Petri Net-Based Scheduling of a Bridge Project

Abstract

Scheduling of construction projects is an important planning function that provides a clear representation of the construction activities, construction sequence, and construction resources to the agencies/parties involved in construction. In this paper, the authors present a Petri Net-based scheduling technique that utilizes simulation to model a construction project and to perform the scheduling computations. Petri Nets are graphical and mathematical modeling tools that can be used to perform static and dynamic analysis of systems. Under the proposed technique, modeling elements of a Generalized Stochastic Petri Net (GSPN)--places, transitions, arcs, tokens, hierarchical transitions, and fusion places--are used to develop the construction schedule for a bridge project. Features such as hierarchy, modularity, resource modeling, and colored tokens are utilized in the schedule development. With the aid of the scheduling of the bridge project, the paper demonstrates the strategies for overcoming deficiencies related to traditional scheduling techniques and in attaining additional benefits. The paper also summarizes the steps required to perform the scheduling of construction projects using the proposed technique highlighting the advantages. Introduction and Background Planning, scheduling, and control of the functions, operations, and resources of a construction project are among the most challenging tasks faced by a professional construction manager (Barrie and Paulson 1992). These functions are gaining additional importance because construction projects are becoming more and more complex. Newer project delivery methodologies are being adopted, and newer means, methods, and materials of construction are being used. Bar chart and other network-based scheduling methods, such as Critical Path Method (CPM), Precedence Diagramming Method (PDM), and Program Evaluation and Review Technique (PERT) are currently used in the construction industry. These methods provide a means of obtaining a time schedule for the various work tasks associated with a construction project. The shortcomings of these methods are numerous and have been documented in many publications (for example, McCrimmon and Rayvec 1964, Levitt et al 1988 and Pritsker et al. 1989). The network-based scheduling methods have been inherited from the aerospace and manufacturing industries with disregard to the nature of the construction projects. As a result of these findings, researchers began to search for tools and techniques that could provide a better construction scheduling system. Discrete event simulation is one of the techniques extensively studied and implemented to overcome deficiencies in the network based scheduling methods. Research efforts were undertaken to examine the use of simulation as a scheduling tool (Van Slyke 1963, Carr 1979, Crandall 1976 and Pritsker 1986). Motivated by these research efforts, the authors developed a simulation-based scheduling system that utilizes Petri Nets as its backbone. 1 Associate Professor, Oel E. Webb School of Construction, Arizona State University, PO Box 870204, Tempe, Arizona 85287-0204, Phone: (480) 965 7417, FAX: (480) 965 1769 and email aniLsawhney@asu.edu. 2 Graduate Research Assistant, Construction Engineering and Management, 2007 Kohrman Hall, Western Michigan University, Kalamazoo, MI 49008-5064 USA