1.0 TENSION
1.1 Bond Failure Mode
Calculations A Na
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
A Na
17.6.5.1.1 ……… A Na is the projected influence area of a single adhesive anchor or an adhesive anchor group that is approximated as a rectilinear area that projects outward a distance c Na from the centerline of the adhesive anchor , or in the case of an adhesive anchor group , from a line through a row of adjacent adhesive anchors ……..…….
17.6.5.1.2 ……………………… where c Na
= 10d a т uncr ( 17 . 6 . 5 . 1 . 2b ) 1100
A Na is a modification factor that accounts for the area of influence assumed to develop in concrete , with respect to bond failure , when a tension load is applied to a single adhesive anchor or a group of adhesive anchors . A Na is calculated with the edge conditions and anchor spacing that have been input into the PROFIS Engineering model . The geometry for A Na is defined by projected distances from the anchors that are in tension . The maximum projected distance from an anchor that is considered when calculating A Na is limited to c Na , where c Na is defined by Equation ( 17.6.5.1.2b ) in Section 17.6.5.1.2 . Therefore , the maximum edge distance parameter used to calculate A Na equals c Na , and the maximum spacing parameter used to calculate A Na equals a projected distance of c Na on either side of the anchor ; or 2.0c Na .
Example of minimum edge distance and spacing requirements given in an adhesive anchor system approval .
ICC-ES ESR-3187 Table 12
DESIGN INFORMATION
Symbol Units
3 / 8 or # 3
1 / 2 or # 4
Nominal Rod Diameter ( in ).
5 / 8 or # 5
3 / 4 or # 6
7 / 8 or # 7
1 or # 8
# 9
1-14 or # 10
Min . anchor spacing s min in . 1-7 / 8 2-1 / 2 3-1 / 8 3-3 / 4 4-3 / 8 5 5-5 / 8 6-1 / 4
Min . edge distance ( Threaded rods )
Min . edige distance ( Reinforcing bars ) c min in . 1-3 / 4 1-3 / 4 2 2-1 / 8 2-1 / 4 2-3 / 4 n / a 3 1 / 8 c min
-
5d ; or see Section 4.1.9.2 of this report for design with reduced minimum edge distances
The figure below illustrates how A Na is calculated for a group of four anchors in tension with fixed edge distances in the -x and + y directions equal to c a1 and c a2 , respectively ; and spacing parameters in the x and y directions equal to s 1 and s 2
, respectively . Both c a1 and c a2 are assumed to be less than the value for c Na calculated per Equation ( 17.6.5.1.2b ). When modeling the parameter A Na
, if no fixed edge is present for a given direction , or the fixed edge distance is greater than the value calculated for c Na
, the maximum projected distance from an anchor ( s ) with respect to that direction is assumed to equal c Na
. For the application illustrated below , there are no fixed edges in the + x and -y directions ; therefore , the maximum projected distance in those directions that is used to model A Na equals c Na
.
Since the maximum projected distance from an anchor that is considered when modeling A Na equals c Na , anchors spaced greater than 2.0c Na from one another would not be considered to act as a group with respect to that spacing . For the illustration below , both s 1 and s 2 are assumed to be less than 2.0c Na
.
A Na
= ( c a1 + s 1
+ c Na ) ( c a2
+ s 2 + c Na
) where : c min ≤ ( c a1 and c a2 ) ≤ c Na s min
≤ ( s 1 and s 2
) ≤ 2.0c Na
Adhesive anchor values for c min and s min are established via testing per the ICC-ES acceptance criteria AC308 , and the ACI test standard ACI 355.4 . These values are given in the ICC-ES evaluation report ( ESR ) for the adhesive anchor system .
Reference the Equations more information on A Na
. Reference the Calculations section for more information on c Na
.
32 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions