Title:
Unified Minimum Flexural Reinforcement Requirements for Reinforced and Prestressed Concrete Members
Author(s):
Clifford L. Freyermuth and Bijan O. Aalami
Publication:
Structural Journal
Volume:
94
Issue:
4
Appears on pages(s):
409-420
Keywords:
applied loads; bonded tendons; cracking load; cracking moment;
flat plates; legal loads; minimum flexural reinforcement; precast sections;
prestressed concrete; reinforced concrete; structural research; T-beams;
supplementary bonded reinforcement;
DOI:
10.14359/492
Date:
7/1/1997
Abstract:
This study was undertaken to simplify, and to the extent possible, to unify ACI 318 minimum flexural reinforcement requirements for reinforced and prestressed concrete members. A major goal was to eliminate the feature of current provisions for prestressed concrete members in which the minimum reinforcement requirement increases with increasing levels of prestress. The concept of increasing minimum reinforcement requirements for prestressed members with increases in the level of prestress is not supported by the research results reviewed in this study, or by the analytical investigations reported herein. This study includes review of relevant research reports, review of existing ACI 318 code provisions for minimum flexural reinforcement, and review of the minimum flexural reinforcement provisions of the CEB-FIP Model Code for Concrete Structures. On the basis of this review, new unified formulas and essentially unified code provisions are proposed for minimum flexural reinforcement of reinforced and prestressed concrete members. The formulas are based on the tensile strength of both prestressed and nonprestressed reinforcement (as contrasted with the previous formula for reinforced concrete based on yield strength of nonprestressed reinforcement). The new formulas include consideration of variations in concrete strength.