Dragan Kostic | University of Niš (original) (raw)

Papers by Dragan Kostic

Facta Universitatis, 2017

The use of renewable energies is imperative nowadays. One of the ways to use clean technologies i... more The use of renewable energies is imperative nowadays. One of the ways to use clean technologies is installation of photovoltaic systems which convert solar energy into electricity, through solar plants. The country's potential for usage of solar energy is determined by the analysis of climatic conditions. The research is conducted on the example of a small-scale solar plant-a pilot project installed in the city of Niš, concerning the analysis of the mounted system and giving the recommendations for their design with the aim of improving efficient energy use. Limitations in the installation of solar plants can occur in the case of an unfavorable position of the building where the installation is planned, and more often, the limitations are related to the investment costs and length of the repayment period of these kinds of technologies. This paper represents a promotion of sustainable electricity supply for our country and it is in correlation with the legal directives of using renewable energies.

Procedia Engineering, 2015

The article deals with the problem of energy saving by optimizing heat loss and measures for ener... more The article deals with the problem of energy saving by optimizing heat loss and measures for energy recovery in the existing preschools. The paper presents a theoretical basis, simulation and computations-calculations of heating energy needs for established models, by using appropriate software packages. The program and development of models for improving energy qualities of the envelope, with the tendency of switching to renewable energy sources, are defined. The methods used in this paper include the method of modelling based on the digital simulation of the representative facility, as well as local visits and interviews with relevant researchers, policy makers and preschool educators. The survey is conducted through a case study on the territory of the City of Nis.

Tehnicki vjesnik - Technical Gazette, 2021

The revitalization of existing masonry buildings, built decades ago, is a very topical and comple... more The revitalization of existing masonry buildings, built decades ago, is a very topical and complex structural engineering issue, especially when the building was built in the area of significant seismic activity. A large number of masonry buildings in the city of Niš, as well as in other places in Serbia, were built in the period before the adoption of technical regulations on the design and construction of seismically resistant structures and they are at insufficient safety level in the event of an earthquake. Therefore, it is necessary that structural strengthening meets the seismic resistance requirements laid down in Eurocode 8 or other relevant codes. In order to choose the method of structural strengthening, detailed seismic analyses must be carried out in several variants along with the application of relevant technical regulations. The effects of five analyzed structural strengthening methods were checked against the provisions of Eurocode 8, Part 1 and Part 3, which relate to the recommendations for the geometric characteristics of shear walls, and they were applied on two types of existing masonry buildings in Niš. On the basis of the performed analyses, conclusions were drawn regarding the methodological approach of the assessment of the condition of the structure, its seismic resistance and decision-making on remediation and/or strengthening measures.

Zbornik radova Građevinskog fakulteta, 2019

The paper provides a multidisciplinary (archeological, architectural, structural and thermo-techn... more The paper provides a multidisciplinary (archeological, architectural, structural and thermo-technical) methodological approach to improve the efficiency of protective structures from the mentioned point of view, at the locations of Mediana and Drenovac. The aim of the paper is to provide optimal architectural and structural solutions based on an analytical multidisciplinary approach related on measured microambient parameters.

Transactions of FAMENA, 2019

The evaluation of the reliability status of complex technical systems is of great importance for ... more The evaluation of the reliability status of complex technical systems is of great importance for their uninterrupted operation at full capacity and with a preventive maintenance plan in place. Limited research on the subject indicates that there is need to improve models of reliability simulation. The goal of the paper is to outline an improved operational reliability model of a thermal power plant using the power plant block "TENT A" as an example. The model is based on the failure interaction of the system components and is based on probability theory-the Weibull distribution, the Monte Carlo simulation and the established mathematical models of failure interaction of components using new software solutions. The results of the simulations show which direction the development of preventive activities should take in the case of failure interaction, which might lead to minimum downtime in power plant operations in the future.

Gradjevinski materijali i konstrukcije, 2020

Facta universitatis - series: Architecture and Civil Engineering, 2021

The presented work is the result of affirmation of synergistic work of experts dealing with archi... more The presented work is the result of affirmation of synergistic work of experts dealing with architectural and acoustic design with the aim and purpose of finding an adequate solution for optimal correction of the effect of GHG systems installed on the facade of the subject (case study) office building in Belgrade. Measurements established that the noise of the constructed GHG systems affected the residential building in the immediate vicinity. The effect of the constructed devices (refers to the installed units) of the office building in question in the case when they operate at full capacity was measuring to be about 58 dB (A). The urban zone in which the building is located (Vracar-Belgrade) belongs to the category of "office residential area" in which the outdoor noise level permitted for the period of day is 60 dB (A), and for the night period is 50 dB (A). Taking into account the stated facts, it has been unequivocally established that GHG systems to a certain extent ...

Journal of the Croatian Association of Civil Engineers, 2013

Determination of prestressing levels for cable trusses as a function of their stability The stabi... more Determination of prestressing levels for cable trusses as a function of their stability The stability of prestressed cable trusses subjected to static and dynamic loads is analysed in the paper. The stiffness of the elastic cable truss system was varied by changing the prestressing force. Modelling results for different levels of tension show that, in terms of satisfying dynamic resistance conditions, a much greater tensile force is required for cable grids with diagonal members, compared to those with vertical rods. The conclusions derived constitute recommendations for the use of calculation methods, as well as for the determination of prestressing forces under which stability criteria are fulfilled.

Tehnicki vjesnik - Technical Gazette, May 1, 2018

Even though membrane structures have been increasingly used in the world, their energy efficiency... more Even though membrane structures have been increasingly used in the world, their energy efficiency is very unfavourable due to poor thermal properties. This causes relatively high consumption of heating energy in the winter, as well energy consumed for the operation of airconditioning during the summer, that is, under circumstances which require thermal comfort. Since thermal comfort depends on the air temperature and temperature of the interior surfaces of the envelope, this paper presents a study of the measurement and comparison of temperatures of single and double membrane structures in the summer period. Data collection was accomplished by measuring two adjacent structures, one covered with single and the other covered by a double membrane. Verification of the measured data was performed by comparing it with the official measured temperatures in the same period. The air temperatures were measured in all the separate air compartments and particular surfaces of each membrane. By analysing the measured data and their classification based on daylight and night-time periods, certain conclusions were drawn about the influence of an additional layer of membrane on the temperature of the air inside a covered structure.

Brain Research, 2003

An experimental approach to achieve robust performance of direct-drive robot motion control is pr... more An experimental approach to achieve robust performance of direct-drive robot motion control is presented in this paper. It consists of: (i) decoupling the robot dynamics via feedback linearisation; (ii) frequency domain identification of the decoupled dynamics; (iii) compensation of these decoupled dynamics using feedback controllers designed via μ-synthesis. The designed controllers ensure robust performance, i.e., guaranteed accuracy of robot motions despite uncertainty in its dynamics and disturbances affecting the robot operation. Theoretical aspects of the control design are formulated. Its practical implementation on a direct-drive robotic arm is demonstrated in detail. Experimental investigation confirms the quality of the design: specifications on performance and robustness are practically realized.

Objects covered by fabric roof membranes are specific in terms of energy consumption, primarily b... more Objects covered by fabric roof membranes are specific in terms of energy consumption, primarily because of the negligible thickness of the material and its good thermal conduction properties. One of the ways of improving the energy efficiency of these objects is the implementation of a double fabric roof membrane structure with an enclosed non ventilated air layer. This paper analyzes the thermal-insulation behaviour of the air layer enclosed between tensile fabric roof membranes which are used for structural purposes. The compilation of the necessary data was carried out by measuring a real object covered by a double fabric roof membrane, semi-cylindrical in shape. The surface temperatures of each membrane were measured, as were the outside and inside air temperature and the air temperature between the membranes during the summer months. In addition, the solar irradiance during the same period was also measured. The analysis of the measured data took into consideration all the pres...

Facta universitatis - series: Architecture and Civil Engineering, 2018

Energy consumption has reached its highest level globally. Buildings have the largest share in to... more Energy consumption has reached its highest level globally. Buildings have the largest share in total energy consumption, so designers must take into account their functioning and the consequences that can arise. Passive solar design is an imperative in modern architecture, and Trombe wall, as one of the principles of this design, is certainly distinguished. The paper presents an overview of the characteristics of the construction of the Trombe Wall in order to improve thermal stability and reduce energy consumption in buildings. Starting from the consideration of climatic influencing factors, through the heat capacity of the materials applied and their thickness and color of the thermal mass, it is very important to know in detail all the factors that can lead to the improvement of the efficiency of this system. The specific heat of the walls in the building, the time delay, the decrement factor and the influence and position of the thermal insulation were also taken into account. The effect of glazing as well as the influence of the ventilation openings were highlighted as significant elements. On the basis of the analysis of the above components, the conclusions and guidelines for designing this type of constructions were made in order to improve the efficiency and reduced energy consumption while providing adequate comfort in the facility.

Thermal Science

The analysis conducted in this paper was initiated by the fact that Serbia emitted around 80 mill... more The analysis conducted in this paper was initiated by the fact that Serbia emitted around 80 million tons of CO2, equivalent in 1990, and in between 85-89 million tons in 2010, which places it among ten countries with the highest emission of CO2 per capita in the world (data by Cener for Ecology and Sustainable Development, Subotica, Serbia). This paper is aimed at making a correlation between the improvement of thermal performance of structural elements of buildings in order to enhance their energy efficiency, which is also economically justified, and reduction of GHG (CO2) emission whose economic benefits are not so easy to assess even though it represents an environmental problem. The case study analysis, presented by this paper, using the example of a select number of kindergartens in the territory of the city of Nis, Serbia, is aimed at determining the correlation of the effects of improvement of their energy performances on the reduction of GHG emission reduction by quantifyin...

Facta universitatis - series Architecture and Civil Engineering

Minimal surfaces are the surfaces of the smallest area spanned by a given boundary. The equivalen... more Minimal surfaces are the surfaces of the smallest area spanned by a given boundary. The equivalent is the definition that it is the surface of vanishing mean curvature. Minimal surface theory is rapidly developed at recent time. Many new examples are constructed and old altered. Minimal area property makes this surface suitable for application in architecture. The main reasons for application are: weight and amount of material are reduced on minimum. Famous architects like Otto Frei created this new trend in architecture. In recent years it becomes possible to enlarge the family of minimal surfaces by constructing new surfaces. Key words: Minimal surface, spatial roof surface, area, soap film, architecture

Facta universitatis - series: Architecture and Civil Engineering, 2008