Stirrup requirements for tank pier/wall per ACI 318-05

[pinballtime]

I have a saddle supported tank on "piers" 3 feet above an elevated slab in Seismic Design Category D. Since the tank needs to expand, the saddle is anchored to only one of the five "piers" along it's long axis, so it needs to take the entire shear. Across the long axis, shear is resisted by all five piers. Since I do not need the vertical steel as compression steel, I can design the piers as a wall and provide minimum horizontal steel. However, I need supplemental r/f (stirrups) to satisfy the anchorage requirements for concrete breakout, blowout, etc. at the single long axis pier. At this pier, I can replace the horizontal wall steel with stirrups. But do the stirrups need to have seismic hooks and meet the spacing requirements of 21.4.4 referenced by section 21.10.4 (Piles, Piers, or caissons) since the "pier" is more like a wall?

Thanks for any guidance!

 

[VoyageofDiscovery]

I am not familiar with the current ACI, however I can say this if I were designing for seismic I would include any beneficial steel and details. Seismic requires a "weak beam strong column" approach so I would not skimp on the shear stiffness where the load path requires.

HTH