1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
4. Design
Introduction
5. Base material
6. Loading
7. Anchor Channel
Design Code
8. Reinforcing
Bar Anchorage
9. Special Anchor
Channel Design
10. Design
Software
11. Best
Practices
12. Instructions
for Use
14. Design
Example
13. Field Fixes
Allowable loads: Under the Allowable Stress Design Method,
the allowable load, or resistance, is based on the application
of a safety factor to the mean result of laboratory testing to
failure, regardless of the controlling failure mode observed in the
tests. The safety factor is intended to account for reasonably
expected variations in loading. Adjustments for anchor spacing
and edge distance are developed as individual factors based on
testing of two- and four-anchor groups and single anchors near
free edges. These factors are multiplied together for specific
anchor layouts. The ultimate load associated with tension failure of the steel
bolt or anchor may be determined with equation N 0u,s = A s .f u
(f u =tensile steel strength, A s = Tensile cross-sectional area).
The failure load corresponding to rupture of the connection
between the anchor and the channel web may be assessed
using ordinary structural steel design principles. In contrast, the
ultimate load associated with distortion of the channel flanges
is quite difficult to establish without testing. The flanges are
to some degree supported by the surrounding concrete and
therefore exhibit a different load-bearing behavior compared to
a free-standing channel. Similarly, the failure load corresponding
to the separation of an anchor element that is swaged onto or
pressed into the back of the channel can only be determined
through testing.
Tension (ΦN n )
Concrete
T allowable , ASD =
Test description f c ∆w Minimum
No. of
tests Channel Anchor Material
[-] Secion
in Annex
A [-] psi
[N/mm 2 ] inch
(mm) [-] [-] [-] [-]
Channel bolt
d s strength
inch
(mm) [-]
Steel failure under tension load
1 7.3 Channel/anchor - - 5 1
2 7.3 Bending of channel lips, pull-out of
channel bolt - - 5 1
3 7.3 Channel bolt head - - 5
4 7.4 Bending strength of the channel 2 Low 0
s = s min inch [mm]
7.5
Torque tests 4
See AC232 section 7.4.2
5
s < s min inch [mm]
5
See AC232 section 7.3.2
5
-
-
5
See AC232 section 7.5.2
Concrete failure under tension load
6 7.6 Splitting failure due to installation 5
c a = c a,min
s < s min h < h min Low 0 5 See AC232 section 7.6.2
7 7.7 Concrete breakout strength Low 0 5 See AC232 section 7.7.2
1
2
3
4
If the coefficient of variation Vof the failure loads is V ≤ 5 percent, the number of tests can be reduced to n = 3.
Tests are only necessary if restraint of channels embedded in concrete shall be taken into account (α r > 4.0, see Section 8.8)
The tests shall only be performed if the conditions in Section 7.4.2.1 of this annex apply.
If the prestressing force is determined in accordance with Section 8.9.2 of this annex, only the smallest, medium and large channel bolts need to be tested in the corresponding medium sized
channel. The most unfavorable combination of material and coating for the channel bolt and the channel shall be tested. No torque tests are required with channel bolts without lubrication or
friction-reducing coatings if the prestressing force is calculated according to AC 232 Eq. (8.11) of this AC 232 annex with k = 0.15. See also Section 7.5.2.1 of AC 232 annex.
5 Only the small, medium and large channel sizes need to be tested if the conditions of Section 7.6.2.1 are fulfilled.
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
163
162
Test Ref
Limit State Design: The limit state design method for anchor
design is described and included in the CSA A23.3 Annex D.
Test no.
Strength Design: The Strength Design Method for anchor
design has been incorporated into several codes such as IBC
and ACI 318. The method assigns specific strength reduction
factors to each of several possible failure modes, provides
predictions for the strength associated with each failure mode,
and compares the controlling strength with factored loads. The
Strength Design Method is a more accurate estimate of anchor
resistance as compared to the ASD approach. The Strength
Design Method, as incorporated in ACI 318-14 Chapter 17.
Strength Design is state-of-the-art and Hilti recommends its use
where applicable.
Table 7.3.1.1 (AC232 Table 4.1) — Test program for anchor channels for use in uncracked and cracked concete
The design of anchors channel is based on an assessment of
the loading conditions and anchorage capacity. Strength design
(SD), limit state design (LSD), and allowable stress design (ASD)
methods are currently in use in North America for the design of
anchors.
where:
T allowable,ASD
V x,allowable,ASD
=
Allowable tension load, lb (N)
= Allowable shear load in longitudinal
channel axis, lb (N)
V y,allowable,ASD
= Allowable shear load perpendicular to the
channel axis, lb (N)
M s,flex,allowable.ASD = Allowable bending moment due to tension
loads, lb-in (Nm)
ϕN n
= Lowest design strength of an anchor,
channel bolt, or anchor channel in tension
for controlling failure mode, lb (N)
ϕV n
= Lowest design strength of an anchor,
channel bolt, or anchor channel in shear
in longitudinal channel axis for controlling
failure mode, lb (N).
ϕV n,Y
= Lowest design strength of an anchor,
channel bolt, or anchor channel in shear
perpendicular to the channel axis for
controlling failure mode lb (N).
α ASD
= Conversion factor calculated as a
weighted average of the load factors
for the controlling load combination. In
addition, α ASD shall include all applicable
factors to account for non-ductile failure
modes and required overstrength.
7.2.9 ANCHOR CHANNEL DESIGN
Figure 7.2.8.5 — Example for the calculation of anchor channels with 6
anchors loaded in shear longitudinal to the channel axis for concrete edge
failure.
Figure 7.3.1 — Possible tensile failure modes of an anchor channel.
f N n
a ASD
f V n , x
V x , allowable , ASD =
a ASD
f V n , y
V y , allowable , ASD =
a ASD
f M s , flex
M s , flex , allowable , ASD =
a ASD
Steel
For anchors designed using load combinations in accordance
with IBC Section 1605.3 (Allowable Stress Design) allowable
loads shall be established using following equations.
Tension Analysis
7.3 ANCHOR CHANNEL DESIGN IN TENSION
In principle, the method follows the strength design concept
with the application of different strength reduction factors.
The limit states design method generally results in a more
accurate estimate of anchor resistance as compared to the ASD
approach.