Concrete Footing Reinforcement
Concrete Footing Reinforcement
(OP)
I am reviewing some old calculations/design of a 4' thick concrete footing. The design engineer placed their required (As.min) flexural reinforcement (tension/compression) on the top and bottom faces in each direction. This I understand. However, they placed an additional layer of reinforcement in the dead center of the footing, and this is where I'm questioning the logic. Based on the calculations, it appeared that the rebar is used simply as temperature reinforcement, but I know there is sufficient quantities in the top and bottom layers to account for this. Additionally, the location of the rebar is basically useless in my opinion because its situated on the neutral axis. Am I missing something here?






RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
I've also been a young engineer on a job that did not require a 3rd layer where the EOR told me to add a middle layer only because it made him feel more comfortable with the design that I had come up with.
RE: Concrete Footing Reinforcement
Mike McCann
MMC Engineering
RE: Concrete Footing Reinforcement
Not saying they are needed, engineers just like to feel good, right?
RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
around nine feet thick or so.. and there was like for 4 or 5 layers of rebars..
dont get the logic for that..
RE: Concrete Footing Reinforcement
RE: Concrete Footing Reinforcement
Granted, I don't believe that I would do this for a spead footing, but the concept is valid.
RE: Concrete Footing Reinforcement
If there was a choice between a top and bottom layer of #8s or 4 layers of #6s, wouldn't it be cheaper to stick with the fewer number of bars?
What would be an example of a failure mechanism that would be prevented by multiple layers of reinforcement over just the top and bottom mat?
RE: Concrete Footing Reinforcement
In regards to the temperature reinforcement in footings, I'm not sure how needed it would be. The ground would have a significant moderating effect so as to prevent large temperature fluctuations. I'm sure shrinkage would be evident, but the relatively tight rebar spacing should compensate effectively.
I think the bottom line that as it was put above, this is pretty much "feel good" rebar in this application. I'm assuming there is no formal documentation or ACI references that really show otherwise.