Multiple-window modified but-for analysis of project delays and accelerations

But-For analysis is a popular technique for apportioning the responsibility for project delays among various parties. In the literature, Modified But-For (MBF) methods utilized Venn representations and set theorem to avoid conflicting results and identify concurrent delays. Moreover, the MBF was extended further to analyse cases involving schedule delays and accelerations. However, due to its single-window implementation, the MBF analysis is not sensitive to event chronology and thus can produce wrong results. This article thus proposes a multiple-window MBF analysis to account for critical path fluctuations and consider the detailed chronology of progress events, which are key requirements of the professional delay analysis guidelines of AACEI and ASCE. The proposed method is comprehensive enough to analyse concurrent delay and acceleration events under multiple baseline updates. After introducing the proposed method, a case study is used to demonstrate its superiority and practical application.