2.0 SHEAR
2.3 Steel Failure Mode
Calculations ψ cp , Na
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
ψ cp , Na
17.6.5.5.1 Modification factor for adhesive anchors designed for uncracked concrete in accordance with 17.6.5.1 without supplementary reinforcement to control splitting , ψ cp , Na
, shall be determined by ( a ) or ( b ) where cac is defined in 17.9.5 .
( a ) If c a , min ≥ c ac
, then ψ cp , Na = 1.0 ( 17.6.5.5.1a )
( b ) If c a , min < c ac
, then ψ cp , Na = c a , min
17.6.5.5.2 For all other cases , ψ cp , Na shall be taken as 1.0 .
c ac
17.6.5.1.2 ………………………………….. where
≥ c Na ( 17 . 6 . 5 . 5 . 1b )
c ac c Na
= 10d a т uncr ( 17 . 6 . 5 . 1 . 2b ) 1100
17.6.5 . 2.4 For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at service load levels …………….
17.9.5 Critical edge distance cac shall be in accordance with Table 17.9.5 unless determined from tension tests in accordance with ACI 355.2 or ACI 355.4 .
Table 17.9.5 – Critical edge distance Post-installed anchor type Torque-controlled Displacement-controlled Screw
Critical edge distance c ac 4 h ef 4 h ef 4 h ef
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter ψ cp , Na is a modification factor that considers splitting failure for an adhesive anchor . Since ACI 318 anchoring-to-concrete provisions do not specifically consider concrete splitting as a failure mode , splitting is addressed through the ψ cp , Na modification factor . The parameter ψ cp , Na is only considered when designing adhesive anchors installed in uncracked concrete .
Splitting failure is influenced by the distance of an anchor from a fixed edge “ in a region of a concrete member where analysis indicates no cracking at service load levels ”. The parameter cac that is used to calculate ψ cp , Na is defined in ACI 318 as the “ critical edge distance required to develop the basic strength as controlled by concrete breakout or bond of a post-installed anchor in tension in uncracked concrete without supplementary reinforcement to control splitting .” ψ cp , Na does not need to be calculated if the smallest fixed edge distance ( c a , min ) is greater than or equal to c ac
, or if cracked concrete conditions are assumed . Testing per the ICC-ES acceptance criteria AC308 and the ACI test standard ACI 355.4 is used to derive c ac values for adhesive anchor systems . c ac values derived from this testing are provided in an ICC-ES evaluation report ( ESR ). ACI 318-19 Table 17.9.5 provides a c ac
-value for adhesive anchors ; however , this value is only intended to be used as a “ guide value ” in the absence of a c ac
-value derived from productspecific testing . PROFIS Engineering uses the c ac
-value that is given in the ICC-ES evaluation report for an adhesive anchor to calculate ψ cp , Na
.
The value for ψ cp , Na that PROFIS Engineering calculates will be limited to MAXIMUM { c a , min
/ c ac : c Na
/ c ac } where c a , min is the smallest fixed edge distance being modeled in the application and c Na is the adhesive anchor edge distance parameter calculated per Eq . ( 17.6.5.1.2b ) for the adhesive anchor being modeled .
It is important to understand that “ ψ cp , Na ” calculated for bond failure in tension is not necessarily the same as “ ψ cp , 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 .
Undercut Adhesive
2.5 h ef 2 h ef
Reference the Equations section of the PROFIS Engineering report for more information on ψ cp , Na
.
Example of critical edge distance requirements given in an adhesive anchor approval . Reference ICC-ES ESR-3187 Section 4.1.10.2 .
The critical edge distance cac must be calculated according to Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 , in lieu of ACI 318-14 17.7.6 or ACI 318-11 D . 8.6 as applicable .
c ac
= h ef т k , uncr
0.4
⁎ 3.1 – 0.7 h 1160 h ef
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
c a , min
: the smallest fixed edge distance being modeled .
c ac
: value derived from testing per AC308 / ACI 355.4 for the adhesive anchor being modeled .
Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
c Na
: edge distance parameter for adhesive anchors .
( Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 )
275 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions