2.0 SHEAR
2.3 Steel Failure Mode
Calculations N ba
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
N ba
17.6.5 . 2.1 Basic bond strength of a single adhesive anchor in tension in cracked concrete , N ba , shall be calculated by Eq . ( 17.6.5.2.1 )
N ba
= λ a т cr πd a h ef
( 17.6.5.2.1 )
17.6.5.2.2 Characteristic bond stress , т cr
, shall be taken as the 5 percent fractile of results of tests performed and evaluated in accordance with ACI 355.4 .
17.6.5 . 2.3 If analysis indicates cracking at service load levels , adhesive anchors shall be qualified for use in cracked concrete in accordance with ACI 355.4 .
17.6.5 . 2.4 For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at service load levels , т uncr shall be permitted to be used in place of т cr in Eq . ( 17.6.5.2.1 ) and shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4 .
Example of a table in an ICC-ES evaluation report ( ESR ) showing characteristic bond stress values that can be used to calculate N ba
.
ICC-ES ESR-3187 Table 14
DESIGN INFORMATION Symbol Units
Nominal Rod Diameter ( in ). 3 / 8 1 / 2 5 / 8 3 / 4 7 / 8 1 1-1 / 4
Minimum Embedment h ef , min in 2-3 / 8 2-3 / 4 3-1 / 8 3-1 / 2 3-1 / 2 4 5 ( mm ) ( 60 ) ( 70 ) ( 79 ) ( 89 ) ( 89 ) ( 102 ) ( 127 )
Maximum Embedment h ef , max in 7-1 / 2 10 12-1 / 2 15 17-1 / 5 20 25 ( mm ) ( 191 ) ( 254 ) ( 318 ) ( 381 ) ( 445 ) ( 508 ) ( 635 )
Temperature Range A
Temperature Range B
Temperature Range C
Characteristic bond strength psi 1045 1135 1170 1260 1290 1325 1380 in cracked concrete т k , cr ( Mpa ) ( 7.2 ) ( 7.8 ) ( 8.1 ) ( 8.7 ) ( 8.9 ) ( 9.1 ) ( 9.5 )
Characteristic bond strength psi 2220 2220 2220 2220 2220 2220 2220 in uncracked concrete т k , uncr ( Mpa ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 )
Characteristic bond strength psi 1045 1135 1170 1260 1290 1325 1380 in cracked concrete т k , cr ( Mpa ) ( 7.20 ) ( 7.80 ) ( 8.00 ) ( 8.67 ) ( 9.00 ) ( 9.00 ) ( 9.50 )
Characteristic bond strength psi 2220 2220 2220 2220 2220 2220 2220 in uncracked concrete т k , uncr ( Mpa ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 )
Characteristic bond strength psi 855 930 960 1035 1055 1085 1130 in cracked concrete т k , cr ( Mpa ) ( 5.9 ) ( 6.4 ) ( 6.6 ) ( 7.1 ) ( 7.3 ) ( 7.5 ) ( 7.8 )
Characteristic bond strength psi 1820 1820 1820 1820 1820 1820 1820 in uncracked concrete т k , uncr ( Mpa ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 )
Reduction for Seismic Tension α N , seis - 0.88 1.0 1.0 1.0 1.0 0.97 1.0
The parameter N ba corresponds to a calculated bond strength for a single adhesive anchor element without any fixed edge or spacing influences . Calculation of N ba is predicated on the characteristic bond stress of the adhesive product ( т cr or т uncr
), and the anchor element geometry ( πd a and h ef
), where d a corresponds to the nominal diameter of the anchor element and h ef corresponds to the effective embedment depth that has been input into PROFIS Engineering for the selected anchor element . Equation ( 17.6.5.2.1 ) also includes a modification factor for lightweight concrete ( λ a
).
PROFIS Engineering defaults to a design assumption that cracked concrete conditions exist . If cracked concrete conditions are assumed , PROFIS Engineering uses the characteristic bond stress for cracked concrete ( т cr
) to calculate N ba
. If uncracked concrete conditions are assumed , PROFIS Engineering uses the characteristic bond stress for uncracked concrete ( т uncr
) to calculate N ba .
PROFIS Engineering uses the characteristic bond stress values derived from testing per the ICC-ES acceptance criteria AC308 and the ACI test standard ACI 355.4 to calculate N ba
. Values are provided in an ICC-ES evaluation report ( ESR ) and are designated “ т k , cr
”, corresponding to the characteristic bond stress in cracked concrete , and “ т k , uncr
”, corresponding to the characteristic bond stress in uncracked concrete . PROFIS Engineering uses the т k , cr and т k , uncr values given in the ICC-ES evaluation report for the adhesive anchor that has been selected to calculate N ba
. Although noted in the ESR as a “ strength ”, т k , cr and т k , uncr are stress parameters having units of psi . The parameter “ α N , seis
” is a seismic reduction factor derived from testing per AC308 / ACI 354 , and is also given in the anchor ESR . The PROFIS Engineering report includes α N , seis as a parameter used to calculate N ba
.
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
λ a
: lightweight concrete modification factor .
т k , xxxx
: characteristic bond stress for cracked or uncracked concrete .
α N , seis
: seismic modification factor .
d a
: anchor element diameter .
h ef
: effective embedment depth that has been selected for the anchor being modeled .
Reference the Equations section of the PROFIS Engineering report for more information on the parameter N ba
.
276 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions