Managing on-site production using an activity and flow-based construction model

Schedule conformance depends on construction activities starting and finishing on time. However, construction activities are often delayed because construction flows necessary to start their execution are unavailable. Construction flows can be classified into: labor, equipment, workspace, materials, precedence, information, and external. Current construction models do not formally represent, measure, and track all flow types. Hence, field managers lack formal methods for managing flows and instead rely on their intuition and experience managing them. This paper presents a construction model based on activities and flows called the activity-flow model (AFM). The AFM formally represents the activities, the flows, and their interactions. The AFM was validated prospectively through its implementation on three building projects that were in different phases (foundations, core and shell, and finishing), at different geographic locations (Bogota, Copenhagen, and Lima), and used different planning and control methods (master schedule and weekly planning, last planner system, and location-based management system). The AFM was able to represent all the activities and flows in the test projects, track variations of activities and flows, and quantify activity and flow variability. Field managers can use the metrics enabled by the AFM to plan and control the project. Such proactive flow management can help field managers improve flow readiness, which should reduce activity delays and improve schedule conformance.