A new model, algorithm and computer tool to optimize overlapping of design activities in construction projects

An effective and well known technique for earlier completion of construction projects is to overlap the project activities or phases that normally would be performed in sequence. Overlapping is inherently risky because it increases project uncertainties, rework, complexity, and eventually cost. For a typical construction project, a huge number of overlapping strategies exist which all can result in the same timesaving. However, the cost of these strategies varies significantly depending on the total rework and complexity they generate. A favourable overlapping strategy is one that generates the required timesaving at the minimum cost. To find the favourable overlapping strategy, the question "Which activities have to be overlapped and to which extent to reduce the project duration at the minimum cost?" should be answered. This research aimed at answering the question through generating an overlapping optimization algorithm. The scope of the research covers any type of activities in the design phase. A combinatory research methodology, a combination of qualitative and analytical approaches, was customized to conduct the research. Interviews and focus groups were the research instruments in the qualitative part. The analytical part included developing the overlapping optimization algorithm and its associated computer tool. The research generated three deliverables: An overlapping model, an overlapping optimization algorithm, and an overlapping optimization computer tool. The overlapping model explains the overlapping mechanism. The computer tool works based on the overlapping optimization algorithm and assesses various overlapping strategies and identifies the least expensive strategies. The tool is actually a cost evaluation module linked to a commercial project scheduling software (MS Project). This computer tool is so user-friendly that any scheduler or cost controller can easily run it and modify the schedule accordingly. The computer tool is unique and new as so far no similar tools exist in industry or academia. It can optimize overlaps in large and complex project schedules in fairly short processing times. It is able to handle multi-path networks and all types of activity dependencies. The tool takes all activities, critical and non-critical, into account and follows the critical path if the critical path changes or new critical paths emerge. The tool can also take resource limitations and schedule constraints into account.