The project schedule risk in the engineering and facility construction industry is increasingly considered as important management factor because the risks in terms of schedule or deadline may significantly affect the project cost. Especially, the project-based operating companies attempt to find the best estimate of the project completion time for use at their proposals, and therefore, usually have much interest in accurate estimation of the duration of the projects. In general, the management of projects schedule risk is achieved by modeling project schedule with PERT/CPM techniques, and then performing risk assessment with simulation such as Monte-Carlo simulation method. However, since these approaches require the accumulated executional data, which are not usually available in project-based operating company, and, further, they cannot reflect various schedule constraints, which usually are met during the project execution, the project managers have difficulty in preparing for the project risks in advance of their occurrence in the project execution. As these constraints may affect time and cost which role as the crucial evaluation factors to the quality of the project result, they must be identified and described in advance of their occurrence in the project management. This paper proposes a Bayesian Net based methodology for estimating project schedule risk by identifying and enforcing the project risks and its response plan which may occur in storage tank engineering and construction project environment. First, we translated the schedule network with the project risks and its response plan into Bayesian Net. Second, we analyzed the integrated Bayesian Net and suggested an estimate of project schedule risk with simulation approach. Finally, we applied our approach to a storage tank construction project to validate its feasibility.

The project-based business companies usually have much interest in predicting the expected finish date and related probability of project completion to refer at their proposals for projects. In general, the management of projects schedule risk is achieved by modeling project schedule with PERT/CPM techniques, then performing risk assessment with Monte-Carlo simulation method. However, since these approaches cannot reflect various schedule constraints, the project managers cannot prepare for the project risks in advance of their. This paper proposed a methodology for predicting project schedule risk by identifying and enforcing the constraints which may occur in a storage tank engineering and construction project environment. We applied our approach to a storage tank construction project to validate its feasibility. By using the methodology proposed in this paper, the project schedule risk can be evaluated and predicted more accurately and practically than the PERT/CPM or Monte-Carlo simulation approach.

In the project management context, the impotance of risk management is increasing because the risks in terms of time and cost may significantly affect the result of the project. In general, the management of projects schedule risk is achieved by modeling project schedule with PERT/CPM techniques, then performing risk assesment with monte-carlo simulation method. However, these approach can not reflect constraints, which may be occurred during the project execution, and cope with uncertainty in the future. As these constraints may affect time and cost which are the crucial evaluation factor to the project, they must be identified and evaluated to manage the future project risk before the project is started. This paper proposes a methodology for project schedule risk management by identifying and enforcing the constraints which may be occurred in complex and uncertain project environment. First, project risk constraints are identified and categorized into time, dependancy, and branching. Then, project schedule model with constraints is converted to CPN(Colored Petri Net) which can represent all the identified constraints to assess and predict schedule risk. Finally, the expected risk of the project (in terms of time and cost) is assessed and predicted by performing Petri Net simulation. By using the methodology proposed in this paper, the risk in terms of time and cost in project schedule model can be assessed and predicted more accurately and practically than the PERT/CPM and/or Monte-carlo simulation method. Furthermore, the constraints, which may occur unexpectedly after the project launch, can be evaluated to determine the schedule risk. The expected risk can be used to decide whether risk mitigation or project termination process undertake.