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Allowable pier or pile loads shall be determined in accordance with Section 1808.2.8.1 through 1808.2.8.9.
1808.2.8.1 Determination of Allowable Loads
The allowable axial and lateral loads on piers or piles shall be determined by load tests or a recognized method of analysis. The allowable load shall be determined by a licensed engineer experienced in geotechnical engineering and shall be approved by the commissioner.
The allowable axial load on a pile shall be the least value permitted by consideration of the following factors (for battered piles, the axial load shall be computed from the resultant of all vertical loads and lateral forces occurring simultaneously):
  1. The capacity of the pile as a structural member.
  2. The allowable bearing pressure on soil strata underlying the pile tips.
  3. The resistance to penetration of the piles, including resistance to driving, resistance to jacking, the rate of penetration, or other equivalent criteria.
  4. The capacity as indicated by load test, where load tests are required.
  5. The maximum loads prescribed in Section 1808.2.8.1.3.
1808.2.8.1.1 Bearing Capacity
The allowable pile load shall be limited by the provision that the pressures in materials at and below the pile tips, produced by the loads on individual piles and by the aggregate of all piles in a group or foundation, shall not exceed the allowable bearing values established in Table 1804.1. The transfer of load from piles to soil shall be determined by a recognized method of analysis. As an alternative, for purposes of this section, piles or pile groups may be assumed to transfer their loads to the underlying materials by spreading the load uniformly at an angle of sixty degrees with the horizontal, starting at a polygon circumscribing the piles, located as follows:
  1. For piles embedded entirely in decomposed rock or granular soils, or in controlled fill materials, the polygon shall be circumscribed at a level located two-thirds of the embedded length of the pile, measured up from the tip.
  2. For piles penetrating through silts and clays into bearing in decomposed rock or granular soils, the polygon shall be circumscribed at the bottom of the strata of silts or clays.
1808.2.8.1.2 Bearing Stratum
The plans for the proposed work shall establish, in accordance with the requirements relating to allowable bearing pressure, the bearing stratum to which the piles in the various sections of the building must penetrate and the approximate elevations of the top of such bearing stratum. Where penetration of a given distance into the bearing strata is required for adequate distribution of the loads, such penetration shall be shown on the plans. The indicated elevations of the top of the bearing strata shall be modified by such additional data as may be obtained during construction. All piles shall penetrate to or into the designated bearing stratum.
1808.2.8.1.3 Maximum Loads
Except as permitted by the provisions of Section 1808.2.8.3.1.6, the maximum allowable pile load shall not exceed the values specified in Table 1808.2.8.1.3.

TABLE 1808.2.8.1.3
MAXIMUM ALLOWABLE PILE LOADS
TYPE OF PILE MAXIMUM ALLOWABLE PILE LOAD (TONS)
Caisson Piles No upper limit
Open-end pipe (or tube) piles bearing on rock of Class 1a, 1b, or 1c 18-in O.D. and greater                            250
14-in to 18-in O.D.                                   200
12-in to 14-in                                           150
10-in to 12-in                                           100
8-in to 10-in                                               60
Closed-end pipe (or tube) piles, H-piles, cast-in-place concrete, enlarged base piles,
and precast concrete piles bearing on rock of Class 1a, 1b, or 1c
150
Piles (other than timber piles) bearing onsoft rock of Class 1d 80
Piles (other than timber piles) that receive their principal support other than by direct
bearing on rock of Class 1a through 1d
75
Timber piles bearing on rock of Class 1a through 1d 25
Timber piles bearing in suitable soils 40 tons maximum permissible with load test, 30 tons
maximum without load test.
For SI: 1 ton = 1000 kg.
1808.2.8.1.4 Minimum Pile Penetrations
Piles shall penetrate the minimum distance required to develop the required load capacity of the pile as established by the required penetration resistance and load tests as applicable.
1808.2.8.1.5 Capacity as Indicated by Resistance to Penetration
Where subsurface investigation and general experience in the area indicate that the soil that must be penetrated by the pile consists of glacial deposits containing boulders, or fills containing riprap, excavated detritus, masonry, concrete or other obstructions in sufficient numbers to present a hazard to the installation of the piles, the selection of type of pile and penetration criteria shall be subject to the approval of the commissioner but in no case shall the minimum penetration resistance be less than that stated in Tables 1808.2.8.1.5A and 1802.8.2.8.1.5B.

TABLE 1808.2.8.1.5A
MINIMUM DRIVING RESISTANCE AND MINIMUM HAMMER ENERGY FOR STEEL H-PILES, PIPE PILES, PRECAST AND CAST-IN-PLACE CONCRETE PILES AND COMPOSITE PILES (other than timber)
MINIMUM DRIVING RESISTANCEa, c, d, e
Pile Capacity
(tons)
Hammer Energyb
(ft. lbs.)
Friction Piles
(blows/ft.)
Piles Bearing on Soft Rock
(Class 1d)
(blows/ft.)
Piles Bearing on Rock
(Class 1a, 1b, and 1c)
Up to 20 15,000 19 48 5 Blows per 1/4 inch
(Minimum hammer energy
of 15,000 ft. lbs.)
19,000 15 27
24,000 11 16
30 15,000 30 72
19,000 23 40
24,000 18 26
40 15,000 44 96
19,000 32 53
24,000 24 34
50 15,000 72 120
19,000 49 80
24,000 35 60
32,000 24 40
60 15,000 96 240
19,000 63 150
24,000 44 100
32,000 30 50
70 & 80
19,000 5 Blows per 1/4 inch
(Minimum hammer energy
of 19,000 ft. lbs.)
24,000
32,000
For SI: 1 foot = 304.8 mm, 1 ton = 1000 kg.
  1. Final driving resistance shall be the sum of tabulated values plus resistance exerted by nonbearing materials. The driving resistance of nonbearing materials shall be taken as the resistance experienced by the pile during driving, but which will be dissipated with time and may be approximated as described in Section 1808.2.8.1.5.1.
  2. The hammer energy indicated is the rated energy.
  3. Sustained driving resistance. Where piles are to bear in soft rock, the minimum driving resistance shall be maintained for the last 6 inches, unless a higher sustained driving resistance requirement is established by load test. Where piles are to bear in soil Classes 2 through 5, the minimum driving resistance shall be maintained for the last that inches unless load testing demonstrates a requirement for higher sustained driving resistance. No pile needs to be driven to a resistance that penetrates in blows per inch (blows per 25mm) more than twice the resistance indicated in this table, nor beyond the point at which there is no measurable net penetration under the hammer blow.
  4. The tabulated values assume that the ratio of total weight of pile to weight of striking part of the hammer does not exceed 3.5. If a larger ratio is to be used, or for other conditions for which no values are tabulated, the driving resistance shall be as approved by the commissioner.
  5. For intermediate values of pile capacity, minimum requirements for driving resistance may be determined by straight line interpolation.
TABLE 1808.2.8.1.5B
MINIMUM DRIVING RESISTANCE AND HAMMER ENERGY FOR TIMBER PILES
PILE CAPACITY
(TONS)
MINIMUM DRIVING RESISTANCE (BLOWS/IN.)
TO BE ADDED TO DRIVING RESISTANCE
EXERTED BY NONBEARING MATERIALS
(NOTES 1,3,4)
HAMMER ENERGY
(ftilbs.) (Note 2)
Up to 20 Formula in Note 4 shall apply 7,500-12,000
Over 20 to 25 9,000-12,000
14,000-16,000
Over 25 to 30 12,000-16,000
(single-acting hammers)
Greater than 30 15,000-20,000
(double-acting hammers)
For SI: 1 ton = 1000 kg, 1 inch = 25.4 mm.
Notes:
  1. The driving resistance exerted by nonbearing materials is the resistance experienced by the pile during driving, but which will be dissipated with time and may be approximated as described in Section 1808.2.8.1.5.1.
  2. The hammer energy indicated is the rated energy.
  3. Sustained driving resistance. Where piles are to bear in soil classes, Soft rock, the minimum driving resistance shall be maintained for the last 6 inches, unless a higher sustained driving resistance requirement is established by load test. Where piles are to bear in soil Classes 2 through 5, the minimum driving resistance measured in blows per inch (blows per 25 mm) shall be maintained for the last 12 inches unless load testing demonstrates a requirement for higher sustained driving resistance. No pile need be driven to a resistance that penetrates in blows per inch (blows per 25 mm) more than twice the resistance indicated in this table nor beyond the point at which there is no measurable net penetration under the hammer blow.
  4. The minimum driving resistance shall be determined by the following formula:

    P = 2WhH (S + 0.1) or P = 2E (S + 0.1)
    where:
    p = Allowable pile load in pounds
    Wp = Weight of pile in pounds.
    Wh = Weight of striking part of hammer in pounds.
    H
    = Actual height of fall of striking part of hammer in feet.
    E = Rated energy delivered by the hammer per blow in foot/lbs.
    S = Penetration of pile per blow, in inches, after the pile has been driven to a depth where successive blows produce approximately equal net penetration.The value Wp shall not exceed three times Wh
1808.2.8.1.5.1 Piles Installed by Use of Steam-Powered, Air-Powered, Diesel-Powered or Hydraulic Impact Hammers
  1. The minimum required driving resistance and the requirements for hammer energies for various types and capacities of piles are given in Tables 1808.2.8.1.5A and 1808.2.8.1.5B. To obtain the required total driving resistance, the indicated driving resistances shall be added to any driving resistance experienced by the pile during installation, but which will be dissipated with time (resistance exerted by nonbearing materials or by materials which are to be excavated). For the purposes of this section, the resistance exerted by nonbearing materials may be approximated as the resistance to penetration of the pile recorded when the pile has penetrated to the bottom of the lowest stratum of nominally unsatisfactory bearing material (Class 6 and uncontrolled fills, but not controlled fill) or to the bottom of the lowest stratum of soft or loose deposits of soils of Class 4 or 5 but only where such strata are completely penetrated by the pile.
  2. Alternate for similitude method—The requirement for installation of piling to the penetration resistances given in Tables 1808.2.8.1.5A and 1808.2.8.1.5B may be waived where the following six conditions are satisfied:

    1. The piles bear on, or in, soil of Classes 2 through 5.
    2. The stratigraphy, as defined by not less than one boring for every 1600 square feet (149 m2) of building area, shall be reasonably uniform or divisible into areas of uniform conditions.
    3. Regardless of pile type or capacity, one load test, as described in Section 1808.2.8.1.5.3, shall be conducted in each area of uniform conditions, but not less than two typical piles for the entire foundation installation of the building or group of buildings on the site, nor less than one pile for every 15,000 square feet (1394 m2) of pile foundation area shall be load tested.
    4. Except as permitted by the provisions of paragraph 2.6 below, all building piles within the area of influence of a given load-tested pile of satisfactory performance shall be installed to the same or greater driving resistance as the successful load-tested pile. The same or heavier equipment of the same type that was used to install the load-tested pile shall be used to install all other building piles, and the equipment shall be operated identically. Also, all other piles shall be of the same type, shape, external dimension, and equal or greater cross-section as the load-tested pile. All building piles within the area of influence represented by a given satisfactory load-tested pile shall bear in, or on the same bearing stratum as the load test pile.
    5. A report by an engineer shall be submitted to the commissioner for review and approval establishing that the soil-bearing pressures do not exceed the values permitted by Table 1804.1 and that the probable differential settlements will not cause stress conditions in the building in excess of those permitted by the provisions of this code.
    6. Where the structure of the building or the spacing and length of the piling is such as to cause the building and its foundation to act as an essentially rigid body, the building piles may be driven to length and/or penetration into the bearing stratum without regard to penetration resistance, subject to the requirement of paragraph 2.5 above, relating to the submission and approval of a report.
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