RickyTheStructuralEngineer
Structural
- Oct 9, 2024
- 3
Can development length be reduced by A_s,required / A_s,provided for tension anchor reinforcement?
This is extremely pertinent for designing anchors in drilled piers or the pedestals of spread footing foundations. ACI 318-29 §25.4.10.2 does not allow reducing development length based on usage "At locations where anchorage or development for fy is required", and in the shear portion of the anchor reinforcement commentary note R17.5.2.1 (b), it says "Because development for full fy is required, the use of excess reinforcement to reduce development length is not permitted for anchor reinforcement.", however in the tension part of the note (a) that comes first, it does not mention that. Additionally, ASCE's Anchorage Design for Petrochemical and other Industrial Facilities §3.5, when talking about tension anchor reinforcement, clearly does allow it in at least some scenarios when it states, "The development length may be reduced when excess reinforcement is provided according to ACI 318-19, Section 25.4.10, as long as the restrictions listed in Section 25.4.10.2 are met." That means this document doesn't think the restrictions in 25.4.10.2 inherently include anchor reinforcement (but perhaps only if you're in seismic design category C and above)?
There doesn't seem to be any reasoning given in R25.4.10.2 that applies to tension anchor reinforcement, R17.5.2.1 is curiously written, and ASCE's industrial anchor design guide clearly allows it in some circumstances. So because of this, it's fuzzy to me if the reduction can be applied to tension anchor reinforcement or not, and if not, it is not clear why. Thanks!
This is extremely pertinent for designing anchors in drilled piers or the pedestals of spread footing foundations. ACI 318-29 §25.4.10.2 does not allow reducing development length based on usage "At locations where anchorage or development for fy is required", and in the shear portion of the anchor reinforcement commentary note R17.5.2.1 (b), it says "Because development for full fy is required, the use of excess reinforcement to reduce development length is not permitted for anchor reinforcement.", however in the tension part of the note (a) that comes first, it does not mention that. Additionally, ASCE's Anchorage Design for Petrochemical and other Industrial Facilities §3.5, when talking about tension anchor reinforcement, clearly does allow it in at least some scenarios when it states, "The development length may be reduced when excess reinforcement is provided according to ACI 318-19, Section 25.4.10, as long as the restrictions listed in Section 25.4.10.2 are met." That means this document doesn't think the restrictions in 25.4.10.2 inherently include anchor reinforcement (but perhaps only if you're in seismic design category C and above)?
There doesn't seem to be any reasoning given in R25.4.10.2 that applies to tension anchor reinforcement, R17.5.2.1 is curiously written, and ASCE's industrial anchor design guide clearly allows it in some circumstances. So because of this, it's fuzzy to me if the reduction can be applied to tension anchor reinforcement or not, and if not, it is not clear why. Thanks!
