Geometric control of short-line match casting using Computational BIM

Short-line match casting is a method of producing segmental pre-cast concrete bridges. This segment-production process is centralized, repetitive, compact, and easily adaptable to geometry variations such as plan, vertical, and transition curves. But the main challenge is the complexity of geometry control and the need for high accuracy. The complexity arises due to the changing coordinate system and the accumulation of errors for each segment. It is susceptible to geometric errors that accumulate over the entire span resulting in significant deviation from the alignment. This calls for rigorous geometry control during the casting process. The current work proposes a framework/workflow, called the Geometric Error Minimization for Bridge Segment Casting (GEMBSC), for minimizing geometric errors in segmental casting alignment in real-time. It involves the formulation of an iterative geometric control algorithm using the least-square method and a software tool to manage the geometric control workflow. Dynamo, a computational BIM tool, was used to extract the coordinates from the BIM model and perform coordinate transformations that feed to the surveying instruments. Subsequently, the tool compares the as-cast data with the planned geometry data and runs the error minimization algorithm to output the corrected coordinates for the casting of subsequent segments. The algorithm was validated based on past real-world data by the results obtained for the same data through a proprietary software application. The results indicated that GEMBSC is effective in minimizing errors along with providing other benefits such as savings in time and effort involved in error corrections with existing software use.