PROFIS Design Guide: US-EN Summer 2021 | Page 243

Pryout Failure Mode ( Pryout Bond )

Calculations ψ _{cp , Na}

Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering

ψ _{cp , Na}

17.4.5.5 The modification factor for adhesive anchors designed for uncracked concrete in accordance with 17.4.5.2 without supplementary reinforcement to control splitting , ψ _{cp , Na}

, shall be calculated as : If c _{a , min}

≥ c _ac , then ψ _{cp , Na}

= 1.0 ( 17.4.5.5a )

but ψ _{cp , Na} determined from Eq . ( 17.4.5.5b ) shall not be taken less than c _Na

/ c _ac , where the critical distance c _ac is defined in 17.7.6 . For all other cases , ψ _{cp , Na} shall be taken as 1.0 .

17.4.5.1 ……………………………………………………………

and the constant 1100 carries the unit of lb / in ² .

c _Na

= 10d _a т uncr 17 . 4 . 5 . 1d 1100

17.4 . 2.6 For anchors located in a region of a concrete member where analysis indicates no cracking at service load levels ……………..

17.7.6 Unless determined from tension tests in accordance with …………….. ACI 355.4 , the critical edge distance c _ac shall not be taken less than : Adhesive anchors ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2h _ef

Example of critical edge distance requirements given in an adhesive anchor approval . Reference ICC-ESR-3187 Section 4.1.10.2 .

The critical edge distance c _ac 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

( Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 )

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 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 .” 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-ESR . ACI 318-14 Section 17.7.6 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 product-specific 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 . ( 17.4.5.1d ) 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 .

Reference the Equations section of the PROFIS Engineering report for more information on ψ _{cp , Na}

.

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

243 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions