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SOILS AND FOUNDATIONS

connected to the pile cap by embedding the element the full axial, bending and shear nominal strength
reinforcement or field-placed dowels anchored in the of the element.
element into the pile cap for a distance equal to their Where the vertical lateral-force-resisting elements
development length in accordance with ACI 318. It are columns, the pile cap flexural strengths shall exceed
shall be permitted to connect precast prestressed piles the column flexural strength. The connection between
to the pile cap by developing the element prestressing batter piles and pile caps shall be designed to resist the
strands into the pile cap provided that the connection is nominal strength of the pile acting as a short column.
ductile. For deformed bars, the development length is Batter piles and their connection shall be designed to
the full development length for compression, or tension resist forces and moments that result from the applica-
in the case of uplift, without reduction for excess rein- tion of seismic load effects including overstrength factor
forcement in accordance with Section 25.4.10 of ACI in accordance with Section 2.3.6 or 2.4.5 of ASCE 7.
318. Alternative measures for laterally confining con-
crete and maintaining toughness and ductile-like 1810.3.12 Grade beams. For structures assigned to Seis-
mic Design Category D, E or F, grade beams shall comply
behavior at the top of the element shall be permitted with the provisions in Section 18.13.3 of ACI 318 for
provided that the design is such that any hinging occurs grade beams, except where they are designed to resist the
in the confined region. seismic load effects including overstrength factor in accor-
The minimum transverse steel ratio for confinement dance with Section 2.3.6 or 2.4.5 of ASCE 7.
shall be not less than one-half of that required for col-
umns. 1810.3.13 Seismic ties. For structures assigned to Seismic
Design Category C, D, E or F, individual deep foundations
For resistance to uplift forces, anchorage of steel shall be interconnected by ties. Unless it can be demon-
pipes, tubes or H-piles to the pile cap shall be made by strated that equivalent restraint is provided by reinforced
means other than concrete bond to the bare steel sec- concrete beams within slabs on grade or reinforced con-
tion. Concrete-filled steel pipes or tubes shall have crete slabs on grade or confinement by competent rock,
reinforcement of not less than 0.01 times the cross-sec- hard cohesive soils or very dense granular soils, ties shall
tional area of the concrete fill developed into the cap be capable of carrying, in tension or compression, a force
and extending into the fill a length equal to two times equal to the lesser of the product of the larger pile cap or
the required cap embedment, but not less than the column design gravity load times the seismic coefficient,
development length in tension of the reinforcement. S , divided by 10, and 25 percent of the smaller pile or
DS
1810.3.11.2 Seismic Design Categories D through F. column design gravity load.
For structures assigned to Seismic Design Category D, Exception: In Group R-3 and U occupancies of light-
E or F, deep foundation element resistance to uplift frame construction, deep foundation elements support-
forces or rotational restraint shall be provided by ing foundation walls, isolated interior posts detailed so
anchorage into the pile cap, designed considering the the element is not subject to lateral loads or exterior
combined effect of axial forces due to uplift and bend- decks and patios are not subject to interconnection
ing moments due to fixity to the pile cap. Anchorage where the soils are of adequate stiffness, subject to the
shall develop not less than 25 percent of the strength of approval of the building official.
the element in tension. Anchorage into the pile cap
shall comply with the following: 1810.4 Installation. Deep foundations shall be installed in
accordance with Section 1810.4. Where a single deep founda-
1. In the case of uplift, the anchorage shall be capa- tion element comprises two or more sections of different
ble of developing the least of the following: materials or different types spliced together, each section
1.1. The nominal tensile strength of the longi- shall satisfy the applicable conditions of installation.
tudinal reinforcement in a concrete ele- 1810.4.1 Structural integrity. Deep foundation elements
ment. shall be installed in such a manner and sequence as to pre-
1.2. The nominal tensile strength of a steel vent distortion or damage that would adversely affect the
element. structural integrity of adjacent structures or of foundation
1.3. The frictional force developed between elements being installed or already in place and as to avoid
the element and the soil multiplied by 1.3. compacting the surrounding soil to the extent that other
Exception: The anchorage is permitted to be foundation elements cannot be installed properly.
designed to resist the axial tension force 1810.4.1.1 Compressive strength of precast con-
resulting from the seismic load effects includ- crete piles. A precast concrete pile shall not be driven
ing overstrength factor in accordance with before the concrete has attained a compressive
Section 2.3.6 or 2.4.5 of ASCE 7. strength of not less than 75 percent of the specified
2. In the case of rotational restraint, the anchorage compressive strength (f  ), but not less than the
c
shall be designed to resist the axial and shear strength sufficient to withstand handling and driving
forces, and moments resulting from the seismic forces.
load effects including overstrength factor in 1810.4.1.2 Casing. Where cast-in-place deep founda-
accordance with Section 2.3.6 or 2.4.5 of ASCE 7 tion elements are formed through unstable soils and
or the anchorage shall be capable of developing concrete is placed in an open-drilled hole, a casing shall

2018 INTERNATIONAL BUILDING CODE ® 455
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