For structures assigned to Seismic Design Category C, precast prestressed piles shall have transverse reinforcement in accordance with this section. The volumetric ratio of spiral reinforcement shall not be less than the amount required by the following formula for the upper 20 feet (6096 mm) of the pile.
|ρs= 0.12f'c / fyh||(Equation 18-5)|
|f' c||=||Specified compressive strength of concrete, psi (MPa).|
|fyh||=||Yield strength of spiral reinforcement ≤ 85,000 psi (586 MPa).|
|ρs||=||Spiral reinforcement index (vol. spiral/vol. core).|
At least one-half the volumetric ratio required by Equation 18-5 shall be provided below the upper 20 feet (6096 mm) of the pile.