基於活動工時風險與系統模擬之專案排程新模式

A New Project Scheduling Method Based on Activity Risk Duration and Systems Simulation

傳統排程方法中處理作業工期不確定性最廣為人知的方法為計劃評核術（Project evaluation and review technique, PERT）。然而傳統的PERT卻很少被應用於工程實務上，主要原因在於其所採用的三時估計（Three-point time estimation）法難以準確估計，且其計算與應用過程採用統計學之機率（Probability）與分配（Distribution）相關理論，較傳統要徑法（Critical path method, CPM）複雜且難以應用。為解決傳統排程方法無法有效應用於專案需時不確定之風險排程問題，本研究提出一種以傳統要徑法為基礎，並考量七階作業風險等級工期，以進行風險要徑排程之方法，稱為風險要徑排程模式（Risk based critical path scheduling method, R-CPSM）。R-CPSM之七階作業風險工期較傳統PERT之三時估計更能精準估算作業之風險工期。此外，本研究應用蒙地卡羅模擬（Monte-Carlo simulation, MCS）法，分析風險工期之合理性，以做為調整作業資源之參考。因此，本研究所提出之R-CPSM除了可以取代傳統PERT對於不確定工期之分析功能外，其所具備之即時作業風險工期更新功能，更可以改善傳統PERT僅能作為初期規劃而不適用於專案執行階段全程監控之缺點。最後，本文參考文獻中之案例，展示所提出R-CPSM之可行性，並比較傳統PERT與所提出之R-CPSM的差異性。

The most well-known traditional approach to deal with the uncertainties of the activity durations in a project was the Project Evaluation and Review Technique (PERT). However, traditional PERT is not widely adopted in the construction industry for two main reasons: first, the three-point time estimates of an activity are hard to obtain; and second, PERT analysis involves statistical, probability and distribution theories, which are too complicated for construction schedulers to understand than the traditional Critical Path Method (CPM). In order to resolve the problem that traditional scheduling method cannot be applied to the uncertain risk durations, current research proposes a Risk-based Critical Path Scheduling Method (R-CPSM) that adopts seven risk-levels of activity durations in schedule analysis, providing a more precise estimation of the activity risk durations than the traditional PERT. Additionally, in this study the Monte-Carlo Simulation (MCS) method is used to analyze the rationality of risk duration, which can be a reference for adjusting operation resources. As a result, the proposed R-CPSM improves on the traditional PERT not only in modeling uncertain durations, but also in providing a more powerful tool for monitoring the schedule of construction projects that face various duration risks. Finally, an example project selected from literature is used to demonstrate the applicability of the proposed solution. The differences between the proposed R-CPSM and the traditional PERT are also compared.