Large concrete column for suspension bridge minimum reinforcing 1

[CTL11]

I am removing and replacing a concrete tower that supports the cable for a pedestrian suspension bridge (150ft long). The existing towers were built in 1922 and are unreinforced (had GPR done to verify). The base of the tower is 6'x6' and at the top it is 3'-8"x3'-8" and the tower is ~16' tall.

Assuming the tower takes only pure compression what is the correct minimum area of reinforcing I need to use? If I use 1% of the gross area (per ACI 318 10.9.1) that seams like a lot. I plan on using #5@12" on all faces for T&S and then add additional bars in the core of the tower, but to meet the 1% gross I would have to have 56 #8 bars for the base of the tower. Can I average the gross areas (top and bottom of tower)? That would get it down to 33 #8 bars required plus the #5's.

One of the four towers was replaced in 1992 and they only used 24-#8 bars. This was done by another engineering firm.

 

[JedClampett]

I'm not sure what AASHTO says, but in ACI 10.8.4, you can use half the reinforcing if you only count on one half the section.
These days, bars are cheap. I wouldn't advise violating any ACI minimum. You can adjust the number of bars based on the cross section, but at the bottom, you better have the minimum.