LOB and CPM Integrated Method for Scheduling Repetitive Projects

Abstract

Repetitive projects require schedules that ensure the uninterrupted usage of resources from a unit to similar units in a repetitive activity while maintaining logical dependency constraints. The critical path method (CPM) is the most widely used and accepted planning and scheduling method for traditional (nonrepetitive) projects. However, CPM does not suit the planning and scheduling needs of repetitive projects. Consequently, resource-driven techniques, such as line of balance (LOB), have been used to schedule repetitive projects that ensure work continuity. LOB is primarily a graphical technique that lacks the analytical qualities of CPM scheduling. A need for an analytical technique fulfilling characteristics of repetitive projects has been reported in the literature. Few attempts have been made to combine the benefits of CPM and LOB techniques in planning and scheduling of repetitive projects. In this paper, an integrated CPM and LOB model has been developed to schedule repetitive projects in an easy nongraphical manner, considering both logic dependency and resource continuity constraints. Overlapping activities of a single typical unit are used to model duration and logical relationships of repetitive activities. The proposed model essentially consists of four steps. In the first step, basic LOB calculations are performed to ensure resource continuity. Activity duration along all repetitive units is calculated in the second step. In the third step, overlapping activities are used to model logical relationships between consecutive activities. Next, CPM time analysis is performed to specify activities’ timings and floats and project completion time. An example application is presented to illustrate implementation and features of the proposed model.