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Evaluating channel anchorage with reinforcement in the slab

question.postedBy Tim Freudensteinover 7 years ago
Evaluating channel anchorage with reinforcement in the slab

*Posted on behalf of a Hilti customer:

We have had project structural engineers say we were not allowed to consider any reinforcement of the slab in the evaluation of the design of the channel anchorage. Is this realistic?

ACI,anchors

1 question.answer.reply
question.postedBy Randyover 7 years ago
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Hi Customer,

well this is a good question. The use of any type of “supplementary reinforcement” should be understood in the context that it cannot be assumed to be the existing reinforcement in the concrete member. The assumption that “supplementary reinforcement” is present in existing concrete (e.g. for cast-in-place anchor channels) should only be made after an analysis of the existing concrete member.
For example, the reference to supplementary reinforcement in ACI 318-14 Part 17.3.3 is with respect to the concrete breakout calculations in tension and shear. “Supplementary reinforcement” is understood to be reinforcement in addition to that required for the strength and serviceability of the member, such that use of supplementary reinforcement permits the calculated design concrete breakout strength in tension (Ncb or Ncbg) or shear (Vcb or Vcbg) to be increased via a higher -factor. The term “supplementary reinforcement” in this context is referring to reinforcement designed (for example) per Fig. R17.4.2.9 for tension or per Figure R17.5.2.9 for shear; but not specifically designed for development. Instead, it is intended to define the use of a higher -factor. Note that these provisions are also independent of whether the concrete is assumed to be cracked or uncracked. The reference to edge reinforcement in ACI 318-14 Part 17.5.2.7 is with respect to the concrete breakout calculations in shear. “Edge reinforcement” could be considered to be that which has been designed for the strength and serviceability of the member, such the calculated nominal concrete breakout strength in shear (Vcb) can be increased via a higher c,V - factor. The edge reinforcement in this context is reinforcement designed (for example) per Part 17.5.2.7. Note that the c,V - factor provisions are dependent on whether the concrete is assumed to be cracked or uncracked. Please feel free to reach out any time, if you need additional information.

Kind Regards
Randall