: It is the "bridge" that allows patented anchors (like wedge or undercut anchors) to be used with standard ACI 318 design equations. Cracked vs. Uncracked Concrete
For the most current technical requirements, you can access official copies of ACI CODE-355.2-19 and the updated ACI CODE-355.2-22 at the American Concrete Institute (ACI) Store. Core Scope and Applications aci 355.2 pdf