Section 27-700
§ 27-700 Allowable axial load. 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 as established in this section.
4. The capacity as indicated by load test, where load tests are
required.
5. The maximum loads prescribed in subdivision (e) of this section.
(a) The capacity of the pile as a structural member.
(1) EMBEDDED PORTION OF THE PILE. The compressive stress on any cross
section of a pile produced by that portion of the design load that is
considered to be transmitted to that section shall not exceed the
allowable values for the construction materials as established in table
11-3. The tensile stress shall not exceed the values established in
subchapter ten of this chapter for like material.
(2) PORTION OF THE PILE THAT IS NOT EMBEDDED. That portion of any pile
that is free standing in air or water shall be designed as a column in
accordance with the provisions of subchapter ten of this chapter, fixed
at a point five feet below the soil contact level in class 8-65 material
or better and ten feet below in any other material. The conditions of
lateral and rotational restraint offered by the pile cap shall be
considered in determining the equivalent unbraced length.
(3) LOAD DISTRIBUTION ALONG EMBEDDED PORTION OF THE PILE. The portion
of the design load acting on any cross-section of a pile may be
determined by analysis, considering time dependent changes in
distribution of the load. As an alternative method for the purposes of
this section, it may be assumed that:
a. For piles embedded forty feet or more in materials of class 10-65
or better, or in controlled fills, and bearing on or in materials of
classes 1-65 to 5-65: seventy-five per cent of the load shall be assumed
to be carried by the tip. For shorter piles, with similar conditions of
embedment and bearing, one hundred per cent of the load shall be assumed
carried by the tip.
b. For piles embedded in materials of class 10-65 or better, or in
controlled fills, and bearing on or in materials of classes 6-65 to
10-65 (or controlled fills): the full load shall be assumed to act at a
cross section located at two-thirds of the embedded length of the pile
measured up from the tip. Where tapered piles are used, the stress at
all sections of the pile shall be determined on the basis that the full
load acts at a location as described above and that one-third of the
full load acts at the tip. The stresses so computed shall not exceed the
allowable values in table 11-3.
c. For conditions not covered in subparagraphs a and b of this
paragraph three the provisions relating to analysis shall apply.
Table 11-3 Allowable Compressive Stress for Pile Materials
========================================================================
Pile Material Allowable Compressive Stress
------------------------------------------------------------------------
Concrete Concrete--The provisions of Reference Standard RS 10-3
relating to short compression members shall apply. For
working stress design use 0.25f'c. For ultimate
strength design use minimum eccentricity of 5 per cent,
phi = 0.70 (phi = 0.75 where a permanent metal shell
having a minimum wall thickness of 1/8 inch is used),
and load factors as specified in Reference Standard RS
10-3. The above provisions shall be deemed applicable
to reinforced and unreinforced sections. For
unreinforced sections use Ds = D and d = t (symbols
refer to those used in Reference Standard RS 10-3).
Reinforcing steel--0.40fy but not greater than 30,000
psi. (The provisions of article five of subchapter
ten of this chapter relating to ties, spirals, and
percentages of reinforcing steel for reinforced
concrete compression members shall apply.)
Timber See timber piles (section 27-707 of article eight of
this subchapter)
Steel H piles--0.35fy, with fy not to be taken as greater
than 36,000 psi. Minimum thickness of metal shall
be 0.40.
Pipe piles, shells for cast-in place concrete piles
and shells of pipe sections used in caisson piles:
0.35fy, (fy not to be taken as greater than 36,000
psi.) for thickness of 1/8 in. or more. Metal thinner
than 1/8 in. shall not be considered as contributing
to the structural strength of the pile section.
Core sections for caisson piles: 0.50fy with fy not to
be taken as greater than 36,000 psi.
========================================================================
Note:
f'c = 28 day compressive strength of concrete.
fy = Minimum specified yield strength of steel.
(b) Allowable bearing pressure on soil strata underlying the pile
tips.
(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 article four of this subchapter. The provisions of
section 27-678 and 27-679 of article four of this subchapter shall
apply. 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:
a. For piles embedded entirely in materials of classes 4-65 to 8-65,
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.
b. For piles penetrating through soils of classes 9-65, 10-65, or
11-65 into bearing in soils of class 8-65 or better, the polygon shall
be circumscribed at the bottom of the strata of class 9-65, 10-65 or
11-65 materials.
c. In the case of piles having enlarged bases, the lateral
distribution of the load to the soil may be assumed to begin at the
junction of the shaft and the enlarged base and to extend as follows:
1. In the case where the enlarged base is formed in loose or medium
compact (N value less than thirty) soils of class 6-65 or 7-65 that
extend twenty feet or more below the junction of the base and shaft, or
that are of lesser extent but are directly underlain by soil of class
5-65 or better, the bearing area may be taken at a plane six feet below
said junction but not lower than the bottom of the soil strata of class
6-65 or 7-65.
2. Where the enlarged base is formed in compact (N value thirty to
sixty) soils of class 6-65 or 7-65, or in any soil of these classes that
extends less than twenty feet below the junction of the base and the
shaft and that is underlain by soil of class 8-65 or poorer, the bearing
area shall be taken at planes less than six feet below said junction,
with a lower limit of three feet where the material is very compact (N
value sixty, or greater) and the extent of the class 6-65 or 7-65
material is ten feet below the junction of shaft and base. (The
provisions of subdivision (e) of section 27-710 of article ten of this
subchapter relating to minimum depth of bearing stratum below the
junction of base and shaft shall apply.) For conditions intermediate
between that described in clause one of this subparagraph and the lower
limit conditions described here, the location of the bearing area may be
determined by linear interpolation between the indicated limits of N
value and extent of bearing material below the junction of shaft and
base, giving equal weight to both variables.
3. Where the enlarged base is formed in or on soils of class 4-65 or
5-65, the bearing area shall be taken at a depth below the junction of
the shaft and base consonant with the size and depth of the base formed,
and as evaluated from the required test piles.
d. For all piles bearing on soils of classes 1-65 to 3-65, analysis of
load distribution will not be required if the requirements relating to
capacity of the pile as a structural member, to resistance to
penetration, to load test where required, and to maximum tabulated loads
are satisfied.
e. For piles bearing in soils of classes 9-65 and 10-65, for cases not
described above, or for any case where the method of installing the pile
utilizes a temporary casing, the provision relating to analysis shall
apply.
f. In no case shall the area considered as supporting the load extend
beyond the intersection of the sixty degree planes of adjacent piles or
pile groups.
(2) BEARING STRATUM. The plans for the proposed work shall establish,
in accordance with the requirements relating to allowable bearing
pressure, the bearing strata to which the piles in the various sections
of the building are to be penetrated and the approximate elevations of
the top of such bearing strata. 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 strata.
(c) Capacity as indicated by resistance to penetration. Where
subsurface investigation, as described in article two of this
subchapter, or general experience in the area, indicates 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 stipulated in Tables 11-4 and 11-5.
(For Table 11-4 see chapter 839 of the laws of 1986)
Notes:
a Final driving resistance shall be the sum of tabulated values plus
resistance exerted by non-bearing materials. The driving resistance of
non-bearing 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 subparagraph a of paragraph one of
subdivision (c) of this section.
b The hammer energy indicated is the rated energy.
c Sustained driving resistance--where piles are to bear in soil
classes 4-65 and 5-65, the minimum driving resistance shall be
maintained for the last six inches, unless a higher sustained driving
resistance requirement is established by load test. Where piles are to
bear in soil classes 6-65 through 10-65, the minimum driving resistance
shall be maintained for the last twelve inches unless load testing
demonstrates a requirement for higher sustained driving resistance. No
pile need be driven to a resistance to penetration (in blows per inch)
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.
d The tabulated values assume that the ratio of total weight of pile
to weight of striking part of 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.
e For intermediate values of pile capacity, minimum requirements for
driving resistance may be determined by straight line interpolation.
Table 11-5 Minimum Driving Resistance and
Hammer Energy for Timber Piles
========================================================================
Minimum Driving Resistance
(blows-in.) to be added
to driving resistance Hammer
Pile Capacity exerted by non-bearing Energy
(tons) materials {1}, {3}, {4} (ft.-lbs.){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)
15,000-20,000
(double-acting hammers)
Greater than 30
========================================================================
Notes:
{1} The driving resistance exerted by non-bearing materials is the
resistance experienced by the pile during driving, but which will be
dissipated with time and may be approximated as described in
subparagraph a of paragraph one of subdivision (c) of this section.
{2} The hammer energy indicated is the rated energy.
{3} Sustained driving resistance. Where piles are to bear in soil
classes 4-65 and 5-65, the minimum driving resistance shall be
maintained for the last six inches, unless a higher sustained driving
resistance requirement is established by load test. Where piles are to
bear in soil classes 6-65 thru 10-65, the minimum driving resistance
measured in blows per inch shall be maintained for the last twelve
inches unless load testing demonstrates a requirement for higher
sustained driving resistance. No pile need be driven to a resistance to
penetration (in blows per inch) 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:
(For Equations see chapter 907 of the laws of 1985)
(1) PILES INSTALLED BY USE OF STEAM-POWERED, AIR-POWERED,
DIESEL-POWERED OR HYDRAULIC IMPACT HAMMERS.
a. The minimum required driving resistance and the requirements for
hammer energies for various types and capacities of piles are given in
tables 11-4 and 11-5. 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 non-bearing materials or
by materials which are to be excavated). For purposes of this section,
the resistance exerted by non-bearing 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 11-65, but not controlled fill)
or to the bottom of the lowest stratum of soft or loose deposits of
class 9-65 or 10-65 but only where such strata are completely penetrated
by the pile. The provisions of articles nine and ten of this subchapter
shall also apply.
b. Alternate for similitude method. The requirement for installation
of piling to the penetration resistances given in tables 11-4 and 11-5
will be waived where the following five conditions prevail:
1. The piles bear on, or in, soil of class 5-65 through class 10-65.
2. The stratigraphy, as defined by not less than one boring for every
sixteen hundred square feet 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
subdivision (d) of this section, 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 fifteen thousand square feet of
pile foundation area shall be load tested.
4. Except as permitted by the provisions of clause six of this
subparagraph, 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 architect or engineer shall be submitted
establishing to the satisfaction of the commissioner, that the soil
bearing pressures do not exceed the values permitted by the provisions
of article four of this subchapter and that the probable differential
settlements will not cause stress conditions in the building in excess
of those permitted by the provisions of subchapter ten of this chapter.
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 clause five of
this subparagraph, relating to submission of report.
(2) PILES INSTALLED BY JACKING OR OTHER STATIC FORCES. The carrying
capacity of a pile installed by jacking or other static forces shall be
not more than fifty per cent of the load or force used to install the
pile to the required penetration, except for piles jacked into position
for underpinning. The working load of a temporary underpinning pile
shall not exceed the total jacking force at final penetration. The
working load of each permanent underpinning pile shall not exceed the
larger of the following values: two-thirds of the total jacking force
used to obtain the required penetration if the load is held constant for
seven hours without measurable settlement; or one-half of the total
jacking force at final penetration if the load is held for a period of
one hour without measurable settlement. The jacking resistance used to
determine the working load shall not include the resistance offered by
non-bearing materials which will be dissipated with time.
(3) PILES INSTALLED BY USE OF VIBRATORY HAMMER. The capacity of piles
installed by vibratory hammer shall not exceed the value established on
the principle of similitude, as follows:
a. Comparison piles, as required by the provisions of subdivision (d)
of this section, shall be installed using an impact hammer and driving
resistances corresponding to the proposed pile capacities as determined
in paragraph one of subdivision (c) of this section or to tip elevations
and driving resistances as determined by the architect or engineer.
b. For each comparison pile, install an identical index pile by use of
the vibratory hammer at a location at least four feet, but not more than
six feet, from each comparison pile. The index piles shall be installed
to the same tip elevation as the comparison pile, except that where the
comparison piles bear on soils of classes 1-65 to 5-65, the index piles
shall bear in, or on, similar material. All driving data for the index
pile shall be recorded.
c. The index piles shall be load tested in accordance with the
provisions of subdivision (d) of this section. Should the specified load
test criteria indicate inadequate capacity of the index piles, steps a,
b, and c shall be repeated using longer, larger, or other types of
piles.
d. All building piles within the area of influence of a given,
satisfactorily tested index pile shall be installed to the same or
lesser rate of penetration (in. per min.) as of the successful index
pile. The same equipment that was used to install the index pile,
identically operated as to rpm, manifold pressure, etc., shall be used
to install the building piles. Also, all building piles shall be of the
same type, size, and shape as the index pile. All building piles within
the area of influence as represented by a given satisfactorily tested
index pile shall bear in, or on, the same bearing stratum as the index
pile.
Table 11-6 Basic Maximum Pile Loads
========================================================================
Basic maximum pile load
Type of pile (tons)
------------------------------------------------------------------------
Caisson piles No upper limit
Open-end pipe (or tube) piles bearing 18 in. O.D. and greater--250
on rock of classes 1-65, 2-65, and 3-65 less than 18 in. O.D.--200
Closed-end pipe (or tube) piles, H 150
piles, cast-in-place concrete and com-
pacted concrete piles bearing on rock
of classes 1-65, 2-65 and 3-65
Piles (other than timber piles) bearing
on soft rock (class 4-65)
1) Displacement piles such as pipe,
cast-in-place concrete, and com-
pacted concrete piles 60
2) Non-displacement piles such as
open-end pipe and H piles 80
Piles (other than timber piles) bearing
on hardpan (class 5-65) overlying rock 100
Piles (other than timber piles) that
receive their principal support other
than by direct bearing on soils of
classes 1-65 to 5-65 60
Timber piles
Bearing in soils of classes 1-65
to 5-65 25
Bearing in soils of classes 6-65
to 10-65 30
========================================================================
(d) Capacity as indicated by load test. Load test of piling shall be
required as follows:
(1) PILES INSTALLED BY STATIC FORCES. The load bearing capacity of all
types and capacities of piles installed by static forces, other than
caisson piles and underpinning piles, shall be demonstrated by load
test.
(2) PILES DRIVEN BY IMPACT HAMMERS. The load bearing capacity of piles
installed by impact hammers shall be demonstrated by load test when the
proposed pile capacity exceeds the following values:
a. Caisson piles.--No load test required.
b. Piles installed open end to rock of class 1-65, 2-65 or 3-65-- one
hundred tons, except as provided in subparagraph d of this paragraph,
and except that no load tests will be required for piles up to two
hundred tons capacity wherein the pile load does not exceed eighty per
cent of the load determined on the basis of limiting stresses in the
pile materials and provided that the pipe or shell be driven to the
resistance indicated in table 11--4.
c. Piles bearing on rock or hardpan (soil classes 1-65 to 5-65) other
than as described in subparagraph b of this paragraph, and except as
provided in subparagraph d of this paragraph--forty tons.
d. Piles bearing on materials of class eight or better, wherein, on
the assumption that one hundred per cent of the load reaches the pile
tip, (or, in case of piles having an enlarged base or other enlargement
of the bearing area, the top of the enlargement) the bearing pressure on
the soil underlying the tips or bases can be demonstrated to be equal to
or less than the values of basic allowable pressure indicated in table
11-2--provided that the class and density of the bearing material
supporting the piles be confirmed by not less than one boring at each
column location, then the commissioner may reduce the required number of
load tests.
e. All other types of piles--thirty tons.
(3) PILES INSTALLED BY USE OF VIBRATORY HAMMERS. The load bearing
capacity of all types and capacities of piles (other than caisson piles)
shall be demonstrated by load test.
(4) LOAD TEST PROCEDURES. Before any load test is made, the proposed
apparatus and structure to be used in making the load test shall be
satisfactory to the commissioner and when required by him or her, all
load tests shall be made under the commissioner's surveillance or that
of his or her representative. A complete record of such tests shall be
filed with the commissioner.
a. Areas of the foundation site within which the subsurface soil
conditions are substantially similar in character shall be established.
In addition, for friction piles bearing on, or on, soil materials of
class 6-65, or poorer, the uniformity of each such area shall be
verified by installing at least three penetration-test piles,
distributed over the area. Continuous records of penetration resistance
shall be made for such piles. If the records of penetration resistance
are not similar or are not in reasonable agreement with the information
obtained from the borings, the assumed areas of similar subsurface
conditions shall be modified in accordance with the information derived
from the penetration-test piles and additional penetration-test piles
shall be installed as required to verify the uniformity of such areas.
b. For piles installed by jacking or other static forces or by impact
hammer, one load test 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, and not less than one pile for each fifteen thousand square feet
of the area of the building wherein said piles are to be used shall be
load tested. For piles installed by use of vibratory hammers, one
comparison pile shall be installed and one index pile shall be load
tested in each area of uniform conditions, but not less than two index
piles shall be tested for the entire foundation installation of the
building or group of buildings on the site, nor less than one index pile
be tested for every seventy-five hundred square feet of pile foundation
area. For piles whose capacity is determined on the basis of similitude,
the provisions of subparagraph b of paragraph one of subdivision (c) of
this section shall apply.
c. The load test shall be conducted by a method that will maintain
constant load under increasing settlement. Settlement observations shall
be made by means of dial extensometers. The extensometers shall provide
readings to the nearest one one-thousandth of an inch. In addition,
settlement observations shall be taken using an engineer's level reading
to one one-thousandth of a foot, properly referenced to a
well-established benchmark.
1. Test loads shall be applied by direct weight or by means of a
hydraulic jack. The loading platform or box shall be carefully
constructed to provide a concentric load on the pile. If direct weight
is employed, the loading increments shall be applied without impact or
jar. The weight of the loading platform or box shall be obtained prior
to the test and this weight shall be considered as the first increment
of load. If a hydraulic jack is employed, facilities for maintaining
each increment of desired load constant under increasing settlement
shall be provided. The gauge and the jack shall be calibrated as a unit
for each project.
2. The test load shall be twice the proposed working load of the pile.
The test load shall be applied in seven increments at a load of fifty
per cent, seventy-five per cent, one hundred per cent, one hundred
twenty-five per cent, one hundred fifty per cent, one hundred
seventy-five per cent, and two hundred per cent of the proposed working
load. After the proposed working load has been applied and for each
increment thereafter, the test load shall remain in place until there is
no measurable settlement in a two hour period. The total test load shall
remain in place until settlement does not exceed one one-thousandth of a
foot in forty-eight hours. The total load shall be removed in decrements
not exceeding twenty-five per cent of the total load at one hour
intervals or longer. The rebound shall be recorded after each decrement
is removed, and the final rebound shall be recorded twenty-four hours
after the entire test load has been removed.
3. Under each load increment, settlement observations shall be made
and recorded at one-half minute, one minute, two minutes, four minutes,
and each four minutes thereafter after application of load increment,
except in the instance of the total load where, after the four minute
reading, the time interval shall be successively doubled until the final
settlement limitation is reached and the load is removed.
4. The allowable pile load shall be the lesser of the two values
computed as follows:
(a) Fifty (50) per cent of the applied load causing a net settlement
of the pile of not more than one one-hundredth of an inch per ton of
applied load. Net settlement in this paragraph means gross settlement
due to the total test load minus the rebound after removing one hundred
per cent of the test load.
(b) Fifty (50) per cent of the applied load causing a net settlement
of the pile of three-quarters of an inch. Net settlement in this
paragraph means the gross settlement as defined in subclause (a) of
clause 4 of this subparagraph, less the amount of elastic shortening in
the pile section due to total test load.
(5) FOUNDATION PILES. Except as provided in clause six of subparagraph
b of paragraph one of subdivision (c) of this section, 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
penetration resistance (or static load) as the successful load-tested
pile. The same equipment (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-tested pile. For friction piles where the actual
pile lengths vary more than fifty per cent from that of the test pile,
the commissioner may require investigation to determine the adequacy of
the piles.
(6) PILE GROUPS. When the commissioner has reasons to doubt the safe
load sustaining capacity of pile groups, he or she may require at the
expense of the owner, group load tests up to one hundred fifty per cent
of the proposed group load.
(7) "CASING-OFF." Any temporary supporting capacity that the soil
might provide to the pile during a load test, but which would be
dissipated with time, shall be obviated by "casing-off" or by other
suitable means. For purposes of this section, temporary supporting
capacity shall include the resistances offered by any strata of
nominally unsatisfactory bearing materials (class 11-65, other than
controlled fill) or of soft or loose deposits of class 9-65 or 10-65
that are completely penetrated by the pile, or any resistance offered by
granular soils that will be dissipated by reason of vibration.
(e) Maximum loads.
(1) BASIC MAXIMUM LOADS. Except as permitted by the provisions of
paragraph two of this subdivision, the maximum allowable pile load,
determined in accordance with the provisions of subdivisions (a) through
(d) of this section, shall not exceed the values specified in table
11-6.
(2) SUBSTANTIATION OF HIGHER ALLOWABLE LOADS. The pile capacities
tabulated in table 11-6 may be exceeded where a higher value can be
substantiated on the basis of test and analysis, as follows:
a. Load tests. The provisions of subdivision (d) of this section shall
be supplemented, as follows:
1. Not less than one single-pile load test shall be conducted for each
ten thousand square feet of pile foundation area.
2. Final load increment shall remain in place for a total of not less
than ninety-six hours.
3. Single test piles shall be subjected to cyclical loading or
suitably instrumented so that the movements of the pile tip and butt may
be independently determined. Other alternate methods or devices,
acceptable to the commissioner which will permit evaluation of the
transfer of load from piles to soil may be used.
4. Where the commissioner deems necessary, the provisions of paragraph
six of subdivision (d) of this section relating to group load tests
shall apply. If required, group load tests shall be performed in groups
of numerically average size. Except where the proposed foundation is
limited to single and/or two pile groups, each test group shall contain
not less than three piles.
5. Individual pile loadings shall not exceed those determined from the
single pile load tests.
6. The provisions of paragraph two of subdivision (d) of this section
shall apply.
b. Analysis and report. A report shall be submitted by the architect
or engineer establishing to the satisfaction of the commissioner (on the
basis of soil and load tests and foundation analysis, including analysis
of the group action of the piles) that the proposed construction under a
one hundred per cent overload of the foundation is safe against failure
of the pile and soil materials, and showing that the probable total
magnitude and distribution of settlement to be expected under design
conditions will not result in instability of the building or stresses in
the structure in excess of the allowable values established in
subchapter ten of this chapter.
c. Penetration resistance. The penetration resistance shall not be
less than that required by the provisions of subdivision (c) of this
section or, where applicable values are not indicated therein, shall be
determined from the required load tests. The pile material shall be
capable of withstanding the driving stresses without being damaged.
(f) Combination of loads. The provisions of section 27-594 of
subchapter ten of this chapter shall apply.
Section 27-701
§ 27-701 Allowable lateral load. For plumb piles fully embedded in the
ground, the lateral load applied at the top of the pile shall not exceed
one ton per pile unless it has been demonstrated by tests that the pile
will resist a lateral load of two hundred per cent of the proposed
working lateral load without lateral movement of more than one inch at
the ground level and will resist the proposed working lateral load
without a movement of more than three-eighths of an inch at the ground
level. For piles projecting above the ground level the shear and bending
stresses computed on the basis of cantilever action to a level of five
feet below grade in soils of class 8-65 or better and to ten feet below
grade in poorer soils shall not exceed the allowable values for like
materials established in subchapter ten of this chapter. The provisions
of subdivision (f) of section 27-700 of this article relating to
combination of loads shall apply.
Section 27-702
§ 27-702 Uplift capacity. A minimum factor of safety against
withdrawal of two shall be provided, except that the factor of safety
against withdrawal shall be greater than two when the piles are
subjected to dynamic uplift loads. The uplift capacity shall be
demonstrated by pull-out tests, except where a factor of safety of three
or more based on analysis is used, pull-out tests need not be conducted.
To the extent possible under law, Friends of Devin Balkind for Public Advocate has waived all copyright and related or neighboring rights to New York City Administrative Code. This work is published from: United States.
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