The Research On Fuzzy Network Planning Technology And Fuzzy Schedule Risk

Network planning technology is a scientific method to make scheduled plan, and it's also an effective measure to manage a construction project. When the durations of activities in a planning network are precisely known, Critical Path Method has been proved to be a effective method to make planning. But in many cases, the durations of activities are uncertain, can't be described with a precise value. Program Evaluation and Review Technique assume the durations of activities are independent and obey the Beta distribution, consider the uncertainty from randomicity. Beside randomicity, another kind of uncertainty is fuzzyness. Fuzzy network use fuzzy sets to describe the duration of activities, indicates the fuzzyness have an effect on duration.According to the fuzzy network with fuzzy numbers, an algorithm to computing the total duration's membership function and the criticalities of paths is presented. The algorithm converts the fuzzy network to a series of interval networks under different fuzzy cut. According on the extension principle, the duration ranges of these interval networks are substantively the total duration's fuzzy cuts of the fuzzy network, so the total duration's membership function can be easily founded through decomposition theorem. At the same time, compute all the path criticalities by utilizing the relationship between the critical path of interval networks and the path criticality of the fuzzy network as well. An example verifies the feasibility of the algorithm.In addition, in the procedure of schedule risk analysis, the traditional PERT method usually only consider the randomicity of the activities durations, but doesn't consider the fuzzyness. In this paper, we try to consider both randomicity and fuzzyness in the schedule risk analysis. Based on the three estimation time of PERT, a fuzzy network is founded. We computing the total duration's membership function with the algorithm mentioned above. Based on the total duration's membership function and the total duration's distribution of PERT, calculate the fuzzy completion possibility under specified duration. An example showed that the fuzzy completion possibility and the completion possibility of PERT have the same variation tendency under different specified total duration, and they are comparable. But, the fuzzy completion possibility is smaller than the completion possibility of PERT under the same specified total duration, that's because compare to PERT, fuzzy completion possibility consider the fuzzyness of activities. The fuzzy completion possibility more fully empresses the influence of the both side of nondeterminacy to the schedule risk.In the end, a large-scale water conservancy and hydropower project example is presented to verify the effectiveness and feasibility of the two methods showed in this paper.