ACI 318-08, Appendix D
IBC 2006 Section 1912
Anchorage to Concrete
Mark Bartlett, PE
Field Engineer
Simpson Anchor Systems
Presentation Topics
•
Brief History of Anchor Design
•
ACI 318-08, Appendix D
•
Design Equations
•
Phi (Ф) Factors
•
Interaction Equation
•
Seismic Provisions
•
Reinforcement to Prevent Breakout
•
Other Issues
•
Edge Distances, Thicknesses & Spacings
•
When to design per App. D
•
IBC 2006
•
Adhesive Anchors and Concrete
Screws
Prior to ACI 318-02
• Cast-In-Place anchors covered by:
– PCI / ACI 349
– UBC / IBC codes listed allowable
stress capacities for CIP bolts
Prior to ACI 318-02
• Design of Post-Installed anchors:
– Individual manufacturers supplied
load values based on testing
– Values found in catalogs and
ICBO/ICC reports
– Methodology was allowable stress
and assumed an uncracked and
unreinforced section.
ACI 318-08, Appendix D
ACI 318, Appendix D
• Strength design method for
anchorage to concrete
(i.e. N
ua
≤ ΦN
n
or V
ua
≤ ΦV
n
)
– Cast-In-Place (CIP) anchors
– Post-Installed (PI) anchors
• Undercut anchors
• Torque-controlled anchors
• Deformation-controlled anchors
– PI anchors must be prequalified per
ACI 355.2
Appendix D Design Equations & Failure
Modes
• Design equations check 5
different failure modes
– Steel capacity
• Tension and Shear
– Concrete breakout capacity
• Tension and Shear
– Pullout/Pull-through capacity
• Tension only
– Concrete Pryout
• Shear only
– Concrete side-face blowout
• Tension and CIP only.
Design Equations
Tension Capacities
N
sa
= nA
se,N
f
uta
N
cb
= A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
N
pn
= Ψ
c,P
N
p
N
sb
= (160c
a1
√A
brg
)λ√f’
c
Shear Capacities
V
sa= n 0.6 A
se,Vf
utaV
cbg= A
Vc/A
Vco(Ψ
ec,VΨ
ed,VΨ
c,VΨ
h,VV
b)
V
cpg= k
cpN
cbgSteel Strength In Tension – D.5.1
N
sa
= nA
se,N
f
uta
(Eq. D-3)
– N
sa– Nominal tensile
strength of an anchor group
– n – Number of anchors
– A
se,N– Effective cross
sectional area of anchor in
tension
– f
uta– Specific ultimate tensile
strength of anchor
Concrete Breakout Strength
in Tension
Concrete Breakout In Tension – D.5.2
N
cb
=A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
(Eq. D-5)
• N
cb
– Concrete breakout strength in
tension
Concrete Breakout In Tension – D.5.2
N
cb
=
A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
• A
Nc
– Projected failure area of group
• A
Nco
= 9 h
ef
2
Projected failure area of
Concrete Breakout In Tension – D.5.2
N
cb
=A
Nc
/A
Nco
(
Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
Modification for eccentric load
Ψ
ec,N
= 1/[1+(2e’
N
/3h
ef
)]
(Eq. D-9)
T
3T
2T
1N
Resultant tension load
e’
NCentroid of anchors
Concrete Breakout In Tension – D.5.2
N
cb
=A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
Modification for edge effects
If c
a,min> 1.5h
efthen:
Eq. D-10
Ψ
ed,N= 1.0
If c
< 1.5h
then:
c
aConcrete Breakout In Tension – D.5.2
N
cb
=A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
Modification for cracking
Ψ
c,N
=1.4 for uncracked section if
k
c
= 17 in eq. (D-7)
Ψ
c,N
per evaluation report (ER) if k
c
from ER used in eq. (D-7)
Ψ
c,N
=1.0 for cracked section
Concrete Breakout In Tension – D.5.2
N
cb
=A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
Ψ
cp,N
– Modification for Post-Installed
anchors
Uncracked concrete
No supplemental reinf. to control splitting
If c
a,min
> c
ac
then:
Ψ
cp,N
= 1.0
(Eq. D-12)
If c
a,min
< c
ac
then:
Ψ
cp,N
= c
a,min
/c
ac
(Eq. D-13)
Where c
ac
= 2.5 h
ef
(undercut anchors)
4 h
ef
(wedge anchors)
Concrete Breakout In Tension – D.5.2
N
cbg
=A
Nc
/A
Nco
(Ψ
ec,N
Ψ
ed,N
Ψ
c,N
Ψ
cp,N
N
b
)
• Basic concrete breakout strength
• N
b
=k
c
λ
√f’
c
h
ef
1.5
(Eq. D-7)
– k
c– Coefficient for basic concrete
breakout strength
• Found in either App. D or per product ER
– λ – Modification factor for lightweight
concrete
– f’
c– Concrete compressive strength
– h
ef– Effective embedment depth
• Tested h
effound in manufacturer’s catalog or
product ER
Pullout Strength In Tension – D.5.3
N
pn
= Ψ
c,P
N
p
(Eq. D-14)
• N
pn
– Nominal pullout strength
•
Ψ
c,P
– Modification for cracking
– 1.0 for cracked
– 1.4 for uncracked
• N
p
– Pullout strength in
tension
Pullout Strength In Tension – D.5.3
N
pn
= Ψ
c,P
N
p
(Eq. D-14)
• N
p
– Pullout strength in tension
• For PI anchors N
p
based on ACI
355.2 test results
• For CIP anchors, N
p
based on:
– N
p= 8 A
brgf’
c(Eq. D-15)
headed bolts
– N
p= 0.9f’
ce
hd
a(Eq. D-16)
hooked bolts
Side-Face Blowout Strength
in Tension
Side-Face Blowout Strength – D.5.4
N
sb
= (160c
a1
√A
brg
)λ√f’
c
(Eq. D-17)
• N
sb– Side-face blowout strength (headed
anchors only)
• c
a1– edge distance
• A
brg– Net bearing area of the head of anchor
Steel Strength in Shear
Steel Strength In Shear – D.6.1
• V
sa
= n A
se,V
f
uta
(eq. D-19) CIP HSA
• V
sa
= n 0.6 A
se,V
f
uta
(eq. D-20)
– n – number of anchors
– A
se,V
– effective cross sectional
area of a single anchor in shear
– f
uta
– specified tensile strength of
Steel Strength In Shear – D.6.1
• V
sa
may also be based on the
results of tests performed and
evaluated according to ACI 355.2
Concrete Breakout Strength
in Shear
Concrete Breakout Strength In Shear –
D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
(Eq. D-22)
• V
cbg
– Concrete breakout strength in
shear
V
cbg
=
A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
– A
Vc
– projected concrete failure area
of a group of anchors
A
Vc
= (1.5c
a1
+ s
1
+ c
a2
) h
a
Concrete Breakout Strength In Shear –
D.6.2
c
a2s
11.5c
a1c
a1h
aV
A
VcConcrete Breakout Strength In Shear –
D.6.2
V
cbg
= A
Vc
/
A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
– A
Vco
– maximum projected concrete
failure area of a single anchor
1.5c
a1c
a11.5c
1V
1.5c
a1A
Vco= 4.5 c
a12(Eq. D-23)A
VcoConcrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(
Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
ec,V
– Modification for eccentric
load
(Eq. D-26)
Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
ed,V
– Modification for edge effects
If c
a2> 1.5c
a1then Ψ
ed,V= 1.0
(Eq. D-27)
If c
a2< 1.5c
a1then Ψ
ed,V= 0.7 + 0.3c
a2/1.5c
a1(Eq. D-28)
V
c
a1c
a2Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
c,V
Modification factor for
cracking
Ψ
c,V
= 1.4 for anchors located in a
region where analysis indicates no
cracking at service loads
Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
c,V
= 1.0 for anchors in cracked
concrete with no supplemental
reinforcement or edge
reinforcement smaller
than a #4 bar
V
<#4
Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
c,V
= 1.2 for anchors in cracked
concrete with reinforcement of a
#4 bar or greater between the
anchor and the edge
V
Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
c,V
= 1.4 for anchors in cracked
concrete with reinforcement of a
#4 bar or greater between the
anchor and the edge, and with the
reinforcement enclosed
within stirrups spaced at
not more than 4”.
V
≥#4
#4@4”
Concrete Breakout In Shear – D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
Ψ
h,V
– Modification factor for shear
strength of anchors located in concrete
members with h
a
< 1.5c
a1
Ψ
h,V
= √1.5c
a1
/h
a
but not less than 1.0
When h
a
< 1.5c
a1
, A
Vc
is reduced.
However, breakout strength is not
directly proportional to member
thickness. Ψ
h,V
adjusts for this.
c
a11.5c
1V
Concrete Breakout Strength In Shear –
D.6.2
V
cbg
= A
Vc
/A
Vco
(Ψ
ec,V
Ψ
ed,V
Ψ
c,V
Ψ
h,V
V
b
)
• V
b
=(7(ℓ
e
/d
a
)
0.2
√
d
a
)λ
√
f’
c
(c
a1
)
1.5 (Eq. D-24)
– ℓ
e
– load bearing length of anchor
• Same as h
efif there is no sleeve on anchor
• Per manufacturer if there is a sleeve
– d
a
– outside diameter of anchor
– λ – adjustment for lightweight concrete
– f’
c
– concrete compressive strength
– c
a1
– edge distance
Concrete Pryout Strength In Shear –
D.6.3
V
cpg
= k
cp
N
cbg
(Eq. D-30)
•
k
cp
= 1.0 for h
ef
< 2.5”
•
k
cp
= 2.0 for h
ef
> 2.5”
•
N
cbg
– Nominal concrete
breakout strength in tension
– Always do tension calcs first
Phi (Φ) factors
• N
ua
≤ ΦN
n
or V
ua
≤ ΦV
n
• Phi (Ф) factors are applied to
nominal capacities before
comparing with factored forces
• Based on:
– Supplemental reinforcement
– Failure mode
– Load type
– Anchor property
Phi (Φ) factors D.4.4
0.70 0.70 CIP 0.70 0.45 Cat. 3 0.70 0.55 Cat. 2 0.70 0.65 Cat. 1 0.70 0.70 Use Condition B CIP Pullout 0.70 0.45 0.75 0.55 Cat. 3 0.70 0.55 0.75 0.65 Cat. 2 0.70 0.65 0.75 0.75 Cat. 1 0.70 0.70 0.75 0.75 CIP Breakout 0.70 0.70 0.75 0.75 CIP Side Face Blowout 0.60 0.65 Brittle 0.65 0.75 Use Condition B Ductile Steel Shear Tension Shear Tension Condition B Condition A Ф Factor Anchor Property Failure ModeSupplemental Reinforcing D.4.4
• Condition A
– Applies where supplementary
reinforcement is present except for
pullout and pryout strengths.
• Condition B
– Applies where supplementary
reinforcement is not present, and for
pullout or pryout strength.
Supplemental Reinforcing
• Supplemental Reinforcement
– Reinforcement that acts to restrain
the potential concrete breakout but is
not designed to transfer the full
design load from the anchors into
the structural member.
– Refer to sections D.5.2.9 and
D.6.2.9 for full design load transfer
requirements
Interaction of Tension and Shear
Interaction of Tension and Shear – D.7
• If V
ua
≤0.2ΦV
n
full tension allowed
– Ignore Shear
• If N
ua
≤0.2ΦN
n
full shear allowed
– Ignore Tension
• Otherwise
N
ua
+ V
ua
< 1.2
ΦN
n
ΦV
n
Seismic Provisions
D.3.3 – When anchor design includes earthquake
forces for structures assigned to Seismic Design
Category C, D, E, or F, the additional requirements of D.3.3.1 through D.3.3.6 shall apply.
D.3.3.1 – The provisions of Appendix D do not
apply to the design of anchors in plastic hinge zones of concrete structures under earthquake forces.
D.3.3.2 – Post-installed structural anchors shall be
qualified for use in cracked concrete and shall have passed the Simulated Seismic Tests in accordance
with ACI 355.2. Pullout strength Np and steel
strength of the anchor in shear Vsashall be based on
the results of the ACI 355.2 Simulated Seismic Tests.
Seismic Provisions
D.3.3.3 – The anchor design strength associated
with concrete failure modes shall be taken as 0.75φNn and 0.75φVn, where φis given in D.4.4 or D.4.5, and
Nnand Vnare determined in accordance with D.5.2,
D.5.3, D.5.4, D.6.2, and D.6.3, assuming the concrete is cracked unless it can be demonstrated that the concrete remains uncracked.
• 0.75 reduction to concrete capacity in
Seismic Design Category C – F
• Impractical to prove concrete remains
uncracked
Seismic Provisions
D.3.3.4 – Anchors shall be designed to be
governed by the steel strength of a ductile steel elementas determined in accordance with D.5.1 and D.6.1, unless either D.3.3.5 or D.3.3.6 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 force level corresponding to anchor forces no greater than the design strength of anchors
specified in D.3.3.3.
D.3.3.6 – As an alternative to D.3.3.4 and D.3.3.5,
it shall be permitted to take the design strength of the anchors as 0.4 times the design strength determined in accordance with D.3.3.3. For the anchors of stud bearing walls, it shall be permitted to take the design strength of the anchors as 0.5 times the design strength determined in accordance with D.3.3.3.
Seismic Provisions
• Summary
– Seismic Design Category C, D, E & F
– No anchors in plastic hinge
– PI anchors must pass Simulated
Seismic Test
– Design strength reduced by 25%
– Ductile steel failure of anchors shall
control, or...
– Ductile yielding of attachment, or...
– Anchor capacity reduced by 60%
Seismic Provisions
• Seismic and edge effects
– At small edge distances, concrete
breakout (non ductile failure mode)
will often control
– If attachment will not experience
ductile yielding before breakout
occurs, then 40% anchor capacity
reduction unless...
– Reinforce section to prevent
breakout from occurring
Reinforcement to Prevent Concrete
Breakout
Reinforcement to Prevent
Concrete Breakout
D.4.2.1 – The effect of reinforcement provided to
restrain the concrete breakout shall be permitted to be included in the design models used to satisfy D.4.2.
Where anchor reinforcement is provided in accor-dance with D.5.2.9 and D.6.2.9, calculation of the concrete breakout strength in accordance with D.5.2 and D.6.2 is not required.
D.5.2.9 – Where anchor reinforcement is developed
in accordance with Chapter 12 on both sides of the breakout surface, the design strength of the anchor reinforcement shall be permitted to be used instead of the concrete breakout strength in determining φNn. A
strength reduction factor of 0.75 shall be used in the design of the anchor reinforcement.
Reinforcement to Prevent
Concrete Breakout
• Refer to Commentary RD.5.2.9 for
more information
Reinforcement to Prevent
Concrete Breakout
D.6.2.9 – Where anchor reinforcement is either
developed in accordance with Chapter 12 on both sides of the breakout surface, or encloses the anchor and is developed beyond the breakout surface, the design strength of the anchor reinforcement shall be permitted to be used instead of the concrete breakout strength in determining φVn. A strength reduction factor of 0.75 shall be used in the design of the anchor reinforcement.
Plan Section
• Refer to Commentary RD.6.2.9 for more info
Reinforcement to Prevent
Concrete Breakout
Bars effec tive as anchor reinforce m ent Plan Edge Reinforcement Anchor Reinforcement SectionReinforcement to Prevent
Concrete Breakout
• Per Commentary RD.5.2.9 and
RD.6.2.9:
– “As a practical matter, use of anchor
reinforcement is generally limited to
cast-in-place anchors.”
• What about post-installed
anchors?
– At small edge distances, anchor
capacity will be greatly reduced for
seismic design.
Capacity Adjustments
• PI anchor pullout capacity
– Tested values of N
pare done in 2500 psi
concrete
– Pullout capacities increase for higher f’
c– Adjustment equations in ER
• Grout pads
– 20% reduction in shear strength (D.6.1.3)
– App. D makes no mention to grout pad
thickness
• Shear load parallel to concrete edge
– Breakout capacity doubled per D.6.2.1(c).
Triple Edge Conditions
D.5.2.3 – Where anchors are located less than 1.5heffrom three or more edges, the value of hefused
in Eq. (D-4) through (D-11) shall be the greater of ca,max/1.5 and one-third of the maximum spacing
between the anchors within the group.
D.6.2.4 – Where anchors are influenced by three or
more edges, the value of ca1 used in Eq. (D-23)
through (D-29) shall be the greatest of ca2/1.5 in
either direction, ha/1.5; and one-third of the maximum
Triple Edge Condition in Tension
Corner Condition D.6.2.1(d)
(d) For anchors located at a corner, the limiting nominal concrete breakout strength shall be deter-mined for each edge, and the minimum value shall be used.
V
c
a1c
a2V
c
a2c
a1Shear Near an Edge D.6.2.1
Where anchors are located at varying distances from the edge and the anchors are welded to the attach-ment so as to distribute the force to all anchors, it shall be permitted to evaluate the strength based on the distance to the farthest row of anchors from the edge. In this case, it shall be permitted to base the value of ca1on the distance from the edge to the axis of the farthest anchor row that is selected as critical, and all of the shear shall be assumed to be carried by this critical anchor row alone.
V
c
0.5V
0.5V
Anchors
welded to
plate
Anchors
not welded
to plate
Shear Near an Edge D.6.2.1
V
c
a1• Increase c
a1
without welding to plate
– Slot holes closest to edge
Required Edge Distances, Spacings,
and Thicknesses
Section D.8
Minimum spacings and edge distances for anchors and minimum thicknesses of members shall conform to D.8.1 through D.8.6, unless supplementary reinforce-ment is provided to control splitting. Lesser values from product-specific tests performed in accordance with ACI 355.2 shall be permitted.
D.8.1 – Unless determined in accordance with D.8.4,
minimum center-to-center spacing of anchors shall be
4dafor untorqued cast-in anchors, and 6dafor torqued cast-in anchors and post-installed anchors.
D.8.2 – Unless determined in accordance with D.8.4,
minimum edge distances for cast-in headed anchors that will not be torqued shall be based on specified cover requirements for reinforcement in 7.7. For cast-in headed anchors that will be torqued, the mcast-inimum edge distances shall be 6da.
Section D.8
D.8.3 – Unless determined in accordance with D.8.4,
minimum edge distances for post-installed anchors shall be based on the greater of specified cover requirements for reinforcement in 7.7, or minimum edge distance requirements for the products as deter-mined by tests in accordance with ACI 355.2, and shall not be less than 2.0 times the maximum aggregate size. In the absence of product-specific ACI 355.2 test information, the minimum edge distance shall be taken as not less than:
Undercut anchors...6da
Torque-controlled anchors...8da Displacement-controlled anchors...10da
Section D.8
D.8.4 – For anchors where installation does not
produce a splitting force and that will remain untorqued, if the edge distance or spacing is less than those speci-fied in D.8.1 to D.8.3, calculations shall be performed by substituting for daa smaller value d’athat meets the
requirements of D.8.1 to D.8.3. Calculated forces applied to the anchor shall be limited to the values corresponding to an anchor having a diameter of d’a.
D.8.5 – The value of heffor an expansion or undercut post-installed anchor shall not exceed the greater of 2/3 of the member thickness and the member thickness minus 4 in.
Section D.8
D.8.6 – Unless determined from tension tests in
accordance with ACI 355.2, the critical edge distance, cac, shall not be taken less than:
Undercut anchors...2.5hef
Torque-controlled anchors...4hef Displacement-controlled anchors...4hef
Limitations of Appendix D
• Applies for CIP and some
Post-Installed anchors
– Specialty inserts, through bolts,
adhesive anchors, screw anchors,
PAT fasteners outside scope of
Appendix D
– ACI Commentary: “Adhesive
anchors are widely used and can
perform adequately. At this
time…outside the scope.”
Limitations of Appendix D
• NW Concrete and LW Concrete
only
– Reductions in capacity in LW
– CMU and Concrete on metal deck
outside scope of App. D
• Grouted CMU will still use existing
post-installed anchor products
Limitations of Appendix D
• Limits to:
– Diameter (≤2”)
– Embedment depth (≤25”)
– Concrete compressive strength
(≤8000 psi PI; <10000 psi CIP).
When to use Appendix D
• Per ACI 318-08, D.2.1
– “…anchors in concrete used to
transmit structural loads by means of
tension, shear, or a combination of
tension and shear between (a)
connected structural elements; or (b)
safety-related attachments and
structural elements.”
– What is a “safety-related
attachment”?
When to use Appendix D
• Per ACI 318-08, RD.2.1
– Commentary lists examples for
safety-related attachments.
– “…safety-related attachments that are
not part of the structure (such as
sprinkler systems, heavy suspended
pipes, or barrier rails) are attached to
structural elements.”
When to Use Appendix D
IBC 2006
IBC 2006, Section 1911
Anchorage To Concrete –
Allowable Stress Design
1911.1 Scope. The provisions of this section shall govern the
allowable stress design of headed bolts, and headed stud
anchors cast in normal-weight concrete for purposes of
trans-mitting structural loads from one connected element to the
other.
These provisions do not apply to anchors installed in
hardened concrete or where load combinations include
earth-quake loads or effects.
The bearing area of headed anchors
shall be not less than one and one-half times the shank area.
Where strength design is used, or where load combinations
include earthquake loads or effects, the design strength of
anchors shall be determined in accordance with Section 1912.
Bolts shall conform to ASTM A 307 or an approved
equivalent.
IBC 2006, Section 1912
Anchorage To Concrete – Strength Design
1912.1 Scope. The provisions of this section shall govern the
strength design of anchors installed in concrete for purposes of transmitting structural loads from one connected element to the other. Headed bolts, headed studs and hooked (J- or L-) bolts cast in concrete and expansion anchors and undercut anchors installed in hardened concrete shall be designed in accordance with Appendix D of ACI 318 as modified by Section 1908.1.16, provided they are within the scope of Appendix D.
The strength design of anchors that are not within the scope of Appendix D of ACI 318, and as amended above, shall be in accordance with an approved procedure.
Exception: Where the basic concrete breakout strength in
tension of a single anchor, Nb, is determined in accordance with Equation (D-7), the concrete breakout strength requirements of Section D.4.2.2 shall be considered satisfied by the design procedures of Sections D.5.2 and D.6.2 for anchors exceeding 2 inches (51mm) in diameter or 25 inches (635mm) tensile embedment depth.
IBC 2006, Section 1908
Modifications to ACI 318
1908.1.16 ACI 318, Section D.3.3. Modify ACI 318, section
D.3.3.2 through C.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 0.75φNnand 0.75φVn, where φ is given in D.4.4 or D.4.5, and Nnand Vnare 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
Adhesive Anchors and
Concrete Screws
Adhesives Anchors and Concrete
Screws
• IBC 2006, Section 1912
– “The strength design of anchors that
do not within the scope of Appendix D
of ACI 318…shall be in accordance
with an approved design procedure.”
• What design procedures are
approved?
• Who decides?
Adhesives Anchors and Concrete
Screws
• IBC 2006, Section 104.11
104.11 Alternative materials, design and methods of construction and equipment. The provisions of this code are not
intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability and safety.
104.11.1 Research reports. Supporting data, where necessary
to assist in the approval of materials or assemblies not specifically provided for in this code, shall consist of valid research reports from approved sources.
