Multiagent systems (MAS) are systems consisting of several autonomous entities, called agents, which interact with each other to either further their own interests (competition) or in pursuit of a joint goal (cooperation). In systems composed of multiple autonomous agents, negotiation is a key form of interaction that enables groups of agents to arrive at a mutual agreement regarding some belief, goal or plan. The aim of this thesis is to develop a multiagent system that simulates the negotiation process between parties about sharing of cost overrun in international construction projects. The developed tool can be used to understand how the risks and associated costs are shared between parties under different scenarios related with the risk allocation clauses in the contract, objectives of parties and level of knowledge about actual sources of cost overrun. MAS can be utilized by decision-makers to predict potential outcomes of a negotiation process.

Existing petroleum and natural gas reserves, which are the major supplies of primary energy demand of the world, are cumulated in a few countries. This causes a serious supply security problem for many countries. On the other side, greenhouse gas emissions caused by mainly fossil fuels are gradually increasing to a point which jeopardizes the future of the earth. By now, countries have to consider both their supply security and this global environmental problem while planning their energy future. For Turkey, a developing country, economic growth is to be added as a third parameter of the solution of this energy equation. In this study, firstly, Turkey&#039 / s existing fossil and alternative energy resources potential is examined. In the second part, international acts against climate change problem and Turkey&#039 / s position in this issue is analyzed. In the third part, the relation between economic growth, energy and environment is discussed. Finally, in consideration with supply security, climate change and economic growth, a brief analyze for Turkey is performed. Study shows that these three parameters are strongly interconnected, especially for fossil resources this leads to some conflictual situations. Comparing with OECD countries, energy is an important factor for economic growth in Turkey. Depending on this fact, Turkey can better give priority to supply security and take an environmental responsibility appropriate to its special condition. It is concluded that Turkey should start with the emission mitigation methods which do not threaten the supply security much, such as forestation, energy conservation and efficiency. Since coal is predicted to continue its popularity in the future, clean coal technologies and carbon capture-storage options gain more importance. For long term, state-sanctioned utilization of renewable resources and carefully planned nuclear development are found to be the most promising solutions for replacing coal and imported natural gas in power generation.

Conceptual estimation techniques play an important role in determining the approximate costs of construction projects especially during feasibility stages. Moreover, pre-design estimates are also crucial for the contractors. With the help of the conceptual predictions companies can determine approximate project costs and can gain several advantages before tendering phase. The main objective of this thesis is to focus on modeling of quantities instead of costs and to develop quantity take-off models for pre-design cost estimation of bridge projects. Majority of the existing studies focus on modeling of costs for conceptual cost estimation. This study includes modeling of the quantity take off items in a specific single span highway bridge using three different techniques namely, linear regression, neural network and case based reasoning. During this study 40 single span highway bridge projects whose owner is Republic of Turkey General Directorate of Railways, Ports and Airports Constructions were investigated and models for each work item were developed. Then by integrating the quantity take off estimations with unit costs, total project costs were calculated. As a result by evaluating the prediction performance of the models, comparison of the methods was achieved. Results are discussed along with the advantages of the proposed method for conceptual cost estimation of bridge projects.

Subsequent to preparation of a valid base estimate for a construction project tender, it is required to add a bid markup on top of the base estimate. While an exaggerated bid markup weakens the competitiveness of the contractor, an underestimated one makes the contractor susceptible to financial losses. Therefore, an effective and reliable bid markup estimation method is indispensable to the success of a contractor both at the tender and the performance stages. The prevalent practice among contractors is to identify a certain percentage to add on the base estimate relying on their judgment without substantial ex! plicit support. In this thesis, a case based decision support system, which will count on the experience of the top experts of Turkish international contractors, will be constructed. Meanwhile, factors which are essential to bid markup estimation are to be identified.

As the construction sector is becoming more competitive in recent years, it has become more important to estimate the duration and cost of the construction projects and to calculate the risks&rsquo / effects correctly. The aim of this thesis is to estimate the duration and cost of construction projects accurately using an activity based risk assessment method which is based on the integrated duration &ndash / cost influence network diagram model proposed by Tah and Poh (2006). Within the context of this thesis, a web based risk assessment tool using the integrated duration &ndash / cost influence network at an activity level is developed to estimate the possible cost overrun and delay in construction projects. Risk breakdown structure for construction projects is created which enables the evaluation of risk effects at an activity level. The developed tool uses Monte Carlo Simulation Technique and Risk Rating Method. The results of the developed tool are compared with those of traditional methods and the reliability of the developed tool is validated.

Energy is increasingly becoming more important in today&rsquo / s world. Ascending of energy consumption due to development of technology and dense population of earth causes greenhouse effect. One of the most valuable energy sources is hydro energy. Because of limited energy sources and excessive energy usage, cost of energy is rising. There are many ways to generate electricity. Among the electricity generation units, hydroelectric power plants are very important, since they are renewable energy sources and they have no fuel cost. Electricity is one of the most expensive input in production. Every hydro energy potential should be considered when making investment on this hydro energy potential. To decide whether a hydroelectric power plant investment is feasible or not, project cost and amount of electricity generation of the investment should be precisely estimated. This study is about cost estimation of hydroelectric power plant projects. Many design parameters and complexity of construction affect the cost of hydroelectric power plant projects. In this thesis fifty four hydroelectric power plant projects are analyzed. The data set is analyzed by using regression analysis and artificial neural network tools. As a result, two cost estimation models have been developed to determine the hydroelectric power plant project cost in early stage of the project.