Structural Slab Reinforcing?
Structural Slab Reinforcing?
(OP)
Hopefully I can explain this properly.
I have a structural slab that is uptight to an existing building. Parallel to the building, I have a grade beam that is 5'-6" away. The slab is being designed as a one-way slab. The question I have relates to the fact that the existing building is set 45 degrees to my one-way slab reinforcing which makes the cantilever reinforcing 45 degrees to the one-way slab reinforcing.
How do you handle this moment with regards to the main one-way reinforcing in the slab? Is it a matter of SRSS (square root of the sum of the squares) or is it much more complicated that this (which I think it is)?
I have a structural slab that is uptight to an existing building. Parallel to the building, I have a grade beam that is 5'-6" away. The slab is being designed as a one-way slab. The question I have relates to the fact that the existing building is set 45 degrees to my one-way slab reinforcing which makes the cantilever reinforcing 45 degrees to the one-way slab reinforcing.
How do you handle this moment with regards to the main one-way reinforcing in the slab? Is it a matter of SRSS (square root of the sum of the squares) or is it much more complicated that this (which I think it is)?






RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
But you don't need to.
If capacities phiMnx = phiMny, and Mnx > Mu, you're okay for any vector angle between Mnx and Mny.
RE: Structural Slab Reinforcing?
Maybe this makes your slab too congested with rebar mats..
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
Otherwise, you probably want to orient the top bars in the cantilever so that the bars work over the shortest length, that is, perpendicular to the cantilever support. You can also extend the main reinforcement into the cantilever to develop it without hooks, if you prefer. Add top bars, hooked at the cantilever end as needed for development, and extending into the backspan for development beyond the negative moment over the support.
RE: Structural Slab Reinforcing?
I assume you're analyzing this one way slab in strips perpendicular to the main beams. In the analysis just increase the length of the cantilever by SQRT(2) and keep your reo running in the same direction.
Also with such a short cantilever you're likely to have hogging where there is a large backspan and will need bottom reo in the slab crossing over the beams.
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
RE: Structural Slab Reinforcing?
I was thinking that it could have been easier to have a bunch of bars that cantilever perpendicular over the top of the grade beam and run a development length into the back span. However, this would mean that the the reinforcing (strong and weak axis) would need to be designed to take the moment that is currently at an angle to the reinforcing in the one-way slab.
I am just not sure if you can do the trig to get the design moments at an angle? It appears from the above that this is possible. So if my moment is 10 ft-kips and my angle is 45 degrees. Then I need to provide an end moment for the reinforcing in the strong and weak axis of .707*10ft-kips = 7.07 ft-kips.
RE: Structural Slab Reinforcing?
Imagine you have no main slab and just a big block of plain concrete, then this is how you would design the cantilever, no?