An application of lean concept to structural steel fabrication process : a case study of steel box girder fabrication for a bridge project

Abstract

This thesis presents an application of lean concept to a structural steel fabrication process through a case study of a box girder bridge project. Relevant data were collected from a fabrication factory in Thailand based on the requirements of a value stream mapping tool. The model of the existing process was analyzed by focusing on the total working time, which consists of process time and waiting time. Lean concept was then applied to improve the process. The process improvement encompassed conserving working performance, reducing waiting time, and eliminating bottleneck activity. Owing to the limitation that the process improvement cannot be implemented in the actual factory, a simulation model was adopted to verify the proposed guidelines. In the simulation model, various process improvement guidelines were represented by different trial cases. It was found that conserving working performance helps reduce process time, merging working activity can reduce waiting time, and increasing working station can eliminate bottleneck. Finally, this thesis provides a guideline of structural steel process improvement to reduce waste by maximizing workers performance and machine usage and reducing working time.