Abstract: Float analysis plays an important role in engineering project management; it aims to determine the amount of time that the duration of a non-critical activity can be extended or the start time of the activity delayed, before it enters the critical path. The critical path method (CPM) has been widely used in the construction industry to determine which activities are on the critical path and which are not. However, there exists another type of construction project, usually referred to as a "repetitive project", for which CPM may not be the best scheduling technique for planners to employ. A repetitive project can be defined as a project which involves a number of units of work to be finished and a set of activities that need be repeated for each unit in the length of the job. Examples of such projects are highways, high-rise buildings and housing projects. Repetitive scheduling model (RSM) is a scheduling technique that may be better suited to repetitive projects than CPM. In RSM, existing float analysis methods are based on the assumption that all activities are performed without interruption. Once the work interruption is in presence, these methods will fail to evaluate the quantification of float. This paper aims to develop a new float analysis method in RSM considering the work interruption. When the work interruption is considered, the amount that the duration of a non-critical activity can be extended may not be equal to the amount that the start time of the activity can be delayed. Therefore, two different ways for a non-critical activity to use float are distinguished, i.e. "changing the start time" or "prolonging the duration". For each way of using float, three types of float are typically calculated, i.e. total float, free float and safety float. A series of numerical algorithms are also proposed to calculate the quantifications of the above floats, which make the float analysis process in RSM can be computerized. Finally, a pipe engineering project is analyzed to validate the proposed method. The results show that the proposed method can provide more effective solutions than existing float analysis methods.

Key words: repetitive scheduling model, float, moving float, prolonging float