I would be more than happy to share with you a reference on how to do it. Butler Foundations Manual used to have an excellent step-by-step procedure. I am not sure if it is available anymore. I am one of the few fortunate engineers who has a copy. But I think as an engineer, you really do not need that manual.
Hairpin relies on bonding between the bar and the concrete to resist the tensile load. It is as simple as that. Make sure you have enough length that will develop the horizontal thrust. Of course use proper factor of safety. I use 1.5 to 2.0 depending on the application. I usually add one hairpin for every set of anchor bolts (i.e. if the column has two anchor bolts, I would add one hairpin, if it has four anchor bolts, I add a second hairpin even if it is not needed). This is a cheap and very inexpensive insurance.
I would bend them at 30 to 60 degrees around the column into the slab. Watch your concrete cover. I have developed a cheat table with horizontal loads and he corresponding bar number and length required.
Make your own and you would be happy if you do many pre-engineered metal building foundation design.
The Metal Building Dealers Association (MBDA) published a handbook many years ago that had a chapter on foundation design for metal buildings and had a proceedure for the design of hairpins in it. The book was written for MBDA by Computerized Structural Design, Inc. in Milwaukee, WI. You might try either of those places for a copy.
