Invisible consumptions and enlargements of activity floats under generalized precedence relations

Abstract

Generalized precedence relations (GPRs) between activities widely exist in modern construction projects. Time floats of activities (activity floats) are indispensable to arrange the activities to cope with unstable external conditions. This paper discovers that the GPRs result in new singularities of activity floats—time floats of an activity can be consumed and enlarged imperceptibly even if the activity has not started and all activities don’t consume their time floats. The singularities are called invisible consumptions and enlargements of activity floats. This paper analyzes the singularities and presents algorithms to identify and quantize them. The new singular characteristics of activity floats may weaken current optimization approaches for project scheduling. Inspired by the characteristics, this paper develops an emergency resource leveling with GPRs that focuses on emergency actions for the dynamic and uncertain environment. An illustration demonstrates that the correct solution relies on the invisible consumptions and enlargements of activity floats.