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Reduction factors for hooked bars in tension

Reduction factors for hooked bars in tension

(OP)
thread167-228427: Development of Hooked bars in compression
The above thread answers some of the questions I have about developing hooked bars in footings, but how do I use ACI 318-11, para 12.5.3.3 when the hooks are in a footing?

PCA Notes on ACI 318-99 is a good example of my question.  On page 24-18, the tension development length for the hooked dowels is reduced by 12.5.3.2, but 12.5.3.3 is ignored.  Clearly, 12.5.3.3 is written to provide a length credit for hooks in beams that are confined, as in Fig. R12.5.3(a).

My question is, why isn't the same reduction allowed for footings, where the bars are "confined" by the large amount of concrete on each side?

RE: Reduction factors for hooked bars in tension

There is no 12.5.3.2 or .3  Are you looking at 12.5.3(a) thru (d)?

12.5 is "development of standard hooks in TENSION", but you mention a thread about hooks in compression.  12.1.1 states that "Hooks and heads shall not be used to develop bars in compression."

Assuming you are looking exclusively at tension, 12.5 allows all applicable factors [12.5.3(a) thru (d)] to be applied, with specific limitations (L_dh=>8d_b, 6")

I have the -11 PCA Notes, but not the -99, so I cannot comment, but I would not necessarily expect the old Notes to reflect the current code.

RE: Reduction factors for hooked bars in tension

(OP)
Thanks, TXStructural for the response.  Yes, my question concerns bars in tension, and I apologize for mixing up ACI318-99 & 11.  Paragraph 12.5.3.3 in 318-99 corresponds to paragraph 12.5.3 (b) in 318-11.

Since the changes to paragraph 12.5 appear to be minor (for plain bars in normal wt concrete) I am still uncomfortable taking advantage of the 0.8 factor where footings or mass concrete is concerned.  Especially since 318-11 shows tied beam examples for application of 12.5.3b (and "a" as well).

Since the PCA example takes advantage of 12.5.3.2, does this mean you can use one, but not both?

RE: Reduction factors for hooked bars in tension

12.5.3.b applies to hooks confined by stirrups or ties very closely spaced along the hook.  A very heavily reinforced footing might provide significant confinement, but would likely not comply with 12.5.3.b unless specially detailed for that purpose.

The commentary in 318-11 states in part:
"The development length for standard hooks ldh of 12.5.2 can
be reduced by all applicable modification factors of 12.5.3.
As an example, if the conditions of both 12.5.3(a) and (c)
are met, both factors may be applied."

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