Optimal domains for strength design of rectangular sections for axial load and moment according to Eurocode 2

Domains associated with the optimal design of reinforcement for rectangular concrete sections according to the provisions of Eurocode 2 are established with respect to N–MN–M coordinates using results obtained with Reinforcement Sizing Diagrams. The characteristics of the optimal reinforcement solutions are identified for each domain, analytical expressions for the domain boundaries are established, and a two-step solution procedure is presented for determining the top and bottom reinforcement required to resist an arbitrary combination of axial load and moment. Examples illustrate the design of columns, singly reinforced beams, and doubly reinforced beams. The two-step design approach provides a direct solution for optimal reinforcement and requires less computation than the Reinforcement Sizing Diagram approach. The optimal reinforcement solutions can result in a significant savings in reinforcement quantities.