Title:
Optimal Domains for Flexural and Axial Loading
Author(s):
Mark Aschheim, Enrique Hernandez-Montes, and Luisa Maria Gil-Martin
Publication:
Structural Journal
Volume:
105
Issue:
6
Appears on pages(s):
720-728
Keywords:
beams; column; cross-section design.
DOI:
10.14359/20100
Date:
11/1/2008
Abstract:
Domains associated with the optimal design of rectangular reinforced concrete sections are established according to the provisions of ACI 318 with respect to P-M coordinates using results obtained with reinforcement sizing diagrams (RSDs). Characteristics of the optimal solutions are identified for each domain, analytical expressions for the domain boundaries are established, and a two-step solution procedure is presented for optimally determining the top and bottom reinforcement required to resist an arbitrary combination of axial load and moment. Examples illustrate the application of this computationally efficient procedure to the design of columns, singly reinforced beams, and doubly reinforced beams.
The optimal domains provide new insight into reinforcement requirements for beam-column sections. A design approach is presented that is applicable to both beams and columns alike. This contrasts with the variety of piecemeal approaches currently used to determine non-optimal reinforcement solutions for beam and column sections, which can involve manual iterations, charts, and trial-and-error procedures. The savings in reinforcement can be significant for sections subjected to nonsymmetric loading and provide an opportunity to improve the sustainability of reinforced concrete construction.