International Building Code Section 1908


International Building Code 1908.1

General. The text ofACI 318 shall be modified as indicated
in Sections 1908.1.1 through 1908.1.16.

ACI 318, Section 10.5. Modify ACI 318, Section
10.5, by adding new Section 10.5.5 to read as follows:
10.5.5 # In structures assigned to Seismic Design Category
B, beams in ordinary moment frames forming part
of the seismic-force-resisting system shall have at least
two main flexural reinforcing bars continuously top and
bottom throughout the beam and continuous through or
developed within exterior columns or boundary elements.

ACI 318, Section 11.11. ModifyACI 318, Section
11.11, by changing its title to read as shown below and by
adding new Section 11.11.3 to read as follows:
11.11# Special provisions for columns.
11.11.3 # In structures assigned to Seismic Design Category
B, columns of ordinary moment frames having a
clear height-to-maximum-plan-dimension ratio of five
or less shall be designed for shear in accordance with
21.12.3.

ACI 318, Section 21.1. Modify existing definitions
and add the following definitions to ACI 318, Section
21.1.
DESIGN DISPLACEMENT. Total lateral displacement
expected for the design-basis earthquake, as specified by
Section 12.8.6 of ASCE 7.

DETAILEDPLAINCONCRETESTRUCTURALWALL.
A wall complying with the requirements of Chapter 22,
including 22.6.7.
ORDINARY PRECAST STRUCTURALWALL. A precast
wall complying with the requirements of Chapters 1 through
18.
ORDINARY REINFORCED CONCRETE STRUCTURAL
WALL. A cast-in-place wall complying with the
requirements of Chapters 1 through 18.
ORDINARY STRUCTURAL PLAIN CONCRETE
WALL.Awall complying with the requirements of Chapter
22, excluding 22.6.7.
WALL PIER. A wall segment with a horizontal
length-to-thickness ratio of at least 2.5, but not exceeding 6,
whose clear height is at least two times its horizontal length.

ACI 318, Section 21.2.1. Modify ACI 318 Sections
21.2.1.2, 21.2.1.3 and 21.2.1.4, to read as follows:
21.2.1.2 # For structures assigned to Seismic Design
Category Aor B, provisions of Chapters 1 through 18 and
22 shall apply except as modified by the provisions of
this chapter. Where the seismic design loads are computed
using provisions for intermediate or special concrete
systems, the requirements of Chapter 21 for
intermediate or special systems, as applicable, shall be
satisfied.
21.2.1.3 # For structures assigned to Seismic Design
Category C, intermediate or special moment frames,
intermediate precast structural walls or ordinary or special
reinforced concrete structural walls shall be used to
resist seismic forces induced by earthquake motions.
Where the design seismic loads are computed using provisions
for special concrete systems, the requirements of
Chapter 21 for special systems, as applicable, shall be
satisfied.
21.2.1.4 # For structures assigned to Seismic Design
Category D, E or F, special moment frames, special reinforced
concrete structural walls, diaphragms and trusses
and foundations complying with 21.2 through 21.10 or
intermediate precast structural walls complying with
21.13 shall be used to resist forces induced by earthquake
motions. Members not proportioned to resist earthquake
forces shall comply with 21.11.

ACI 318, Section 21.2.5. Modify ACI 318, Section
21.2.5, by renumbering as Section 21.2.5.1 and adding
new Section 21.2.5.2 to read as follows:
21.2.5 # Reinforcement in members resisting earthquake-
induced forces.
21.2.5.1 # Except as permitted in 21.2.5.2, reinforcement
resisting earthquake-induced flexural and axial forces in
frame members and in structural wall boundary elements
shall comply with ASTM A 706. ASTM 615,
Grades 40 and 60 reinforcement, shall be permitted in
these members if (a) the actual yield strength based on
mill tests does not exceed the specified yield, fy, strength
by more than 18,000 psi (124 MPa) [retests shall not
exceed this value by more than an additional 3,000 psi
(21 MPa)], and (b) the ratio of the actual tensile strength
to the actual yield strength is not less than 1.25.
For computing shear strength, the value of fyt for transverse
reinforcement, including spiral reinforcement,
shall not exceed 60,000 psi (414 MPa).
21.2.5.2 # Prestressing steel shall be permitted in flexural
members of frames, provided the average prestress,
fpc, calculated for an area equal to the member’s shortest
cross-sectional dimension multiplied by the perpendicular
dimension shall be the lesser of 700 psi (4.83MPa) or
f _
c /6 at locations of nonlinear action where prestressing
steel is used in members of frames.

ACI 318, Section 21.2. Modify ACI 318, Section
21.2, by adding new Section 21.2.9 to read as follows:
21.2.9 # Anchorages for unbonded post-tensioning tendons
resisting earthquake induced forces in structures
assigned to Seismic Design Category C, D, E or F shall
withstand, without failure, 50 cycles of loading ranging
between 40 and 85 percent of the specified tensile
strength of the prestressing steel.

ACI 318, Section 21.3. Modify ACI 318, Section
21.3, by adding new Section 21.3.2.5 to read as follows:
21.3.2.5 # Unless the special moment frame is qualified
for use through structural testing as required by 21.6.3,
for flexural members prestressing steel shall not provide
more than one-quarter of the strength for either positive
or negative moment at the critical section in a plastic
hinge location and shall be anchored at or beyond the
exterior face of a joint.

ACI 318, Section 21.7. Modify ACI 318, Section
21.7, by adding new Section 21.7.10 to read as follows:
21.7.10 # Wall piers and wall segments.
21.7.10.1 #Wall piers not designed as a part of a special
moment frame shall have transverse reinforcement
designed to satisfy the requirements in 21.7.10.2.
Exceptions:
1. Wall piers that satisfy 21.11.
2. Wall piers along a wall line within a story
where other shear wall segments provide lateral
support to the wall piers and such segments
have a total stiffness of at least six times
the sum of the stiffness of all the wall piers.
21.7.10.2 # Transverse reinforcement with seismic hooks
at both ends shall be designed to resist the shear forces
determined from 21.4.5.1. Spacing of transverse reinforcement
shall not exceed 6 inches (152 mm). Transverse
reinforcement shall be extended beyond the pier
clear height for at least 12 inches (305 mm).
21.7.10.3 # Wall segments with a horizontal
length-to-thickness ratio less than 2.5 shall be designed
as columns.

ACI 318, Section 21.8. Modify Section 21.8.1 to
read as follows:
21.8.1 # Special structural walls constructed using precast
concrete shall satisfy all the requirements of 21.7 for
cast-in-place special structural walls in addition to Sections
21.13.2 through 21.13.4.

ACI 318, Section 21.10.1.1. Modify ACI 318,
Section 21.10.1.1, to read as follows:
21.10.1.1 # Foundations resisting earthquake-induced
forces or transferring earthquake-induced forces
between a structure and the ground shall comply with the
requirements of Section 21.10 and other applicable provisions
of ACI 318 unless modified by Chapter 18 of the
International Building Code.

ACI 318, Section 21.11. Modify ACI 318, Section
21.11.2.2 to read as follows:
21.11.2.2 # Members with factored gravity axial forces
exceeding (Agf c/10) shall satisfy 21.4.3, 21.4.4.1(c),
21.4.4.3 and 21.4.5. The maximum longitudinal spacing
of ties shall be so for the full column height. Spacing, so,
shall not exceed the smaller of six diameters of the smallest
longitudinal bar enclosed and 6 inches (152 mm). Lap
splices of longitudinal reinforcement in such members
need not satisfy 21.4.3.2 in structures where the seismic-
force-resisting system does not include special
moment frames.

ACI 318, Section 21.12.5. ModifyACI 318, Section
21.12.5, by adding newSection 21.12.5.6 to read as follows:
21.12.5.6 # Columns supporting reactions from discontinuous
stiff members, such as walls, shall be designed
for the special load combinations in Section 1605.4 of
the International Building Code and shall be provided
with transverse reinforcement at the spacing, so, as
defined in 21.12.5.2 over their full height beneath the
level at which the discontinuity occurs. This transverse
reinforcement shall be extended above and below the
column as required in 21.4.4.5.

ACI 318, Section 21.13. Modify ACI 318, Section
21.13, by renumbering Section 21.13.3 to become
21.13.4 and adding new Sections 21.13.3, 21.13.5 and
21.13.6 to read as follows:
21.13.3 # Except for Type 2 mechanical splices, connection
elements that are designed to yield shall be capable
of maintaining 80 percent of their design strength at the
deformation induced by the design displacement.
21.13.4 # Elements of the connection that are not
designed to yield shall develop at least 1.5 Sy.
21.13.5 # Wall piers not designed as part of a moment
frame shall have transverse reinforcement designed to
resist the shear forces determined from 21.12.3. Spacing
of transverse reinforcement shall not exceed 8 inches
(203 mm). Transverse reinforcement shall be extended
beyond the pier clear height for at least 12 inches (305
mm).
Exceptions:
1. Wall piers that satisfy 21.11.
2. Wall piers along a wall line within a story
where other shear wall segments provide lateral
support to the wall piers and such segments
have a total stiffness of at least six times
the sum of the stiffnesses of all the wall piers.
21.13.6 # Wall segments wi th a horizontal
length-to-thickness ratio less than 2.5 shall be designed
as columns.

ACI 318, Section 22.6. ModifyACI 318, Section
22.6, by adding new Section 22.6.7 to read:
22.6.7 # Detailed plain concrete structural walls.
22.6.7.1 # Detailed plain concrete structural walls are
walls conforming to the requirements of ordinary structural
plain concrete walls and 22.6.7.2.
22.6.7.2 – Reinforcement shall be provided as follows:
(a) Vertical reinforcement of at least 0.20 square
inch (129 mm2) in cross-sectional area shall be
provided continuously from support to support at
each corner, at each side of each opening and at
the ends of walls. The continuous vertical bar
required beside an opening is permitted to substitute
for one of the two No. 5 bars required by
22.6.6.5.
(b) Horizontal reinforcement at least 0.20 square
inch (129 mm2) in cross-sectional area shall be
provided:
1. Continuously at structurally connected roof
and floor levels and at the top of walls;
2. At the bottom of load-bearing walls or in the
top of foundations where doweled to the
wall; and
3. At a maximum spacing of 120 inches (3048
mm).
Reinforcement at the top and bottom of openings,
where used in determining the maximum spacing specified
in Item 3 above, shall be continuous in the wall.

ACI 318, Section 22.10. Delete ACI 318, Section
22.10, and replace with the following:
22.10 # Plain concrete in structures assigned to Seismic
Design Category C, D, E or F.
22.10.1 # Structures assigned to Seismic Design Category
C, D, E or F shall not have elements of structural
plain concrete, except as follows:
(a) Structural plain concrete basement, foundation
or other walls below the base are permitted in
detached one- and two-family dwellings three
stories or less in height constructed with
stud-bearing walls. In dwellings assigned to

Seismic Design CategoryDor E, the height of the
wall shall not exceed 8 feet (2438 mm), the thickness
shall not be less than 71/2 inches (190 mm),
and the wall shall retain no more than 4 feet
(1219 mm) of unbalanced fill. Walls shall have
reinforcement in accordance with 22.6.6.5.
(b) Isolated footings of plain concrete supporting
pedestals or columns are permitted, provided the
projection of the footing beyond the face of the
supported member does not exceed the footing
thickness.
Exception: In detached one- and two-family
dwellings three stories or less in height, the projection
of the footing beyond the face of the supported
member is permitted to exceed the
footing thickness.
(c) Plain concrete footings supporting walls are
permitted, provided the footings have at least two
continuous longitudinal reinforcing bars. Bars
shall not be smaller than No. 4 and shall have a
total area of not less than 0.002 times the gross
cross-sectional area of the footing. For footings
that exceed 8 inches (203 mm) in thickness, a
minimum of one bar shall be provided at the top
and bottom of the footing. Continuity of reinforcement
shall be provided at corners and intersections.
Exceptions:
1. In detached one- and two-family dwellings
three stories or less in height and
constructed with stud-bearing walls,
plain concrete footings without longitudinal
reinforcement supporting walls are
permitted.
2. For foundation systems consisting of a
plain concrete footing and a plain concrete
stemwall, a minimum of one bar
shall be provided at the top of the
stemwall and at the bottom of the footing.
3. Where a slab on ground is cast
monolithically with the footing, one No. 5
bar is permitted to be located at either the
top of the slab or bottom of the footing.

ACI 318, Section D.3.3. Modify ACI 318, Sections
D.3.3.2 through D.3.3.5, to read as follows:
D.3.3.2 # In structures assigned to Seismic Design Category
C, D, E or F, post-installed anchors for use under
D.2.3 shall have passed the Simulated Seismic Tests of
ACI 355.2.
D.3.3.3 # In structures assigned to Seismic Design Category
C, D, E or F, the design strength of anchors shall be
taken as 0.75?Nn and 0.75?Vn, where ? is given in D.4.4
or D.4.5, and Nn and Vn are determined in accordance
with D.4.1.
D.3.3.4 # In structures assigned to Seismic Design Category
C, D, E or F, anchors shall be designed to be governed
by tensile or shear strength of a ductile steel element,
unless D.3.3.5 is satisfied.
D.3.3.5 # Instead of D.3.3.4, the attachment that the
anchor is connecting to the structure shall be designed so
that the attachment will undergo ductile yielding at a load
level corresponding to anchor forces no greater than the
design strength of anchors specified in D.3.3.3, or the
minimum design strength of the anchors shall be at least
2.5 times the factored forces transmitted by the attachment.

International Building Code 1908.1.1

ACI 318, Section 10.5. Modify ACI 318, Section
10.5, by adding new Section 10.5.5 to read as follows:
10.5.5 # In structures assigned to Seismic Design Category
B, beams in ordinary moment frames forming part
of the seismic-force-resisting system shall have at least
two main flexural reinforcing bars continuously top and
bottom throughout the beam and continuous through or
developed within exterior columns or boundary elements.

International Building Code 1908.1.10

ACI 318, Section 21.10.1.1. Modify ACI 318,
Section 21.10.1.1, to read as follows:
21.10.1.1 # Foundations resisting earthquake-induced
forces or transferring earthquake-induced forces
between a structure and the ground shall comply with the
requirements of Section 21.10 and other applicable provisions
of ACI 318 unless modified by Chapter 18 of the
International Building Code.

International Building Code 1908.1.11

ACI 318, Section 21.11. Modify ACI 318, Section
21.11.2.2 to read as follows:
21.11.2.2 # Members with factored gravity axial forces
exceeding (Agf c/10) shall satisfy 21.4.3, 21.4.4.1(c),
21.4.4.3 and 21.4.5. The maximum longitudinal spacing
of ties shall be so for the full column height. Spacing, so,
shall not exceed the smaller of six diameters of the smallest
longitudinal bar enclosed and 6 inches (152 mm). Lap
splices of longitudinal reinforcement in such members
need not satisfy 21.4.3.2 in structures where the seismic-
force-resisting system does not include special
moment frames.

International Building Code 1908.1.12

ACI 318, Section 21.12.5. ModifyACI 318, Section
21.12.5, by adding newSection 21.12.5.6 to read as follows:
21.12.5.6 # Columns supporting reactions from discontinuous
stiff members, such as walls, shall be designed
for the special load combinations in Section 1605.4 of
the International Building Code and shall be provided
with transverse reinforcement at the spacing, so, as
defined in 21.12.5.2 over their full height beneath the
level at which the discontinuity occurs. This transverse
reinforcement shall be extended above and below the
column as required in 21.4.4.5.

International Building Code 1908.1.13

ACI 318, Section 21.13. Modify ACI 318, Section
21.13, by renumbering Section 21.13.3 to become
21.13.4 and adding new Sections 21.13.3, 21.13.5 and
21.13.6 to read as follows:
21.13.3 # Except for Type 2 mechanical splices, connection
elements that are designed to yield shall be capable
of maintaining 80 percent of their design strength at the
deformation induced by the design displacement.
21.13.4 # Elements of the connection that are not
designed to yield shall develop at least 1.5 Sy.
21.13.5 # Wall piers not designed as part of a moment
frame shall have transverse reinforcement designed to
resist the shear forces determined from 21.12.3. Spacing
of transverse reinforcement shall not exceed 8 inches
(203 mm). Transverse reinforcement shall be extended
beyond the pier clear height for at least 12 inches (305
mm).
Exceptions:
1. Wall piers that satisfy 21.11.
2. Wall piers along a wall line within a story
where other shear wall segments provide lateral
support to the wall piers and such segments
have a total stiffness of at least six times
the sum of the stiffnesses of all the wall piers.
21.13.6 # Wall segments wi th a horizontal
length-to-thickness ratio less than 2.5 shall be designed
as columns.

International Building Code 1908.1.14

ACI 318, Section 22.6. ModifyACI 318, Section
22.6, by adding new Section 22.6.7 to read:
22.6.7 # Detailed plain concrete structural walls.
22.6.7.1 # Detailed plain concrete structural walls are
walls conforming to the requirements of ordinary structural
plain concrete walls and 22.6.7.2.
22.6.7.2 – Reinforcement shall be provided as follows:
(a) Vertical reinforcement of at least 0.20 square
inch (129 mm2) in cross-sectional area shall be
provided continuously from support to support at
each corner, at each side of each opening and at
the ends of walls. The continuous vertical bar
required beside an opening is permitted to substitute
for one of the two No. 5 bars required by
22.6.6.5.
(b) Horizontal reinforcement at least 0.20 square
inch (129 mm2) in cross-sectional area shall be
provided:
1. Continuously at structurally connected roof
and floor levels and at the top of walls;
2. At the bottom of load-bearing walls or in the
top of foundations where doweled to the
wall; and
3. At a maximum spacing of 120 inches (3048
mm).
Reinforcement at the top and bottom of openings,
where used in determining the maximum spacing specified
in Item 3 above, shall be continuous in the wall.

International Building Code 1908.1.15

ACI 318, Section 22.10. Delete ACI 318, Section
22.10, and replace with the following:
22.10 # Plain concrete in structures assigned to Seismic
Design Category C, D, E or F.
22.10.1 # Structures assigned to Seismic Design Category
C, D, E or F shall not have elements of structural
plain concrete, except as follows:
(a) Structural plain concrete basement, foundation
or other walls below the base are permitted in
detached one- and two-family dwellings three
stories or less in height constructed with
stud-bearing walls. In dwellings assigned to
378 2006 INTERNATIONAL BUILDING CODE
CONCRETE
?
?
Seismic Design CategoryDor E, the height of the
wall shall not exceed 8 feet (2438 mm), the thickness
shall not be less than 71/2 inches (190 mm),
and the wall shall retain no more than 4 feet
(1219 mm) of unbalanced fill. Walls shall have
reinforcement in accordance with 22.6.6.5.
(b) Isolated footings of plain concrete supporting
pedestals or columns are permitted, provided the
projection of the footing beyond the face of the
supported member does not exceed the footing
thickness.
Exception: In detached one- and two-family
dwellings three stories or less in height, the projection
of the footing beyond the face of the supported
member is permitted to exceed the
footing thickness.
(c) Plain concrete footings supporting walls are
permitted, provided the footings have at least two
continuous longitudinal reinforcing bars. Bars
shall not be smaller than No. 4 and shall have a
total area of not less than 0.002 times the gross
cross-sectional area of the footing. For footings
that exceed 8 inches (203 mm) in thickness, a
minimum of one bar shall be provided at the top
and bottom of the footing. Continuity of reinforcement
shall be provided at corners and intersections.
Exceptions:
1. In detached one- and two-family dwellings
three stories or less in height and
constructed with stud-bearing walls,
plain concrete footings without longitudinal
reinforcement supporting walls are
permitted.
2. For foundation systems consisting of a
plain concrete footing and a plain concrete
stemwall, a minimum of one bar
shall be provided at the top of the
stemwall and at the bottom of the footing.
3. Where a slab on ground is cast
monolithically with the footing, one No. 5
bar is permitted to be located at either the
top of the slab or bottom of the footing.

International Building Code 1908.1.16

ACI 318, Section D.3.3. Modify ACI 318, Sections
D.3.3.2 through D.3.3.5, to read as follows:
D.3.3.2 # In structures assigned to Seismic Design Category
C, D, E or F, post-installed anchors for use under
D.2.3 shall have passed the Simulated Seismic Tests of
ACI 355.2.
D.3.3.3 # In structures assigned to Seismic Design Category
C, D, E or F, the design strength of anchors shall be
taken as 0.75?Nn and 0.75?Vn, where ? is given in D.4.4
or D.4.5, and Nn and Vn are determined in accordance
with D.4.1.
D.3.3.4 # In structures assigned to Seismic Design Category
C, D, E or F, anchors shall be designed to be governed
by tensile or shear strength of a ductile steel element,
unless D.3.3.5 is satisfied.
D.3.3.5 # Instead of D.3.3.4, the attachment that the
anchor is connecting to the structure shall be designed so
that the attachment will undergo ductile yielding at a load
level corresponding to anchor forces no greater than the
design strength of anchors specified in D.3.3.3, or the
minimum design strength of the anchors shall be at least
2.5 times the factored forces transmitted by the attachment.

International Building Code 1908.1.2

ACI 318, Section 11.11. ModifyACI 318, Section
11.11, by changing its title to read as shown below and by
adding new Section 11.11.3 to read as follows:
11.11# Special provisions for columns.
11.11.3 # In structures assigned to Seismic Design Category
B, columns of ordinary moment frames having a
clear height-to-maximum-plan-dimension ratio of five
or less shall be designed for shear in accordance with
21.12.3.

International Building Code 1908.1.3

ACI 318, Section 21.1. Modify existing definitions
and add the following definitions to ACI 318, Section
21.1.
DESIGN DISPLACEMENT. Total lateral displacement
expected for the design-basis earthquake, as specified by
Section 12.8.6 of ASCE 7.
376 2006 INTERNATIONAL BUILDING CODE
CONCRETE
?
?
?
?
?
DETAILEDPLAINCONCRETESTRUCTURALWALL.
A wall complying with the requirements of Chapter 22,
including 22.6.7.
ORDINARY PRECAST STRUCTURALWALL. A precast
wall complying with the requirements of Chapters 1 through
18.
ORDINARY REINFORCED CONCRETE STRUCTURAL
WALL. A cast-in-place wall complying with the
requirements of Chapters 1 through 18.
ORDINARY STRUCTURAL PLAIN CONCRETE
WALL.Awall complying with the requirements of Chapter
22, excluding 22.6.7.
WALL PIER. A wall segment with a horizontal
length-to-thickness ratio of at least 2.5, but not exceeding 6,
whose clear height is at least two times its horizontal length.

International Building Code 1908.1.4

ACI 318, Section 21.2.1. Modify ACI 318 Sections
21.2.1.2, 21.2.1.3 and 21.2.1.4, to read as follows:
21.2.1.2 # For structures assigned to Seismic Design
Category Aor B, provisions of Chapters 1 through 18 and
22 shall apply except as modified by the provisions of
this chapter. Where the seismic design loads are computed
using provisions for intermediate or special concrete
systems, the requirements of Chapter 21 for
intermediate or special systems, as applicable, shall be
satisfied.
21.2.1.3 # For structures assigned to Seismic Design
Category C, intermediate or special moment frames,
intermediate precast structural walls or ordinary or special
reinforced concrete structural walls shall be used to
resist seismic forces induced by earthquake motions.
Where the design seismic loads are computed using provisions
for special concrete systems, the requirements of
Chapter 21 for special systems, as applicable, shall be
satisfied.
21.2.1.4 # For structures assigned to Seismic Design
Category D, E or F, special moment frames, special reinforced
concrete structural walls, diaphragms and trusses
and foundations complying with 21.2 through 21.10 or
intermediate precast structural walls complying with
21.13 shall be used to resist forces induced by earthquake
motions. Members not proportioned to resist earthquake
forces shall comply with 21.11.

International Building Code 1908.1.5

ACI 318, Section 21.2.5. Modify ACI 318, Section
21.2.5, by renumbering as Section 21.2.5.1 and adding
new Section 21.2.5.2 to read as follows:
21.2.5 # Reinforcement in members resisting earthquake-
induced forces.
21.2.5.1 # Except as permitted in 21.2.5.2, reinforcement
resisting earthquake-induced flexural and axial forces in
frame members and in structural wall boundary elements
shall comply with ASTM A 706. ASTM 615,
Grades 40 and 60 reinforcement, shall be permitted in
these members if (a) the actual yield strength based on
mill tests does not exceed the specified yield, fy, strength
by more than 18,000 psi (124 MPa) [retests shall not
exceed this value by more than an additional 3,000 psi
(21 MPa)], and (b) the ratio of the actual tensile strength
to the actual yield strength is not less than 1.25.
For computing shear strength, the value of fyt for transverse
reinforcement, including spiral reinforcement,
shall not exceed 60,000 psi (414 MPa).
21.2.5.2 # Prestressing steel shall be permitted in flexural
members of frames, provided the average prestress,
fpc, calculated for an area equal to the member’s shortest
cross-sectional dimension multiplied by the perpendicular
dimension shall be the lesser of 700 psi (4.83MPa) or
f _
c /6 at locations of nonlinear action where prestressing
steel is used in members of frames.

International Building Code 1908.1.6

ACI 318, Section 21.2. Modify ACI 318, Section
21.2, by adding new Section 21.2.9 to read as follows:
21.2.9 # Anchorages for unbonded post-tensioning tendons
resisting earthquake induced forces in structures
assigned to Seismic Design Category C, D, E or F shall
withstand, without failure, 50 cycles of loading ranging
between 40 and 85 percent of the specified tensile
strength of the prestressing steel.

International Building Code 1908.1.7

ACI 318, Section 21.3. Modify ACI 318, Section
21.3, by adding new Section 21.3.2.5 to read as follows:
21.3.2.5 # Unless the special moment frame is qualified
for use through structural testing as required by 21.6.3,
for flexural members prestressing steel shall not provide
more than one-quarter of the strength for either positive
or negative moment at the critical section in a plastic
hinge location and shall be anchored at or beyond the
exterior face of a joint.

International Building Code 1908.1.8

ACI 318, Section 21.7. Modify ACI 318, Section
21.7, by adding new Section 21.7.10 to read as follows:
21.7.10 # Wall piers and wall segments.
21.7.10.1 #Wall piers not designed as a part of a special
moment frame shall have transverse reinforcement
designed to satisfy the requirements in 21.7.10.2.
Exceptions:
1. Wall piers that satisfy 21.11.
2. Wall piers along a wall line within a story
where other shear wall segments provide lateral
support to the wall piers and such segments
have a total stiffness of at least six times
the sum of the stiffness of all the wall piers.
21.7.10.2 # Transverse reinforcement with seismic hooks
at both ends shall be designed to resist the shear forces
determined from 21.4.5.1. Spacing of transverse reinforcement
shall not exceed 6 inches (152 mm). Transverse
reinforcement shall be extended beyond the pier
clear height for at least 12 inches (305 mm).
21.7.10.3 # Wall segments with a horizontal
length-to-thickness ratio less than 2.5 shall be designed
as columns.

International Building Code 1908.1.9

ACI 318, Section 21.8. Modify Section 21.8.1 to
read as follows:
21.8.1 # Special structural walls constructed using precast
concrete shall satisfy all the requirements of 21.7 for
cast-in-place special structural walls in addition to Sections
21.13.2 through 21.13.4.