Sources of Uncertainties in Offsite Logistics of Modular Construction for High-Rise Building Projects

A critical concern in the supply chain of modular construction is offsite logistics that involve complicated module manufacturing, storage, and transportation processes. However, numerous uncertainties exist in a supply chain that could detrimentally affect the performance of offsite logistics and thereby the success of modular construction projects. A systematic exploration of sources of uncertainties (SoUs) in offsite logistics is needed, as they have not yet been sufficiently investigated. This study aimed to identify and categorize SoUs affecting the offsite logistics of high-rise modular building projects in high-density cities. A multicase study method was adopted involving three modular high-rise projects. Data were collected through documentation, site visits, and interviews, drawing on the uncertainty circle model. A total of 30 key SoUs were identified in five areas: the offsite logistics process, the demand side, the supply side, planning and control systems, and the environment. A framework for SoUs was derived, which showed the multifaceted, interconnected, and context-specific features of SoUs and illustrated their probabilities and impacts. Most SoUs arise from offsite logistics processes and planning and control systems. The demand-side SoUs were found to have higher probabilities and impacts. The supply-side SoUs were less probable but could have significant impacts on offsite logistics. Suggestions are made that would allow practitioners to break uncertainty circles and policymakers to promote the development of a robust modular construction supply chain.