PART 3 TENSION LOAD
Concrete Breakout Failure Mode
Calculations A Nc0
Calculations ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
A Nc0
= 9h ef
2
17.4 . 2.1 …….. A Nc0 is the projected concrete failure area of a single anchor with an edge distance equal to or greater than 1.5h ef
.
A Nc0
= 9h ef
2
( 17.4.2.1c ) 17.7.5 Unless determined from tests in accordance with ACI 355.2 , the value of h ef for an expansion or undercut post-installed anchor shall not exceed the greater of 2 / 3 of the member thickness , h a
, and the member thickness minus 4 in .
Example :
Example of embedment depth and concrete thickness requirements given in a mechanical anchor approval .
ICC-ESR-3187 Table 3
DESIGN |
|
|
Nominal Anchor Diameter ( in ). |
|
INFORMATION Symbol Units
|
|
3 / 8 |
1 / 2 5 / 8 |
3 / 4 |
Effective minimum embedment
Minimum member thickness
Example : h ef in . 1-1 / 2 2 2-3 / 4 2 3-1 / 4 3-1 / 8 4 3-1 / 4 3-3 / 4 4-3 / 4 h min in . 3-1 / 4 4 5 5 4 6 6 8 5 6 8 5-1 / 2 6 8 8
Example of embedment depth and concrete thickness requirements given in an adhesive anchor system approval .
ICC-ESR-3187 Table 12
DESIGN INFORMATION
Minimum embedment
Maximum embedment
Maximum concrete thickness
Symbol Units
3 / 8 or # 3
1 / 2 or # 4
Nominal Rod Diameter ( in ).
5 / 8 or # 5
3 / 4 or # 6
7 / 8or # 7
1 or # 8 h ef , min in . 2-3 / 8 2-3 / 4 3-1 / 8 3-1 / 2 3-1 / 2 4 4-1 / 2 5
# 9
1 / 4 or # 10 h ef , max in . 7-1 / 2 10 12.5 15 17-1 / 2 20 22.5 25 h min
- h ef + 1-1 / 4 h ef
+ 2d 0
A Nc0 is a modification factor that accounts for the area of influence assumed to develop in concrete when a tension load is applied to a single anchor without the influence of any fixed edges . A Nc0 is calculated with the effective embedment depth of the anchor ( h ef ) input into the PROFIS Engineering file . A Nc0 is always defined as a square that has sides equal to 3.0h ef
. The length of the side in the x direction corresponds to a projected distance of 1.5h ef from the anchor in the + x and -x directions . The length of side in the y direction corresponds to a projected distance of 1.5h ef from the anchor in the + y and -y directions .
For cast-in-place anchor design , PROFIS Engineering uses the following embedment depth and concrete thickness parameters :
embedment depth ( h ef )
4d a
< h ef < 25 in d a
= nominal anchor diameter minimum concrete thickness ( h min
) h min
= h ef + t h
+ 0.375 in t h
= anchor head thickness
Values for t h are taken from product data for ASTM F1554 hex , heavy hex , square and heavy square bolts ; and from AWS D1.1 headed studs .
Post-installed mechanical anchors can be shown compliance under the International Building Code via testing per the ICC-ES acceptance criteria AC193 in conjunction with the ACI standard ACI 355.2 . Post-installed adhesive anchor systems can be shown compliance under the International Building Code via testing per the ICC-ES acceptance criteria AC308 in conjunction with the ACI standard ACI 355.4 . For postinstalled anchor design , PROFIS Engineering uses the embedment depth and concrete thickness parameters derived from AC193 / ACI 355.2 or AC308 / ACI 355.4 testing , as given in the ICC-ESR for the anchor .
PROFIS Engineering will not perform calculations for an anchor if the embedment depth or concrete thickness are outside the limits noted above .
The figure below illustrates how A Nc0 is calculated .
A Nc0
= ( 1.5h ef + 1.5h ef
) ( 1.5h ef + 1.5h ef
)
= ( 9.0h ef
) 2
Reference the Variables section of the PROFIS Engineering report for more information on h ef
.
Reference the Equations section of the PROFIS Engineering report for more information on A Nc0
.
67 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions