1811.6.3.2.1 Design in Seismic Design Category C.
BC § 1811.6.3.2.1
Where a structure is assigned to Seismic Design Category C in accordance with Section 1613, precast prestressed concrete piles shall have transverse reinforcement in accordance with this section. The minimum 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 precast prestressed concrete pile. (Equation 18-1) where: Ag = Pile cross-sectional area square inches (mm 2 ). f 'c = Specified compressive strength of concrete, psi (MPa). fyh = Yield strength of spiral reinforcement ≤ 85,000 psi (586 MPa). P = Axial load on pile, pounds (kN), as determined from Equations 16-5 and 16-7. ρs = Spiral reinforcement index (vol. spiral/vol. core). Not less than one-half the volumetric ratio required by Equation 18-1 shall be provided below the upper 20 feet (6096 mm) of the pile. Exception: The minimum spiral reinforcement index required by Equation 18-1 shall not apply in cases where the design includes full consideration of load combinations specified in ASCE 7, Section 2.3.6 and the applicable overstrength factor, Ω0 . In such cases, minimum spiral reinforcement index shall be as specified in Section 1811.6.1.2 of this code.
