Adjust Footing Rebar Area for proper ACI 318 Development Length
Adjust Footing Rebar Area for proper ACI 318 Development Length
(OP)
For typical 3 ft, 4 ft and 5 ft square footings (f'c = 3,000 psi and net soil bearing = 2,500 psf), it appears that I must hook the ends of the footing rebar on each end or increase the number of bars per Section 12.2.5 or increase the size of the footing. This is because the length of the bar from the critical moment location to the end of the bar is shorter than the development length [cantilever length-cover].
Most of the time, the area of steel required is governed by 0.0018bh (Temp steel). Is the "As required by analysis" in Section 12.2.5 referring to Temp steel if it is the minimum that governs or the As calculated for flexure only?
Or does 12.2.5 not apply to spread footings?
Most of the time, the area of steel required is governed by 0.0018bh (Temp steel). Is the "As required by analysis" in Section 12.2.5 referring to Temp steel if it is the minimum that governs or the As calculated for flexure only?
Or does 12.2.5 not apply to spread footings?






RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
Then put in the rebar for good measure. I think hooking (cogging per hokie) in footings like this is rarely done in my area.
Not sure if the As(req'd)/As(provided) reduction would apply to the min. 0.0018Ag steel. I wouldn't think so. The word "analysis" would imply it is the calculated As, not a code minimum.
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
For footings (and any cantilever) flexural design theory requires the free end of the bars to be hooked/cogged to provide at least partial development, depending on the length of the cantilever and the bar diameter. At least minimum reinforcement should be fully developed. As you suggested, for deeper footings, strut tie theory would require full development
Historical precedence should not be en excuse for continuing a bad practice!
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
I guess I can't justify my bad habits any longer.
Back to my original post, I will need to cog my rebar (I like that word), add more bars or increase the plan dimensions of the footing. One other option is to increase the depth until it can be designed as plain concrete.
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
Have you checked the development length using fs instead of fy?
M.
RE: Adjust Footing Rebar Area for proper ACI 318 Development Length
That said, hooking bars in footings is routine in many areas of the US. In most buildings, making footings larger or using hooked bars is really irrelevant to building cost. In my opinion, don't waste engineering time saving trivial quantities of materials on a few footings, when you can just move on to the next detail. Rebar costs about $1/lb., installed, so the amounts saved will usually be very small.