Dual-level resource-constrained multi-project scheduling framework for prefabrication in construction

Abstract: Construction prefabrication projects, where engineered systems or components of large size and heavy weight are fabricated with limited workplace and storage areas, typically are executed in a multi-project environment. So, frequent inter-project resource transfers are not feasible and should be mitigated. Nonetheless, existing multi-project scheduling approaches give rise to extensive resource links among projects, thereby negatively impacting the stability and feasibility of resultant project schedules and increasing management difficulties in processing each project. Furthermore, the project planning and the workface operation realities are separated from each other in current practice. As a result, it is common that the project planning overestimates the actual construction productivity, while changes and variations (e.g., material logistics) during operations cannot be timely reflected to the project or general managers and present their impacts on the project’s and program’s schedule and cost. This research explores a systematic dual-level resource planning framework for addressing these issues identified in conventional resource planning and project scheduling methods for multiple concurrent projects. A dual-level resource-constrained multi-project scheduling framework is proposed to provide achievable resource allocation decisions for program planning and activity scheduling for projects and operations for prefabrication projects in construction. The proposed framework is capable of (1) generating robust resource use plans for multiple concurring projects, (2) interconnecting and synchronizing schedules for various management functions, and (3) analytically evaluating the impact of inherent material logistics uncertainties on individual project schedules and costs. These advantages are illustrated and demonstrated through two literature case studies and two actual case studies of bridge girder fabrication projects from a partner company in Edmonton, Canada. The academic contributions of this research are identified as (1) advancement of conventional multi-project scheduling approaches by proposing a generic dual-level scheduling framework, which generates more robust schedules and integrates schedules for various management functions; (2) development of an integrated scheduling optimization model which incorporates material supplies as constraints for resource-constrained project scheduling so as to analyze the impact of material logistics uncertainties on project schedule and cost performances; and (3) the provision and definition of a new indicator (i.e., resource use robustness) for evaluating construction schedule performance.In terms of practical contributions, the outcomes of this research would (1) provide production managers with reliable and feasible work plans at a fabrication facility, which ensure crew work continuity on individual projects, enhance resource utilization efficiency, and improve communication efficiency among project management teams; (2) create reliable program schedule, project schedule, and operation schedules, which are dynamically interconnected with each other, thereby, facilitating schedule maintenance and updating, saving the efforts for progress report among management personnel, and guiding various management functions such as evaluation of remaining fabrication capacities, prediction of project delivery performances, and execution of daily fabrication work within fabrication facilities; and (3) provide crucial decision support for practitioners to determine allowable time windows of certain critical material deliveries so as to keep the total project cost under pre-set limits and provide alternative plans in coping with disruptions and changes.