Enhancing Subcontractors' Participation in BIM-Based Design Coordination under a DBB Contract

This paper introduces a two-step subcontracting process for building information modeling (BIM)-based design coordination under a design-bid-build (DBB) contract. Although integrated project delivery (IPD) is known to be an ideal contractual method for BIM projects, DBB still has been the dominant contracting method, owing to the complexity of IPD, as well as regional regulations. BIM-based design coordination under DBB can effectively reduce design errors through the value engineering process. However, in practice, the cost reduction realized under DBB is minimal because, unlike under IPD, DBB contracts do not provide incentives for subcontractors to reduce costs. This study proposes that subcontracting be divided into two phases: preconstruction and construction. Only subcontractors who meet the target costs during BIM-based design coordination in the preconstruction phase win the right to work during the construction phase. From case studies, this study finds quantitative cost reductions from this change in the preconstruction process. This study also reveals the manner in which this two-phase process impacts subcontractors' attitudes toward cost-reduction efforts. These findings contribute to maximizing the efficiency of BIM-based design coordination, which will eventually contribute to more efficient delivery of construction projects.