HAC_Technical-Guide

402 403
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
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
13. Field Fixes
14. Design
Example
Code Discussion Calculations
Step 7: Concrete strength
ESR-3520 section
4.1.3.2.3
ACI 318-14 Chapter 17
Concrete breakout strength in Tension continued…
Calculate the modification factor for corner influence (ψ
co,N,3
).
c
a2
is measured parallel to the anchor channel longitudinal axis, and is considered
when calculating the modification factor for corner influence (ψ
co,N
).
Since the calculated value for concrete breakout in tension (N
cb
) is dependent on
the concrete geometry, it is important to note that values for ca1 and ca2 must be
taken with respect to the relevant edge distances from the anchor element being
considered.
1.0
c
c
1.0
c
c
0.5
Ncr,
x)a2(
N,3co,
0.5
Ncr,
x)a2(
N,3co,
£
÷
÷
ø
ö
ç
ç
è
æ
=--£
÷
÷
ø
ö
ç
ç
è
æ
=
-+
yy and
ESR-3520 Equation (16)
The parameter c
cr,N
corresponds to the maximum edge distance that is assumed with
respect to values for c
a1
and c
a2
. Any c
a1
or c
a2
value less than c
cr,N
must be considered
when calculating ψ
ed,N
and ψ
co,N
. If more than one c
a1
value is less than c
cr,N
, the
smallest c
a1
value will be used to calculate ψ
ed,N
. If more than one c
a2
value is less than
c
cr,N
, ψ
co,N
will be calculated for each c
a2
value and the product of these ψ
co,N
values will
be used to calculate the nominal concrete breakout strength in tension (N
cb
).
Calculate the modification factor for cracked/uncracked concrete (ψ
c,N,3
)
Concrete is typically assumed to be cracked under normal service load conditions. If
uncracked concrete conditions are assumed, an increase in N
cb
is permitted via the
modification factor ψ
c,N
.
if uncracked concrete conditions are assumed,ψ
c,N,3
=1.25.
Calculate the modification factor for splitting (ψ
cp,N
c
ac
= critical edge distance for splitting
c
cr,N
= critical anchor edge distance
c
a,min
= minimum edge distance
Concrete breakout: ФN
cb
c
a2(+ x)
= 6.00 in + 0.984 in
c
a2(+ x)
= 6.984 in
907.0
1.0
8.49in
6.984in
49.8
1
c
c
N,3co,
0.5
N,3co,
,
0.5
Ncr,
x)a2(
)(2
=\
<
÷
ø
ö
ç
è
æ
=
=
=
÷
÷
ø
ö
ç
ç
è
æ
®¥=
-
-
y
y
inc
c
Ncr
xa
Cracked concrete conditions
→ ψ
c,N,3
= 1.0
Cracked concrete conditions
→ ψ
cp,N,3
= 1.0
Uncracked concrete with no supplementary reinforcement ψ
cp,N
if c
a,min
≥ c
ac
1
if c
amin
< c
ac
⎧⎛ c
a,min
⎞ ⎛ c
cr,N
⎞ ⎫
ψ
cp,N
= MAX ⎨ ⎜
______
⎜ ; ⎜
_____
⎜ ⎬
⎩⎝
c
ac
⎠ ⎝
c
ac
⎠ ⎭
Uncracked concrete with supplementary reinforcement 1
Cracked concrete 1
Code Discussion Calculations
Step 7: Concrete strength
ESR-3520 section
4.1.3.2.3
ACI 318-14 Chapter 17
Concrete breakout strength in Tension continued….
Nominal concrete breakout strength in tension for anchor element #3
ФN
cb
≥ N
a
ua
N
cb
= N
b
· ψ
s,N
· ψ
ed,N
· ψ
co,N
· ψ
cp,N
· ψ
c,N
ESR-3520 Equation (6)
The calculated value for N
cb,3
will be multiplied by a strength reduction factor (φ-factor)
to give a design strength (φ
Ncb,3
). Design strengths for this example are summarized in
the table on this page titled Summary for Concrete Breakout in Tension.
The calculated φ
Ncb,3
value for anchor element #3 will be checked against the factored
load acting on anchor element #3 (N
aua,3
) to obtain the % utilization (N
aua,3
/ φ
Ncb3
).
The anchor element with the highest % utilization will control the design with respect
to concrete breakout failure in tension.
φ-factors for concrete breakout in tension are given in ESR-3520 Table 8-4.
Ф factor:
Condition A (Ф =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
Condition B (Ф =0.70) is considered when
• No Supplementary reinforcement is present
Assume Condition B
Ф =0.70
The concrete breakout calculations (φ
Ncb
) were influenced by the anchor location and
the concrete geometry via the modification factors ψ
s,N
, ψ
ed,N
and ψ
co,N
Concrete breakout: ФN
cb
cb b s,N ed,N co,N cp,N c,N
s,N
ed,N
co,N
cp,N
c,N
3
,3
,3
cb,3
a
ua,3
, ,3
NNψψψψψ
ψ 0.658
ψ 0.767
ψ 0.907
ψ 1.0
ψ 1.0
14634
14634 0.658 0.767 0.907 1.0 1.0
6699
0.7
N 4689lbs
N 786
78
b
cb
cb
cb N
N lbs
N xxxxx
N lbs
Condition B
lbs
j
j
b
= ×××××
=
=
=
=
=
=
=
=
=
=
=
=
6
100% 17%
4690
x
æö
=
ç÷
èø