Petri net based simulation of construction schedules

Scheduling of a construction project requires: a) hierarchical decomposition of the project; b) incorporation of risk and uncertainty in the activity time and cost estimates; and c) modeling of dynamically allocated resources. Traditional network techniques that are being currently used by the construction industry provide limited modeling versatility and are ineffective in modeling a dynamic and stochastic system such as a construction project. In this paper a description of a hybrid scheduling technique that utilizes Petri Nets is provided. Petri Nets are graphical and mathematical modeling tools that can be used to perform static and dynamic analysis of systems. Under the proposed technique transitions and places, the two key elements of a Generalized Stochastic Petri Net (GSPN) are used to model the work tasks in a construction project. This automatically allows the incorporation of risk and uncertainty in the time and cost estimates of work tasks. Dynamic modeling of resources required to accomplish various construction work tasks is performed in the proposed system by using the concept of colored tokens and fusion places. Hierarchical transitions allow a systematic top-down breakdown of a construction project. The paper summarizes the steps required to perform scheduling of construction projects under the proposed hybrid technique and highlights its advantages. The objective of this paper is to illustrate the dynamic simulation capabilities of the proposed Petri Net based construction scheduling technique.