2.0 SHEAR
2.2 Pryout Failure Mode
Variables k cp
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
k cp
17.7.3.1 Nominal pryout strength , V cp for a single anchor or V cpg of an anchor group satisfying
17.5.1.3.1 , shall not exceed ( a ) or ( b ), respectively . ( a ) For a single anchor
( b ) For an anchor group
V cp
= k cp
N cp
( 17.7.3.1a )
V cpg
= k cp
N cpg
( 17.7.3.1b )
The parameter “ k cp
” is defined in ACI 318-19 as the “ coefficient for pryout strength ”. The commentary R17.7.3.1 states : “……………………… the pryout shear resistance can be approximated as one to two times the anchor tensile resistance with the lower value appropriate for h ef less than 2.5 in .”
PROFIS Engineering applies k cp per Section 17.7.3.1 for the cast-in anchors and post-installed anchors in its portfolio . where
k cp
= 1.0 for h ef < 2.5 in . k cp
= 2.0 for h ef ≥ 2.5 in .
Variables h ef
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
h ef
17.6.2.1.1 A Nc is the projected concrete failure area of a single anchor or of an anchor group that is approximated as the base of the rectilinear geometrical shape that results from projecting the failure surface outward 1.5h ef from the centerlines of the anchor , or in the case of an anchor group , from a line through a row of adjacent anchors . A Nc shall not exceed nA Nc0
, where n is the number of anchors in the group that resist tension .
17.6 . 2.1.4 A Nc0 is the projected concrete failure area of a single anchor with an edge distance of at least 1.5h ef and shall be calculated by Eq . ( 17.6.2.1.4 ).
A Nc0
= 9h ef
2
( 17.6.2.1.4 ) h ef is defined as the “ effective embedment depth of an anchor ”. This parameter corresponds to the embedded portion of the anchor that is “ effective ” in transferring tension load from the anchor into the concrete . Excerpted ACI 318-19 anchoring-to-concrete provisions that include h ef for calculating concrete breakout strength in tension are shown to the left . These provisions are also used to calculate concrete pryout strength in shear . It is important to understand that the calculated value for some of the parameters defined in these provisions will be dependent on whether concrete breakout failure in tension is being considered or concrete pryout failure in shear is being considered since the number of anchors in tension may be different from the number of anchors in shear . However , the parameter h ef will not change when used in these provisions to calculate either concrete breakout in tension or concrete pryout in shear .
17.6.2.3.1 Modification factor for anchor groups loaded eccentrically in tension , ψ ec , N shall be calculated by Eq . ( 17.6.2.3.1 ).
For cast-in-place anchors , PROFIS Engineering permits users to input h ef values ranging between 4d anchor and 25 ”.
|
ψ ec , N
=
|
1 |
( 17.6.2.3.1 ) |
cast-in-place headed studs |
|
1 + e ́N
1.5h ef
|
|
|
216 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions