Heuristic Repetitive Activity Scheduling Process for Networking Techniques

Project scheduling is a key activity in construction process. Networking Techniques are useful instruments to accomplish project planning and control. But Networking Techniques develop a discrete model of Construction Process which has instead a continuous nature. New Production theories like Critical Chain or Lean Construction recognize this as a major cause of construction process inefficiency. The difference between model and real building process can lead to managing problems for unexperienced planners, especially in repetitive projects like high rise buildings, housing, highways and other infrastructures, in which crews perform repetitive activities moving from one space unit to another. In particular networking techniques minimize construction total duration but do not satisfy the requirement of work continuity through repetitive units of the project. To satisfy the work continuity constraint many methods have been proposed by researchers and practitioners. Although the effectiveness of these methods, which give notable insights in repetitive construction process, construction scheduling is still performed in most real cases with a commercial software, working with a CPM based network like Precedence Diagramming Method (PDM). The objective of this paper is to present a simple, flexible and easy to implement optimization algorithm for resource-driven scheduling for repetitive projects. The algorithm is based on a PDM network plotted on a resource/space chart, thus identifying resource paths and unit paths in the network. After traditional PDM time analysis is performed, the algorithm seeks, for every repetitive activity to be performed on a repetitive space unit of the project, the Planned Start and the Planned Finish that are best suitable to satisfy the work continuity requirement. In order to maintain minimum project total duration the work continuity requirement is relaxed when encountering a network limit. According with Critical Chain Theory, time buffers are inserted at the end of every resource path, to prevent delays on project completion, due to resource unavailability. The method has been tested on a simple repetitive project from pertinent literature. The proposed algorithm is an heuristic resource-driven scheduling method for repetitive projects, easy to be implemented by practitioners.