Nikša Jajac | University of Split, Croatia (original) (raw)
Papers by Nikša Jajac
Sustainability
Renovation of flat roofs typically involves repairing or replacing the existing roof to improve i... more Renovation of flat roofs typically involves repairing or replacing the existing roof to improve its performance and extend its lifespan. The renovation process may include a range of tasks depending on the condition of the roof, such as repairing leaks, replacing damaged or deteriorated materials, adding insulation, or upgrading drainage systems. This research aim was to establish the priority of renovation of flat roofs of the public building based on the principles of multi-criteria analysis and fuzzy set theory, using the multi-criteria method PROMETHEE II in fuzzy logic form (F-PROMETHEE II). The proposed approach is adequate due to its ability to transform the uncertain and vague information received from an expert into a fuzzy number. This way, the objective outcome can be obtained, the criteria conflict removed and the alternatives ranking and mutual comparison enabled. It was necessary to analyze the existing literature, the flat roofs of a public building in terms of their ...
Applied Sciences
This paper presents a systematic and sustainable approach to nonurban road network maintenance ma... more This paper presents a systematic and sustainable approach to nonurban road network maintenance management based on the integration of multicriteria decision-making methods and methods of monitoring and control in the service of planning, implementation and monitoring and control as the basic management processes. This approach is based on the developed maintenance management model for nonurban road network, which consists of a weighting sub-model based on the AHP method, a priority road ranking sub-model based on TOPSIS method and a monitoring and control sub-model based on the combination of TOPSIS and Earned Value Analysis (EVA). The described model with all its supporting sub-models is tested on the case study of the regional road network of Herzegovina-Neretva County. The analysis of the obtained results shows the effectiveness of the presented approach to road maintenance management and the possibility of its practical application.
Sustainability
The dynamic nature and increasing complexity of construction projects impose many challenges for ... more The dynamic nature and increasing complexity of construction projects impose many challenges for project planning and control. For years, there has been a debate about the success of construction projects and how to achieve them. A bibliometric study was developed based on 750 scientific papers on project success, decision support system, optimization, and project performance. Data are collected from the Scopus and Web of Science databases and cover the period from January 2000 to February 2022. Several types of analysis were made—data information, research growth, most productive country, most productive institution, most relevant source, most influential authors, collaborations between countries, institutions, authors, most relevant or most cited publication, highest frequency, and keyword occurrence. It is pointed out which are the important authors and journals and in which direction further research should be directed. This paper identifies that construction is one of the least...
Croatian Operational Research Review, 2010
Urban road infrastructure management deals with complex decision making process. There are severa... more Urban road infrastructure management deals with complex decision making process. There are several reasons for a complexity such as: multi-disciplinarity, lots of participants, huge quantity of information, limited budget, conflict goals and criteria. These facts indicate that decision making processes in urban road infrastructure management belong to ill-defined problems. In order to cope with such complexity and to help managers during decision making processes this research proposes an application of multicriteria methods. Therefore, a generic concept of decision support for urban road infrastructure management based on multicriteria analysis is proposed. Three multicriteria methods: AHP, SAW and PROMETHHE, in a combination with 0-1 programming are used. The main advantage of an application of multicriteria analysis is that all stakeholders could be objectively included into decision process. Therefore, setting up of criteria weights involves opinions from all stakeholders’ group...
Croatian Operational Research Review ( …
This paper aims to propose a decision support system for maritime crisis situation, due to fact t... more This paper aims to propose a decision support system for maritime crisis situation, due to fact that Croatia has decided to implement Directive 2002/59/EC to define places of refuge for ships in need of assistance off their coasts, or to develop techniques for providing assistance to such ships. In order to fulfill this Directive it is necessary to build an effective Decision Support System (DSS) based on GIS and mathematical modeling. The basic module of the proposed system is GIS, for all levels of DSS, that comprise information subsystems about spatial and other data and serves the other modules with data and information. Starting points for analysis are shipping corridors, and 380 potential locations for places of refuge designated in the official navigational pilot book. Multicriteria analysis, with GIS-generated input data, has been used to establish "worthiness" of a place of refuge for each ship category, taking into account kinds of accident. Proposed mathematical models facilitate optimal usage of "available intervention resources".
Infrastructures
Management of nonurban road network maintenance is a complex management process that requires the... more Management of nonurban road network maintenance is a complex management process that requires the inclusion of many technical, economic, and other characteristics of the problem, as well as the continuous application of new knowledge and approaches, to maintenance management. To effectively manage the maintenance of the road network in conditions of limited financial resources, maintenance is examined through three interrelated management functions of planning: implementation, monitoring, and maintenance control. This paper includes an analysis of current and relevant papers on this topic. Based on the conducted analysis, the paper gives a theoretical framework and proposes a management model for road network maintenance between urban areas. This model supports the previously mentioned management functions using Multicriteria Decision-Making Methods. The AHP method and the TOPSIS method are engaged in the process of generating a priority road maintenance plan and Earned Value Analys...
Proceedings of the EWGT2006 Joint Conferences, 2006
Zbornik radova 8. simpozija ovlaštenih inženjera geodezije - GEODETSKA POLITIKA ZA BUDUĆNOST, 2015
Ranking zones model – a multicriterial approach to the spatial management of urban areas
Journal of Marine Science and Engineering, 2021
The focus of this paper is to define anchorage management model for concession planning purposes ... more The focus of this paper is to define anchorage management model for concession planning purposes to provide quality support to experts in spatial planning when developing maritime spatial plans. The research aim is to develop an anchorage management model that includes decision and concession support concept. Decision support concept is defined in order to support the processes of identifying potential anchorage locations, their evaluation and comparison, and finally, the priority ranking and selection of locations for their construction. The final step is modelling the concession support concept that includes financial analysis to concession parameters definition. The problem of decision making and concession of the anchorage location selection is complex and ill-structured because of the unsystematic and ad-hoc decisions by all included stakeholders. Additionally, the involvement of several stakeholders’ groups with different preferences and background knowledge, a large amount of...
Tehnicki vjesnik - Technical Gazette, 2018
The increasing complexity of construction projects imposes the need to address various aspects of... more The increasing complexity of construction projects imposes the need to address various aspects of project management in more detail. The success of a construction project depends on many variables and the process of supplier selection is certainly one of them. In recent years, the importance of electronic reverse auctions use in public sector construction procurement has been increasing, since they can bring substantial price savings. However, auctions are also criticized since they may result in the submission of abnormally low bids. This paper therefore aims to explore the impact of electronic reverse auctions on the competitive environment in public works contracts and on the occurrence of abnormally low bids. The results of quantitative research on Czech construction tenders revealed that the use of auctions decreases the number of bidders while increasing the probability of occurrence of abnormally low bids.
This research will show an approach to the conceptualisation of decision support systems (DSS) fo... more This research will show an approach to the conceptualisation of decision support systems (DSS) for an emergency management especially for natural disaster management. The original paradigm of DSS data-dialog-models has to be adjusted to the various needs of emergency systems. Presentation will discuss various organisational aspects of DSS regarding both model and functional management, such as hierarchic approach that is quite helpful because it gives the framework for the definition of the basic entities for the further analysis. Furthermore, wide use of Geographical Information System (GIS) as a part of data segment of DSS makes it more powerful. Special attention will also be paid on application of multicriteria analysis as decision tool within DSS for risk analysis as well as priority setting processes during disaster preparedness. For example, after the analysis it could be estimated where the territories which cannot be reached in reasonable time are situated and what strategy...
Problems related to the management of projects, specifically priority ranking problems, can be fo... more Problems related to the management of projects, specifically priority ranking problems, can be found in all stages of projects’ life cycles, mostly as the result of inadequate decision making. Such place where engineering students can be challenged both creatively and by knowledge in a complex project environment can be found in the graduate study programme under the course of Project Management at the Faculty of Civil Engineering in Rijeka. Priority ranking of student papers in faculty environment deals with complex decision making problems which is characterized by lots of participants, multidisciplinarity, huge quantities of information, different opinions as well as conflicting goals and criteria. In order to cope with such complexity and to help professors during evaluation process of student papers, the use of concept based on multi- criteria analysis for solving priority setting problem is proposed. The starting point of proposed concept is goal analysis and development of ad...
The paper presents the concept of the decision support system that helps decision-makers to solve... more The paper presents the concept of the decision support system that helps decision-makers to solve problems of risk management in the tourist regions. Accepting the international agreements and protocols, as well as hosting numerous tourists during summer, Croatia faces the need for establishment of Enhanced Emergency Call Services. Furthermore, support from information and telecommunication technology to both civil services and services for crises situations, profoundly contributes for lowering the human life threats, as well as materials, goods and environment protection, covering, at the same time, needs for private and public information. In order to make Enhanced Emergency Call Services (Centers 112) more efficient in tourist regions, based on collected data, Decision Support System (DSS) for Centers 112 is conceptualized. It consists of several modules containing model and software support for "Centre 112" functioning. Starting point was result from risk analysis and ...
Regarding the factthat ready-mixed concret has both great importance and economic effect that arr... more Regarding the factthat ready-mixed concret has both great importance and economic effect that arrive from the particular characteristics of the distribution system, a system analysis of production, transport and usage of the concrete was performed resulting in the conceptualisation of the "Decision Suppot System" (DSS) for the ready-mixed concrete management. The three decision and management levels was analysed and a DSS for production and distribution of ready-mixed concrete is conceptualised, accordingly. The DSS presented in this paper combines various mathematical models and computer support at all decision levels as well as georaphical information system (GIS) as a logistic support to ready-mixed concrete distribution. The model management system of DSS is presented by following examples: a procedure for finding the optimal concrete mixture, method for a selection of an optimal techno-economic solution for the ready-mixed concrete distribution for the certain area an...
Sustainability
Renovation of flat roofs typically involves repairing or replacing the existing roof to improve i... more Renovation of flat roofs typically involves repairing or replacing the existing roof to improve its performance and extend its lifespan. The renovation process may include a range of tasks depending on the condition of the roof, such as repairing leaks, replacing damaged or deteriorated materials, adding insulation, or upgrading drainage systems. This research aim was to establish the priority of renovation of flat roofs of the public building based on the principles of multi-criteria analysis and fuzzy set theory, using the multi-criteria method PROMETHEE II in fuzzy logic form (F-PROMETHEE II). The proposed approach is adequate due to its ability to transform the uncertain and vague information received from an expert into a fuzzy number. This way, the objective outcome can be obtained, the criteria conflict removed and the alternatives ranking and mutual comparison enabled. It was necessary to analyze the existing literature, the flat roofs of a public building in terms of their ...
Applied Sciences
This paper presents a systematic and sustainable approach to nonurban road network maintenance ma... more This paper presents a systematic and sustainable approach to nonurban road network maintenance management based on the integration of multicriteria decision-making methods and methods of monitoring and control in the service of planning, implementation and monitoring and control as the basic management processes. This approach is based on the developed maintenance management model for nonurban road network, which consists of a weighting sub-model based on the AHP method, a priority road ranking sub-model based on TOPSIS method and a monitoring and control sub-model based on the combination of TOPSIS and Earned Value Analysis (EVA). The described model with all its supporting sub-models is tested on the case study of the regional road network of Herzegovina-Neretva County. The analysis of the obtained results shows the effectiveness of the presented approach to road maintenance management and the possibility of its practical application.
Sustainability
The dynamic nature and increasing complexity of construction projects impose many challenges for ... more The dynamic nature and increasing complexity of construction projects impose many challenges for project planning and control. For years, there has been a debate about the success of construction projects and how to achieve them. A bibliometric study was developed based on 750 scientific papers on project success, decision support system, optimization, and project performance. Data are collected from the Scopus and Web of Science databases and cover the period from January 2000 to February 2022. Several types of analysis were made—data information, research growth, most productive country, most productive institution, most relevant source, most influential authors, collaborations between countries, institutions, authors, most relevant or most cited publication, highest frequency, and keyword occurrence. It is pointed out which are the important authors and journals and in which direction further research should be directed. This paper identifies that construction is one of the least...
Croatian Operational Research Review, 2010
Urban road infrastructure management deals with complex decision making process. There are severa... more Urban road infrastructure management deals with complex decision making process. There are several reasons for a complexity such as: multi-disciplinarity, lots of participants, huge quantity of information, limited budget, conflict goals and criteria. These facts indicate that decision making processes in urban road infrastructure management belong to ill-defined problems. In order to cope with such complexity and to help managers during decision making processes this research proposes an application of multicriteria methods. Therefore, a generic concept of decision support for urban road infrastructure management based on multicriteria analysis is proposed. Three multicriteria methods: AHP, SAW and PROMETHHE, in a combination with 0-1 programming are used. The main advantage of an application of multicriteria analysis is that all stakeholders could be objectively included into decision process. Therefore, setting up of criteria weights involves opinions from all stakeholders’ group...
Croatian Operational Research Review ( …
This paper aims to propose a decision support system for maritime crisis situation, due to fact t... more This paper aims to propose a decision support system for maritime crisis situation, due to fact that Croatia has decided to implement Directive 2002/59/EC to define places of refuge for ships in need of assistance off their coasts, or to develop techniques for providing assistance to such ships. In order to fulfill this Directive it is necessary to build an effective Decision Support System (DSS) based on GIS and mathematical modeling. The basic module of the proposed system is GIS, for all levels of DSS, that comprise information subsystems about spatial and other data and serves the other modules with data and information. Starting points for analysis are shipping corridors, and 380 potential locations for places of refuge designated in the official navigational pilot book. Multicriteria analysis, with GIS-generated input data, has been used to establish "worthiness" of a place of refuge for each ship category, taking into account kinds of accident. Proposed mathematical models facilitate optimal usage of "available intervention resources".
Infrastructures
Management of nonurban road network maintenance is a complex management process that requires the... more Management of nonurban road network maintenance is a complex management process that requires the inclusion of many technical, economic, and other characteristics of the problem, as well as the continuous application of new knowledge and approaches, to maintenance management. To effectively manage the maintenance of the road network in conditions of limited financial resources, maintenance is examined through three interrelated management functions of planning: implementation, monitoring, and maintenance control. This paper includes an analysis of current and relevant papers on this topic. Based on the conducted analysis, the paper gives a theoretical framework and proposes a management model for road network maintenance between urban areas. This model supports the previously mentioned management functions using Multicriteria Decision-Making Methods. The AHP method and the TOPSIS method are engaged in the process of generating a priority road maintenance plan and Earned Value Analys...
Proceedings of the EWGT2006 Joint Conferences, 2006
Zbornik radova 8. simpozija ovlaštenih inženjera geodezije - GEODETSKA POLITIKA ZA BUDUĆNOST, 2015
Ranking zones model – a multicriterial approach to the spatial management of urban areas
Journal of Marine Science and Engineering, 2021
The focus of this paper is to define anchorage management model for concession planning purposes ... more The focus of this paper is to define anchorage management model for concession planning purposes to provide quality support to experts in spatial planning when developing maritime spatial plans. The research aim is to develop an anchorage management model that includes decision and concession support concept. Decision support concept is defined in order to support the processes of identifying potential anchorage locations, their evaluation and comparison, and finally, the priority ranking and selection of locations for their construction. The final step is modelling the concession support concept that includes financial analysis to concession parameters definition. The problem of decision making and concession of the anchorage location selection is complex and ill-structured because of the unsystematic and ad-hoc decisions by all included stakeholders. Additionally, the involvement of several stakeholders’ groups with different preferences and background knowledge, a large amount of...
Tehnicki vjesnik - Technical Gazette, 2018
The increasing complexity of construction projects imposes the need to address various aspects of... more The increasing complexity of construction projects imposes the need to address various aspects of project management in more detail. The success of a construction project depends on many variables and the process of supplier selection is certainly one of them. In recent years, the importance of electronic reverse auctions use in public sector construction procurement has been increasing, since they can bring substantial price savings. However, auctions are also criticized since they may result in the submission of abnormally low bids. This paper therefore aims to explore the impact of electronic reverse auctions on the competitive environment in public works contracts and on the occurrence of abnormally low bids. The results of quantitative research on Czech construction tenders revealed that the use of auctions decreases the number of bidders while increasing the probability of occurrence of abnormally low bids.
This research will show an approach to the conceptualisation of decision support systems (DSS) fo... more This research will show an approach to the conceptualisation of decision support systems (DSS) for an emergency management especially for natural disaster management. The original paradigm of DSS data-dialog-models has to be adjusted to the various needs of emergency systems. Presentation will discuss various organisational aspects of DSS regarding both model and functional management, such as hierarchic approach that is quite helpful because it gives the framework for the definition of the basic entities for the further analysis. Furthermore, wide use of Geographical Information System (GIS) as a part of data segment of DSS makes it more powerful. Special attention will also be paid on application of multicriteria analysis as decision tool within DSS for risk analysis as well as priority setting processes during disaster preparedness. For example, after the analysis it could be estimated where the territories which cannot be reached in reasonable time are situated and what strategy...
Problems related to the management of projects, specifically priority ranking problems, can be fo... more Problems related to the management of projects, specifically priority ranking problems, can be found in all stages of projects’ life cycles, mostly as the result of inadequate decision making. Such place where engineering students can be challenged both creatively and by knowledge in a complex project environment can be found in the graduate study programme under the course of Project Management at the Faculty of Civil Engineering in Rijeka. Priority ranking of student papers in faculty environment deals with complex decision making problems which is characterized by lots of participants, multidisciplinarity, huge quantities of information, different opinions as well as conflicting goals and criteria. In order to cope with such complexity and to help professors during evaluation process of student papers, the use of concept based on multi- criteria analysis for solving priority setting problem is proposed. The starting point of proposed concept is goal analysis and development of ad...
The paper presents the concept of the decision support system that helps decision-makers to solve... more The paper presents the concept of the decision support system that helps decision-makers to solve problems of risk management in the tourist regions. Accepting the international agreements and protocols, as well as hosting numerous tourists during summer, Croatia faces the need for establishment of Enhanced Emergency Call Services. Furthermore, support from information and telecommunication technology to both civil services and services for crises situations, profoundly contributes for lowering the human life threats, as well as materials, goods and environment protection, covering, at the same time, needs for private and public information. In order to make Enhanced Emergency Call Services (Centers 112) more efficient in tourist regions, based on collected data, Decision Support System (DSS) for Centers 112 is conceptualized. It consists of several modules containing model and software support for "Centre 112" functioning. Starting point was result from risk analysis and ...
Regarding the factthat ready-mixed concret has both great importance and economic effect that arr... more Regarding the factthat ready-mixed concret has both great importance and economic effect that arrive from the particular characteristics of the distribution system, a system analysis of production, transport and usage of the concrete was performed resulting in the conceptualisation of the "Decision Suppot System" (DSS) for the ready-mixed concrete management. The three decision and management levels was analysed and a DSS for production and distribution of ready-mixed concrete is conceptualised, accordingly. The DSS presented in this paper combines various mathematical models and computer support at all decision levels as well as georaphical information system (GIS) as a logistic support to ready-mixed concrete distribution. The model management system of DSS is presented by following examples: a procedure for finding the optimal concrete mixture, method for a selection of an optimal techno-economic solution for the ready-mixed concrete distribution for the certain area an...