PROFIS Design Guide: US-EN Summer 2021 | Page 228

Pryout Failure Mode ( Pryout Bond )

Variables c _ac

Variables 318-14 Chapter 17 Provision Comments for PROFIS Engineering

c _ac

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 ψcp , Na determined from Eq . ( 17.4.5.5b ) shall not be taken less than c _Na / c _ac

, where the critical distance cac 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 355.2 or ACI 355.4 , the critical edge distance c _ac shall not be taken less than : Adhesive anchors ............................................... 2h _ef Undercut anchors ............................................... 2.5h _ef Torque-controlled expansion anchors ............................... 4h _ef Displacement-controlled expansion anchor .......................... 4h _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 these strengths 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 318-14 Section 17.7.6 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}

.

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