Time, Cost, and Environmental Impact Analysis on Construction Operation Optimization Using Genetic Algorithms Gulbin Ozcan-Deniz, M.ASCE 1 ; Yimin Zhu, M.ASCE 2 ; and Victor Ceron 3 Abstract: Environmentally conscious construction has become a subject of research during the last decades. Even though construction literature involves plenty of studies that emphasize the importance of environmental impact during the construction phase, most of the previous studies failed to combine environmental analysis with other project performance criteria in construction. To achieve environmentally conscious construction and successfully manage a complex construction environment, multiple project objectives and their relationships need to be considered. In this study, the authors propose a framework on the basis of the concept of control accounts to determine optimal con- struction operations when project time, cost, and environment impact (TCEI) are considered as project objectives during project planning. The framework also supports decision-making by using sensitivity analysis. Life cycle assessment is applied to the evaluation of environ- mental impact in terms of global warming potential (GWP). The nondominated sorting genetic algorithm II, or NSGA-II, is selected for implementation in MATLAB to determine optimal construction operations. A case study is used to illustrate the application of the framework. It is shown by the case study that the application of the genetic algorithm to search problems, such as the case study, is promising in terms of determining optimal solutions, but computation speed can be an issue, if it involves a large set of data. In addition, data collection and processing is a major challenge, especially the processing of environmental impact data. Tools are needed to facilitate data collection and processing. Currently, the proposed framework includes a critical path method, on the basis of fixed logical relationships among activ- ities, to determine the duration of a project. The effect of resource and other constraints on such logical relationships, and potentially the duration of a project, is not addressed in this study. DOI: 10.1061/(ASCE)ME.1943-5479.0000098. © 2012 American Society of Civil Engineers. CE Database subject headings: Algorithms; Environmental issues; Optimization; Sensitivity analysis; Construction management; Costs; Time factors. Author keywords: Genetic algorithms; Environmental impact; Optimization; Sensitivity analysis. Introduction The environmental impact of buildings and their operations have received a significant amount of research attention, e.g., optimiza- tion of building operations (Zhu 2006). Even though a better under- standing of the environmental impact of construction processes is critical (e.g., Hendrickson and Horvath 2000), such environmental impact is not well studied or well understood (Bilec et al. 2006; Sharrard et al. 2007). The lack of emphasis is perhaps in part because of conflicting information presented by previous studies. For exam- ple, some empirical studies seem to suggest that the environmental impact of a construction phase is less significant than other phases, such as building operations and maintenance (e.g., Junnila and Horvath 2003). Other studies show that the environmental impact of the construction phase is significant, such as 2.6–3% of the entire energy consumption of the United States (Sharrard et al. 2007) and, thus, needs more research attention (Bilec et al. 2006). A recent EPA report (EPA 2009) has further enforced the latter view, suggesting that in 2002, the construction industry generated approximately 1.7% of total greenhouse gas emissions (GHG) in the United States, which is equivalent to 6% of total industry-related GHG emissions in the country and puts the construction industry at the third place among key industrial sectors. Thus, overlooking the environmental impact of construction processes can have serious adverse effects on the environment, given the large number of annual construction projects worldwide. Environmentally conscious construction has been investigated for decades, and there is a significant body of knowledge on envi- ronmental performance criteria (e.g., Shen et al. 2005), methods of environmental impact analysis (e.g., Shen et al. 2005; Sharrard et al. 2007; Li et al. 2010), and environmentally conscious construction management (e.g., Chen et al. 2005). Although these studies have clearly demonstrated the significance of managing environmental impact during construction phases, gaps still exist between the ul- timate goal of environmentally conscious construction and findings in those studies. This is because most of the studies have focused on a specific dimension, i.e., environmental impact, and overlooked the multiobjective nature of construction projects. Only recently, 1 Assistant Professor, Dept. of Civil and Architectural Engineering and Construction Management, Milwaukee School of Engineering, Milwaukee 53202 (corresponding author). E-mail: gozca001@fiu.edu; ozcan@ msoe.edu 2 Associate Professor, Dept. of Construction Management, College of Engineering and Computing, Florida International Univ., Miami 33174. E-mail: zhuy@fiu.edu 3 Ph.D. Student, PE, Dept. of Civil Engineering, Engineering, College of Engineering and Computing, Florida International Univ., Miami 33174. E-mail: vcero001@fiu.edu Note. This manuscript was submitted on October 29, 2010; approved on September 16, 2011; published online on September 19, 2011. Discussion period open until December 1, 2012; separate discussions must be sub- mitted for individual papers. This paper is part of the Journal of Manage- ment in Engineering, Vol. 28, No. 3, July 1, 2012. ©ASCE, ISSN 0742- 597X/2012/3-265–272/$25.00. JOURNAL OF MANAGEMENT IN ENGINEERING © ASCE / JULY 2012 / 265 J. Manage. Eng. 2012.28:265-272. Downloaded from ascelibrary.org by Illinois Inst Of Technology on 08/12/12. For personal use only. No other uses without permission. Copyright (c) 2012. 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