Enhancing Activity-on-Node Network Diagramming Technique for Modeling Interdependent Workflows in Planning Fabrication Projects
Creators: Shuvo,Badhon Das
Publisher: name: University of Alberta Library
Year: 2022

<p>Fabrication operations produce made-to-order structural components (such steel elements or precast concrete) for multiple construction projects, which require crews to repeat their work at a number of workstations or locations in a special manufacturing facility. Scheduling these interdependent concurring workflows often requires maximizing work continuity for these crews while minimizing resource idle time and crew interruptions. Many attempts have been made in the past to account for the complexities and uncertainties inherent in these complex construction environments and many tools and techniques have been developed to facilitate modelling and analysis. However, these existing scheduling approaches fail to address the extensive resource links among projects, thereby negatively impacting the stability and feasibility of resultant project schedules and increasing management difficulties in different stages of the project. Hence, the workface operation realities often deviate away from the actual planning bringing down the overall productivity. Unless the changes and variations (e.g., material logistics) during operations can be sufficiently and cost-effectively reflected in the planning, the project team would only encounter misleading and unachievable plans and schedules throughout a project. </p>

<p>This research explores a novel resource-constrained scheduling framework named Activity-on-Node Plus (AON+), which fills these gaps by facilitating communication and finding solution to workface planning problems by Discrete Event Simulation or Optimization. The proposed methodology is capable of (1) generating robust resource use plans for multiple interdependent concurring workflows, (2) interconnecting and synchronizing schedules while accounting for both technological and resource constraints, (3) analyzing crew performance in regard to resource use, productivity, and ‘lean’ at various levels of granularity, and (4) considering crew interruption duration while adjusting production capacity to generate proper schedules with reduced waste. These advantages are illustrated and demonstrated through an in-depth literature review, two example problems (Bridge deck reinforcement and Bored pile concreting), and one real-life project based on the fabrication of bridge girders in collaboration with a partner company in Edmonton, Canada. SDESA is the DES (Discrete Event Simulation) platform selected for these case studies; however, any other DES platform can be applied to establish this proposed scheduling framework.</p>

<p>The academic contributions of this research are identified as (1) identifying the practical challenges and constraints associated with scheduling and control of different phases of repetitive construction projects based on an in-depth literature review of the current practices; (2) proposing an Enhanced Activity-on-Node (AON+) network diagramming method to account for project complexities and uncertainties while circumventing the aforementioned limitations in the existing models; (3) enabling construction managers to represent details in workflows in a streamlined network diagram by sufficiently factoring in logical constraints imposed by both technology and resource; (4) improving resource utilization efficiency while maintaining modelling simplicity and transparency to improve communication efficiency at different levels of project management, which is crucial to civil engineering applications; (5) analyzing the ‘mura’ (variations) inherent in product design and reducing the ‘muda’ (waste) in typical or nontypical repetitive projects of any size or complexity, which is instrumental in planning a lean environment. This developed job-shop production scheduling approach can be applied beyond the steel fabrication productivity modelling and scaled up for typical prefabrication projects of practical size and complexity in construction.</p>