PART 4 SHEAR LOAD
Pryout Failure Mode ( Concrete Breakout )
Variables c a , min
Variables 318-14 Chapter 17 Provision Comments for PROFIS Engineering
c a , min
17.4 . 2.1 …….. A Nc is the projected concrete failure area of a single anchor or group of anchors that shall be approximated as the base of the rectilinear geometrical figure that results from projecting the failure surface outward 1.5h ef from the centerlines of the anchor , or in the case of a group of anchors , from a line through a row of adjacent anchors ……..
17.4.2.1 …….. A Nc0 is the projected concrete failure area of a single anchor with an edge distance greater than 1.5h ef .
A Nc0
= 9h ef
2
( 17.4.2.1c )
17.4 . 2 . 5 The modification factor for edge effects for single anchors or anchor groups loaded in tension , ψ ed , N
, shall be calculated as If c a , min
≥ 1.5h ef , then ψ ed , Na
= 1.0 ( 17.4.2.5a )
If c a , min < 1.5h ef
, then ψ ed , Na = 0.7 + 0.3 c a , min ( 17 . 4 . 2 . 5b )
1.5h ef
17.4 . 2.7 The modification factor for post-installed anchors designed for uncracked concrete in accordance with 17.4 . 2.6 without supplementary reinforcement to control splitting , ψ cp , N
, shall be calculated as follows using the critical distance c ac as defined in 17.7.6
If c a , min ≥ 1.5c ac
, then ψ cp , N = 1.0 ( 17.4.2.7a )
If c a , min < c ac
, then ψ cp , N = c a , min
( 17.4.2.7b ) c ac but ψ cp , N determined from Eq . ( 17.4.2.7b ) shall not be taken less than 1.5h ef
/ c ac , where the critical distance c ac is defined in 17.7.6 . 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 318-14 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 . 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 .
269 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions