1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
A
B 0.75
0.7
Condition B (ϕ =0.70) is considered when
• No Supplementary reinforcement is present
Concrete Breakout Strength фN cb
8. Reinforcing
Bar Anchorage
N b
ψ s,N
ψ ed,N
ψ co,N
ψ c,N
ψ cp,N
=
=
=
=
=
=
9. Special Anchor
Channel Design
10. Design
Software
11. Best
Practices
basic concrete breakout strength in tension
modification factor for anchor spacing
modification factor for edge effects
modification factor for corner effects
modification factor cracked/uncracked concrete
modification factor for splitting
Figure 7.3.2.6 — Concrete cone breakout of a group of anchors. (Picture
from Anchorage in Concrete Construction, R. Eligehausen).
N b = Basic concrete breakout strength
loaded by tension load at an edge.
Figure 7.3.2.5 — Concrete cone in tension. (Picture from Anchorage in
Concrete Construction, R. Eligehausen).
168
α ch factor to account for the influence of channel size on
concrete breakout strength in tension. It decreases the concrete
breakout capacity for the anchor channels with embedment
depth less than 7.1”.
The presence of the channel profile in the breakout cone may
influence the load-carrying capacity depending on the ratio of
the height of the channel to embedment depth. As shown in
Fig 7.3.2.7. It has been observed in testing that having less
concrete because of profile occupying the volume of concrete
reduces the concrete breakout capacity in tension by the
reduction factor α ch,N . Another observation that has been seen is
that the anchor channels with effective embedment greater than
7.1" the reduction in this capacity is negligible. This observation
has been included in the reduction ESR-3520 Equation (8).
ESR-3520 Equation (7)
ACI 318-14: Equation17.4.2.2a
æ h ö
α ch, N = ç ç ef ÷ ÷
è 7 . 1 ø
0 . 15
æ h ö
α ch, N = ç ç ef ÷ ÷
è 180 ø
£ 1 . 0
0 . 15
£ 1 . 0
(inch-pound)
ESR-3520 Equation (8)
(SI-units)
According to ACI 318-14 of section 17.4.2.2 the basic concrete
breakout strength of a single anchor in tension in cracked
concrete, N b , shall not exceed ESR-3520 Equation 7 or ACI
318-14: 17.4.2.2a. Alternatively in accordance to ACI 318-14, for
cast-in headed studs and headed bolts with 11 in. ≤ h ef ≤ 25 in.,
N b shall not exceed ACI 17.4.2.2b. Hence in case of an anchor
channel with 11 in. ≤ h ef ≤ 25 in., N b shall not exceed ACI 318-
14 Equation 17.4.2.2b. The values of 24 in Eq. (17.4.2.2a) were
determined from a large database of test results in uncracked
concrete (Fuchs etal. 1995) at the 5 percent fractile. The values
were adjusted to corresponding 24 value for cracked concrete
(Eligehausen and Balogh 1995; Goto 1971). For anchors with
a deeper embedment (h ef >11 in.), test evidence indicates the
use of h ef 1.5 can be overly conservative for some cases. An
alternative expression (Eq. (17.4.2.2b)) is provided using h ef 5/3 for
Figure 7.3.2.7 — Concrte Breakout cone in tension
Anchor channel h ef can be found in ESR-3520 Table 8-1
Where anchor channels with h ef > 7.1 in. (180 mm) are located in
an application with three or more edges (as illustrated in Figure
7.3.2.8 & 7.3.2.9) with edge distances less than c cr,N (c cr,N in
accordance with Eq. (14)) from the anchor under consideration,
the values of h ef used in Eq. (7), (8), and (11) may be reduced to
h ef,red in accordance with Eq. (9).
ö
æ c
s
h ef , red = max ç ç a , max . h ef ;
. h ef ÷ ÷ , in .( mm )
s cr , N
ø
è c cr , N
ESR-3520 Equation (9)
where:
c a,max = maximum value of edge or corner distance, in. (mm)
The values c cr,N and s cr,N in Eq. (9) shall be computed with h ef .
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
169
ESR-3520 Equation (6)
A practical solution to assess the failure loads of anchors is via
empirically derived equations that encompass theoretical models.
This approach has led to the development of the CCD (Concrete
Capacity Design) Method. Concrete cone failure loads subjected
to concentric tension as a function of embedment depth.
N cb = N b × ψ s, N × ψ ed, N × ψ co, N × ψ cp, N × ψ c, N
,N
ACI 318-14: Equation17.4.2.2b
f N cb ³ N aua
N b = 10 × l × α ch, N × f c ' × h 1.5
ef
æ 5 ö
ç ÷
f ' c h ef è 3 ø
Figure 7.3.2.4 Arrangement of anchor reinforcement for anchor
channels loaded by tension load in a narrow member.
Per ESR-3520 Section 4.1.3.2.3, nominal concrete breakout
strength (N cb ) is calculated using ESR 3520 Equation (6). The
value calculated for concrete breakout strength in tension
(N cb ) is based on the location of the anchor element being
considered. The basic concrete breakout strength in tension
(N b )is not dependent on the anchor element being considered
or the concrete geometry. Therefore, the calculated value for N b
will be the same for each anchor element.
,lb
N b = 16 l a
If the anchors are short, or if they are closely spaced or
positioned near a free edge, a cone-shaped concrete breakout
may limit the tension capacity of the anchor. For this type of
failure the load-bearing behavior of channels with two anchors
or of channels with more than two anchors and equal load on
each anchor mimics that of headed studs. The presence of the
channel profile in the breakout cone may influence the load-
carrying capacity depending on the ratio of the height of the
channel to embedment depth.
N b = 24 × l × α ch, N × f c ' × h 1.5
ef
evaluation of cast-in headed studs and headed bolts with
11 in. ≤ h ef < 25in.
Figure 7.3.2.3 — Arrangement of anchor reinforcement for anchor channels
14. Design
Example
λ= modification factor for lightweight concrete
λ = 1 for Normal weight concrete
λ = 0.85 for Sand Light weight concrete
λ = 0.75 for All Light weight concrete
f’ c = concrete compressive strength
13. Field Fixes
The basic concrete breakout strength of a single anchor
in tension in cracked concrete, N b , shall be determined in
accordance with Eq. (7).
12. Instructions
for Use
Concrete breakout strength
also known as concrete cone
failure, the concrete breakout
failure mode is characterized
by the formation of a cone-
shaped fracture surface in
the concrete. The full tensile
capacity of the concrete is
utilized. Anchor channels
with an adequately large bearing surface will generate concrete
cone breakout failures if the steel capacity is not exceeded.
Headed studs transfer the tensile force into the base material
through bearing (mechanical interlock). Consequently, for the
same load, the amount of displacement depends on the bearing
contact area.
7. Anchor Channel
Design Code
ϕ
6. Loading
Condition
5. Base material
ϕ factor:
Condition A (ϕ =0.75) is considered when
• Supplementary reinforcement is present
• Reinforcement does not need to be explicitly designed for the
anchor channel
• Arrangement should generally conform to anchor
reinforcement
• Development is not required
4. Design
Introduction