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# Section 1809 Driven Pile Foundations

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Timber piles shall be designed in accordance with the AFPA NDS.

Round timber piles shall conform to ASTM D 25. Sawn timber piles shall conform to DOC PS-20.

Timber piles used to support permanent structures shall be treated in accordance with this section unless it is established that the tops of the untreated timber piles will be below the lowest ground-water level assumed to exist during the life of the structure. Preservative and minimum final retention shall be in accordance with AWPA U1 (Commodity Specification E, Use Category 4C) for round timber piles and AWPA U1 (Commodity Specification A, Use Category 4B) for sawn timber piles. Preservative-treated timber piles shall be subject to a quality control program administered by an approved agency. Pile cutoffs shall be treated in accordance with AWPA M4.

Any substantial sudden increase in rate of penetration of a timber pile shall be investigated for possible damage. If the sudden increase in rate of penetration cannot be correlated to soil strata, the pile shall be removed for inspection or rejected.

The allowable stresses shall be in accordance with the AF&PA NDS.

The materials, reinforcement and installation of precast concrete piles shall conform to Sections 1809.2.1.1 through 1809.2.1.4.

The minimum lateral dimension shall be 8 inches (203 mm). Corners of square piles shall be chamfered.

Longitudinal steel shall be arranged in a symmetrical pattern and be laterally tied with steel ties or wire spiral spaced not more than 4 inches (102 mm) apart, center to center, for a distance of 2 feet (610 mm) from the ends of the pile; and not more than 6 inches (152 mm) elsewhere except that at the ends of each pile, the first five ties or spirals shall be spaced 1 inch (25 mm) center to center. The gage of ties and spirals shall be as follows:

For piles having a diameter of 16 inches (406 mm) or less, wire shall not be smaller than 0.22 inch (5.6 mm) (No. 5 gage).

For piles having a diameter of more than 16 inches (406 mm) and less than 20 inches (508 mm), wire shall not be smaller than 0.238 inch (6 mm) (No. 4 gage).

For piles having a diameter of 20 inches (508 mm) and larger, wire shall not be smaller than 0.25 inch (6.4 mm) round or 0.259 inch (6.6 mm) (No. 3 gage).

For piles having a diameter of 16 inches (406 mm) or less, wire shall not be smaller than 0.22 inch (5.6 mm) (No. 5 gage).

For piles having a diameter of more than 16 inches (406 mm) and less than 20 inches (508 mm), wire shall not be smaller than 0.238 inch (6 mm) (No. 4 gage).

For piles having a diameter of 20 inches (508 mm) and larger, wire shall not be smaller than 0.25 inch (6.4 mm) round or 0.259 inch (6.6 mm) (No. 3 gage).

Piles shall be handled and driven so as not to cause injury or overstressing, which affects durability or strength.

The minimum amount of longitudinal reinforcement shall be 0.8 percent of the concrete section and shall consist of at least four bars.

Where a structure is assigned to Seismic Design Category C in accordance with Section 1613, the following shall apply. Longitudinal reinforcement with a minimum steel ratio of 0.01 shall be provided throughout the length of precast concrete piles. Within three pile diameters of the bottom of the pile cap, the longitudinal reinforcement shall be confined with closed ties or spirals of a minimum

^{3}/_{8}inch (9.5 mm) diameter. Ties or spirals shall be provided at a maximum spacing of eight times the diameter of the smallest longitudinal bar, not to exceed 6 inches (152 mm). Throughout the remainder of the pile, the closed ties or spirals shall have a maximum spacing of 16 times the smallest longitudinal bar diameter not to exceed 8 inches (203 mm).Where a structure is assigned to Seismic Design Category D, E or F in accordance with Section 1613, the requirements for Seismic Design Category C in Section 1809.2.2.2.1 shall apply except as modified by this section. Transverse confinement reinforcement consisting of closed ties or equivalent spirals shall be provided in accordance with Sections 21.4.4.1, 21.4.4.2 and 21.4.4.3 of ACI 318 within three pile diameters of the bottom of the pile cap. For other than Site Class E or F, or liquefiable sites and where spirals are used as the transverse reinforcement, a volumetric ratio of spiral reinforcement of not less than one-half that required by Section 21.4.4.1(a) of ACI 318 shall be permitted.

The allowable compressive stress in the concrete shall not exceed 33 percent of the 28-day specified compressive strength (

*f '*) applied to the gross cross-sectional area of the pile. The allowable compressive stress in the reinforcing steel shall not exceed 40 percent of the yield strength of the steel (_{c}*f*) or a maximum of 30,000 psi (207 MPa). The allowable tensile stress in the reinforcing steel shall not exceed 50 percent of the yield strength of the steel (_{y}*f*) or a maximum of 24,000 psi (165 MPa)._{y}Reinforcement for piles that are not manufactured under plant conditions shall have a concrete cover of not less than 2 inches (51 mm).

Reinforcement for piles manufactured under plant control conditions shall have a concrete cover of not less than 1.25 inches (32 mm) for No. 5 bars and smaller, and not less than 1.5 inches (38 mm) for No. 6 through No. 11 bars except that longitudinal bars spaced less than 1.5 inches (38 mm) clear distance apart shall be considered bundled bars for which the minimum concrete cover shall be equal to that for the equivalent diameter of the bundled bars.

Reinforcement for piles exposed to seawater shall have a concrete cover of not less than 3 inches (76 mm).

Reinforcement for piles manufactured under plant control conditions shall have a concrete cover of not less than 1.25 inches (32 mm) for No. 5 bars and smaller, and not less than 1.5 inches (38 mm) for No. 6 through No. 11 bars except that longitudinal bars spaced less than 1.5 inches (38 mm) clear distance apart shall be considered bundled bars for which the minimum concrete cover shall be equal to that for the equivalent diameter of the bundled bars.

Reinforcement for piles exposed to seawater shall have a concrete cover of not less than 3 inches (76 mm).

Precast prestressed concrete piles shall conform to the requirements of Sections 1809.2.3.1 through 1809.2.3.5.

Precast prestressed piles shall be designed to resist stresses induced by handling and driving as well as by loads. The effective prestress in the pile shall not be less than 400 psi (2.76 MPa) for piles up to 30 feet (9144 mm) in length, 550 psi (3.79 MPa) for piles up to 50 feet (15 240 mm) in length and 700 psi (4.83 MPa) for piles greater than 50 feet (15 240 mm) in length.

Effective prestress shall be based on an assumed loss of 30,000 psi (207 MPa) in the prestressing steel. The tensile stress in the prestressing steel shall not exceed the values specified in ACI 318.

Effective prestress shall be based on an assumed loss of 30,000 psi (207 MPa) in the prestressing steel. The tensile stress in the prestressing steel shall not exceed the values specified in ACI 318.

Where a structure is assigned to Seismic Design Category C in accordance with Section 1613, the following shall apply. The minimum volumetric ratio of spiral reinforcement shall not be less than 0.007 or the amount required by the following formula for the upper 20 feet (6096 mm) of the pile.

where:

ρ

At least one-half the volumetric ratio required by Equation 18-4 shall be provided below the upper 20 feet (6096 mm) of the pile.

The pile cap connection by means of dowels as indicated in Section 1808.2.23.1 is permitted. Pile cap connection by means of developing pile reinforcing strand is permitted provided that the pile reinforcing strand results in a ductile connection.

ρ

*= 0.12*_{s}*f'*/_{c}*f*(Equation 18-4)_{yh}where:

*f '*= Specified compressive strength of concrete, psi (MPa)._{c}*f*= Yield strength of spiral reinforcement ≤ 85,000 psi (586 MPa)._{yh}ρ

*= Spiral reinforcement index (vol. spiral/vol. core).*_{s}At least one-half the volumetric ratio required by Equation 18-4 shall be provided below the upper 20 feet (6096 mm) of the pile.

The pile cap connection by means of dowels as indicated in Section 1808.2.23.1 is permitted. Pile cap connection by means of developing pile reinforcing strand is permitted provided that the pile reinforcing strand results in a ductile connection.

Where a structure is assigned to Seismic Design Category D, E or F in accordance with Section 1613, the requirements for Seismic Design Category C in Section 1809.2.3.2.1 shall be met, in addition to the following:

- Requirements in ACI 318, Chapter 21, need not apply, unless specifically referenced.
- Where the total pile length in the soil is 35 feet (10 668 mm) or less, the lateral transverse reinforcement in the ductile region shall occur through the length of the pile. Where the pile length exceeds 35 feet (10 668 mm), the ductile pile region shall be taken as the greater of 35 feet (10 668 mm) or the distance from the underside of the pile cap to the point of zero curvature plus three times the least pile dimension.
- In the ductile region, the center-to-center spacing of the spirals or hoop reinforcement shall not exceed one-fifth of the least pile dimension, six times the diameter of the longtitudinal strand, or 8 inches (203 mm), whichever is smaller.
- Circular spiral reinforcement shall be spliced by lapping one full turn and bending the end of the spiral to a 90-degree hook or by use of a mechanical or welded splice complying with Sec. 12.14.3 of ACI 318.
- Where the transverse reinforcement consists of circular spirals, the volumetric ratio of spiral transverse reinforcement in the ductile region shall comply with the following:

ρ= 0.25(_{s}*f '*_{c }/*f*)(_{yh}*A*/_{g}*A*- 1.0)[0.5 + 1.4_{ch}*P*/(*f '*_{c }*A*)] (Equation 18-5)_{g}

but not less than:

ρ= 0.12(_{s}*f '*/_{c}*f*)[0.5 + 1.4_{yh}*P*/(*f '*) (Equation 18-6)_{c}A_{g}

and need not exceed:

ρ= 0.021 (Equation 18-7)_{s}

where:

*A*_{g }= Pile cross-sectional area, square inches (mm^{2}).

*A*= Core area defined by spiral outside diameter, square inches (mm_{ch}^{2}).

*f '*= Specified compressive strength of concrete, psi (MPa)._{c}

*f*= Yield strength of spiral reinforcement≤ 85,000 psi (586 MPa)._{yh}

*P*= Axial load on pile, pounds (kN), as determined from Equations 16-5 and 16-6.

ρ_{s}= Volumetric ratio (vol. spiral/ vol. core).

This required amount of spiral reinforcement is permitted to be obtained by providing an inner and outer spiral. -
When transverse reinforcement consists of rectangular hoops and cross ties, the total cross-sectional area of lateral transverse reinforcement in the ductile region with spacings, and perpendicular to dimension,
*h*, shall conform to:_{c}

*A*= 0.3_{sh}*sh*(_{c}*f '*_{c }/*f*)(_{yh}*A*_{g }/*A*- 1.0)[0.5 + 1.4_{ch}*P*/(*f '*) (Equation 18-8)_{c}A_{g}

but not less than:

*A*_{sh}= 0.12*sh*_{c}(*f'*_{c}/*f*_{yh})[0.5 + 1.4*P*(*f '*_{c}A_{g}) (Equation 18-9)

where:

*f*= ≤ 70,000 psi (483 MPa)._{yh}

*h*= Cross-sectional dimension of pile core measured center to center of hoop reinforcement, inch (mm)._{c}

*s*= Spacing of transverse reinforcement measured along length of pile, inch (mm).

*A*= Cross-sectional area of tranverse reinforcement, square inches (mm_{sh}^{2}).

*f '*= Specified compressive strength of concrete, psi (MPa)._{c}

The hoops and cross ties shall be equivalent to deformed bars not less than No. 3 in size. Rectangular hoop ends shall terminate at a corner with seismic hooks.

Outside of the length of the pile requiring transverse confinement reinforcing, the spiral or hoop reinforcing with a volumetric ratio not less than one-half of that required for transverse confinement reinforcing shall be provided.

Prestressing steel and pile reinforcement shall have a concrete cover of not less than 1

^{1}/_{4}inches (32 mm) for square piles of 12 inches (305 mm) or smaller size and 1^{1}/_{2}inches (38 mm) for larger piles, except that for piles exposed to seawater, the minimum protective concrete cover shall not be less than 2^{1}/_{2}inches (64 mm).Structural steel piles, steel pipe and fully welded steel piles fabricated from plates shall conform to ASTM A 36, ASTM A 252, ASTM A 283, ASTM A 572, ASTM A 588, ASTM A 690, ASTM A 913 or ASTM A 992.

The allowable axial stresses shall not exceed 35 percent of the minimum specified yield strength (

*F*)._{y}**Exception:**Where justified in accordance with Section 1808.2.10, the allowable axial stress is permitted to be increased above 0.35*F*, but shall not exceed 0.5_{y}*F*._{y}Sections of H-piles shall comply with the following:

- The flange projections shall not exceed 14 times the minimum thickness of metal in either the flange or the web and the flange widths shall not be less than 80 percent of the depth of the section.
- The nominal depth in the direction of the web shall not be less than 8 inches (203 mm).
- Flanges and web shall have a minimum nominal thickness of
^{3}/_{8}inch (9.5 mm).

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