insufficiently trained and even medically incompetent drivers might produce. The lack of professional drivers directly increases the costs of recruitment, employment and training of potential staff, as well as the costs of their retention in the sector. Survey Further study was performed in the form of a personal interview survey. Four-category rating scale was used (0 – no impact, 1 – moderate impact, 2 – intermediate impact, and 3 – extreme impact) for rankings to be assigned to the groups of issues and particular issues. The study was carried out from March to September 2007 in the hauliers’ offices. Most of the respondents (90%) were owners/top managers. Apart from ranking the issues with an impact on the effectiveness, productivity and quality of the service, the purpose of the study was to identify characteristics of the sector and its segments (see Chapter 2) along with the overall conditions and modus operandi in the industry. The population whose features and views were the target of the research is composed of the hauliers offering their services in international road transportation. Since there are also hauliers that engage in this business activity occasionally, the sample frame for this research has been based on the following criteria: • The haulier has a permit distribution plan for 2007 and Journal of Applied Engineering Science 9(2011)1, 190


Mr Olivera Medar and etc. - International road haulage industry in Serbia: critical issues analysis

The haulier averagely performs more than two journeys per vehicle per month to or via a neighbouring state.

Based on these criteria, the sample frame includes 460 of 623 hauliers with the fixed annual distribution plan for 2007. A stratified random sample has been established within this framework – within the defined regions, which cover one or more administrative counties (Figure 5), a random choice of hauliers was made from among the hauliers classified by the size of vehicle fleet (small – up to five vehicles; and medium – between six and 20 vehicles) (Table 2). The hauliers with vehicle fleets of over 20 vehicles were the least represented and it was impossible to define a regional random sample, so they were chosen based on the location close to the randomly chosen small and medium ones. The sample included 177 hauliers: 38.5 percent of the hauliers that made up the sample frame and 41.7 percent of the number of vehicles owned by the hauliers. Critical issues The hauliers described the Time losses group as the one that affects their operations the most. The following two were Cost increases and Unfair competition (Table 3). Having studied the inTable 2. Hauliers in the sample classified by vehicle fleet size Vehicle fleet size

Total

Sample frame

Sample

<6

296

194

47

(24.2 %)

6-20

283

224

104

(46.4 %)

> 20

44

42

26

(61.9 %)

Figure 5. Hauliers by place of establishment in the regions as determined by the study [%]

dividual issues and their rankings and the average group ratings based on these assessments (Figure 6) the negative impact of most individual issues is readily observable in the following groups: Market access, Payment collection and Lack of professional and trained staff. Following the analysis of the results, the decision was made to denote as critical those problems which more than 50 percent of respondents say were making their operations very difficult, i.e. having extreme impact (Figure 7, Table 4). The insufficient permit quotas come first, with the average grade 2.65. Seventy-four percent of the

Table 3. Groups of issues – Average and Frequencies of Ratings Group of issues

Average

Extreme impact

Intermediate impact

Moderate impact

No impact

I

Time losses

2,43

102

50

22

2

II

Cost increases

2,33

78

77

19

1

III

Unfair competition

2,02

66

62

27

18

V

Market access

1,89

53

66

44

14

VII

Legislation

1,84

46

64

49

12

IV

Payment collection

1,75

54

49

46

26

VI

Status

1,72

48

45

45

24

1,51

40

51

43

41

VIII Staff

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Mr Olivera Medar and etc. - International road haulage industry in Serbia: critical issues analysis

interviewed gave it a grade 3 (extreme impact). The two following issues were inner customs delays and border-crossing delays, rated 2.62 and 2.57, respectively. The rest of the list includes tolls, fuel prices, permit allocation to individual hauliers, a shortage of drivers and unfair competition based on insufficient knowledge of costs.

Each of the critical issues, including their causes and effects on the haulage industry, as well as potential solutions that could help avoid or mitigate some of the negative effects on productivity and service quality should be discussed in detail. In addition, they are recapitulated [8]:

Figure 6. Issues group average rankings based on average ranking of the group and rankings of the issues in the group

Figure 7. Distribution of ratings for the critical issues

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Mr Olivera Medar and etc. - International road haulage industry in Serbia: critical issues analysis

Table 4. Critical issues averages

Rank Issue

Average

1.

Insufficient quotas of permits

2,65

2.

Inner customs delays

2,62

3.

Border-crossing delays

2,57

4.

Road charges and tolls

2,47

5.

Fuel price increase

2,34

6.

Permits allocation to hauliers

2,33

7.

Driver shortage

2,25

8.

Insufficient knowledge of costs

2,24

Insufficient quotas exchanged between Serbia and some other countries and the allocation of permits to hauliers are highly ranked issues. By positioning insufficient quotas before the number of permits allocated to each haulier, the interviewed actually unveiled a clear attitude toward the allocation procedure: the biggest problem is what is allocated, not how it is done. The long-term strategy is harmonization and integration, while the short-term solutions are activities to upgrade the present position of Serbia in negotiations. Apart from that, permit allocation procedure should be fully transparent and any amendments should be known well in advance. Inner customs and border-crossing delays represent a severe problem in Serbia, as well as in other transition economies. In addition to documentation processing and control activities performed by custom officers, delays are prolonged by the absence of non-stop specific inspections, such as ecological, veterinary, and phytosanitary controls, and by additional controls of doubtful necessity, such as radioactivity controls. During one journey, vehicles are trapped for a couple of days causing inefficient vehicle utilisation (average mileage per year of 110 000 km) and poor quality of service (unreliable delivery). These are problems that demand serious state action to improve facilities, simplify control procedures, improve coordination between different administrations, train and motivate control personnel and fight corruption. Road charging continues to be a controversial issue for the haulage industry, and the emerging charges, together with the costs not easily transferable to customers – a main concern for hauliers. In Serbia, the rates are

Journal of Applied Engineering Science 9(2011)1, 190

not adjusted to the level of services that infrastructure provides, because, in this way, the government is trying to compensate for the lack of funds elsewhere. Possible government and public actions are to minimize highway funding diversions and develop alternative highway funding/pricing options – new and different tax allocation approaches. The increase and instability of fuel prices is a global trend and affects all hauliers equally. Many hauliers have little or no ability to absorb rapid changes in fuel costs. One of the possible strategies is to promote a program to improve hauliers’ fuel efficiency and make savings in fuel costs. Driver shortage has been one of the top three issues in the European and USA haulage industry over the past several years. Driver recruitment, retention and turn-over are the major problems. This issue is looming large In Serbia - drivers are already joining foreign employers (most often Slovenia’s) or leaving the profession altogether due to harsh working conditions. The government should introduce provisions on driver professional competence and establish the criteria for training facilities, as well as adequate testing procedures. Likewise, a government-funded program should be designed to support noncompulsory continuous training initiatives and retention campaigns on non-traditional labour sources. The lack of correct costing has forced many hauliers to perform illegal operations, including driver’s hours violations, wages in cash, illegal use of fuel or lack of insurance cover. Continuous financial training, particularly in basic costing procedures, should be a mandatory requirement for holding a road operators license.

CONCLUSIONS In spite of its considerable economic role, road transport is constantly challenged by largely interdependable, short-term and long-term problems. It is a highly competitive industry where operators work with low profit margins and high barriers, which makes it necessary for the public sector to use different mechanisms to solve these problems or at least diminish their effects. For this purpose, it is necessary to define a set of priorities for the sector, rank the critical issues in the industry and explore different mechanisms

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to address them. The outcome of the study discussed in this paper is that major problems in the sector have been defined and the critical ones underlined. These can be used in the subsequent steps to prepare the options for formal assessment, consultation and decision making. Involvement by all stakeholders at the beginning of the process can allow for the problems to be identified and described properly. It can also open a realistic opportunity for feasible solutions to be identified in order to reach a higher level of confidence in the public sector. This is very important for countries in transition, where a policy impact assessment and relevant decision-making process are usually based on incomplete and unreliable information. It is common knowledge that hauliers are not interested in academic research and do not trust public sector initiatives. The approach described above might help overcome the problem. REFERENCES 1) American Transportation Research Institute (2007). Top Industry Issues 2006: Critical Issues in the U.S. Trucking Industry – 2006, Research Summary for ATA, http://www.atrionline.org/research/results/ 2) American Transportation Research Institute (2006). Top Industry Issues 2005: Critical Issues for the Trucking Industry – Today and Tomorrow, Research Summary for ATA, http://www.atri-online.org/research/results/ 3) Burns R. (2005). Burns Freight Taxes Inquiry Report, http://www.freight-taxes.co.uk/docs/ index.jsp 4) Fleet Management (2004). The Twelve Economic ills facing the Irish Transport Industry, Transport Magazine, http://www.fleet. ie/news.htm 5) Geurts J.L.A., Joldersma C. (2001) Methodology for participatory policy analysis. European Journal of Operational Research, 128 (2), 300-310. 6) ICF Consulting (2003). Evaluation of U.S. Commercial Motor Carrier Industry Challenges and Opportunities, Study Final Report, Washington, DC: U.S. DOT, FHWA, Office of Freight Management and Operations. 7) Kaplanović, S. (2007). Porez na pogonska goriva u transportnom sektoru – instrument

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u funciji zaštite životne sredine, Istraživanja i projektovanja za privredu, Vol 16, pp 39-46 8) Medar O., Manojlović A. (2007). Transport policy analysis: Identification and evaluation of critical issues for the trucking industry, Proceedings, The International Conference Transport Science & Technology Congress TRANSTEC, Prague, 13-15 September 2007, 89-93. 9) Ministry of Infrastructure (2010) Annually Distribution Plan of Permits for 2011: Hauliers Singular Plans (in Serbian), http://www. mi.gov.rs/sektor%20za%20drumski%20tran sport.html 10) Statistical Office of the Republic of Serbia. International flows of goods by modes of transport on the territory of the Republic of Serbia, 2006. http://webrzs.stat.gov.rs/axd/ en/drugastrana.php?Sifra=0005&izbor=odel &tab=49 11) Statistical Office of the Republic of Serbia (2006) Entry, exit and transit of freight road vehicles, by countries of vehicles registration, 2005. COMMUNICATION SV31, LVI (82), Statistics of Transport and Communications. Belgrade: Statistical Office of the Republic of Serbia. 12) Statistical Office of the Republic of Serbia (2008) Entry, exit and transit of freight road vehicles, by countries of vehicles registration, 2006 – 2007. COMMUNICATION SV31, LVIII (170), Statistics of Transport and Communications. Belgrade: Statistical Office of the Republic of Serbia. 13) Statistical Office of the Republic of Serbia (2010) Entry, exit and transit of freight road vehicles, by countries of vehicles registration, 2008 – 2009. COMMUNICATION SV31, LXI (159), Statistics of Transport and Communications. Belgrade: Statistical Office of the Republic of Serbia. 14) Strange N., Michaelis C. (2003). Impact Assessment of the Freight Element of TransportEnergy BestPractice - Final Report, Birmingham, UK: DATABUILD Research & Solutions. 15) Walters L.C., Aydelotte J., Miller J. (2000). Putting More Public in Policy Analysis. Public Administration Review, 60 (4), 349-359. Paper sent to revision: 01.02.2011. Paper ready for publication: 16.03.2011. Journal of Applied Engineering Science 9(2011)1, 190


Paper number: 9(2011)1,191, 253 - 258

VISITORS’ CENTERS AT ARCHEOLOGICAL SITES IN SERBIA AS AN IMPUT FOR SUSTAINABLE DEVELOPMENT OF THE COUNTRY Mr Marko Nikolić* The Faculty of Architecture, University of Belgrade Tourism is over world in intensive development and provides considerable income in many countries. International organization for protection cultural heritage recommends that historical monuments and localities of cultural heritage have to be utilized as tourist destinations also. The presentation of cultural heritage should be realized very carefully, so as to avoid endangering their historical and artistic values. Building various types of “Visitors centers” at archeological sites is one of the most effective ways to present valuable heritage. In Serbia there are several archeological sites which are very interesting for cultural tourism, particularly Viminacijum, Sirmiјum and Gamzigrad. The analysis of existing state at these localities has shown that a significant progress is made. There are plans for further development. However, the already built visitors centers, as well as those which are planned for future, are not based sufficiently on the principles accepted and recommended by world experts and international organizations. Therefore a lot has to be done to include our archeological sites and other valuable localities and monuments in an effective tourist offer. This will create conditions that the archeological sites and cultural heritage in Serbia represent a real input to provide an effective sustainable development of the whole country. Key words: Archeological site, Cultural tourism, Visitors center, Sustainable development INTRODUCTION In the last decades tourism is over world in intensive development and provides considerable income in many countries. Beside that, the tourist destinations are more and more connected to historical monuments and localities of cultural heritage. Even in the famous Venice charter from 1964. it is underlined that it is necessary to pay more attention to istorical urban areas, particularly to those devasted in past times due to the wars, indstrial developments and other human activities, paritularly traffic [1]. It is advised that such areas may be restored for touristic and commerical purposes. Such restoration are in course in many countries. However, in order to provide more profits in short times, restorations often go out of control. Therefore it is necessary that all such activities in these areas, particularly related to tourism, are strictly monitored and controlled. Good examples in this sence are Greek and Italy. It explains why all relevant factors dealing with protection of cultural heritage pay more atten-

tio to tourism. It is supported by a number of conventions and documents dealing with cultural heritage in Europe and adopted at various conferences, as well as the recommenndation Rec(2003)1, defined by Committy of Ministers in charge of cultural heritage of Europen Council in january 2003, under title „Promotion of tourism in order to improve cultural heritage as a factor of sustainable development“. This recommendation is based on previous activities in the European Council, such as Recommendation R(94)7 “General policy of sustainable tourism and tourism development which is in line with environment”, the Recommendation R(95)10 “The policy of sustainable tourism in protected areas”, the Recommendation 1133(1990) “European policy of tourism” and Recommendation 1148(1998) “The need to improve tourism in Central and East Europe” [2], as well as on declarations adopted on congresses of local and regional authorities on European historical cities. These recommendations propose to the members of European Union that in defining their policy of cultural tourist programs take care about necessary protec-

* The Faculty of Architecture, Bulevar Kralja Aleksandra 73/II, Beograd; marconis@eunet.rs

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Mr Marko Nikolić - Visitors’ centers at archeological sites in Serbia as an imput for sustainable development of the country

tion of heritage and use cultural tourism to promote heritage and to develop control methods which will be support sustainable development and encourage people to exploit natural resources in a right way. THE IMPORTANCE OF CULTURAL SITES FOR ECONOMIC DEVELOPMENT The interest for landscapes started in the 18th century by authors which traveled around the world. An American geographer Carl Sauer gave a definition of a cultural site by words “a cultural landscape is shaped from a natural landscape by a cultural group” [3]. In such a way determined sites in our natural environment by human activities obtained cultural values. In before mentioned Venice charter it was explained that the concept of a historical monument have to be understand broadly, which means not only building or construction but urban and rural environement as well, proving about certain civilization, historical development or events, also. The concept of a monumet place is also introduced and in the Convention of the Commitee for world cultural heritage from 1972, it is defined as a combined act of nature and man. In the Convention on protection of architectural heritage of Europe (Granada, 1985) [4] localities are also defined as combined act of men and nature, meaning the areas which are partially arranged and sufficiently and homogenous to be defined topographically and which are of extreme historical, archeological, artistic, scientific, social or professional importance. The Convention for the protection of the architectural heritage of Europe (Florence, 2000) linked a cultural landscape to the necessary sustainable development, based on balanced and harmonized relations between social needs, economy and environment. It is especially emphasized that landscape has an important role not only for environment, but for cultural and social aspects. It has to be understood as a significant potential for economy and as a “fundamental component of people environment, as a sign of equality of their common cultural and natural heritage and a basis of their identity” [4]. The preservation of authenticity is one of the most important problems in all activities related to protection of cultural heritage. It is clearly un-

254

derlined in the “Nara document of authenticity” (Nara, 1994) by a statement that a historical site should be a real testimony of culture and tradition which represents, and that its authenticity should be expressed in material and nonmaterial aspects [4]. Another important problem is preservation of integral site, meaning a position which a certain site got up to date. The identification of possible contemporary functions inside historical sites is of an extreme importance. It is also important to have a good knowledge of the historical site and building inside, which may have an impact on future site development. The “Recommendation on safeguarding and contemporary role of historic areas”, adopted by UNESCO in 1976, advices us that: Each historic area and its environment should be considered in its totality, as a coherent entirety, which balance and specific nature depends on the conditions of the integral units, including not only human activities but buildings, site organization and environment as well. The Convention concerning the protection of the world cultural and natural heritage, adopted by UNESCO in 1972, emphasizes that the target of protection and presentation has to become a factor of further development. Heritage is concidered as a crucial factor of local and regionnal planning in general. The preparation and definition of correspoinding policy of use and presentation of heritage should start with full knowledge and understanding of history and resource potentials, in order to achieve a balanced integration of all relevant factors. It is esential to provide a solution which sould preserve the importance and value of monuments in the history. ARCHEOLOGICAL SITES VIMINACIJUM, SIRMIJUM AND GAMZIGRAD The archeological site Viminacijum is located near the mouth of river Mlava to Danube, at the today’s Kostolac, some 12 km from the city Pozarevac. It was a largest urban settlement in the Upper Mesija and a significant military center. The Roman camp and city originated in the 1st century and lasted until the 7th century. The very first archeological investigation of this site started in the beginning of the 20th century, under the leadership of Mihailo Valtrovic and his assistant Miloje Vasic. These investigations were interrupted and continued from 70is, being active Journal of Applied Engineering Science 9(2011)1, 191


Mr Marko Nikolić - Visitors’ centers at archeological sites in Serbia as an imput for sustainable development of the country

still nowadays [5]. The most significant results are obtained after the year 2000, under the leadership of Miomir Korac from the Archeological Institute in Belgrade. In this period of time the modern methods and technologies were used (satellite and air recording, geophysical investigations). The remnants of the North door of Military camp, parts of Terms and Mausoleum with several tombs were uncovered. The remnants of two memories, triconhosne graves and the Rustic villa were found, as well as parts of a large settlement, and a 1000m of a Roman aqueduct. Today there are archeological investigation and uncovering of a large Amphitheater.

tion. It will be organized around seven atriums. It will have laboratories for scientific investigations, accommodation capacities and necessary economic and service part (Figure 1 and Figure 2).

The presentation of the North door of Military camp, parts of uncovered Terms and Mausoleum started after the year 2000. The permanent protecting building realized with laminated wood was erected. Some new objects were built, as an entrance hall, souvenir shop, coffee bar and sanitary block with toilets. In last few years there are plans to build a Visitors’ center, as a copy of the Rustic villa, and to present immaterial heritage [5]. The Rustic villa is a new building at the archeological site. This building or Viminacijum center has a multiple function, in commercial and scientific sense. It is a component of the complex, beside the roman settlement and military camp. The Viminacijum center is imagined as a place which enable gathering of business and intellectual elite in an ambient of old roman city and military camp. In other days it will be open to visitors and tourists. It means that the Center will have several levels: scientific and research, education, marketing, all in function to promote the Center as an attractive scientific and tourist loca-

Figure 1. Viminacium, Visitorscenter atrium Journal of Applied Engineering Science 9(2011)1, 191

Figure 2. Viminacium, Visitorscenter atrium

With such plans and programs the Center will contribute to improving cultural and economic situation in this region – Branicevo, and in particularly to enrich tourist offer. Since the Viminacijum is located on an attractive place close to river Danube, there are already a number of arrangements with European ship operators, it is expected that some 70.000 tourist will visit this site in the year 2011. It will enable more employment on local and regional level and an important sustainable development [6]. The archeological site Sirmijum, today’s Sremska Mitrovica, is an antic city built in the 1st century, on the mouth of river Bosut to river Sava, on the south hillsides of mountain Fruska Gora. The first sketches of Sirmijum are made by count Marsilio at the end of the 17th century. He noted in these drawings all that was visible from roman architecture at that time. However, the first serious investigations on this site started in 50is of the 20th century by Regional office for protection of cultural heritage in Novi Sad. Later, from the

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Mr Marko Nikolić - Visitors’ centers at archeological sites in Serbia as an imput for sustainable development of the country

1962. the investigations were taken over by the Archeological Institute, in cooperation with the Museum of Srem and the Institute for protection of cultural monuments in Sremska Mitrovica.

his book Bergmanische Reise in Serbie im Jahre 1835. During the second half of the 19th century a known archeologist, traveler and writer Felix Kamnitz paid particular attention to this locality.

The most important building complex, the remnants of Residential Palace, was undercover in 1956. Since only a smaller part is undiscovered, it is not clear neither internal space organization, or the total dimensions were. Hippodrome, warehouses, corn depots are uncovered in the palace. A very important space complex is undercover in closeness – Villa Urbana, the area of public terms (Terms Litinie), public corn depot or Horeum. The remnants of Forum, craft and commercial complex, apartment’s blocks and street collectors are also undiscovered [5]. In last several years a particular attention is paid to organization and presentation of a part of Imperial Palace. The remnants of the palace are covered by a permanent structure, opened for visitors in the 2009. This new building, beside the protection, has a function of a Visitors’ center also. The center include a gallery for selling souvenirs and publications, wardrobe, coffee bar, official block for personal, depots and pantry, as well the rooms for custodians. Construction of the building is realized by laminated wood. Above archeological remnants there is a light steel construction, with trails for visitors, enabling full view of the site in the whole [7] (Figure3 and Figure 4).

Figure 3. Sirmijum, Visitors center

The archeological site Gamzigrad, a late antic imperial palace Romuliana, is built in the Eastern Serbia, in the valley of river Timok, some 11 km from city Zajecar. The first description and evaluation of the site is given by Baron Von Herder, in

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Figure 4. Sirmijum, Visitors center construction

Investigations of Gamzigrad started in the 1950. when Djurdje Boskovic made first layout of the fortress, indicating the most important buildings in its interior. Archeological investigations started by the National Museum in Zajecar, while excavating were organized by the Archeological Institute. The works on protection of the uncovered buildings were committed to the Yugoslav, or later to Republic Institute for |Protection of Cultural Monuments. The remnants of old and younger fortification were undiscovered. In the north part of the fortress remnants of a Church, Palace 1, Palace 2 and a big building with corridor were undiscovered, and in the south part remnants of a Church, Horeum, Tribunal and Thearme [7]. Similar to other archeological sites in Serbia, for Gamzigrad are in course designs of a new permanent building for protection and presentation of these valuable findings. The design of the Visitors’ center is already finished. This new building will be in the wide zone of site protection, some 500 m from the fortress, enabling the complete look at archeological remnants. The complex is designed with separate functions located as separate buildings: space for visitors, lodging area for researchers and investigation and research center. Area for visitors has a large hall for guests, souvenir and publication shop, ticketing office, offices with library, rooms for security and technical staff and guides, multipurpose hall and sanitary block. The lodging area has twin beds rooms with bathrooms. The investigation and research center has laboratory with workJournal of Applied Engineering Science 9(2011)1, 191


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ing areas, a hall for lectures and presentation, a workshop and a sanitary block. There are also

ten rooms for accommodation of researchers, dining room and studio (Figure 5).

Figure 5. Gamzigrad, Visitors center project

CONCLUSIONS The international conventions and recommendations have important impact to the changes of perception and relation towards protection of archeological sites and presentation of remnants of buildings in these sites. It is very important because historical areas with remnants of archeological building are in essence cultural landscapes, particularly those outside today’s urban areas, and may be characterized as cultural areas, in which the mutual and unbreakable connections between material remnants, as result of human activities, and natural environment is evident. It may explain what influenced people to stay in these areas in ancient times, to build their settlements and various buildings. Archeological sites may be considered as landscapes or organic nature, because they most often are results of certain social, administrative or religious needs. In today’s form they represent a form of interconnection with environment, or as a response to natural environment. The modern time and needs for revitalization and space utilization require a more active approach to the restoration or building redesigns, as well as erecting new buildings, enabling better utilization. Partial or total restoration, or redesign, so as to achieve previous look and authenticity, has also an educative importance, for understanding the importance of the position and purpose Journal of Applied Engineering Science 9(2011)1, 191

of the space, tradition, rituals and similar, as well as its natural characteristics and values. A problem of preservation of place integrity, the status which it obtained up to nowadays, is also very important for all archeological sites. Their protection and presentation represents therefore a very complex task, which have to include all actors in planning and managing. A certain balance has to be made between the present state and planned intervention in aim to protect and utilize the place. The construction of visitors centers should be realized with an adequate relation to the heritage, but with modern materials and designs, so as to provide effective protection and presentation. These centers should be included in contemporary life, using media and new IT technologies. They also have to enable an effective development of cultural tourism. Archeological heritage in connection with natural environment is considered today as one of the basic components for all regional planning, and for society development in general. Therefore it is necessary to affirm the roles which they have as elements of cultural landscape and factors of sustainable society development, based on balanced and harmonic relations between the needs of smaller and larger social subjects, between industry, economy and environment. It means that archeological sites should be considered not only on regional, but particularly on

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local level, with intention to improve the activities of local authorities. Similarly, an important role should have nongovernmental organizations. It is worthwhile to underline that archeological sites described in this paper, which are the most important in Serbia have not based sufficiently on these principles. Therefore a lot has to be done to include these valuable sites and localities in an effective tourist offer and to create conditions that the archeological sites in Serbia represent a real input to provide an effective sustainable development of the whole country. REFERENCES 1) Jokileto, J. “New international trends in protection of cultural heritage” (in Serbian), Гласник Друштва Конзерватора, бр. 27 (2003), стр. 10. 2) European conventions and recommendations on cultural heritage (in Serbian), Котор: EXPEDITIO, 2005), стр. 50-54. 3) Stovel, H., “The cultural landscape: new approach to protection of cultural heritage” (in Serbian) Гласник Друштва конзерватора Србије, бр. 27 (2003), стр. 14.

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4) Jokileto, J. „Conservation between theory and practice” (in Serbian), Гласник Друштва Конзерватора, бр. 27 (2003), стр. 11-12. 5) Nikolic, M.: A comparative analysis and valorization of principles and methods of protection and presentation by examples of characteristic archeological sites in Serbia (in Serbian), Mr. Thesis, Faculty of Architecture, Belgrade, 2010. 6) http:// www.viminacium.org.rs 7) Nikolic, M.: The possibilitis of protection and presentation of urban complex by example of archeological site Sirmium, Proc. of the 5th Regional conference on integrative protection – integrative conservation and sustainable development (in Serbian), Banja Luka, 2010 Paper sent to revision: 01.03.2011. Paper ready for publication: 21.03.2011.

Journal of Applied Engineering Science 9(2011)1, 191


Paper number: 9(2011)1,192, 259 - 266

COMPARATIVE ANALYSIS OF CHARACTERISTICS OF PASSENGER CAR TIRES IN SERBIA Dr Gradimir Danon* Faculty of Forestry, University of Belgrade Dr Branko Vasić Faculty of Mechanical Engineering, University of Belgrade Bojan Jokić Faculty of Mechanical Engineering, University of Belgrade Žikica Simović Faculty of Mechanical Engineering, University of Belgrade Marko Marjanović Faculty of Mechanical Engineering, University of Belgrade The paper presents the results of the condition and characteristics of tires that are in use in Serbia. Data on wear patterns, sizes, ages, brand, type, more than 700 tire and vehicle information to which they are mounted. Data about tread depth, dimensions, tire age, brand and type of more then 700 tested tires were gathered, as well as information about vehicles to which they are mounted on. Primary conclusion on tire condition is positive, notably better then than the Serbian vehicle fleet condition. Average age of tires was around three years and measured tread depth about 5 mm. A significant part of the examined vehicles was equipped with winter tires. First survey (Belgrade, November 2009) for winter tire usage had good showings with around 25% cars equipped with such tires. During the second survey (Belgrade, July 2010) decline of about 5% was found. In Užice, where survey was conducted in November of 2010 it was found that the percentage of winter tires increased up to 50%. Structure and age of the passenger cars fleet in Serbia have been assessed as unsatisfactory. With the current level of fleet renewal such a situation will be very slowly changing for the better and that will affect both the structure and characteristics of tires that will be bought in Serbia in the coming years. With the current level of renewal of the fleet, such situation will be very slowly changed for the better that will affect the structure and characteristics of tires that that will be purchased in the coming years in Serbia. Keywords: Tires, Winter tires, Tread depth, Tire age, Car age. INTRODUCTION Tires are very important for safety of transportation, its economy and comfort. They are subject to a diversity of use and operating conditions: depending on the vehicles they are mounted on, way of use and maintenance practice of their consumers, the environment in which they operate, and random events that can cause damage or affect their operation. The kind of tires used in some countries, the way they are used and their overall condition depends on the level of knowledge, taste and financial situation of its citizens as well as on the charac-

teristics of the vehicles used, road network condition, climate and many other factors. In order to see a real picture in the field of tires in Serbia the following has to be considered: Serbia has a population of 7.4 million and about 1.5 million passenger cars in use in 2008 (Table 1). As a result, there are about 202 cars per 1,000 inhabitants. These numbers makes Serbia medium motorized country. Average household in Serbia has 3 (2.97) members. With an assumption that 7% of passenger cars [7] are used as a second car in household, it is easy to calculate that about sixty present of the households in Serbia have at least one car.

* Faculty of Forestry, Kneza Višeslava 1, 11000 Beograd; gradimirdanon@gmail.com

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Table 1. Registered passenger cars in Serbia between 2004 and 2008

Registered cars in Serbia

Year 2004

2005

2006

2007

2008

2009

Total registered cars 1,422,578 1,481,497 1,511,837 1,476,642 1,486,174 1,637,002 First registered cars 85,430 42,286 67,044 77,303 87,284 126,382 First registered new cars 21,197 21,523 25,530 32,684 36,085 44,682 Imported used cars first registered in Serbia

64,233

20,763

41,514

44,619

51,199

81,700

Sources: Republic of Serbia Ministry of Interior and Association for Motor Vehicles Manufactures of Serbia

Table 1 shows that the number of the first registered cars increased slightly, but on the other hand the total number of registered cars in Serbia stagnated up to 2009. A possible reason was that the number of written off cars in the monitored years was only slightly smaller than the number of first registered ones. According to the preliminary data in disposal (the data had certain illogicality) number of cars in use has risen by 10%. Simultaneously the number of the first time registered cars was also on the rise. Direct comparison between 2004 and 2009 statistics is 21,197 to 44,682 respectively. The number of used cars (imported from abroad) also grew in this period.

The first oscillation in the number of first time registered used cars happened between 2004 and 2005. The application of the new regulations regarding vehicles import started in 2005. The second change was caused by the Government decision to allow unconditional three-month import of used cars in 2009. Interestingly, it did not hinder the rise in number of new cars. This happened primarily due to the Government subsidies for the purchase of Fiat Punto models. The average age of registered vehicles in Serbia in 2008 was about 16 years. More than 55% of vehicles were older then 15 years (Figure 1).

Figure 1. Cars in Serbia – Age Distribution in 2008 [2]

The average age of vehicles has not changed significantly regardless of new purchases in tha last five years [3]. A possible reason was that purchases of new cars were still insignificant (only 3% of registered vehicles). This situation was also affected by the large import of used cars, which were from four to seven years old. Based on the research that the “Synovat” Company and the Serbian magazine “Vrele gume” [10] carried out in 2008, the structure of the Serbian fleet with respect to manufacturers and brands presented Zastava and Fiat models as one third of all registered cars, followed by Opel

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and Volkswagen. All these cars had up to 1.4 litre engines and belonged to the group of small cars. Cars sale in 2010 confirms this. Figure 2 gives an insight to sales in year 2010, made class-wise [5]. As shown in diagram, class B cars represent 50% of the total sales, with models like Punto (30.31%), Dacia (8.83%) and Škoda (8.34%) which dominate the market [5]. Currently, there are three tire plants operating in Serbia. These are: Tigar Tires from Pirot, Trayal Corporation from Kruševac and Rumaguma from Journal of Applied Engineering Science 9(2011)1, 192


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Ruma. However, there is a fourth tractor tire factory in Belgrade, named Rekord whose production has been stalled for a long time.

Figure 2. Passenger cars sold in Serbia by for 2010 – Distribution by vehicle class [5]

Tigar was founded in the year 1935. The first radial passenger tire produced in Serbia was made in Pirot in 1972. Two years later, Tigar started the cooperation with BF Goodrich from the USA. When Michelin took over Goodrich in 1997, Tigar signed the Joint Venture Agreement with Michelin North America. Presently, the tire factory is a part of the Michelin group with the new name “Tigar Tyres” and the production of 6 million car and light truck tires per year. Trayal Corporation was founded in the 19th century. Factory’s name and its modern production of road vehicle tires date back to 1974 as the result of the joint venture and technology adopted from French factory Kleber. The current owner of the company is the Bulgarian company Brikel. Trayal’s average production over the past five years has been 1.8 million tires, 1.8 million tubes, plus another 700,000 two-wheeler tires. Rumaguma has been operating in the rubber industry since 1981. In 2003 the plant was bought by company Galaxy from USA. In 2008 Czech company Mitas has taken over the factory from Galaxy. Rumaguma produces the tires for heavy vehicles, agricultural machines and building machines. Factory has a production capacity of 15,000 tonnes of tyres per year. The production of car and commercial vehicle tires in Serbia in 2008 was about 8 million pieces. In 2008 approximately 1,500,000 tires for passenger cars have been sold. It amounts to one tire per registered vehicle in Serbia in 2008. The market share of domestic manufacturers was slightly higher. Journal of Applied Engineering Science 9(2011)1, 192

MATERIALS AND METHODS This paper is about characteristics and condition of tires used in Serbia, as well as about vehicles utilising them. Majority of research (3 out of 4) were conducted by University of Belgrade - Faculty of Mechanical Engineers. It took place in period of two years: October and November 2009 [6] and June and July 2010 in Belgrade [8], and in December 2010 in Užice [10]. These researches have been part of student’s diploma works [5, 6, 8]. Total number of cars surveyed was 842 with 592 (244+348) cars in Belgrade and 250 cars in Užice. Cars included in Belgrade survey were found on parking spots near faculties, public buildings and shopping centres. For the purpose of this research, measurement of tread depth was taken by “Мitutoyo 571-100” depth gage.

Figure 3. Depth Gage “Мitutoyo 571-100”

In addition, for the observed tires and vehicles the following data were recorded: • Vehicles: brand, type, model, year of a model launch (estimated), year of production (estimated); • Tires: tire size, tire width, tire design (winter or no winter use). There was an intention to engage measuring tire pressure in the research. From this we gave up, regardless of its importance for the tires reliability and lifetime [4, 1]. We gave up because it was impossible to obtain the approval of the absent car owners for such operation. Form used for gathering data for further analyzes is shown on Figure 4. Survey in Užice was concentrated on gathering information from vehicles brought to technical inspection, and was further expanded to cars on public parking lots. Similar survey organized by “SAT Plus” automo-

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bile magazine took place in November 2010 [9]. The journalists interviewed, with the help of traffic police, about 20 passenger vehicles (120 tires) on the main road Belgrade – Užice.

Figure 4. The form that was used to record data

THE RESULTS AND ANALYSIS OF THE RESULTS A part of the research results is presented in this paper. The first part of the results is related to the characteristics of cars that are observed. Analysis showed, as expected, that the largest number of the observed vehicles were Fiat and Zastava models, mostly small cars, such as Yugo, Punto and Panda. In Belgrade these were followed by the Opel models i.e. Kadett, Corsa and Astra.

VW Polo and Golf models, and Felicia and Fabia “Škoda” models (Figure 5) succeeded. In Užice the situation is similar except that the Opel and VW brands swap their places. The age distribution of the observed vehicles during the survey is shown in the Figure 6. The age of model of vehicles was estimated based on the data obtained from the drivers or from a catalogues or Internet. The average age of cars included in the re-

Figure 5. Structure of the Observed Vehicles – Manufacturer distribution [5, 6, 8]

Figure 6. Observed vehicle Characteristics - Age Distribution [3, 5, 6, 8]

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search was lower then the average age of Serbian passenger car fleet. Note that the average car age was lower in Belgrade surveys opposing to Užice.

Also interesting is the analysis of year when the models of observed cars were launched. The results conducted in Užice are presented below (see Figure 7).

Figure 7. Observed vehicle Characteristics – Model Age Distribution [5], location Užice

The figures 5, 6 and 7 clearly suggest that customers choose older (and cheaper) vehicle models. In Užice, 20% of vehicles in the control group were younger than 5 years, but only 5% of that number is models younger than 5 years. A good example is the best-selling car in Serbia Punto

which is last time redesigned by FIAT in 2003. The second part includes the results for observed tires including the type and brand of tires. Diagram on the Figure 8 shows tire brand distribution on surveyed vehicles with a notation that the only tire measured was the front left tire.

Figure 8. Tires on Observed Cars - Tire brands distribution [5, 6, 8, 9]

Most reviewed cars have Tigar Tyre tires as it is shown in the Figure 8. Michelin, Sava, Kumho, Continental, Goodyear tires follow. There are some differences between surveys conducted in Belgrade and those in Užice where Sava (14%) and Trayal (6.4%) tires have a considerable share. Research on “Ibarska magistrala” conducted by “Sat plus” have shown bigger share of Tiger tires (38%). Furthermore, the research also included the analysis of a tread depth on the observed tires. The first conclusion was that the observed tires Journal of Applied Engineering Science 9(2011)1, 192

were in a satisfying condition (Figure 9). Average measured tread depth was about 5 mm. This turned out to be far better than expected in the onset of the study. Only two percent of observed tires were below the legal limit (1.6 mm). It is important to mention that more than 70% of the observed tires in Belgrade have more than 4 mm of tread depth, which should guarantee a good grip in wet and winter conditions. Situation in Užice is even better with 84% of tires with more then 4 mm of tread depth. This is logical if one takes into account where the survey was conducted (vehicle technical inspection).

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Figure 9. Tires on Observed Cars – Tread depth distribution [5, 6, 8]

Results of measured thread depth in “Sat-Plus” survey (Figure 10).

Figure 10. Tires on Observed Cars – Tread depth distribution [9]

Results are even better with 89% of vehicles with tires with tread depth deeper than 4 mm. However, a number of vehicles (2%) had worn tires. According to [9] the lowest value was 1.27 mm. A considerable number of vehicles were equipped with winter tires, which is understandable if we

take into account that the research was conducted at the end of autumn 2009 in Belgrade, and nearly in same time in Užice in 2010 (Figure 11). The average tread depth on winter tires (Belgrade) was slightly higher than the overall average and amounted to 5.87 mm [3, 6, 2].

Figure 11. Winter Tires on Observed Cars – Tread Depth Distribution [2, 4, 5, 10]

Winter tires were found on every fourth vehicle (at least at the front wheels). In Užice situation was even better [5]. Winter set of tires were found on half of observed vehicles (51.2%) with the average tread depth nearly same as in [6]. The results of research of tire sort published in

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[9] are shown in Table 2. From the presented data it is clearly concluded that the 76% vehicles from all those observed, had at least one winter tire. Rest had summer tires (20%), and (4%) so called “all season tires”. Journal of Applied Engineering Science 9(2011)1, 192


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Table 2. Sort of tires on observed vehicles [9] All winter tires

46%

All summer tires

20%

Winter tires on drive axle

20%

Winter tires on no drive axle

10%

Universal – All season tires

4%

Total

100%

It is important to say that the all season tires despite its undoubted quality cannot compare with winter tires. All season tires didn’t pass winter condition tests so it can not be part of winter equipment proposed by the Law. Positive thing is that the most of the vehicles have winter tires despite the fact that the law on obligatory use of winter tires is not up till 20112112. In November 2009 this percentage was 25%, in November 2010 even 50% and, to our pleasure, passenger cars checked on the road had winter tires in 76% cases. This may be caused by increased awareness of the drivers regarding changed regulations announced by new Law. Shown numbers go down after taking

into account July and August research done in Belgrade in 2010. In July share was 20 %, slightly lower then the November 2009 reading. However, as seen before, not many of them decided to store tires for next winter season and used them during summertime period. For survey period July and November 2010 [5, 8, 2] age of tires was concluded from the research. Special code written on the side of the tire that can trace to the exact date of production of the tire was taken. Figure12 shows placement of production years among control sample. Almost 70% of control tires in Belgrade are manufactured after 2006, and the average age is less the 3 years (2.86). Only 6% is older then 6 years. Survey in Užice, once again, had different results governing the fact that was already discussed, with 20.8% brand new tires used. Further, this reflected on average age of 2.77% and on the fact that no tire older then 8 years was found. However, the number of old tires which have to be replaced is greater (8.4%). Survey conducted by the Sat-Plus gives slightly, but not much, different results (Figure 13).

Figure 12. Tires on observed cars - Age distribution [5, 8]

Figure 13. Tires on observed cars - Age of controlled tires distribution “Sat – Plus” [9] Journal of Applied Engineering Science 9(2011)1, 192

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Survey done on Ibarska Magistrala showed higher average age then the one done by the Faculty of Mechanical engineering [5, 8]. Around 16% of tested tires were older the 8 years and no matter their preserved condition, they had to be replaced. CONCLUSIONS Before giving any conclusions, it must be taken into account that this was not an extensive study. Survey included only around 1,000 vehicles. The surveys were carried out in Belgrade, Užice and on the road Belgrade - Užice. For the purpose of this research, the tread depths were measured only on left front wheel. Regardless of possible remarks, certain conclusions are unquestionable. The situation in Serbia in regard to tires may be defined as satisfying. The results from the research showed that tread depths are in most cases deeper than it is legally required (1.6 mm). Only small part of the observed tires (less then 1%) was below this limit. It is worth mentioning that more than 70% of observed tires have more than 4 mm of tread wear depth, which should guarantee a good grip for both wet and winter conditions. Such positive results may stem from the recently enacted Law on road safety which imposes more rigorous penalties, among others, for driving with improper tires. This is particularly relevant for the increase in purchasing of winter tires. Observed average tire age was satisfying. 8% of tires is older than 6 years and according to the criteria established by Mechanical Faculty in Belgrade, those tires are considered to be old and fall into expired category [5, 8, 2]. During road surveys [9] situation were much worse. There was found that 16% of tires were older than 8 years. The Serbian tire market is widely open. Also, drivers have a wide range of products to choose from. Owing to the strong domestic industry, more than 30% of tires purchased in this country were manufactured in Serbia. The remaining 70% were mostly imported from Europe, though they have lately been imported also from the Far East. Number found in Belgrade was around 30%, while Užice had 37% which was similar to the finding of the SAT plus journalists.

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Finally, as the Serbian car fleet continues to change, slowly though, the choice of buyers will simultaneously modify. The owners of newer, bigger and more expensive cars would prefer to buy premium tires with modern design which will eventually affect the traffic safety and environmental protection. REFERENCES 1) Danon G., Mitrović, Č.: Possible Beneficial of Application of TMPS on city buses. Istraživanja i projektovanja za privredu Vol 6 (21), 2008: pp 35-44 2) Danon, G., Vasić, B., Simović, Ž.: Kakve pneumatike vozimo, VI naučno stručni skup “Pneumatici 2010”, Zbornik radova, Zlatibor, 2010: pp 1 – 7 3) Danon, G., Vasić, B.: Serbia’s Evolving Tire Market: Wider Choice, and a Strong Domestic Industry, Tire Technology International 2010 – The Annual Review of Tire Materials and Tire Manufacturing Technology, 2010: pp. 108 – 111 4) Gavrić P, Danon G., Momčilović V., Bunčić S.: Exploitation and maintenance of commercial vehicle tires. Istraživanja i projektovanja za privredu, Vol 7 (25), 2009: pp 1-10 5) Jokić, B.: Analiza stanja i karakteristika pneumatika na vozilima u Srbiji, Diplomski rad, Univerzitet u Begradu – Mašinski fakultet, Beograd, 2011: pp 32 6) Marjanović, M.: Analiza vrsta, tipova i karakteristika pneumatika koji se koriste na vozilima u Srbiji, Diplomski rad, Univerzitet u Begradu – Mašinski fakultet, Beograd, 2009: pp 54 7) Pucci, A. et al: General Master Plan for the Transport in Serbia, Anex 1 – Road Transport, 2009: pp 135 8) Simović, Ž.: Analiza pneumatika koji se koriste na vozilima u Srbiji, Diplomski rad, Univerzitet u Begradu – Mašinski fakultet, Beograd, 2010: pp 46 9) Vujanović, T.: Na kakvim gumama se vozimo, Sat-plus, Broj 251, god X, 2010: pp 50 – 55 10) www.vrelegume.rs

Paper sent to revision: 07.02.2011. Paper ready for publication: 18.03.2011.

Journal of Applied Engineering Science 9(2011)1, 192


Paper number: 9(2011)1,193, 267 - 275

ADVANCED THEORETICAL-EXPERIMENTAL METHOD FOR OPTIMIZATION OF DYNAMIC BEHAVIOUR OF FIREFIGHTING VEHICLE MODULAR SUPERSTRUCTURES Mr Saša R. Mitić * Faculty of Mechanical Engineering, University of Belgrade Dr Branislav B. Rakićević Faculty of Mechanical Engineering, University of Belgrade Dragan D. Stamenković Faculty of Mechanical Engineering, University of Belgrade Dr Vladimir M. Popović Faculty of Mechanical Engineering, University of Belgrade This paper shows elaborated theoretical-experimental method used to optimize dynamic behaviour of modular superstructures of firefighting vehicles. Harsh exploitation conditions under which firefighting vehicles operates and special requirements for this type of vehicles require dedicated approach to optimization of superstructures in terms of stress, deformation, fatigue, noise, comfort and effectiveness. Optimization implies selection of optimal shapes, materials, dimensions, mountings, suspension, damping and insulation of modules to attain optimal dynamic behaviour of superstructure. Method described in this paper can be divided into two interconnected parts – theoretical and experimental. Theoretical part consists of numerical modelling of superstructure variants and calculation of their responses to dynamic excitations using FEM, whose results are later validated through experiments. Experimental part of this method is based on excitation of superstructure physical models with, for this purpose specially developed, mechanical exciter, monitoring of superstructure response and changing of the input parameters in the design of superstructure to create the superstructure with best possible dynamic characteristics. Natural frequencies of structures, important in terms of resonant zones, are obtained using bump tests and FFT analysis. This method has proved suitable for optimization of dynamic behaviour of modular superstructures such as those of firefighting vehicles. Complete testing installation used in this method is illustratively shown in this paper. Also, there are guidelines for further development and improvement of this method. Key Words: Special-purpose vehicles, Modular superstructure, Optimization, Dynamic behaviour, Mechanical exciter, FEM, FFT analysis, Bump test INTRODUCTION Identification of dynamic behavior of vehicle superstructures is very important in process of creating the superstructure with optimized dynamic characteristics. It is very demanding and complex activity, especially when it comes to superstructures of special-purpose vehicles. Harsh conditions in which these vehicles operate and wide spectrum of special requirements they have to meet lead to rise of complexity of such optimiz-

itaion [3]. Another fact that adds to complexity of this type of research is lack of adequate recommendations from the chassis producers for builders of this type of superstructures. That creates the necessity for establishing effective method for their optimization [11]. Modular structures present actual conceptual orientation of leading world producers of firefighting vehicles. Modular concept includes several independent and separated units, with different characteristics and different influence to vehicle

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Beograd; smitic@mas.bg.ac.rs

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chassis and separately suspended to a chassis [1]. This modules also interact with each other by transferring the loads and damping excited vibrations [2]. In the case of firefighting vehicles, dynamic excitation of superstructures comes from road sur-

face and installed devices in operation. These excitations could cause fatigue, exceeding of permissible stresses and noise levels, unwanted movements, lower the level of comfort and reduce the efectiveness of vehicle, which is, in case of firefighting vehicles, of great importance [4].

Figure 1. FEM model of one superstructure variant (beam and plate finite elements)

Therefore, it is essential to determine the integral dynamic behaviour of complete superstructure to enable its optimization. Complexity of development and optimization process reflects in necessity of incorporation of modern numerical and experimental methods [8]. Different variants of superstructure modules and their joints were numerically modelled and their dynamic behaviour was simulated using numerical prototyping. Experiments have been conducted to validate the results acquired by numerical prototyping and to identify parameters that can not be obtained by analysis of numerical model. NUMERICAL SUPERSTRUCTURE MODELLING Finite Element Method (FEM) has been used for making numerical models and dynamic behavior simulations of superstructure modules and superstructure in general. FEM analysis has been done using “KOMIPS” software package [5]. During this process, variable inputs are material, dimensions, shapes, damping and suspension. Several different variants of superstructure have

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been made by varying these inputs [6]. Outputs from this analysis are rigidity of modules and joints, stresses, deformations and accelerations of superstructure points. Results obtained through this analysis are later validated by experimental testing of physical models of superstructure variants. FEM models of one variant of superstructure are shown on Figure 1. TESTING INSTALLATION Testing installation shown on Figure 2 consists of frequency converter, mechanical exciter with built-in force transducer, accelerometers (whose number depends on acceleration measurement points of superstructure), digital acquisition system and computer with installed all software needed for recording and post-processing of data [9]. The role of mechanical vibration exciter is to apply harmonic force of desired amplitude and frequency, in desired direction and on desired position of the analyzed superstructure, which allows us to monitor its dynamic behaviour under the effect of such force. Harmonic force is applied as an inertia force generated by rotation Journal of Applied Engineering Science 9(2011)1, 193


Mr Saša Mitić and etc. - Advanced theoretical-experimental method for optimization of dynamic behaviour of firefighting vehicle modular superstructures

of exchangeable weights acting as unbalanced masses. By choosing the mass of weights and their angular velocity we can attain the amplitude and frequency of force we need. Rotating motion is transferred from electro-motor to flywheels by belt drive. Exchangeable weights are attached to flywheels with bolts. Force generated by rotation of unbalanced masses is transmitted to the structure through the two spherical joints and force transducer, as shown on Figure 3. Dynamic response of tested superstructure is measured by accelerometers placed on desired measurement points of superstructure in desired directions. Recorded data are postprocessed by spectral analysis software to determine the amplitudes and frequencies of measured accelerations. Spectral analysis is done by FFT (Fast Fourier Transform), a computer algorithm for computing the DFT (Discrete Fourier Transform)

using the “Sigview 1.99.0” software [12]. Presented installation is also used for bump tests to determine the natural frequencies of superstructures. This is done by measuring the dynamic response of superstructures after a transient impact on desired point of superstructure and in desired direction. Determination of superstructure natural frequencies is important from the aspect of identification of resonant zones in which the excited superstructure may get during testing or exploitation. Resonance is a very dangerous phenomenon which causes increase of stresses, deformations and noise level, decrease of comfort and could lead to failure of whole system. Because of that, it is necessary to optimize the structure in such way that it doesn’t get into resonant zones in everyday operation. One of the diagram obtained by bump test is shown on Figure 4.

Figure 2. Testing installation

Figure 3. Mechanical vibration exciter Journal of Applied Engineering Science 9(2011)1, 193

Figure 4. Natural frequencies of one of the superstructure variants

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OPTIMIZATION METHOD As mentioned before, optimization method is consisted of theoretical and experimental part. Since the optimization of dynamic behaviour of firefighting vehicles superstructures present a complex task, this two parts must be interconnected to ensure its maximum effectiveness. Making of physical models and carrying out the experiments takes time and money. Use of numerical modelling cuts down the number of experiments needed, and thus decreases the cost and duration of research. Experiments are conducted to validate the data acquired from numerical analysis and to determine parameters that cannot be analyzed by numerical methods used, such as noise level. Whole optimization process is shown on Figure 5. Process inputs are maximum permissible values of stress, deformation and noise, desirable comfort and dynamic superstructure behaviour in terms of resonant zones avoiding. Process begins with making of numerical models using FME. Several models are made with different dimensions, shapes and materials used, and with different mountings, joints and metal sheeting. Same software package used for creation of numerical models is used for analysis of stresses and deformations under dynamic load. After numerical analysis, physical models of superstructures are made based on numerical models. First experiment carried on these physical models is comprised of transient impact and analysis of response of superstructure to such excitation. This experiment is called “bump test” and is used for determination of natural frequencies of structures. Next step is testing of physical models using mechanical vibration exciter in order to observe dynamic behaviour of structure under

such excitation. When, using numerical modelling and experiments, most optimal variant of superstructure is found, we can proceed to the design of superstructure. After design and construction of superstructure is done and vehicle with this superstructure is put into operation, it is necessary to track its dynamic behaviour in real exploitation conditions, to prove that the output superstructure has optimal dynamic characteristics, and to collect data needed for further improvements of superstructure. RESULTS AND DISCUSSION For the purpose of obtaining adequate test results, mechanical vibration exciter was attached to several structures. Structures used in this experiment are: • foundation • beam girder • post – two heights of mounting • fire-fighting vehicle superstructure fixed to foundation – two positions of mounting [7] • fire-fighting vehicle superstructure on wheels (free) – three positions of mounting These structures are shown on Figure 6(a-h). Figure 7(a-i) shows the results of experiments that have been performed. On these diagrams FR represents the theoretical values of force, while FS represents the actual, real values. This values are represented depending on mass of weights and frequency of rotation of these weights, for previously mentioned analyzed structures [10]. Also, the natural frequencies of structures are shown for consideration of the effect of resonance on deviation of actual values of force from theoretical values.

Figure 5. Optimization method scheme

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Figure 6a) exciter attached to foundation

Figure 6c) exciter attached to post

Figure 6e) exciter attached to fixed superstructure in Z direction

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Figure 6b) exciter attached to beam girder

Figure 6d) exciter attached to fixed superstructure in X direction

Figure 6f) exciter attached to free superstructure in X direction

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Figure 6g) exciter attached to free superstructure in Figure 6h) exciter attached to free superstructure in Y direction Z direction Figure 6. Analyzed structures

Figure 7a) exciter attached to foundation

Figure 7b) exciter attached to beam girder

Figure 7c) exciter attached to post at the height of 1290 mm

Figure 7d) exciter attached to post at the height of 1675 mm

Figure 7e) exciter attached to fixed superstructure in X direction

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Figure 7f) exciter attached to fixed superstructure in Z direction Journal of Applied Engineering Science 9(2011)1, 193


Mr Saša Mitić and etc. - Advanced theoretical-experimental method for optimization of dynamic behaviour of firefighting vehicle modular superstructures

Figure 7g) exciter attached to free superstructure in X direction

Figure 7h) exciter attached to free superstructure in Y direction

Figure 7i) exciter attached to free superstructure in Z direction Figure 7. Actual and theoretical values of force

Relation between actual force and acceleration measured at the point and in direction of application of force in case when exciter is attached to post is shown on Figure 8. Figure 9 shows the ratios of actual and theoretical values of force for various frequencies and various masses of weights for specified stiffness of structures. Horizontal axis represents the reciprocal value of stiffness of structures which are shown in Table 1. Points marked with X represent ratios of actual and theoretical force in resonant zones, while points marked with empty circle represent ratios of actual and theoretical force for values of force not high enough to attain wanted signal-to-wanted ratio. That is the reason why some of these points lays out of acceptable zone, marked with 5%, 10% and 15% area.

Journal of Applied Engineering Science 9(2011)1, 193

Table 1. Stiffness of structures

Structure Foundation Beam girder Fixed superstructure (Z direction) Post (1290 mm) Post (1675 mm) Fixed superstructure (X direction)

Stiffness c [N/mm] ∞ 6250 2941.17 741.17 336 94.78

Ratios with values lower than 0.8 are not shown on Figure 9 and are all results of resonance. Also, ratios with values higher than 1.8, which are result of unfavourable signal-to-noise ratio, are not shown.

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CONCLUSIONS Identification of dynamic behaviour is important activity in modelling, analysis, testing and control of firefighting vehicle superstructures. It is desirable to implement identification of dynamic behaviour into all this processes. Method shown in this paper make this possible by incorporating theoretical and experimental activities to optimize the superstructure dynamic characteristics. All tests have been made with empty, unloaded structures. Increasing of mass of vehicle should bring to more acceptable results, so the resonant zones should be moved higher and the complete vehicle structure should have much better behaviour applying higher forces.

8a) exciter attached to post at the height of 1290 mm

It can be noticed that deviations grow with decrease of stiffness of structures. For the values of stiffness inherent in vehicle structures these deviations are in satisfactory limits. The mechanical vibration exciter is entirely applicable outside resonant zones for values of force higher than 10 N and for values of stiffness characteristical for vehicle structures. Method showed good results in reducing of superstructure stresses, deformations and noise levels generated by dynamic load in firefighting vehicle exploitation. It also led to creation of superstructure capable of performing all required tasks without getting into resonant zones and threatening the vehicle functionality.

8b) exciter attached to post at the height of 1675 mm

Figure 8. Actual force and acceleration

Figure 9. Ratios of actual and theoretical values of force depending on stiffness of structure

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As a future activities, it is necessary to analyze the influence of interconnection of separate modules, as well as the influence of module supports. These analysis, together with previous achievements, should bring us to defining of knowledge base, which should provide real and reliable state identification of modular structures in early phases of design and product development process. ACKNOWLEDGEMENT This paper is a part of projects of The Ministry of Science and Technological Development of Serbia (project number TR035045 - “ScientificTechnological Support to Enhancing the Safety of Special Road and Rail Vehicles” and project number TR035040 - “Developed New Methods for Diagnosis and Examination of Mechanical Structures”). REFERENCES 1) Bosnjak, S. (2010) Some of the Problems on Dynamic and Strength of the High Performance Machines (in Serbian), Istraživanja i projektovanja za privredu, vol. 8(2010)1,167, 1-12 2) Changhai, Y., Wenku, S., Kaiyan, W. (2010) Vibration Analysis of Commercial Vehicle Cab Suspension and DOE Optimization, International Conference on Computer, Mechatronics, Control and Electronic Engineering (CMCE), 430-433 3) Gatti, P., Ferrarri, V. (2003) Applied Structural and Mechanical Vibrations, London: Taylor & Francis Group 4) Maksimovic, S., Blazic, M., Maksimovic, M. (2010) Design of Constructions With Respects to Fatigue and Fracture Mechanics, Research and Design in Commerce & Industry, vol. 8(2010)3,184, 181-188 5) Maneski, T. (1998) Computer Modeling and Structures Calculation (in Serbian), Belgrade: Faculty of Mechanical Engineering 6) Maneski, T. (2002) Structural Problem Solving (in Serbian), Belgrade: Faculty of Mechanical Engineering 7) Maneski, T., Milosevic-Mitic, V., Andjelic, N. (2009), Numerical Dynamic Analysis of the Influence of the Supports and Interconnections of Fire Engine Structural Parts, 2nd International Congress of Serbian Society Journal of Applied Engineering Science 9(2011)1, 193

of Mechanics (IConSSM 2009), Conference Proceedings, 1-9 8) Maneski, T., Milosevic-Mitic, V., Ostric, D. (2002) Base Strength of Constructions, (in Serbian), Belgrade: Faculty of Mechanical Engineering 9) Rakicevic, B., Vorotovic, G., Mitic, S. (2009) Experimental Determination of The Influence of Suspension and Conjoined Modules Connections of Firefighting Bodies on Their Dynamic Behaviour, 2nd International Congress of Serbian Society of Mechanics (IConSSM 2009), Conference Proceedings, 1-11 10) Stamenkovic, D. (2009) Possibilities for Identification of Mechanical Structures Dynamic Behaviour Using Mechanical Vibration Exciter With Excentrical Masses (in Serbian) – Master thesis, Belgrade: Faculty of Mechanical Engineering 11) Wang, H., Li, R., Xue, H., Pan, H. (2010) The Vibration Identification of Military Vehicle Seat Based on Wavelet-Scale Energy Coefficients, 2010 IEEE 10th International Conference on Signal Processing (ICSP), 203-206 12) http://www.sigview.com/ Paper sent to revision: 02.02.2011. Paper ready for publication: 21.03.2011.

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CONTRIBUTION TO REVIEW OF THE EFFECTS LEKHNITSKII INFLUENCE TO DYNAMIC PARAMETERS OF COMPOSITE STRUCTURES Dr Radoljub Tomić * Prva petoletka-S&R JSC, Trstenik Dr Predrag Petrović Institute “Kirilo Savić”, Belgrade Dr Tomislav Jovanović Institute “Kirilo Savić”, Belgrade Dynamic analysis of anisotropic (in this paper generalized orthotropic) structure is often reduced to the analysis of quasi isotropic structures. In this way, it is possible to obtain results of acceptable accuracy. Improvement of results can be achieved primarily through the appropriate stiffness matrix, which includes specifics of composite (anisotropic) material concerning the interactions of normal stress and shear strain, apropos shear stress and dilatation (based on the effects of Leknitskii). Results of the analysis for the two above-mentioned models of a composite structure (generally orthotropic and quasi-orthotropic), are presented in graphical and tabular form. Key words: Dynamic analysis, Composite materials, Lekhnitskii effects

INTRODUCTION Structural analysis will be based on the theoretical concept of composites in accordance with [1]. It is evident that the concept of structural analysis of isotropic structures can not be applied, therefore, through the model matrix of elasticity and stiffness of orthotropic structures, the specific characteristics of the considered structures will be entered, as it normally done when calculating the composite structure. This paper is prepared and presented based on the methodological developments of different authors [8,9,10] and basically is a rational attempt to be reasonable contribution to the R& D of interest for the design of structures on the basis of modern composite materials with use of computers. [6,7,9]. Here will be carried out analysis of the impact of some of the most significant effects that are not necessarily seen in the spatial structure based on different materials.

276

Determination of natural frequencies and eigen modes of oscillation is reduced to the solution of homogeneous differential equations of motion. In principle there are two possible cases: • •

determination of dynamic parameters of the model without damping; determination of dynamic parameters of the model with the damping [2].

Simpler is the first case and it will be here analyzed (using the finite element method - FEM), with a full emphasis on specifics loaded through the stiffness matrix for plate anisotropic structures based on the interaction between normal stress and shear strain and shear stress and dilatation respectively [1,3]. Specifically, all members of the matrix of matherial stiffness or elasticity - and flexible - would be different from zero, equations (01) and (02).

* Industry of Hidraulics and Pneumatics,”PRVA PETOLETKA-S&R“ JSC, Cara Dušana Str. 101”, 37240 Trstenik, Serbia; radetomic@ppt.co.rs

(1)


Dr Radoljub Tomić and etc. - Contribution to review of the effects Lekhnitskii influence to dynamic parameters of composite structures

: - Q - basic orthotropic elasticity matrix of material (E1, E2, v12, G12), in which the geometric(2) xy and material-12 coordinate system coincide;

Comparing the results of the analysis of a model for the various concepts of dynamic analysis will be discussed under chapter Results analysis dynamic parameters

- T - transformation matrix, the expression (10), where xy and 12 do not coincide (θ - angle of transformation), ), Figure 1.

BASIC THEORETICAL RELATION Set problem is defined by differential equations, (03) to (08), according to [2], (3) For the vector of node displacements, (4)

Figure 1. Geometric-xy and material-12 coordinate systems

the problem is reduced to, (10)

(5) respectively, for the determination of non-trivial solutions need to be a determinant of this system is equal to zero,

Based on the eq. (09) and (10), comes to the relation (11) and (12), according to [1].

(6) (11)

where M and K the global stiffness matrix and matrix of inertia are obtained on the basis of elementary matrices, -matrix of inertia of elements.

(7)

-matrix of stiffness of elements.

(8)

Expressions (07) and (08) for elements with isotropic material are well known from the literature [2]. Closer will be discussed only matrix that brings the substantive changes to the structural concept of elements. Geometric concept of composite plate is the same with isotropic element. Matrix has been adopted for the concept of symmetric composite plates with respect to the middle plane of elements [1,5], equation (09). (9)

(12)

where: - coefficient of mutual influence of the first and second row, known as the coefficients of Leknitskii. In principle, functional dependence (θ) is shown in Figure 2. It can be concluded that, in describing the model with orthotropic or quasi-orthotropic structure, the greater difference in the accuracy of the analysis results is if we have larger absolute values of coefficients η.

where Journal of Applied Engineering Science 9(2011)1,

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Inertia matrix and stiffness matrix of elements, as well as the matrix of inertia and stiffness of the system, defined by the foregoing equations and theoretical relations set out in [2]. RESULTS ANALYSIS DYNAMIC PARAMETERS Modeling, calculation and the results were carried out on computers, the application of FEM to define dynamic parameters and the modal matrix of a graphic interpretation of its own modes of oscillation is done by applying generally accepted MATLAB 6.5 package. Figure 2. Functional dependency  (θ)

* Eigen value of frequency [s ]

STRUCTURAL ANALYSIS OF THE MODEL Analysis of the basic dynamic parameters, based on the above mentioned equations, will be carried out for model shown in Figure 3. Now, for the next calculation and comparing results, for the model of quasi-orthotropic structure, the concept (13), and for the model with generalized orthotropic structure, the concept (01), are adopted.

- The concept quasi-orthotropic structure: 1=

205, 5 = 950;

2

= 375,

3

= 556,

4

= 669,

- The concept generalized orthotropic structure: 1 = 131, 2 = 223, 3 = 334, 4 = 433, 5 = 573. The relative error is very pronounced, for the adopted base material is even greater than 50%. S are in more accurate for generalValues of ized orthotropic concept (second concept). * Eigen value of oscillation modes

(13)

t = 10 – plate thickness b = 100– length of finite element cathetus “ ” E1 = 10 000 daN/mm2, E2 = 1 000 daN/mm2 v12 = 0,3, G12 = 500 daN/mm2, θ = 45 0 , = 2,4 kg/dm3

Eigen value of oscillation modes are determined by [2]. It is evident that modes of oscillation of the discussed concepts in the appropriate measure are different. The largest discrepancies are present in modes III and IV. Relative displacements (without the written of displacement of node 5) in relation to their eigenvalue perception of the oscillation modes are shown in the form of modal matrix ’ i ’’: So, for two different concepts of where the budget for the concept (15) deliberately entered error to show the obvious way, as are differences, even very important, may appear and give the wrong picture about the dynamic behavior of real structures (14) should be she descriptions inadequate mechanical concept.

Figure 3. Structural model

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All this is further reflected at the level of graphical display modes, the differences are evident. Graphical display modes I and III is shown in Figure 4. Of course, possible jegraficki show and all the other modes, but here the emphasis is primarily only on the qualitative perception of Journal of Applied Engineering Science 9(2011)1, 194


Dr Radoljub Tomić and etc. - Contribution to review of the effects Lekhnitskii influence to dynamic parameters of composite structures

the difference in the budget for the exact and approximate structure model, which is also shown. - for generalized orthotropic structure

(14)

Inconsistency results from the dynamic analysis of the concepts outlined generalized orthotropic structures, shows that the correct calculation must include all specific of materials expressed by the mechanical characteristics of the stiffness matrix. Graphic, as very indicative, are presented modes I and III. Given the modal matrix with clearly distinct zones in which a significant discrepancy of the real and approximate concept are appeared as evident result. CONCLUSIONS

- for quasi-orthotropic structure

(15)

Graphical display of modes I and III is given in Figure 4. I - mode

III - mode

In the introduction, it was pointed out that the dynamic analysis of anisotropic (in this paper generalized orthotropic) structure is often reduced to the analysis of quasi-isotropic structure and, thus, possible to obtain results of acceptable accuracy. In further consideration is proved, that the improvement in results can be achieved primarily by application of appropriate stiffness matrix, in which they included specific composite (anisotropic) material concerning the interaction of normal stresses and strains smičućnih or shear stresses and dilatation (based on the effects Lekhnitskog). The findings of two relevant model of a composite structure (generalized orthotropic and quasi-orthotropic), are presented in graphical and tabular form. Inconsistency results indicated generalized concepts of dynamic analysis of orthotropic structures, shows that the correct Budget must include all specific materials expressed by the mechanical properties of the matrix stiffness. Graphically, as very indicative, show a numerical modes and modal matrix with clearly identified areas where significant discrepancy is evident in the results the real and the approximate concept. Compatibility analysis would relate to aspects of viscoelasticity and viscoplasticity of composite structures for what will be focused our further work. REFERENCES

quasi-orthotropic structure for generalized orthotropic structure

1) Robert M. J.:, “Mechanics of Composite Materials”: Scripta Book Company, Washington, D.C. McGraw-Hill Internaional Book Company, 1975, pp. 355.

Figure 4. Graphical display of modes I and III Journal of Applied Engineering Science 9(2011)1,

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2) Sekulović M.: „Finite elements“, Construction book (Građevinska knjiga), Belgrade, 1984 3) Tomic R.: „Optimisation of composite structure for an engineering model with regard to fiber orientation“, Conference “STRUCEENG - 89, Los Angeles, 1989., pp.113-118th. 4) Tomic R.: „Definition of parameters of the structural analysis of generalized orthotropic prismatic beam with aspect distortion functions“, “Technique”, No. 7, XLIX, Belgrade, 1994., pp.36M-40M 5) Tomić R., Maneski T., Nestorovic M. „Optimization of geometric and materia parameters of the orthotropic plate with elliptic openings with respect to stress concentration“, Congress of Mechanics “24.YUMEH”, Belgrade, 2003. (Work on CD)

8) Maneski T., Ignjatović D.:“ Dijagnostika čvrstoće konstrukcija u funkciji održavanja”, Istraživanja i projetovanja za privredu, broj 7. 9) Vasić Z., Petrović Z.:“ Savremeni kompozitni materijali u projektovanju i proizvodnji vazduhoplovnih konstrukcija“, Istraživanja i projetovanja za privredu, 2009-Vol.7, broj 4, broj 26. 10) Vasić Z., Petrović Z.:“ Razvoj baze projektnih podataka aviona“, Istraživanja i projetovanja za privredu 3, 2010, Vol8, broj 29. Paper sent to revision: 18.02.2011. Paper ready for publication: 21.03.2011.

6) Bosnjak S.:“Neki problemi dinamike i čvrstoće mašina visokih performansi, some of the problems on dynamics and strength of the high performance machines“, Istraživanja i projetovanja za privredu, 1, 2010, Vol 8, broj 27. 7) Gaben Abu Mohamed, Slobodan Krčevinac, Mirko Vujošević: „Modelujući sistemi u optimizaciji”, Istraživanja i projetovanja za privredu, broj 18.

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ANNOUNCEMENT OF EVENTS

IIPP MAINTENANCE MANAGEMENT SCHOOL Maintenance Management School presents practical experience in combination with adopted theoretical knowledge, thus creating maintenance management experts capable to perform and coordinate the maintenance of complex technical systems. Use unique opportunity to expand knowledge in the field of technical systems maintenance. This year, training will be held two times. During both five days training focus will give to the following topics: • • • • • • • • • • • • •

Maintenance Objectives and Policies Maintenance Concepts Maintenance Terminology Laws and Regulations Condition Monitoring Fault Finding Techniques Spare Part Management Corporate/Company Environment Work Planning Team Working and Communications Information Technology Quality Assurance (Systems) Environment and Occupational Health and Safety

The school program merges best local knowledge and experience modernized and harmonized with the recommendations of European Federation of National Maintenance Societies. Since Maintenance Management School connected and unified local tradition and experience in the maintenance process with the European norms and requirements, it’s result is thus twofold - to all who signed up gives a chance to gain national certificate ’’Expert for maintenance management” and to those who can and want more, Maintenance management school opens the possibility of obtaining the International certificate “European maintenance manager”. Result: More than 240 national certificates and 16 internationally recognized certificates: European Maintenance Manager. Duration: five days in total Time and location: Spring 2011: 26.03. and 02.04. (first part) – Faculty of Mechanical Engineering, Belgrade 07-09.04.2011.(second part) - Hotel Aleksandar, Vrnjačka Banja Autumn 2011: 12.11. and 19.11.2011. (first part) – Faculty of Mechanical Engineering, Belgrade 24-26.11.2011. (second part) - Hotel Izvor, Aranđelovac Contact: Research and design in commerce & industry Jurija Gagrina 12 b, 11070 New Belgrade; Phone: 011/6300750; Fax: 011/6300751; E-mail: office@iipp.rs; web: www.iipp.rs Journal of Applied Engineering Science 9(2011)1

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IIPP QUALITY MANAGEMENT SCHOOL Considering business conditions of European market, quality has a significant role, not only in providing new markets, but also in maintaining the existing ones. Nowadays, customers do not only expect a quality product, but they require a proof that the company is capable to produce high quality products and provide quality services. Obtaining of this evidence should be the first goal for each company that has high aspirations when it comes to new markets but also standard’s procedure in order to maintain its reputation. Implementation is not complete if employees are not familiar with standards. With the aim to closer inform the employees of the meaning and significance of ISO standards, Institute for research and design in commerce & industry – IIPP organize training “School of Quality”. During the training participants will: • expend their knowledge about implementation of ISO standards, • learn how to maintain and improve quality level of companies • learne how to verify and improve business performance of companies Training will be held during five days in two locations. First lectures will be held at the Faculty of Mechanical Engineering in Belgrade, while the final lecture and the test will take place in attractive location in Serbia: Vrnjačka Banja – during first cycle and Aranđelovac – during second. Programme • Fundamentals of quality concepts, definitions, approaches • Standards, review and interpretation • Management Responsibility • System and process approach • Data management, information system • Statistical methods (engineering methods, quality management methods) • RISK, FMEA, FTA • Supply and storage, evaluation of supplier • Maintenance • Evaluation, audit, certification • Examples, practice, Deming management experiment • PAS 99 - Integrated Management Systems Result After implemented training, Qiipp consultant is able to assume responsibility for independent work in the following fields of activity: • Implementation of quality standards • Maintaining a high level of quality • Constant improvement of the quality system • Assessment and audits of own companies and their suppliers Candidates who passe the test will get a diploma “Qiipp consultant for implementation, maintenance, analysis, evaluation and testing, design and improvement of the quality system”. Duration: five days in total Time and location: Spring 2011: 26.03. and 02.04. (first part) – Faculty of Mechanical Engineering, Belgrade 07-09.04.2011.(second part) - Hotel Aleksandar, Vrnjačka Banja Autumn 2011: 12.11. and 19.11.2011. (first part) – Faculty of Mechanical Engineering, Belgrade 24-26.11.2011. (second part) - Hotel Izvor, Aranđelovac Institute for research and design in commerce & industry Phone: 011/6300750; Fax: 011/6300751; E-mail: office@iipp.rs; web: www.iipp.rs

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ANNOUNCEMENT OF EVENTS

XXXVI Conference - MACHINERY AND EQUIPMENT MAINTENANCE 16.06. i 17.06.2011. - Faculty of Mechanical Engineering, Belgrade 21-24.06.2011. - Hotel Aleksandar, Budva DOTS - Serbian Maintenance Society has good, long-term cooperation with Institute for research and design in commerce & industry. The main goal of cooperation is to improve maintenance function of technical systems in all fields of commerce and industry, and to promote roll of maintenance. One of the results of the cooperation is to bring together leading experts from Serbia and the region. OMO 2011 is the ideal occasion to listen to various experienced top speakers and to share knowledge with them. This event will brought on important issues of our community with purpose to stimulate reflection and debate on both the challenges and solutions. Topics include the latest developments in the field of maintenance of technical systems, with special emphasis on practical application of new knowledge. The program is balanced and focused on the needs of the Serbian economy. All papers are peer reviewed, which ensures high quality information and the possibility of their application directly. Conference will take place over five day period in two different venues: opening ceremony including presentations from invited lecturers will be held at the Faculty of Mechanical Engineering in Belgrade, followed by presentation of scientific papers, experience exchange and networking - on attractive location in Montenegro, Hotel Aleksandar in Budva.

CALL FOR SPEAKERS OMO independent expert Advisory Board is responsible for setting the conference themes and suggested topics and for selecting papers to be included in the programme. The Board represents a wide cross section of the industry and gathers experineced professionals from leading Serbian utility companies, equipment suppliers, manufacturers, service providers, associations and consultancies. We are looking for high profile and competent speakers who are willing to share their experience, knowledge and best practices with Maintenance Managers & Engineers. Send your paper to astevanic@iipp.rs. SUBMISSION DEADLINE : May 31 st 2011 This event is not only an informational gathering, but strong opportunity for business networking. OMO 2011 is must for everyone dedicated to industrial maintenance!

PRESENTATION OF PAPERS OPENING CEREMONY

Contact: DOTS - Serbian Maintenance Society Phone: 011/3302451; Fax: 011/3302450 E-mail: office@dots.rs; web: www.dots.rs Journal of Applied Engineering Science 9(2011)1

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ANNOUNCEMENT OF EVENTS HANNOVER MASS Venue: Hannover, Germany Date: Apr 04, 2011 - Apr 08, 2011 The 13 leading trade fairs that make up HANNOVER MESSE 2011 will present a unique crosssection of key industrial technologies. The declared goal of HANNOVER MESSE is to create a platform for the interplay between all relevant sectors and technologies - a goal that has now been achieved. No other trade show presents all the elements in the industrial value chain in such a comprehensive and integrated form. The key industrial sectors can display their individual strengths and at the same time engage in interdisciplinary knowledge transfer. AUTORAI Venu: Amsterdam, Netherlands Date: Apr 13, 2011 - Apr 23, 2011 The Autorai is the biggest carshow in the netherlands and is being held every 2 years at the Rai Convention Center in Amsterdam. This year the Autorai is being held on from 13 until 23 April. Every year thousends of people watch the newest releases, concept cars and much mo0re car related things. This year the show holds a huge outside park with testtracks, a 4x4 testtrack and a classiccarpavillion. Also demonstartions will be held here. ElectronTechExpo Moscow Venue: Crocus Expo International Exhibition Center, Moscow, Russia Date: Apr 19, 2011 - Apr 21, 2011 Electron Tech Expo is an International Exhibition of technological equipment and materials for the electronic and electrical industry being conducted along with the exhibition of electronic components - ExpoElectronica. It will gather Professionals from Electronics, electrotechnology, Instrument making, Military-industrial complex, Machine-tool construction, Telecommunications, Aircraft construction, Safety systems, Fuel and energy industry, Medicine, Motor-car construction, Petrochemical industry, Construction, Metallurgy industry. TRANSRUSSIA - 16th International Transport and Logistics Conference Venue: Moscow, Russia Date: Apr 26, 2011 - Apr 29, 2011 In 2011, the conference will be held in the same venue as the TransRussia exhibition, in the conference hall of Pavilion 8. This means that delegates will be able to attend both the exhibition and the conference.For three days, conference sessions will run from 11:00 till 15:00, leaving time for meetings at the exhibition. Over the last six years, a minimum of 300 participants from more than 20 countries have attended the conference every year. Participants include leading experts and managers of the largest transportation companies. EUROMAINTENANCE 2012 Venue: Belgrade, Serbia Date: May 14, 2012 - May 16, 2012 Come to biggest exchange market of maintenance knowledge and meet experts and world class maintenance managers that will present how to improve your business while improving maintenance techniques. Learn to avoid common traps, implement proper maintenance, decrease total cost and all with accent on environmental safety. It doesnâ&#x20AC;&#x2122;t matter what level of experience you have with maintenance - there is something here for everyone and always more than you expect. Call for spekers: www.euromaintenance.org

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BOOK RECOMMENDATION Process Risk and Reliability Management Operational Integrity Management By Ian Sutton Ian Sutton is a chemical engineer with over thirty years of experience in the process industries. He has worked on the design and operation of chemical plants, offshore platforms, refineries, pipelines and minerals processing facilities. He has extensive experience in the development and implementation of process safety management and operational excellence programs. He has published extensively on these topics, and is an active member of many professional societies. Mr. Sutton is a professional engineer registered in the state of Texas. He holds chemical engineering degrees from the University of Nottingham (U.K.) and a masters in literature from the University of Houston (Clear Lake). He is currently employed as Process Risk & Reliability Engineer in Houston. In the last twenty years considerable progress has been made in process safety, particularly in regard to regulatory compliance. Many companies are now looking to go beyond mere compliance; they are expanding their process safety management (PSM) programs to improve performance not just in safety, but also in environmental compliance, quaility control and overall profitability. Techniques and principles are illustrated with numerous examples from chemical plants, refineries, transportation, pipelines and offshore oil and gas. This book helps executives, managers and technical professionals achieve not only their current PSM goals, but also to make the transition to a broader operational integrity strategy. The book focuses on the energy and process industries- from refineries, to pipelines, chemical plants, transportation, alternative energy and offshore facilities. The techniques described in the book can also be applied to a wide range of non-process industries. The book is both thorough and practical. It discusses theoretical principles in a wide variety of areas such as management of change, risk analysis and incident investigation, and then goes on to show how these principles work in practice, either in the design office or in an opperating facility. Hardbound, 856 pages Published: 09 APR-2010 ISBN 13: 978-1-4377-7805-2 Imprint: WILLIAM ANDREW The book is recommended by :

Doc. dr Vladimir PopoviÄ&#x2021;

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INSTRUCTIONS FOR AUTHORS

Send to: Institut za istraživanja i projektovanja u privredi Jurija Gagarina 12b, 11 070 Novi Beograd Phone: +381 11 6300750 Fax: +381 11 6300751 E-mail: nstanojevic@iipp.rs; astevanic@iipp.rs All manuscripts must be in English free of typing errors (please use Spell Checking).The maximum length of contributions is 10 pages. Every manuscript submitted to IIPP will be considered only if the results contained in the paper were not already published, that are not currently in the process of publishing and not to be published in another journal. Each paper is sent to a review by two independent experts and the authors are obligated to adopt the observations and comments of the reviewers. THE FORMAT OF THE MANUSCRIPT The manuscript should be written in the following format: • A Title, which adequately describes the content of the manuscript. • An Abstract should not exceed 250 words. The Abstract should state the principal objectives and the scope of the investigation, as well as the methodology employed. It should summarize the results and state the principal conclusions. • Not more than 10 significant key words should follow the abstract to aid indexing. • An Introduction, which should provide a review of recent literature and sufficient background information to allow the results of the article to be understood and evaluated. • A Theory or experimental methods used. • An Experimental section, which should provide details of the experimental set-up and the methods used for obtaining the results. • A Results section, which should clearly and concisely present the data using figures and tables where appropriate. • A Discussion section, which should describe the relationships and generalizations shown by the results and discuss the significance of the results making comparisons with previously published work. (It may be appropriate to combine the Results and Discussion sections into a single section to improve the clarity). • Conclusions, which should present one or more conclusions that have been drawn from the results and subsequent discussion and do not duplicate the Abstract. • References, which must be cited consecutively in the text using brackets [1] and collected together in a reference list at the end of the manuscript and in alphabetic order. Units - standard SI symbols and abbreviations should be used. Abbreviations should be spelt out in full on first appearance, e.g., variable time geometry (VTG). Meaning of symbols and units belonging to symbols should be explained in each case or quoted in a special table at the end of the manuscript before References Figures must be cited in a consecutive numerical order in the text and referred to in both the text and the caption as Fig. 1, Fig. 2, etc. Figures should be prepared without borders and on white grounding and should be sent separately in their original formats. Pictures may be saved in resolution good enough for printing in any common format, e.g. BMP, GIF or JPG. Tables should carry separate titles and must be numbered in consecutive numerical order in the text and referred to in both the text and the caption as Table 1, Table 2, etc. The tables should each have a heading. Tables should not duplicate data found elsewhere in the manuscript. Acknowledgement of collaboration or preparation assistance may be included before References. Please note the source of funding for the research.

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INSTRUCTIONS FOR AUTHORS REFERENCES must be written in alphabetical order and in the following form: Journal: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication). Article title: secondary title. Title of the Journal (italic), volume number (number of the journal), page number. // Petrović, G., Petrović, N., Marinković, Z. (2008). Primena teorije Markova u mrežnim sistemima masovnog opsluživanja. FACTA UNIVERSITATIS Series Mechanical Engineering, 6 (1), 45 – 56. Book: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication) Book title: secondary title, Place of publishing: Publisher. /2/ Vasić, B., Popović, V. (2007) Inženjerske metode menadžmenta, Beograd: Institut za istraživanja i projektovanja u privredi. Book chapter: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication) Chapter title: secondary title, Book title: secondary title, Place of publishing: Publisher, page numbers. /3/ Vasić, B. (2004) Model Hardverskog resursa, Menadžment i inženjering u održavanju, Beograd: Institut za istraživanja i projektovanja u privredi, 95 – 97. Internet source: /Number/ (must match number in the text), link to the page from which the text is taken, retrieved on (state the date) /4/ http://www.autogume.net/veleprodaje/kelena/, retrieved on November 7th, 2010 INDEXING Starting from 2006., only three years since the launch of the journal “Istraživanja i projektovanja za privredu“, all published articles are indexed in international ELSEVIER database through SCOPUS service. In this way, the work and results of the local scientiest are widely available as the SCOPUS is the largest database of abstracts and citations in terms of scientific publications and quality web sources which, above all, give the results of research in various fields.This database provides excellent information necessary for further work and scientists training with extensive search capabilities.

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SADRŽAJ

Od uređivačkog odbora Dr Jovan Todorović JOURNAL OF APPLIED ENGINEERING SCIENCE

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Rezimei radova Dr Veselin Batalović, Dr Dušan Danilović, Dr Marija Živković MODEL ČIŠĆENJA GASOVODA I NAFTOVODA TOKOM FLUIDA

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Mr Olivera Medar, Mr Aleksandar Manojlović SEKTOR MEĐUNARODNOG DRUMSKOG TRANSPORTA ROBE: ANALIZA KRITIČNIH PROBLEMA

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Mr Marko Nikolić VIZITORSKI CENTRI NA ARHEOLOŠKIM LOKALITETIMA U SRBIJI KAO PODSTICAJ EKONOMSKOM RAZVOJU ZEMLJE

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Dr Gradimir Danon, Dr Branko Vasić, Bojan Jokić, Žikica Simović, Marko Marjanović KOMPARATIVNA ANALIZA KARAKTERISTIKA PNEUMATIKA PUTNIČKIH VOZILA U SRBIJI

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Mr Saša Mitić, Dr Branislav Rakićević, Dragan Stamenković, Dr Vladimir Popović TEORIJSKO-EKSPERIMENTALNA METODA ZA OPTIMIZACIJU DINAMIČKOG PONAŠANJA MODULARNIH NADGRADNJI VATROGASNIH VOZILA

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Dr Radoljub Tomić, Dr Predrag Petrović, Dr Tomislav Jovanović PRILOG RAZMATRANJU UTICAJA EFEKATA LEKHNITSKOG NA OSNOVNE DINAMIČKE PARAMETRE KOMPOZITNE STRUKTURE

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OD UREĐIVAČKOG ODBORA Journal of Applied Engineering Science

Prof. dr Jovan Todorović

Časopis Istraživanja i projektovanja za privredu ulazi u devetu godinu objavljivanja. U prethodnih 30 izdanja objavljeno je skoro 190 radova, a autori su sa univerziteta, naučnih instituta, industrijskih preduzeća (malih, srednjih i velikih preduzeća) iz Srbije i nekoliko drugih zemalja. Uprkos veoma različitim temama, sve radove objavljene u časopisu karakterišu direktne ili indirektne veze sa privredom. To je u skladu sa glavnim oblastima i ciljevima časopisa, prihvaćenim od samog njegovog nastanka. Objavljeni radovi bave se razvojem i primenom novih tehnologija, novih proizvoda i proizvodnih sistema, novih metoda upravljanja i kontrole i to u različitim sektorima privrede i trgovine.

Imajući u vidu aktuelnu situaciju u privredi Srbije, namera je da se posebna pažnja posveti proizvodnom sektoru u Srbiji, domaćim industrijskim i drugim proizvodnim centrima. Izdavač i Uređivački odbor su potpuno svesni činjenice da se samo značajno uvećanim obimom proizvodnje i kvalitetno poboljšanim proizvodima (u svim proizvodnim sektorima, a posebno u industriji, u energetici, u poljoprivredi i svim ostalim sektorima), mogu dostići neophodni i pravi uslovi za zdravu i efikasnu privredu i napredak zemlje. Odgovarajuća poboljšanja u sektoru upravljanja i zaštite životne sredine su neophodnan uslov za efikasan i održiv razvoj zemlje, što je povezano sa prostornim planiranjem i regionalnim razvojem, kao i sa odgovarajućim poboljšanjima u svim važnim društvenim sektorima, nauci, prosveti, zdravstvu, kulturi i umetnosti. Obuhvaćena je veoma široka oblast delatnosti koja zahteva ozbiljno razmišljanje, veliki senzibilitet, upornost i puno ambicija. Da bi se postigao uspeh potrebno je potpuno angažovanje svih dostupnih intelektualnih kapaciteta, svih naučnika, inženjera i profesionalca iz brojnih sektora privrede. Njihova znanja se moraju stalno poboljšavati, u skladu sa ekstremno brzim tehnološkim napretkom u današnjem svetu. Na kraju, možda, najvažnije: neophodno je da se svi putevi našeg razvoja povežu sa odgovarajućim tendencijama u svetu, omogućavajući razmenu ideja i rezultata sa inženjerima, naučnicima i ostalim profesionalcima iz drugih zemalja, od razvijenih do onih koji su u sličnim periodima tranzicije kao i naša zemlja. Ovi zadaci Izdavača i Uredništva, prihvaćeni od samog početka, su na dobar način demonstrirani u činjenici da se časopis od poslednjeg broja objavljuje na engleskom jeziku (uz šire preglede na srpskom jeziku). Naša želja je da međunarodnoj javnosti predstavimo ono što znamo i ono što možemo, ubeđeni da smo toga dostojni, ali i da se poboljša komunikacija naših autora sa odgovarajućim stručnjacima u drugim zemljama. Na taj način, naši profesionalci su motivisani da poboljšaju praktična znanja engleskog jezika, koji je vodeći jezik u današnjem svetu nauke, tehnologije i privrede. U skladu sa tim, naš časopis od ovog broja ima i novi naslov na engleskom jeziku - Journal of Applied Engineering Science. Fokus je na svim inženjerskim aktivnostima kao što su razvoj, proizvodnja, operativa, održavanje, upravljanje i slično.

Prof. dr Jovan Todorovic

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MODEL ČIŠĆENJA GASOVODA I NAFTOVODA TOKOM FLUIDA Dr Veselin Batalović - Rudarsko - geološki fakultet, Univerzitet u Beogradu Dr Dušan Danilović - Rudarsko - geološki fakultet, Univerzitet u Beogradu Dr Marija Živković - Rudarsko - geološki fakultet, Univerzitet u Beogradu

Cevovodi i kanali uređaja za transport nafte i gasa su izloženi nečistoćama (prašina, garež, opiljci, produkti oksidacije fluida, itd.) koje su tu najčešće prisutne zbog loše filtracije ili akumulacije tokom transporta. Nataložene nečistoće smanjuju protočni presek cevovoda i povećavaju gubitke pritiska. Posledice su: nizak stepen korisnog dejstva, česti kvarovi, porast troškova rada, itd. Čišćenjem taloga značajno se povećava pouzdanost hidrauličkih uređaja. Cilj ovog rada je da, analizirajući postojeće postupke čišćenja, formira kriterijume (optimalan protok i vreme čišćenja) koje treba zadovoljiti da bi se realizovao proces čišćenja uz minimalne troškove. Ključne reči: Model, Gas, Cevovod, Čišćenje, Protok

1. Ispiranje cevovoda 2. Implant (umetak) sa veštački umetnutim nečistoćama 3. Merenje napona smicanja 4. Oscilograf 5. Punjenje izvora 6. Pulsator 7. Baterija gasa 8. Merač protoka 9. Ventil Slika 1. Šema uređaja za testiranje

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SEKTOR MEĐUNARODNOG DRUMSKOG TRANSPORTA ROBE: ANALIZA KRITIČNIH PROBLEMA Mr Olivera Medar - Saobraćajni fakultet, Univerzitet u Beogradu Mr Aleksandar Manojlović - Saobraćajni fakultet, Univerzitet u Beogradu U radu se prezentira prva faza istraživanja koje se bavi analizom transportne politike u sektoru međunarodnog drumskog transporta robe. Cilj istraživanja je bio da se definišu problemi, prioriteti i mogući instrumenti politike, ili njihova kombinacija, koji, po mišljenu najviše zainteresovane strane prevoznika, imaju najpovoljniji uticaj. Određivanjem ključnih problema sektora, njihovim rangiranjem i utvrđivanjem prioriteta od strane onih koji su najviše zainteresovani stvara se osnova za definisanje ciljeva, politika i instrumenata kojima vlada može delovati u ovom sektoru. Na osnovu raspoloživih izvora podataka i rezultata dobijenih anketom prevoznika, opisani su osnovni segmenti sektora i njihove karakteristike. Prikazana je i metodologija identifikacije, izbora i rangiranja ključnih problema, kao i rezultati istraživanja. Određeni su i opisani kritični problemi od značaja za ovaj sektor. Na kraju, opisani su uzroci i efekti problema, kao i mogući načini delovanja vlade u pravcu njihovog eliminisanja ili ublažavanja negativnog efekta. Ključne reči: Analiza politike, Međunarodni drumski transport, Prevoznici, Anketa Gubitci vremena

Osoblje

Porast troškova

Nelojalna konkurencija

Status

Naplata

Pristup tržištu

Pitanja zakonodavstva Grupa

Problemi u grupi

Prvorangirani problem u grupi

Slika 6. Prosečan rang grupe problema zasnovan na prosečnom rangu grupe i rangu problema u grupi

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VIZITORSKI CENTRI NA ARHEOLOŠKIM LOKALITETIMA U SRBIJI KAO PODSTICAJ EKONOMSKOM RAZVOJU ZEMLJE Mr Marko Nikolić - Arhitektonski fakultet, Univerziteta u Beogradu Turizam je u celom svetu u intenzivnom razvoju i u mnogim zemljama predstavlja značajan izvor prihoda. Međunarodne organizacije za zaštitu kulturnog nasleđa preporučuju da se istorijski spomenici, lokaliteti kulturnog nasleđa koriste i kao turističke destinacije. Prezentacija ovih spomenika kulture treba da bude veoma pažljiva, kako se ne bi ugrozila njihova istorijska i umetnička vrednost. Izgradnja „Vizitorskih centara“ na arheološkim lokalitetima je jedan od najefektinijih načina za prezentaciju ovog vrednog nasleđa. U Srbiji ima nekoliko arheoloških nalazišta koji su vrlo interesantni za razvoj kulturnog turizma, posebno Viminacijum, Sirmijum i Gamzigrad. Analiza stanja na ovim lokalitetima pokazuje da je na ovim lokalitetima ostvaren značajn napredak. Postoje i planovi za dalji razvoj. Međutim, već izgrađeni centri i oni čija se gradnja planira, nisu u dovoljnoj meri zasnovani na principima i preporukama usvojenim i preporučenim od strane svetskih eksperata i međunarodnih organizacija. Stoga još dosta treba da se uradi kako bi se naši arheološki lokaliteti i spomenici kulture efektivno uključili u našu turističku ponudu. Ovo će stvoriti potrebne preduslove da arheološki lokaliteti i drugi spomenici našeg kulturno nasleđa postanu stvarni input za održivi razvoj cele zemlje. Ključne reči: Arheološki lokalitet, Kulturni turizam, Vizitorski centri, Održivi razvoj

Slika 1. Viminacium, atrijum vizitorski centar

Slika 3. Sirmijum, vizitorski centar

Slika 5. Gamzigrad, projekat vizitorskog centra

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KOMPARATIVNA ANALIZA KARAKTERISTIKA PNEUMATIKA PUTNIČKIH VOZILA U SRBIJI Dr Gradimir Danon - Šumarski fakultet, Univerziteta u Beogradu Dr Branko Vasić - Mašinski fakultet, Univerziteta u Beogradu Bojan Jokić - Mašinski fakultet, Univerziteta u Beogradu Žikica Simović - Mašinski fakultet, Univerziteta u Beogradu Marko Marjanović - Mašinski fakultet, Univerziteta u Beogradu

U radu su predstavljeni rezultati istraživanja stanja i karakteristika pneumatika koji se voze u Srbiji. Prikupljeni su podaci o pohabanosti dezena, dimenzijama, starosti, marki, tipu više od 700 pneumatika kao i podaci o vozilima na kojima su montirani. Osnovni zaključak je da je stanje pneumatika dobro, odnosno znatno bolje nego što je sanje voznog parka u Srbiji. Prosečna izmerena dubina šare protektora bila je oko 5 mm, a prosečna starost kontrolisanih pneumatika oko 3 godine. Značajan deo pregledanih vozila bio je opremljen zimskim pneumaticima. Prva istraživanja (Beograd, novembar 2009) o korišćenju zimskih dala su dobre rezultate sa oko 25% automobila opremljenih sa takvim gumama. Tokom drugog istraživanja (Beograd, juli 2010) uočen je pad od oko 5%. U Užicu, gde su sprovedena istraživanja u novembru 2010 godine utvrđeno je da se taj procenat popeo na 50%. Struktura i starost voznog parka u Srbiji su ocenjeni kao nezadovoljavajući. Sa sadašnjim stepenom obnove voznog parka, takvo stanje će se veoma polako menjati na bolje što će uticati i na strukturu i karakteristike pneumatika koje će vozači u Srbiji kupovati u narednim godinama. Ključne reči: Pneumatici, Zimski pneumatici, Dubina šare, Starost pneumatika, Starost vozila

Slika 1. Vozila u Srbiji - starosna struktura u 2008. godini

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TEORIJSKO-EKSPERIMENTALNA METODA ZA OPTIMIZACIJU DINAMIČKOG PONAŠANJA MODULARNIH NADGRADNJI VATROGASNIH VOZILA Mr Saša R. Mitić - Mašinski fakultet, Univerziteta u Beogradu Dr Branislav B. Rakićević - Mašinski fakultet, Univerziteta u Beogradu Dragan D. Stamenković - Mašinski fakultet, Univerziteta u Beogradu Doc. dr Vladimir M. Popović - Mašinski fakultet, Univerziteta u Beogradu U radu je predstavljena teorijsko-eksperimentalna metoda razvijena sa ciljem optimizacije dinamičkog ponašanja modularnih nadgradnji vatrogasnih vozila. Teški uslovi eksploatacije u kojima se vatrogasna vozila koriste, kao i posebni zahtevi za ovu vrstu vozila zahtevaju posvećenost u pristupu optimizaciji nadgradnji sa stanovišta napona, deformacija, zamora, buke, kao i udobnosti i efektivnosti vozila. Optimizacija podrazumeva izbor optimalnih oblika, materijala, dimenzija, veza, oslanjanja, prigušenja i izolacije modula, sa ciljem postizanja optimalnog dinamičkog ponašanja nadgradnje. Metoda opisana u radu sastoji se od dva međusobno povezana dela – teorijskog i eksperimentalnog. Teorijski deo sastoji se od numeričkog modeliranja varijanti nadgradnje i proračuna odziva na dinamičke pobude korišćenjem metode konačnih elemenata, čiji se rezultati naknadno verifikuju kroz eksperimente. Eksperimentalni deo zasniva se na pobudi fizičkih modela nadgradnji pomoću posebno razvijenog mehaničkog pobudnog uređaja, praćenju odziva nadgradnji, kao i promeni ulaznih parametara u procesu projektovanja nadgradnji, sa ciljem dobijanja nadgradnje sa što boljim dinamičkim karakteristikama. Sopstvene frekvencije nadgradnje, važne u smislu rezonantnih zona, dobijene su korišćenjem testa udarom i FFT analize. Ova metoda se pokazala adekvatnom za optimizaciju dinamičkog ponašanja modularnih nadgradnji, kao što su one kod vatrogasnih vozila. Celokupna ispitna instalacija korišćena kroz ovu metodu ilustrativno je prikazana u radu. Takođe, date su smernice za dalje aktivnosti, razvoj i unapređenje ove metode. Ključne reči: Vozila za specijalne namene, Modularna nadgradnja, Optimizacija, Dinamičko ponašanje, Mehanička pobudni uređaj, Metoda konačnih elemenata, FFT analiza, Test udarom

Slika 1. MKE - model jedne varijante nadogradnje (greda i ploča konačnih elemenata)

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REZIMEI RADOVA Broj rada: 9(2011)1,194

PRILOG RAZMATRANJU UTICAJA EFEKATA LEKHNITSKOG NA OSNOVNE DINAMIČKE PARAMETRE KOMPOZITNE STRUKTURE Dr Radoljub Tomić - Industrija hidraulike i pneumatike - Prva petoletka, Trstenik Dr Predrag Petrović - Institut “Kirilo Savić”, Beograd Dr Tomislav Jovanović - Institut “Kirilo Savić”, Beograd

Dinamička analiza anizotropnih (u ovom radu generalisano ortotropna) struktura često se svodi na analizu kvazi izotropnih struktura. Na taj način, moguće je dobiti rezultate prihvatljive tačnosti. Poboljšanje rezultata se može postići prvenstveno posredstvom odgovarajućih matrica krutosti, kod kojih su uključene specifičnosti kompozitnih (anizotropnih) materijala u vezi interakcije normalnih napona i smičućnih deformacija odnosno smičućnih napona i dilatacija (bazirano na efektima Lekhnitskog). Rezultati analize, za dva napred navedena modela jedne kompozitne strukture (generalisano ortotropne i kvazi ortotropne), dati su u grafičkoj i tabelarnoj formi. Ključne reči: dinamička analiza, kompozitni materijal, efekti Lekhnitskog I - mod

III - mod

kvaziortotropska struktura generisano ortotropska struktura Slika 4. Grafički prikaz modova I i III

Journal of Applied Engineering Science 9(2011)1

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Journal of Applied Engineering Science 9(2011)1

Istraživanja i projektovanja za privredu - Applied Engineering Science 9(2011)1  

Journal of Applied Engineering Science publish original and review articles covering the concept of technical science, energy and environmen...

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