PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Equation A Na
Equation 318-14 Chapter 17 Provision Comments for PROFIS Engineering
A Na
17.4.5.1 …….. A Na is the projected influence area of a single adhesive anchor or group of adhesive anchors that shall be approximated as a rectilinear area that projects outward a distance c Na from the centerline of the adhesive anchor , or in the case of a group of adhesive anchors , from a line through a row of adjacent adhesive anchors ……..
17.4.5.1 The nominal bond strength in tension , N a of a single adhesive anchor or N ag of a group of adhesive anchors , shall not exceed : ( a ) For a single adhesive anchor
( b ) For a group of adhesive anchors
N a
= A Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1a )
A Na0
N ag
= A Na ψ ec , Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1b )
A Na0
………………………………………………………
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter A Na is a modification factor that accounts for the area of influence assumed to develop in concrete when a shear load applied to a single anchor or a group of anchors creates a prying ( i . e . tension ) action on the anchor ( s ). 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 shear . The maximum projected distance from an anchor that is considered when calculating A Na is limited to the parameter
“ c Na
”. 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
2.0c Na
. The figure below illustrates how A Na is calculated for pryout when a shear load acts on a group of four anchors with fixed edge distances equal to c a1 and c a2 , and spacing parameters equal to s 1 and s 2
. Note that the maximum edge distance parameter used to calculate 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 .
A Na
= ( c a1 + s 1
+ c Na ) ( c a2
+ s 2 + c Na
) where : c a1 and c a2 are ≤ c Na s 1 and s 2 are ≤ 2.0c Na It is important to understand that “ A Na
” calculated for bond failure in tension is not necessarily the same as “ A Na
” calculated for concrete pryout failure in shear since the number of anchors in tension may not be the same as the number of anchors in shear .
Reference the Calculations section of the PROFIS Engineering report for more information on c Na and A Na
.
210 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions