ACI-349 Approval for KB-TZ2 Expansion Anchor

Applicability of the KB-TZ2 Anchor
13
August 2021
Figure 4 - Example calculation
Given:
(2) CS 1/2” KB-TZ2 anchors under static tension load as shown.
hef = 3-1/4 in.
Slab on grade with f ‘c = 3,000 psi.
No supplementary reinforcing.
Assume cracked normal-weight concrete.
Calculate the design strength in tension for this configuration.
Calculation per ACI 349-01 Appendix B and this document. ACI 349-01 Guide Ref.
Step 1. Calculate steel strength of anchor in tension
N
sa
= nA
sa,N
f
ut
= 2 × 0.099 × 114,000 = 22,572 lbf
B.5.1. 2 Table 2
Step 2. Calculate steel capacity
ΦN
sa
= 0.8 × 22,572 = 18,058 lbf
B.4.4 a Table 2
Step 3. Calculate concrete breakout strength of anchor in tension
N
cbg
=
A
N
Ψ
1
Ψ
2
Ψ
3
N
b
A
No
B.5.2.1
Step 4. Verify minimum spacing and edge distance:
h
min
= 5-1/2 in. < 6 in. okay
c
min
= 2-1/4 in. < 4 in. okay
s (@ c
min
) = 5-1/4 in. < 6 in. okay
B.8 Table 6
Step 5. Calculate ANo and AN for the anchorage:
A
No
= 9h
ef
2
= 9(3.25)
2
= 95.06 in
2
A
N
= (1.5h
ef
+ c) × (3h
ef
+ s) = (1.5 × 3.25 +4) × (3 × 3.25 +6 ) = 139.78 in
2
B.5.2.1 Table 2
Step 6. Calculate
N
b
= k
cr
√(f
c
’
) h
ef
1.5
= 17√3,000 (3.25)
1.5
= 5,456 lbf
B.5.2.2 Table 2
Step 7. Modification factor for eccentricity
no eccentricity →
Ψ
1
= 1.0
B.5.2.4 -
Step 8. Modification factor for edge
c
min
= 4 in < 1.5h
ef
= 1.5 × 3.25 = 4.875 in →Ψ
2
= 0.7 + 0.3
c
min
= 0.7 + 0.3
4
= 0.95
1.5h
ef
4.875
B.5.2.5 Table 2
Step 9. Modification factor for cracked concrete
Ψ
3
= 1.0
B.5.2.2
B.5.2.8
Table 2
Step 10. Calculate
N
cbg
=
A
N
Ψ
1
Ψ
2
Ψ
3
N
b
=
139.78
x 1.0 x 0.95 x 1.0 x 5,456 = 7,622 lbf
A
No
95.06
B.5.2.1 -
Step 11. ΦN
cbg
= 0.75 × 7,622 = 5,717 lbf ← controls B.4.4.c Table 2
Step 12. Calculate pullout strength: N/A; pullout does not need to be considered B.5.3.2 Table 2
Step 13. Ductility check according to B.3.6.1
For tension Φmin[N
cbg
; N
p,cr
] ≥ A
se
f
uta
where Φ= 0.85
0.85 (7,619 lb) < 22,572 lb => ductility not met
B.3.6.3 requires an additional reduction factor of 0.6 for non-ductile anchors
ΦN
cbg
= 0.6 x 5,717 = 3,430 lbf
Note: According to B.3.6.2, alternatively the attachment / base plate can be designed to yield at a load
level of 75% of the anchor design strength. In this case, the 0.6 factor would not have to be applied.
B.3.6.1
B.3.6.3
B.4.1
Table 2