| Construction industry, as one of the most important fields in national economical productions, plays an important role not only on the economical development, but also on the people’s normal life. For a long time, the construction industry has been playing an irreplaceable role on transportation and infrastructure construction and regional economic development. In30years of reform and opening up, with the support from the government, our infrastructure has became into the sustainable and rapid development stage. Especially in the financial crisis in2008, the Chinese government also launched a series of promotional measures of economic policy, taking the4-trillion investment plan, and most of the funds was invested in infrastructure construction sector directly. In early2012, it is the first time that the population of Chinese towns and cities overtook the population of Chinese villages, and the geographical scope of Chinese cities’ extending means a new round of urbanization process has already begun. However, in the stage of promoting infrastructure development and increasing the rate of urbanization by every level of governments, the competition between construction enterprises would be intensified. So for large construction enterprises in China, the opportunities and challenges coexist. Therefore, improving the management levels, especially the level of construction enterprises’ cost controlling, would be the priority of enhancing the enterprises’ abilities of comprehensive competition and dealing with the challenges.However, our project cost management is still in a primary stage, and construction enterprises excessively rely on the experienced analysis and are lack of reliable cost control, which tend to occur large deviations between actual costs and scheduled costs and cost overruns from time to time. Engineering project cost management directly affects the enterprises’economic benefit and profit margins, so research deeply on the factors of engineering project cost and improving the understanding the project cost form factors is beneficial to strengthening the engineering project managements, improving budgeting efficiency and the level of determination of goal responsibility cost, which is meaningful for the distribution to engineering project cost management.The cost of the project process is complex, and each part of the cost can be influent by various factors to different extent. Throughout the domestic and foreign researches, macro economy, construction organization, the weather, the characteristics, construction environment and the accident and uncertainty factors in the construction of the project will affect total cost from different angles in different level. According to the elements cost integrated management theory, elements in projects would interact from different degree, and then affect the whole project construction process. As the two of important factors in project, the construction duration and the project size would greatly affect the total cost of the project engineering respectively, and the size of the project would affect the project duration, and then with the engineering project duration, the project size affect the project construction with the total cost, so project duration and size in project cost integrated management system are the two of the factors which are supposed to considered deeply. This study through the investigation, the interview with practice workers, understanding engineering project status, the project process and the cost structure by the detailed discussion, looks for the main factors which impact the project construction cost. Then through a wide range of literature search and reading, this paper focuses on the project duration and project size defined and carrying out research.By using the mathematical modeling thoughts, this study considered the project period and project size in the same system, and fully considered the synergies between them. Based on the basic theory from the deep interview and literature material, this paper simulates the form of project size affecting the total construction cost in some given project durations and the form of project duration affecting the total construction cost in some given project sizes, and then deducts the natural theory and construct theoretical model. Then the two models get simultaneous, through the theory and model the properties of their respective simplified, and get the final mathematical model of project duration and project size common affecting total construction cost. By collecting nearly200groups of sample data from a state-owned large-scale construction enterprise, this paper makes an empirical test of the theoretical model, and proves the concrete form of project duration and project size common affecting total construction cost, which provides the reference to construction enterprise.This research mainly is divided into six parts, and each part of the main contents is as follows:The first part:introduction. it describes the background, purpose, research ideas of this paper. The paper suggests that in the current research on engineering project cost, because of the complexity of the project, the influence of various aspects must be further researched, especially project duration which need to be further analyzed and thought. Practice workers often judge the project size experienced, without scientific and effective basis. Then this paper offers a research framework.The second part:the literature review. Engineering project cost structure is complex, impacted by various factors. This chapter analyzes of all kinds of factors throughout the domestic and foreign literature review, including macroeconomic, engineering characteristics, construction organization, weather, construction environment and the accident and influence of uncertainty factors. After the previous literature research, this paper puts forward that the project duration have an important impact on the total construction cost, and there would be a reasonable duration which produces the minimum total construction cost in a given construction project. However, the sizes of different projects are different, which makes the empirical test of the theory very difficult. This paper tries to draw on the method of mathematical modeling in economics, econometrics, the application in analysis for U curve quantitative research method, and tries to make a preliminary discussion about form of project duration and project size common affecting total construction cost.The third part:theoretical basis. This part describes the concept and characteristic of construction project and construction project cost, which have one-time and goal, binding and life of the periodic characteristics, so the project cost is more complex and more affected factors than the cost of general manufactured goods. Then, by analyzing and defining project size and project duration, this paper determines the main research objects. In this paper, project size refers to the project itself nature, it does not change with the change of project durations the total project cost. To complete the main research problems, the writer draws on the research idea of mathematical modeling. Through the mathematical description and abstract, the writer simulates the quantitative relation and essence of project duration and size with the total construction cost, and tries to make quantitative analysis by theoretical construction process.The fourth part:the hypothesis and modeling. Because this paper is based on the main research guiding ideology of the mathematical modeling, this chapter is the core content in this paper. For discussing the concrete form of project duration and project size common affecting total construction cost, based on the interview with the practical workers and predecessor’s theory, this paper qualitatively discusses the form of project size affecting the total construction cost in different given project durations, and then qualitatively discusses the form of project duration affecting the total construction cost in different given project sizes. After that, through the quantitative analysis of the integrated research and comb, and according to the curves of project size-total construction cost and project duration-total construction cost, which cover the main characters of them, this paper puts forward the hypotheses, and establishes the mathematical model of project size-total construction cost and project duration-total construction cost. For considering project size and duration in one system and making empirical test, the writer make the two mathematical models above simultaneous, then get the final empirical theory model.The fifth part:empirical test. After collecting samples from a state-owned construction enterprise, drawing on previous researches, this paper adds some crucial control variables, which is essential for empirical test of theory model. Because the empirical theory model fully shows the form of project duration and size with the total construction cost function graphic as well as their features, and the important features are also the suggested hypothesis in this paper. So if the empirical model could be proved, this paper’s hypothesis could be proved.The sixth part:conclusion and policy suggestions. Summarized the results from the empirical analysis through the theoretical analysis and mathematical modeling, the paper explained the theory, which is helpful for the determination of reasonable project duration and provide the reference for the budget, then points out the limitations and the shortages of this study, as well as the future researches.The main contribution of this paper reflects in the following aspects:First, the total construction cost would increase with the project size increasing. The greater the size of the project, the higher the project construction cost, but the total cost of the construction project is not in proportion change with the size of project.Secondly, with the extension of the project duration, the sensitivity of the total construction cost to the project size would become smaller. In another word, using short construction duration, if the size of the project discrepancies has deviation, it could cause the total cost of the project construction and the budget more deviation.Third, with the extension of the project duration, the total construction cost would decrease firstly, and then increase. So there is a reasonable period, when actual project duration is less than or more than the reasonable project duration, it could lead to the total construction cost rise.The last, the reasonable project duration is positively related to the project size. Because the mathematical model established has a relatively high goodness of fit. it is reasonable that the reasonable duration could be about which provides the reference to construction enterprise and project managers.Compared with the existing research, this paper has made the following innovation:Firstly, this study offers a new dimension for elements project cost integration management system. This paper is based on lots of factors integrate, accounting the project size into the study. Considering their relation by deduction, induction and the analysis, it is the first time to establish a complete project time-scale-cost3D function model, which is through empirical test.Secondly, through mathematical modeling, this paper constructed the "U" shape function of the project duration and total construction cost. Following task group, The author conducted in-depth research and interviews in a construction enterprise, and had a deeper understanding about construction projects. Then the author produced a nonlinear mathematical model to display the main characteristics of the research objects by graphics and so on. Because the mathematical model established has a relatively high goodness of fit, it is reasonable that the model is valuable, which provides the reference to construction enterprise and project managers.The limitations and shortages of this paper:This paper only considers two factors of the total construction cost, the project size and duration, which has not fully consider other factors of comprehensive interaction. This paper used the simplified mathematical model to study the basic characteristics of the elements, which may not fully comply with actual situation. Sometimes, the shorter project duration would give opportunities to construction enterprises to get more construction projects, therefore, the reasonable duration of project does not the maximization of enterprise profit, that is because this paper does not take the opportunity cost caused by this problem into account. |
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