studied the plan buffer settings of critical chain by considering the three attributes related to specific projects, namely the number of processes, the uncertainty of processes’ execution time and the flexibility of commencement. Chu proposed a calculation method to adjust the buffer by comprehensively measuring the influencing factors such as project material tension, network composition complexity, and decision-maker risk preference, so that no matter how many processes are on the link, the buffer can be appropriate. proposed a buffer calculation method considering resource tension and network complexity and the impact of the project’s own factors on buffer determination, which generated a new direction for buffer determination research. This method is to improve the root variance method by measuring the risk factors affecting the construction schedule in order to adjust the buffer setting. The first is the method based on project attributes. The existing research results are divided into three categories. Later, in view of the limitations of these two basic methods, many scholars have made various improvements to the calculation method of critical chain buffer size by comprehensively considering various risk factors affecting project progress. However, the shortcoming is that this method determines the buffer based on the independence of activity duration. Newbold considered the probability of project completion and used the central limit theorem to propose the root variance method to calculate the buffer size. Herroelen and Leus argued that the cut-and-paste method is relatively simple and suitable for calculating critical chain buffer for smaller scale projects, but stated larger projects with this calculation method would have an oversized buffer. Goldratt proposed the concept of buffer along with the cut-and-paste method to determine the buffer.
The calculation example analysis shows that this method can improve the accuracy of the calculation of process safety time, reduce the influence of the complexity of process adjacency correlation on the project construction schedule, reasonably control the buffer size, and effectively shorten the planned project duration.įor the calculation of critical chain buffer size, many domestic and foreign scholars have conducted related research. This methodology provides comprehensive consideration of the relationship between cost, quality, safety, environment and process duration, the influence of process’s resource demand intensity, resource constraints and process duration on the buffer size, the influence of the relay potential of mutual cooperation and cross construction between processes, as well as the influence of adjacent complexity of processes on the project construction schedule. Therefore, this paper proposes a buffer calculation model of critical chain based on adjacency information entropy. In addition, the three-point time estimation method and Monte Carlo simulation are mostly used in the current research for the estimation of process duration, while less research exists on the estimation of process optimal duration under multi-objective constraints. In the existing relevant studies, many scholars have considered the influence of direct adjacent processes but ignored the influence of indirect adjacent processes. In project network planning, the correlation complexity of the processes is not only related to the immediately preceding and following processes, but also closely related to indirect adjacent processes.
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