Page 479 - 2018_Complete_14_Collection (1)_Neat

SOILS AND FOUNDATIONS

but not less than: exceeds the design cracking moment determined in
A = 0.12s h (f  /f ) [0.5 + 1.4P/(f  A )] accordance with Section 1810.3.9.1, cast-in-place deep
c
sh
g
foundations not enclosed by a structural steel pipe or
c
yh
c
(Equation 18-9) tube shall be reinforced.
where: 1810.3.9.3 Placement of reinforcement. Reinforce-
f yh = yield strength of transverse ment where required shall be assembled and tied
reinforcement  70,000 psi (483 MPa). together and shall be placed in the deep foundation ele-
h c = Cross-sectional dimension of pile core ment as a unit before the reinforced portion of the ele-
measured center to center of hoop ment is filled with concrete.
reinforcement, inch (mm). Exceptions:
s = Spacing of transverse reinforcement 1. Steel dowels embedded 5 feet (1524 mm) or
measured along length of pile, inch less shall be permitted to be placed after con-
(mm). creting, while the concrete is still in a semi-
A sh = Cross-sectional area of tranverse fluid state.
2
reinforcement, square inches (mm ). 2. For deep foundation elements installed with a
f  = Specified compressive strength of hollow-stem auger, tied reinforcement shall be
c
concrete, psi (MPa). placed after elements are concreted, while the
The hoops and cross ties shall be equivalent to concrete is still in a semifluid state. Longitudi-
deformed bars not less than No. 3 in size. Rectangu- nal reinforcement without lateral ties shall be
lar hoop ends shall terminate at a corner with seis- placed either through the hollow stem of the
mic hooks. auger prior to concreting or after concreting,
Outside of the length of the pile requiring trans- while the concrete is still in a semifluid state.
verse confinement reinforcing, the spiral or hoop 3. For Group R-3 and U occupancies not exceed-
reinforcing with a volumetric ratio not less than one- ing two stories of light-frame construction,
half of that required for transverse confinement rein- reinforcement is permitted to be placed after
forcing shall be provided. concreting, while the concrete is still in a
semifluid state, and the concrete cover
1810.3.8.3.4 Axial load limit in Seismic Design requirement is permitted to be reduced to 2
Categories C through F. For structures assigned to inches (51 mm), provided that the construction
Seismic Design Category C, D, E, or F, the maxi- method can be demonstrated to the satisfac-
mum factored axial load on precast prestressed piles tion of the building official.
subjected to a combination of seismic lateral force
and axial load shall not exceed the following values: 1810.3.9.4 Seismic reinforcement. Where a structure
1. 0.2f  A for square piles is assigned to Seismic Design Category C, reinforce-
ment shall be provided in accordance with Section
c
g
2. 0.4f  A for circular or octagonal piles 1810.3.9.4.1. Where a structure is assigned to Seismic
c
g
1810.3.9 Cast-in-place deep foundations. Cast-in-place Design Category D, E or F, reinforcement shall be pro-
deep foundation elements shall be designed and detailed vided in accordance with Section 1810.3.9.4.2.
in accordance with Sections 1810.3.9.1 through Exceptions:
1810.3.9.6. 1. Isolated deep foundation elements supporting
1810.3.9.1 Design cracking moment. The design posts of Group R-3 and U occupancies not
cracking moment (M ) for a cast-in-place deep foun- exceeding two stories of light-frame construc-
n
dation element not enclosed by a structural steel pipe tion shall be permitted to be reinforced as
or tube shall be determined using the following equa- required by rational analysis but with not less
tion: than one No. 4 bar, without ties or spirals,
where detailed so the element is not subject to
M = 3 f S (Equation 18-10) lateral loads and the soil provides adequate
n
c m
lateral support in accordance with Section
For SI: M = 0.25 f S 1810.2.1.
c m
n
where: 2. Isolated deep foundation elements supporting
f  = Specified compressive strength of concrete or posts and bracing from decks and patios
c
grout, psi (MPa). appurtenant to Group R-3 and U occupancies
S = Elastic section modulus, neglecting reinforcement not exceeding two stories of light-frame con-
struction shall be permitted to be reinforced as
m
and casing, cubic inches (mm ). required by rational analysis but with not less
3
1810.3.9.2 Required reinforcement. Where subject to than one No. 4 bar, without ties or spirals,
uplift or where the required moment strength deter- where the lateral load, E, to the top of the ele-
mined using the load combinations of Section 1605.2 ment does not exceed 200 pounds (890 N) and

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