PROFIS Design Guide - AC 318-19 July 2022 | Page 220

2.2 Pryout Failure Mode

Variables c _{a , min}

Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering

c _{a , min}

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 )

17.6 . 2.4.1 Modification factor for edge effects for single anchors or anchor groups loaded in tension , ψed , N , shall be determined by ( a ) or ( b ). c _{a , min} is defined as the “ minimum distance from the center of an anchor shaft to the edge of concrete .” When one or more fixed edges are modeled in PROFIS Engineering , the report will show the smallest fixed edge as “ c _{a , min}

” in the

Variables section . Excerpted ACI 318-19 anchoring-to-concrete provisions that include c _{a , min} 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 . Therefore , the parameter for c _{a , min} used to calculate concrete breakout in tension may be different from the parameter for c _{a , min} used to calculate concrete pryout in shear .

( a ) If c _{a , min} ≥ 1.5h _ef

, then ψ _{ed , N} = 1.0 ( 17.6.2.4.1a )

( b ) If c _{a , min} < 1.5h _ef

, then ψ _{ed , N} = 0.7 + 0.3 c a , min ( 17 . 6 . 2 . 4 . 1b )

1.5h _ef

17.6.2.6.1 Modification factor for post-installed anchors designed for uncracked concrete in accordance with 17.6.2.5 without supplementary reinforcement to control splitting , ψ _{cp , N}

, shall be determined by ( a ) or ( b ) using the critical distance c _ac as defined in 17.9.5 .

Reference the parameters A _Nc and A _Nc0 in the Equations section of the PROFIS Engineering report for more information on the following parameters :

c _a1

: distance from the center of an anchor shaft to the edge of concrete in one direction ( e . g . the x + direction ). For pryout calculations , c _a1 is the smallest fixed edge distance . c _a2

: distance from the center of an anchor shaft to the edge of concrete in a direction perpendicular to c _a1

( e . g . the y + direction ).

Reference the parameters ψ _{ed , N} and ψ _{cp , N} in the Equations and Calculations sections of the PROFIS Engineering report for more information on how c _{a , min} is used to calculate these parameters when considering pryout in shear .

( a ) If c _{a , min} ≥ c _ac

, then ψ _{cp , N} = 1.0 ( 17.6.2.6.1a )

220 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions