Overlapping design and construction activities and an optimization approach to minimize rework

• This study presents a framework to overlap design and construction activities.
• Overlapping significantly shortens project duration with expense of some rework.
• Different factors that affect total duration and rework have been described.
• Also presents an integrated framework to optimize the schedule with minimal rework.
• Optimization model eliminates some rework while maintaining project contract date.

Construction industry often faces challenge to complete project in minimum possible time. Overlapping design and construction activities with early information from the precedent activities shortens project completion with the expense of rework in downstream design and construction activities. However, the expected amount of rework must be properly quantified to decide on the overlapping strategy. This study presents an integrated framework to overlap design and construction activities using the concepts of upstream evaluation and downstream sensitivity characteristics and develops a simulation model in order to ascertain project performance in terms of total project duration and expected amount of rework. The results indicate that reduction in project duration and expected rework amount vary based on the accuracy of upstream early information and sensitivity of downstream activities. Moreover, unplanned overlapping may not necessarily reduce project duration but may result in excessive design and construction rework which can be very costly. This study also describes a decision-making framework to optimize project schedule with minimal rework. The search for an optimal overlapping strategy is carried out using an Overlapping Strategy Matrix (OSM) with the genetic algorithm (GA) to eliminate unnecessary rework. The proposed optimization method minimizes the expected amount of rework while maintaining the project completion contract date and provides an effective means to decide on the overlapping strategy.