§ 27-708 Precast concrete piles (including prestressed sections).
AC § 27-708
(a)Materials. Materials for precast concrete piles shall conform to the requirements of article five of subchapter ten of this chapter.
(b)Construction.
(1)HANDLING. Precast concrete piles shall be proportioned, cast, cured, handled, and driven so as to resist the stresses induced by handling and driving as well as by loads. Handling stresses shall be computed on the basis of fifty per cent of the weight of the pile as an allowance for impact. Handling equipment shall be constructed so as to equalize the reactions on the several lines of the pile pickups. Loading conditions induced by handling and driving shall be considered as of infrequent occurrence.
(2)DIMENSIONS. The minimum lateral dimension of the pile shall be ten inches, except for the taper at the tip.
(3)STRUCTURAL DESIGN. Piles shall be proportioned in accordance with the provisions of article eight of this subchapter, subject to the following additional requirements: a. For a length equal to at least three times the minimum lateral dimension at each end of the pile, lateral tie reinforcement consisting of 0.225 in. diameter rods or larger shall be spaced not more than three inches center-to-center, or an equivalent spiral shall be provided. Elsewhere, the spacing of the ties or the pitch of the spiral may be increased to twelve inches The minimum amount of longitudinal reinforcement shall be two per cent of the concrete section placed in a symmetrical pattern of at least four bars. If prestressed piles are used, the minimum residual compression in the pile section shall be seven hundred psi. For piles designed with voids, the three inch spacing of the ties or spiral at each end of the pile shall be extended for a distance of twelve feet or one-third the length of the pile, whichever is smaller. b. For piles designed with voids, the minimum wall thickness of the concrete in any section of the piles shall be four inches. Voids may extend through either or both ends of the pile. If the void extends through the lower end of the pile, the pile head shall be vented to prevent buildup of internal hydraulic pressure during driving. c. Reinforcing steel shall be covered with at least one and one-half inches of concrete on the surface against the ground.
(c)Tolerances. Voids, when used, shall be located within three-eighths of an inch of the position shown in the plans. The maximum departure of the pile axis from a straight line, measured while the pile is not subject to bending forces, shall not exceed one-eighth of an inch in ten feet or three eighths of an inch in forty feet, or 0.1 per cent of the pile length.
(d)Installation. Precast concrete piles shall not be handled or driven until they have cured sufficiently to develop the necessary strength.
