Austin, MarkPreston, J.L.This 2-part paper describes a solid modeling methodology for the interactive design and analysis of reinforced concrete (RC) beam structures. Part I covers the data structure and algorithms for steel reinforcing bar trajectories, and a three dimensional boundary representation of the concrete beam solid. Algorithms are given for slicing the beam, extracting cross sections, and computing the ultimate strength. Part 2 of this series discuss the design and implementation of an interactive design environment called Beam Tool.en-UScomputer aided designdata structuressolid modelingIntelligent ServomechanismsTechnical Report