PART 3 TENSION LOAD
Concrete Breakout Failure Mode
Variables h ef
Variables ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
h ef
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 equal to or greater than 1.5h ef
.
A Nc0
= 9h ef
2
( 17.4.2.1c ) 17.4.2.4 The modification factor for anchor groups loaded eccentrically in tension , ψ ec , N shall be calculated as
h ef is defined as the “ effective embedment depth of an anchor ”. This parameter corresponds to the embedded portion of the anchor that is “ effective ” in transferring tension load from the anchor into the concrete . Excerpted ACI 318-14 anchoring-to-concrete provisions and equations that include hef for calculating concrete breakout strength in tension are shown to the left .
For cast-in-place anchors , PROFIS Engineering permits users to input h ef values ranging between 4d anchor and 25 ”. cast-in-place headed studs
4d anchor
< h ef < 25 ” ψ ec , N
=
1
1 + 2e ́N
3h ef
( 17.4.2.4 )
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 , N
= 1.0 ( 17.4.2.5a )
cast-in-place headed bolts
4d anchor
< h ef < 25 ”
If c a , min < 1.5h ef
, then ψ ed , N = 1.0 c a , min ( 17 . 4 . 2 . 5a )
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 cac as defined in 17.7.6
c Na
If c a , min ≥ c ac
, then ψ cp , N = 1.0 ( 17.4.2.7a )
For post-installed mechanical anchors , PROFIS Engineering permits users to input specific h ef values that are relative to a specific diameter as given in the ICC-ES evaluation report for the anchor .
post-installed expansion anchor ( reference product approval for h ef
)
|
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 .
17.4.2.2 The basic concrete breakout strength of a single anchor in tension in cracked concrete , N b , shall not exceed
N b
= λ a k c f ́c h ef
1.5
( 17.4.2.2a )
Alternatively , for cast-in headed studs and headed bolts with 11 in . < h ef
< 25 in ., N b , shall not exceed
N b
= 16λ a f ́c h ef
5 / 3
( 17.4.2.2b )
For post-installed adhesive anchors , PROFIS Engineering permits users to input a range of h ef values that are relative to a specific diameter as given in the ICC-ES evaluation report for the anchor .
post-installed adhesive anchor
h ef , min
< h ef
< h ef , max ( reference product approval for h ef , min and h ef , max
)
56 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions