2.0 SHEAR
2.3 Steel Failure Mode
Variables c ac
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
c ac
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 c ac 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
≥ c Na ( 17 . 6 . 5 . 5 . 1b )
c ac
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 Undercut Adhesive
Critical edge distance c ac 4 h ef 4 h ef 4 h ef 2.5 h ef
Example of critical edge distance requirements given in an adhesive anchor approval . Reference ICC-ES ESR-3187 Section 4.1.10.2 .
4.1.10.2 Threaded Rod , Steel Reinforcing Bars , and Hilti HIS-N and HIS-RN Inserts : The modification factor ψ cp , Na must be determined in accordance with ACI 318-14 17.4.5.5 or ACI 318-11 D . 5.5 as applicable , except as noted below .
For all cases where c Na / c ac
< 1.0 , ψ cp , Na determined from ACI 318-14 Eq . 17.4.5.5b or ACI 318-11 Eq . D-27 , as applicable , need not be taken less than c Na
/ c ac . For all other cases ψ cp , Na shall be taken as
1.0 .
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
2 h ef
0.4
⁎ 3.1 – 0.7 h 1160 h ef ψ cp , Na is a modification factor that considers splitting failure for an adhesive anchor when calculating the nominal concrete pryout strength in shear ( V cp or V cpg ). ψ cp , Na is only considered when designing adhesive anchors installed in uncracked concrete . Concrete cracks when tensile stresses in the concrete imposed by loads or restraint conditions exceed its tensile strength . ACI 318 anchoring-to-concrete provisions assume cracked concrete as the baseline condition for designing anchors . Uncracked concrete conditions can be assumed if it can be shown that cracking of the concrete at service load levels will not occur over the anchor service life . PROFIS Engineering defaults to cracked concrete conditions .
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 c ac 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 .” Nominal concrete breakout strength in tension ( N cb or N cbg ) and nominal bond strength ( N a or N ag
) are considered when calculating nominal pryout strength in shear . Calculation of nominal bond strength includes the parameter ψ cp , Na when uncracked concrete conditions are assumed . Therefore , the parameter c ac is also relevant to pryout calculations when uncracked 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 for adhesive anchor systems is calculated using the effective embedment depth ( h ef
), and characteristic bond stress in uncracked concrete ( т k , uncr ).
The c ac
-values for post-installed anchors noted in ACI 318-19 Section 17.9.5 are only intended to be used as “ guide values ” in the absence of c ac values derived from product-specific testing . PROFIS Engineering always uses the c ac
-value that is given ( mechanical anchor ) or calculated ( adhesive anchor system ) in the ICC-ES evaluation report for the anchor .
Reference the Equations and Calculations sections of the PROFIS Engineering report for more information on the parameter ψ cp , Na
.
Reference the Variables section of the PROFIS Engineering report for more information on the parameter h ef
.
Reference the Variables section of the PROFIS Engineering report for more information on the parameter т k , uncr
.
( Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 ) where h
h ef
need not be taken as larger than 2.4 ; and is the characteristic bond strength in uncracked concrete , h is the member thickness , and h ef is the embedment depth . т k , uncr need not be taken greater than : т k , uncr
= k uncr h ef ƒ ́c Eq . ( 4-1 ) π d
263 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions