Recent developments in optimal reinforcement of RC beam and column sections

Recent advances in approaches to the design of reinforced concrete sections have culminated in a theorem of optimal (minimum) sectional reinforcement. This theorem is articulated on the basis of patterns observed in the optimal reinforcement of rectangular sections, obtained with a new approach for the analysis and design of reinforcement. Using the hypotheses for ultimate strength design sanctioned by ACI 318-05 (2008), the minimum total reinforcement area required to provide adequate resistance to axial load and moment is shown to occur for particular constraints on longitudinal reinforcement area or distributions of strain. These constraints are identified along with the solutions for minimum total reinforcement area. Optimal reinforcement may be selected from among the potential solutions identified by the theorem. An example illustrates the application of the theorem to the design of a reinforced concrete cross-section. Implications for teaching and practice of reinforced concrete design are discussed.