Rebar Development Length (with or without hook)

[KimWT]

Hi!

I would like to hear other engineer's opinion about reinforcement development length.

[Straight Rebar, P1 & P2]
When concrete covers rebar well, L2 can be considered as development length, Ld.
What about rebar located close to the edge, P1?
If side cover S1 satisfies minimum concrete cover condition around P1 rebar,
can I still consider L2 as Ld?
(What is boundary condition S1 to consider L2 as Ld rather than L1? Minimum concrete cover?)

[Rebar attached with hook, P3]
The same question can be asked.
Let's assume #6 rebar, P3, is 4" (S2) off the edge.
Can I consider L2 as development length?

Is there any difference between case P1 and P3?
Doesn't a hook make any difference?


Thanks!

WT.

 

[TehMightyEngineer]

If side cover S1 satisfies minimum concrete cover condition around P1 rebar,can I still consider L2 as Ld?

Yes, the bar is fully developed. However, this doesn't mean you have full tensile capacity of the bar. The development length simply means you've transferred the tension force into the concrete by anchoring the bar a sufficient depth. This definitely does not mean that the concrete has sufficient capacity to resist failure. Somewhat ACI appendix D (now chapter 17 in ACI), P1 and P3 will have very similar frustum breakout planes and thus will have similar capacities. P2 is away from edges and thus the tensile load P2 before failure of the concrete is a lot higher than P1 or P3.

See below:

Yes, as long as the hook and the straight section have the appropriate clear cover.

Is there any difference between case P1 and P3?

Of course, the hook shortens the required development length so you transfer more force into the concrete at the end of the hook. This would help significantly in preventing sideface blowout.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)