A Quantitative Model for Measuring the Project and Feeding Buffers in CCM Method by Fuzzy Approach (Case Study: Construction of Industrial Wastewater Treatment Unit at Lorestan Petrochemical Company, Iran)

Uncertainties in a project's environment are one of the most significant reasons for its incompletion based upon a predetermined schedule. Today, it is unavoidable for project managers to face uncertainties. Therefore, they strongly require a systematic method considering not only resource constraints, but also uncertain conditions in project scheduling. Limits in the common methods of scheduling have encouraged researchers to use the approaches in the theory of constraints. Goldratt (1997) developed the new method of critical chain management (CCM) creating considerable changes in various projectcentered organizations and industries. However, it lacked mathematical relations and quantitative models. Due to the main drawback of the CCM method in estimating project activity duration and determining project and feeding buffer sizes, this study tries to remove uncertainties by applying the proposed fuzzy critical chain method (FCCM), integrating both CCM and fuzzy logic (FL) methods. While solving the problems, it may provide project execution time and delivery date safety. Finally, by comparing the scheduling results of a practical project with those of FCCM, CPM, and critical path method (CPM), it is concluded that the planned duration of project scheduling by FCCM is shorter than those of the other two.