1.0 TENSION
1.3 Pullout Failure Mode
Calculations ( f ́c / 2500 ) n
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
( f ́c / 2500 ) n 17.6.3.1 Nominal pullout strength of a single cast-in anchor , or a single post-installed expansion , screw , or undercut anchor in tension , N pn
, shall be calculated by :
17.6.3.2 Basic single anchor pullout strength , N p .
N pn
= ψ c , p
N p
( 17.6.3.1 ) ………………………………………….
17.6.3.2.1 For post-installed expansion , screw or undercut anchors , the values of N p shall be based on the 5 percent fractile of results of tests performed and evaluated according to ACI 355.2 . It is not permissible to calculate the pullout strength in tension for such anchors .
PROFIS Engineering calculates nominal pullout strength in tension ( N pn
) per ACI 318-19 Eq . ( 17.6.3.1 ). For mechanical anchors , the Equations and Results section of the report designate N pn as “ N pn , f ́c ”. Nominal pullout strength is calculated with the parameter “ N p
” which is defined in ACI 318-19 Chapter 2 as the pullout strength in tension of a single anchor in cracked concrete .
Mechanical anchor N p
-values derived from testing per the ICC-ES acceptance criteria AC193 in conjunction with the ACI standard ACI 355.2 ( a ) are provided in an ICC-ES evaluation report ( ESR ), ( b ) are specific to the concrete condition ( cracked or uncracked ), and ( c ) are specific to anchor diameter ( d a
) and effective embedment depth ( h ef ). PROFIS Engineering uses these N p
-values to calculate the nominal pullout strength for a mechanical anchor .
PROFIS Engineering uses this equation to calculate a nominal pullout strength for mechanical anchors :
N pn , f ́c
= N p , 2500 λ a
( ƒ ́c / 2500 ) n
Excerpt from ESR-1917 for the Hilti Kwik Bolt-TZ ( KB-TZ ) expansion anchor referencing provisions for calculating nominal pullout strength in tension .
4.1.4 Requirements for Static Pullout Strength in Tension : The nominal pullout strength of a single anchor in accordance with ACI 318-14 17.4.3.1 and 17.4.3.2 or ACI 318-11 D . 5.3.1 and D . 5.3.2 , respectively , as applicable , in cracked and uncracked concrete ,
N p , cr and N p , uncr , respectively , is given in Tables 3 and 4 . For all design cases , ψ c , p
= 1.0 . In accordance with ACI 318-14 17.4.3 or ACI 318-11 D . 5.3 , as applicable , the nominal pullout strength in cracked concrete may be calculated in accordance with the following equation :
N p , f ́c
= N p , cr ƒ ́c ( Eq-1 ) 2500
In regions where analysis indicates no cracking in accordance with ACI 318-14 17.4.3.6 or ACI 318-11 D . 5.3.6 , as applicable , the nominal pullout strength in tension may be calculated in accordance with the following equation :
N p , f ́c
= N p , uncr ƒ ́c ( Eq-2 ) 2500
Where values for N p , cr or N p , uncr are not provided in Table 3 or Table 4 , the pullout strength in tension need not be evaluated .
N p
-values in the ESR are derived from testing in 2500 psi concrete ; therefore , the Variables section of the PROFIS Engineering report designates the N p
-value from the ESR as “ N p , 2500 ”. The ESR provisions shown to the left illustrate how the N p
-value given in the ESR design tables ( derived from testing in 2500 psi concrete ) can be increased for design purposes when the concrete compressive strength ( ƒ ́c ) for the application is greater than 2500 psi . Generally speaking , the factor by which “ N p , 2500
” can be increased equals ( ƒ ́c / 2500 ) 0 . 5 ; however , the parameter ( ƒ ́c / 2500 ) may be raised to another power . Reference Section 4.1.4 of the mechanical anchor ESR for specific information about this factor . PROFIS Engineering multiplies “ N p , 2500
” by ( ƒ ́c / 2500 ) n when calculating nominal pullout strength for a mechanical anchor . The calculated value for ( ƒ ́c / 2500 ) n is shown in the Calculations section of the mechanical anchor report . If pullout is not a possible controlling failure mode for a particular anchor diameter and embedment depth , the ESR will show “ NA ”, and no N p
-value will be given . PROFIS Engineering does not perform pullout calculations for anchor diameters / embedment ’ s for which “ NA ” is given in the ESR .
Reference the Variables section of the report for more information on the following parameters :
• N p , 2500 — tested pullout value in 2500 psi concrete .
• λ a
— lightweight concrete modification factor .
• ƒ ́c — concrete compressive strength .
Reference the Results section of the report for more information on the parameter
N pn , ƒ ́c
.
When modeling cast-in anchors , PROFIS Engineering calculates nominal the pullout strength in tension ( N pn
) per ACI 318-19 Eq . ( 17.6.3.1 ), and the parameter
N p per ACI 318-19 Eq . ( 17.6.3.2.2a ). Reference the cast-in anchor report sections relevant to pullout strength in tension for more information .
93 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions