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16.2—Connections of precast members, p. 217
18.5—Intermediate precast structural walls, p. 299
18.9— Special moment frames constructed using precast concrete, p. 314
18.11— Special structural walls constructed using precast concrete, p. 336
26.9—Additional requirements for precast concrete, p. 543
CH-1
(b) For precast concrete piles supporting structures assigned to Seismic Design Categories A and
B (13.4)
connection—region of a structure that joins two or more members; a connection also refers to a
region that joins members of which one or more is precast.
connection, ductile—connection between one or more precast elements that experiences
yielding as a result of the earthquake design displacements.
connection, strong—connection between one or more precast elements that remains elastic
while adjoining members experience.
moment frame, ordinary—cast-in-place or precast concrete beam-column or slab-column
frame complying with 18.3.
moment frame, special—cast-in-place beam-column frame complying with 18.2.3 through
18.2.8; and 18.6 through 18.8. A precast beam-column frame complying with 18.2.3 through
18.2.8 and 18.9.
structural wall, intermediate precast—a wall complying with 18.5.
structural wall, special—a cast-in-place structural wall in accordance with 18.2.3 through
18.2.8 and 18.10; or a precast structural wall in accordance with 18.2.3 through 18.2.8 and
18.11.
CH-4
Table 4.10.2.1—Minimum requirements for structural integrity
Precast joints and connections
16.2.1.8
4.12.1 Precast concrete systems
4.12.1.1 Design of precast concrete members and connections shall include loading and
restraint conditions from initial fabrication to end use in the structure, including form removal,
storage, transportation, and erection.
4.12.1.2 Design, fabrication, and construction of precast members and their connections shall
include the effects of tolerances.
4.12.1.3 When precast members are incorporated into a structural system, the forces and
deformations occurring in and adjacent to connections shall be included in the design.
4.12.1.4 Where system behavior requires in-plane loads to be transferred between the members
of a precast floor or wall system, (a) and (b) shall be satisfied:
(a) In-plane load paths shall be continuous through both connections and members.
(b) Where tension loads occur, a load path of steel or steel reinforcement, with or without splices,
shall be provided.
4.12.1.5 Distribution of forces that act perpendicular to the plane of precast members shall be
established by analysis or test.
4.12.4 Structural plain concrete systems
4.12.4.1 The design of structural plain concrete members, both cast-in-place and precast, shall
be in accordance with Chapter 14.
CH-7
7.6.3 Minimum shear reinforcement
7.6.3.1 A minimum area of shear reinforcement, Av,min, shall be provided in all regions where
Vu > ϕVc. For precast prestressed hollow-core slabs with untopped h > 315 mm, Av,min shall
be provided in all regions where Vu > 0.5ϕVcw.
7.7.3.8 Termination of reinforcement
7.7.3.8.1 At simple supports, at least one-third of the maximum positive moment
reinforcement shall extend along the slab bottom into the support, except for precast slabs
where such reinforcement shall extend at least to the center of the bearing length.
CH-9
9.5.4.7 For solid precast sections with an aspect ratio h/bt ≥ 4.5, it shall be permitted to use an
alternative design procedure and open web reinforcement, provided the adequacy of the
procedure and reinforcement have been shown by analysis and substantial agreement with
results of comprehensive tests. The minimum reinforcement requirements of 9.6.4 and
detailing requirements of 9.7.5 and 9.7.6.3 need not be satisfied.
9.7.3.8 Termination of reinforcement
9.7.3.8.1 At simple supports, at least one-third of the maximum positive moment
reinforcement shall extend along the beam bottom into the support at least 150 mm, except
for precast beams where such reinforcement shall extend at least to the center of the bearing
length.
CH-10
10.7.6.1.6 If mechanical couplers or extended bars for connection to a precast element are
placed in the ends of columns or pedestals, the mechanical couplers or extended bars shall be
enclosed by transverse reinforcement. The transverse reinforcement shall be distributed within
125 mm of the ends of the column or pedestal and shall consist of at least two No. 13 or three
No. 10 ties or hoops.
CH-11
11.7.2 Spacing of longitudinal reinforcement
11.7.2.2 Spacing s of longitudinal bars in precast walls shall not exceed the lesser of (a) and (b):
(a) 5h
(b) 450 mm for exterior walls or 750 mm for interior walls
If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h,
450 mm, and ℓw/3.
11.7.3 Spacing of transverse reinforcement
11.7.3.2 Spacing s of transverse bars in precast walls shall not exceed the lesser of (a) and (b):
(a) 5h
(b) 450 mm for exterior walls or 750 mm for interior walls
If shear reinforcement is required for in-plane strength, s shall not exceed the least of 3h, 450
mm, and ℓw/5.
CH-12
(b) Diaphragms that comprise a cast-in-place topping slab on precast elements
(c) Diaphragms that comprise precast elements with end strips formed by either a cast-in-place
concrete topping slab or edge beams
(d) Diaphragms of interconnected precast elements without cast-in-place concrete topping.
12.5.2 Moment and axial force
12.5.2.2 It shall be permitted to resist tension due to moment by (a), (b), (c), or (d), or those
methods in combination:
(a) Deformed bars conforming to 20.2.1
(b) Strands or bars conforming to 20.3.1, either prestressed or nonprestressed
(c) Mechanical connectors crossing joints between precast elements
(d) Precompression from prestressed reinforcement
12.5.2.4 Mechanical connectors crossing joints between precast elements shall be designed
to resist required tension under the anticipated joint opening.
R12.5.2.4 In an untopped precast diaphragm resisting in-plane forces and responding in the
linear range, some joint opening (on the order of 2.5 mm or less) should be anticipated. A larger
joint opening may occur under earthquake motions exceeding the design level. Mechanical
connectors should be capable of maintaining design strength under the anticipated joint
opening.
12.5.3.5 For diaphragms that are cast-in-place concrete topping slabs on precast elements, (a)
and (b) shall be satisfied:
(a) Vn shall be calculated in accordance with Eq. (12.5.3.3), and cross-sectional dimensions shall
be selected to satisfy Eq. (12.5.3.4). Acv shall be calculated using the thickness of the topping
slab for noncomposite topping slab diaphragms and the combined thickness of cast-in-place and
precast elements for composite topping slab diaphragms. For composite topping slab
diaphragms, the value of fc′ in Eq. (12.5.3.3) and (12.5.3.4) shall not exceed the lesser of fc′ for
the precast members and fc′ for the topping slab.
(b) Vn shall not exceed the value calculated in accordance with the shear-friction provisions of
22.9 considering the thickness of the topping slab above joints between precast elements in
noncomposite and composite topping slab diaphragms and the reinforcement crossing the
joints between the precast members.
12.5.3.6 For diaphragms that are interconnected precast elements without a concrete topping,
and for diaphragms that are precast elements with end strips formed by either a cast-in-place
concrete topping slab or edge beams, it shall be permitted to design for shear in accordance with
(a), (b), or both.
(a) The nominal strength of grouted joints shall not exceed 0.55 MPa. Reinforcement shall be
designed to resist shear through shear-friction in accordance with 22.9. Shear-friction
reinforcement shall be in addition to reinforcement designed to resist tension due to moment and
axial force.
(b) Mechanical connectors crossing joints between precast elements shall be designed to
resist required shear under anticipated joint opening.
CH-13
Table 13.4.2.1—Maximum allowable compressive strength for deep foundation members
Precast
nonprestresse
d concrete
pile
Pa =
0.33fc′Ag +
0.4fyAs
(d)
16.2—Connections of precast members
16.2.1.1 Transfer of forces by means of grouted joints, shear keys, bearing, anchors, mechanical
connectors, steel reinforcement, reinforced topping, or a combination of these, shall be permitted.
16.2.1.2 Adequacy of connections shall be verified by analysis or test.
16.2.1.3 Connection details that rely solely on friction caused by gravity loads shall not be
permitted.
16.2.1.4 Connections, and regions of members adjacent to connections, shall be designed to resist
forces and accommodate deformations due to all load effects in the precast structural system.
16.2.1.5 Design of connections shall consider structural effects of restraint of volume change in
accordance with 5.3.6.
16.2.1.6 Design of connections shall consider the effects of tolerances specified for fabrication
and erection of precast members.
16.2.1.7 Design of a connection with multiple components shall consider the differences in
stiffness, strength, and ductility of the components.
16.2.1.8 Integrity ties shall be provided in the vertical, longitudinal, and transverse directions
and around the perimeter of a structure in accordance with 16.2.4 or 16.2.5.
16.2.2 Required strength
16.2.2.1 Required strength of connections and adjacent regions shall be calculated in
accordance with the factored load combinations in Chapter 5.
16.2.2.2 Required strength of connections and adjacent regions shall be calculated in
accordance with the analysis procedures in Chapter 6.
16.2.2.3 For bearing connections, Nuc shall be (a) or (b), but need not exceed Nuc,max, where
Nuc,max is the maximum restraint force that can be transmitted through the load path of a bearing
connection multiplied by the load factor used for live loads in combinations with other factored
load effects.
(a) For connections not on bearing pads, Nuc shall be calculated simultaneously with Vu using
factored load combinations in accordance with 5.3.6. The restraint force shall be treated as a live
load.
(b) For connections on bearing pads, Nuc shall be 20 percent of the sustained unfactored
vertical reaction multiplied by a load factor of 1.6.
16.2.2.4 If the friction coefficient for a bearing material has been determined by results of
tests, Nuc,max shall be permitted to be determined by multiplying the sustained unfactored
vertical reaction by the friction coefficient and a load factor of 1.6.
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