1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
4. Design
Introduction
5. Base material
6. Loading
7.6.1 SEISMIC CONSIDERATIONS
Option b)
Yielding
11. Best
Practices
12. Instructions
for Use
13. Field Fixes
Design of Attachment
Option c)
Non-yielding
14. Design
Example
Seismic Load
Option d)
Overstrength Factor
According to ACI 318-14 Section 17.2.3.2: The provisions of the
chapter 17 do not apply to the design of anchors in plastic hinge
zones of concrete structures under earthquake forces.
a) A nchor resistance governed
by ductile anchor yield
17.2.3.4.3(a)
d) A nchorage designed for a multiple of the
calculated seismic force 17.2.3.4.3(d)
Option b)
(Ductile yield
mechanism in
attachment)
Seismic Detailing: Tension
Seismic Design for
SDC C, D or F
Option a)
Ductility
check anchor
OK
Option c)
(Non-yielding
attachment)
NG
OK
Option d)
Design for E
OK
Finish
OK
o
Refer to Figure 7.6.2.1 and 7.6.2.2 explaining the
requirements in ACI 318-14 Section 17.2.3.4.3 in figure and
in a flow chart.
The design of anchors in accordance with option (a) should be
used only where the anchor yield behavior is well defined and
where the interaction of the yielding anchor with other elements
in the load path has been adequately addressed
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
193
Please note that when it comes to anchor channel none of
the manufacturers satisfy ductility requirements. We are now
left with satisfying one of the other three seismic requirement
options.
• The requirements of 17.2.3.4.3 need not apply where the
applied earthquake tensile force is a small fraction of the total
factored tension force.
• Option a): For tension loadings, anchor strength should be
governed by yielding of the ductile steel element of the anchor.
For single anchors, the concrete-governed strength shall be
greater than the steel strength of the anchor. For anchor groups,
the ratio of the tensile load on the most highly stressed anchor
to the steel strength of that anchor shall be equal to or greater
than the ratio of the tensile load on tension loaded anchors to
the concrete-governed strength of those anchors. In each case:
(i) The steel strength shall be taken as 1.2 times the nominal
steel strength of the anchor.
(ii) The concrete-governed strength shall be taken as the
nominal strength considering pullout, side-face blowout,
concrete breakout, and bond strength as applicable.
For consideration of pullout in groups, the ratio shall be
calculated for the most highly stressed anchor. In addition,
the following shall be satisfied:
(iii) Anchors shall transmit tensile loads via a ductile steel
element with a stretch length of at least eight anchor
diameters unless otherwise determined by analysis.
(iv) Where anchors are subject to load reversals, the anchor
shall be protected against buckling.
(v) Where connections are threaded and the ductile steel
elements are not threaded over their entire length, the ratio
of f uta /f ya shall not be less than 1.3 unless the threaded
portions are upset. The upset portions shall not be
included in the stretch length.
(vi) Deformed reinforcing bars used as ductile steel elements
to resist earthquake effects shall be limited to ASTM A615
Grades 40 and 60 satisfying the requirements of
ACI 318-14 20.2.2.5(b) or ASTM A706 Grade 60.
• 17.2.3.4.2 Where the tensile component of the strength level
earthquake force applied to anchors exceeds 20 percent of
the total factored anchor tensile force associated with the
same load combination, anchors and their attachments shall
be designed in accordance with 17.2.3.4.3 as described in
Figure 7.6.2.1 and 7.6.2.2 . The anchor design tensile strength
shall be determined in accordance with 17.2.3.4.4, which
states that an additional seismic reduction factor of 0.75 is
applied to the concrete or non steel tensile design strengths.
Figure 7.6.2.2 — Flow chart — Seismic provisions for tension; ACI 318-14 Section 17.2.3.4.3
• 17.2.3.4.1 Where the tensile component of the strength
level earthquake force applied to a single anchor or group
of anchors is equal to or less than 20 percent of the total
factored anchor tensile force associated with the same load
combination, it shall be permitted to design a single
• anchor or group of anchors.
nchorage designed for capacity of
c) A
structural system 17.2.3.4.3(c)
Figure 7.6.2.1— Seismic provisions for tension; ACI 318-14 Section 17.2.3.4.3.
7.6.2 SEISMIC CONSIDERATIONS TENSION
The Requirements for tensile loading is stated in section
17.2.3.4 of ACI 318-14
b) A nchorage designed for a plastic
hinge 17.2.3.4.3(b)
• The possible higher levels of cracking and spalling in plastic
hinge zones are beyond the conditions for which the nominal
concrete governed strength values are applicable.
• Plastic hinge zones are considered to extend a distance equal
to twice the member depth from any column or beam face,
and also include any other sections in walls, frames, and
slabs where yielding of reinforcement is likely to occur as a
result of lateral displacements.
• Where anchors must be located in plastic hinge regions, they
should be detailed so that the anchor forces are transferred
directly to anchor reinforcement that is designed to carry
the anchor forces into the body of the member beyond the
anchorage region. Configurations that rely on concrete tensile
strength should not be used.
192
Anchor
Option a)
Anchor Ductility
10. Design
Software
• The most recent development of structural classification
has been the establishment of seismic design categories
to determine seismic detailing requirements. Recognizing
that building performance during a seismic event depends
not only on the severity of subsurface rock motion, but also
on the type of soil upon which a structure is founded, the
Seismic Design Category (SDC) is a function of location,
building occupancy, and soil type.
• Seismic provisions are applicable for all the load
combinations if the condition is in a project located in SDC C,
D, E or F.
• The behavior of concrete under static and seismic loading is
• different. Concrete member statically loaded have defined
tensile and compression zones. Cracking of the concrete due
to static loads is predictable, well understood, and the crack
width is limited to 0.3 mm.
• Concrete members that undergo seismic loads deal with more
unpredictable loads. Additional safety factors are built-in the
seismic design to deal with such variances. Due to the cycling
nature of seismic loads, tension and compression zones can
be inverted and cracking of the concrete can occur through
the structure. Moreover, according to extensive research
results, the crack width can be up to 0.5mm during seismic
events. Crack open and closes dramatically, concrete tends to
pushing anchor out during crack closing. Where as crack open
and close with changing of live load, crack close naturally.
• The wind analysis should also have the seismic design provision
of reduced tensile strengths associated with concrete failure
modes. This is applicable to account for increased cracking and
spalling in the concrete resulting from seismic actions.
• Non-structural systems (suspended ceilings, conduit
attachments, mechanical, plumbing, electrical and
communications equipment, doors, windows, wood sill
plates, cold-formed steel track attachments, and architectural
components) suffer the largest damage in commercial
buildings during an earthquake. Since nonstructural elements
of a building are not a part of the main load resisting system,
they are often neglected from the structural design point
of view. It’s important to include seismic design for both
structural and non-structural elements as Seismic conditions
significantly change the behavior of anchors, compared to
static conditions. Research is compelling! The percentage of
damage caused by non-structural elements is significantly
higher than structural elements.
9. Special Anchor
Channel Design
The anchors in structures assigned to Seismic Design Category
(SDC) C, D, E, or F shall satisfy the additional requirements
of 17.2.3.2 through 17.2.3.7 of ACI 318-14.Unless 17.2.3.4.1 or
17.2.3.5.1 apply, all anchors in structures assigned to Seismic
Design Categories (SDC) C, D, E, or F are required to satisfy the
additional requirements of 17.2.3.1 through 17.2.3.7, regardless
of whether earthquake loads are included in the controlling load
combination for the anchor design.
8. Reinforcing
Bar Anchorage
7.6 SEISMIC DESIGN
7. Anchor Channel
Design Code