Using Hairpins to Take "Kickout" force
Using Hairpins to Take "Kickout" force
(OP)
I am planning on using full length #5 bars as hairpins to take the kickout force from the dead/collateral load in a premanufactured steel building. The idea is that the force will be transmitted to the slab and thus reduces the req'd size of my ftg. It is my belief that since I am using the slab to transmit load from the structure to the slab, the slab design is governed by ACI 318 (22.1.1.2). Because of this I am limited to the maximum reinforcement spacing (18") and minimum reinforcing ratios set by 7.12.2. (temp/shrinkage reinf.)
The reason that I am asking this is becasue the contractor wants to use #4's @ 24"oc in a 6" slab which violates both spacing and temp./shrinkage req's. Does anyone happen to know spacing/min ratio exceptions for this condition?
Thank you in advance for any thoughts on this issue.
The reason that I am asking this is becasue the contractor wants to use #4's @ 24"oc in a 6" slab which violates both spacing and temp./shrinkage req's. Does anyone happen to know spacing/min ratio exceptions for this condition?
Thank you in advance for any thoughts on this issue.






RE: Using Hairpins to Take "Kickout" force
I am certain you will get other opinions in defence of the use of hairpins.
RE: Using Hairpins to Take "Kickout" force
RE: Using Hairpins to Take "Kickout" force
RE: Using Hairpins to Take "Kickout" force
I agree with haynewp. If it's greater than 10 kips go for a tie beam. Either way, look at your overall elongation. If you have 50 kips over 100 feet, your tie reinforcing may stretch a couple of inches if based only on strength.
RE: Using Hairpins to Take "Kickout" force
haynewp, care to elaborate on that? I'm not disagreeing, I'm just curious what those (other) reasons are.
jmaddox, it seems to me that if the concrete is being used as a tension element, or a part thereof, that ACI318 would have to become the governing code and the element designed accordingly. In other words, it now becomes a "structural" element (for lack of a better description) and is no longer just a slab on grade. That's just my take on it. On the other hand you might be able to resolve the thrust with a continuous rod that wraps around bolts of opposing columns, thus removing the concrete from the equation and returning the slab to it's origninal status of being a slab on grade.
RE: Using Hairpins to Take "Kickout" force
Using a rod continuous across the building and wrapping it around the anchors would be a tie beam when encased in concrete.