PART 3 TENSION LOAD
Concrete Breakout Failure Mode
Variables e c2 , N
Variables ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
e c2 , N
17.4.2.4 The modification factor for anchor groups loaded eccentrically in tension , ψ ec , N shall be calculated as ψ ec , N
=
1
1 + 2e ́N
3h ef
( 17.4.2.4 ) but ψ ec , N shall not be taken greater than 1.0 . If the loading on an anchor group is such that only some anchors are in tension , only those anchors that are in tension shall be considered when determining the eccentricity e ́N for use in Eq . ( 17.4.2.4 ) and for the calculation of N cbg according to
Eq . ( 17.4.2.1b ). In the case where eccentric loading exists about two axes , the modification factor , ψ ec , N
, shall be calculated for each axis individually and the product of these factors used as ψ ec , N in Eq . ( 17.4.2.1b ). e c2 , N is a PROFIS Engineering parameter to define tension eccentricity with respect to the y direction . The value for e c2 , N corresponds the distance in the y direction of a resultant tension load from the centroid of anchors that are loaded in tension . PROFIS Engineering uses e c2 , N to calculate the ACI 318 modification factor for tension eccentricity ( ψ ec , N ), and designates this modification factor ψ ec2 , N to indicate eccentricity is being considered in the y direction . PROFIS Engineering calculations for tension eccentricity with respect to the y direction are as follows :
• Calculate a resultant tension load acting on the anchors
• Calculate the distance in the y direction ( e c2 , N
) between this load and the centroid of the anchors loaded in tension
• Calculate a modification factor for tension eccentricity ( ψ ec2 , N ) with respect to the y direction
If the resultant tension load acting on the anchorage is eccentric with respect to both the x and y directions ; PROFIS Engineering calculates the eccentricity for each direction ( e c1 , N with respect to the x direction and e c2 , N with respect to the y direction ), and the ψ ec , N modification factor for each direction ( ψ ec1 , N for eccentricity with respect to the x direction and ψ ec2 , N for eccentricity with respect to the y direction ). ψ ec1 , N and ψ ec2 , N are multiplied together to give a total modification factor for eccentricity per ACI 318-14 Section 17.4.2.4
Reference the Variables section of the PROFIS Engineering report for more information on :
e c1 , N
: Parameter for tension eccentricity with respect to the x direction
Below is an illustration showing how PROFIS Engineering accounts for eccentricity with respect to the y direction when calculating concrete breakout strength in tension . ψ ec2 , Na
=
1
1 + ( 2 ) ( 1 . 67 ”) = 0.86 ( 3 ) ( 7.0 ”)
58 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions