Design of Bell & Shaft Drilled Pier Foundation for Pre-Engineered METAL BUILDING

[oengineer]

I am working on designing a metal building foundation using bell & shaft drilled piers. The foundation is a slab-on-grade with perimeter grade beams. The net allowable bearing pressure is 3000 psf for dead load plus sustained live load which can be increased 25 percent for total load conditions. The issue that I am having are the reaction forces provided by the metal building fabricator for the columns. For one of the columns I am getting DL(vert.)= 10k, LL(vert.)= 15k, Floor Load(vert.)= 17.2 k, Wind Load (vert.) = -16 k, and Wind Load (horiz.) = 11.0k. Is it normal to have such high horiz. loads for a column? I am new to designing foundations for Pre-Engineered Metal Buildings. For most buildings, I designed the piers to resist the downward gravity loads. Using the reactions provided by the metal Building manufacturer, I am getting that I need a ridiculously large shaft/bell size, like a 34/102. I am interested in any insight in what I may be doing wrong, what I am not considering, or if I am allowed to just mostly rely on the gravity loads for my design. Any suggestions/comments are appreciated.

 

[oengineer]

After further research in the PIP STE05121 Anchor Bolt Design Guide, I see that it actually provides a table with the Vert. & Horiz. Hairpin capacities. A detail for the shear reinforcement of horizontal hairpin is also shown. The capacity of a #6 hairpin is 27.84 kips. I believe this should be enough to take care of my horizontal loads. Thank you everyone for the insight.