Section 9.7.6/Reinforcement at Supports
ACI 318 Section 9.7.6 covers reinforcement development, cutoff, and lap splice requirements at beam supports.
At simple supports, at least one-third of the positive moment reinforcement must extend at least 6 inches into the support. At continuous supports, at least one-fourth of the positive moment reinforcement must extend at least 6 inches past the face of support. Negative moment reinforcement must extend beyond the point of inflection by at least the development length, 12 bar diameters, or 1/16 of the clear span, whichever is greatest. Lap splices of flexural reinforcement must not be located within tension zones unless specific requirements are met.
Why this section exists
The location where reinforcing bars are cut off or spliced is critical to structural performance. Bars that are cut too short leave the concrete unreinforced at a location where moment still exists. Splices in high-tension zones are weaker than continuous bars. These requirements ensure that the reinforcement layout provides continuous strength through the entire beam span, including at the critical support and midspan locations.
What plan reviewers look for
Plan reviewers check beam reinforcing details for bar cutoff locations, embedment past supports, and splice positions. They verify that the required fraction of reinforcement extends into supports per 9.7.3.8. They check that bar cutoff points provide adequate development length beyond the theoretical cutoff point. They verify splice locations are outside high-tension zones when possible.
Common violations
Related ACI 318 requirements
Section 25.4.2 covers development length calculations. Section 25.5 covers lap splice length requirements. Section 9.7.3 covers beam reinforcement detailing. Section 18.6 covers special requirements for reinforcement in seismic moment frames.