A fuzzy-based integrated framework for assessing time contingency in construction projects

Assessing time contingency is an important part of construction project scheduling because it helps generate a more reliable schedule. Traditionally, the assessment is made using expert judgment and inherently inserted to the estimated activity duration and/or comprehensively placed at the project level. This practice has a major drawback in that project-specific risks that require time contingency are not explicitly identified and treated. Risk management is performed in isolation to project scheduling. This paper presents a new framework for assessing the time contingency required for activities exposed to multiple risks. Fuzzy set theory is employed to model the imprecision and vagueness associated with the possibility of risk occurrence and the impact of those risks on activity durations. Alternative risk responses can be explored and their impacts on the project duration can be evaluated. A real-life case example was used to demonstrate the application of the framework. The results indicate that risk management can systematically be incorporated into scheduling. The impact of multiple risks on activity time contingency can effectively be estimated. The robustness of the schedule can be enhanced through iterative response planning. The newly developed framework thus provides construction planners with a practical tool for proactively assessing the impact of the project-specific risks on major milestones and project deadlines. This study advances the current practice of time contingency estimations by introducing an integrated approach for risk management and project scheduling. It also advances the application of fuzzy sets theory in assessing impact on activity durations subjected to multiple risks.