In design example 2.6.2 from "Post installed Reinforcing Bar Guide (Jan 2023)", #5 at 16in bottom bars are specified for shear friction reinforcement. Is this really required? Based on my understanding of shear friction, the #8 at 12in top bars provide adequate shear friction resistance. Specifically I am referring to the ACI 318-19 commentary for clause 22.9.4.6 and additionally R22.9.5.1 where it is stated: "If a moment acts across the shear plane, the shear-transfer reinforcement should be placed primarily in the flexural tension zone". In addition to this the slab appears to fail in one-way shear, as I believe the resistance is 5.7 kips/ft.
Hi Colin
The decision of whether the whole area of the member’s cross section is resisting shear or only the upper part is left to the engineer. It would be a case by case decision and in the example you shared the calculations were based on the reinforcement to be considered in upper and bottom part.
Please see this article for more information, and this article for the Hilti method.
Hi Colin
We are looking at your question and we will get back to you as soon as possible.
Hi Colin,
The design example is merely for illustration purposes, and is not intended to be considered as a specific design application, although the shear friction parameters being considered could be utilized in an actual design. As mentioned, the decision to consider the additional #5 bars as shear reinforcement is one that should be made by the engineer of record.