PROFIS Design Guide - AC 318-19 July 2022 | Page 59

1.2 Concrete Breakout 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 , ψ _{ed , N}

, shall be determined by ( a ) or ( b ).

( 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 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 and equations that include c _{a , min} for calculating concrete breakout strength in tension are shown to the left . 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 tension 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 ca1 ( 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 ca , min is used to calculate these parameters .

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 .

( a ) If c _{a , min} ≥ c _ac

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

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