PART 3 TENSION LOAD
Sustained Tension Load — Bond Strength
Results N ba
Results ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
N ba
= λ a т cr π da h ef
17.3.1.2 For the design of adhesive anchors to resist sustained tension loads , in addition to 17.3.1.1 , Eq . ( 17.3.1.2 ) shall be satisfied .
0.55 ϕN ba ≥ N ua , s
( 17.3.1.2 )
Where N ba is determined in accordance with 17.4.5 . 2 . 17.4.5 . 2 The basic bond strength of a single adhesive anchor in tension in cracked concrete , N ba
, shall not exceed
N ba
= λ a т cr π da h ef
( 17.4.5 . 2 )
PROFIS Engineering parameters for calculating N ba :
N ba
= λ a т kxxx α N , seis πd a h ef
PROFIS Engineering calculations for N ba when used to calculate the sustained load parameter 0.55 ϕN ba
:
N ba
=
( λ a т xxxx α N , seis πd a h ef
) α N , seis
17.2.6 Modification factor λ a for lightweight concrete shall be taken as : Adhesive anchor bond failure per Eq . ( 17.4.5.2 ) ........................ 0.6 λ
where λ is determined in accordance with 19.2.4 . It shall be permitted to use an alternative value of λ a where tests have been performed and evaluated in accordance with ACI 355.2 or ACI 355.4 .
Example : Example of a table in an ICC-ESR showing the following parameters for calculating N ba
:
• т kcr and т k , uncr
— characteristic bond stress values
• α N , seis — seismic reduction value
• d a
— anchor element diameter
• h ef
— anchor effective embedment depth ICC-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 , max
|
in
( mm )
|
2-3 / 8
60
|
2-3 / 4
70
|
3-1 / 8
79
|
3-1 / 2
89
|
3-1 / 2
89
|
4
102
|
5
127
|
Maximum Embedment |
h ef , min
|
in
( mm )
|
7-1 / 2
( 191 )
|
10
( 254 )
|
12-1 / 2
( 318 )
|
15
( 381 )
|
17-1 / 5
( 445 )
|
20
( 508 )
|
25
( 635 )
|
Temperature Range A
Temperature Range B
Temperature Range C
Permissible Installation Conditions
Characteristic bond strength in cracked concrete
Characteristic bond strength in uncracked concrete
Characteristic bond strength in cracked concrete
Characteristic bond strength in uncracked concrete
Characteristic bond strength in cracked concrete
Characteristic bond strength in uncracked concrete
Dry and water saturated concrete
т k , cr
|
psi
( Mpa )
|
1045
( 7.2 )
|
1135
( 7.8 )
|
1170
( 8.1 )
|
1260
( 8.7 )
|
1290
( 8.9 )
|
1325
( 9.1 )
|
1380
( 9.5 )
|
т k , uncr
|
psi
( Mpa )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
т k , cr
|
psi
( Mpa )
|
1045
( 7.2 )
|
1135
( 7.8 )
|
1170
( 8.0 )
|
1260
( 8.67 )
|
1290
( 9.0 )
|
1325
( 9.0 )
|
1380
( 9.5 )
|
т k , uncr
|
psi
( Mpa )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
2220
( 15.3 )
|
т k , cr
|
psi
( Mpa )
|
855
( 5.0 )
|
930
( 6.4 )
|
960
( 6.6 )
|
1035
( 7.1 )
|
1055
( 7.3 )
|
1085
( 7.5 )
|
1130
( 7.8 )
|
t k , uncr
|
psi
( Mpa )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
1820
( 12.6 )
|
|
Anchor
Category
|
- |
|
|
|
1 |
|
|
|
ϕ d
, ϕ ws - 0.65
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 the “ basic bond strength ” for a single adhesive anchor element without any fixed edge or spacing influences . N ba is calculated per
Eq . 17.4.5.2 ; and is predicated on the following parameters :
• тxxxx — characteristic bond stress of the adhesive product ; designated in ACI 318-14 as “ т cr
” for cracked concrete conditions , and “ т uncr ” for uncracked concrete conditions
• πd a
— anchor element circumference based on the nominal diameter of the element
• h ef — effective embedment depth of the anchor
• λ a
— modification factor for lightweight concrete
Testing per the ICC-ES acceptance criteria AC308 and the ACI test standard ACI 355.4 is used to derive characteristic bond stress values ( т xxxx
) that are provided in an ICC-ESR . The parameter designated “ т k , cr
” in the report corresponds to the characteristic bond stress in cracked concrete , and the parameter designated “ т k , uncr
” in the report corresponds to the characteristic bond stress in uncracked concrete . PROFIS Engineering calculates N ba with the т k , cr and т k , uncr values given in the adhesive anchor ICC-ESR . The parameter “ α N , seis
” is a reduction factor derived from testing per the ICC-ES acceptance criteria AC308 . It is used to calculate N ba when seismic load conditions are assumed . Adhesive anchor systems can be shown compliance under the International Building Code ( IBC ) via testing per AC308 in conjunction with the ACI test standard ACI 355.4 , but ACI 355.4 does not include any provisions for determining α N , seis
. Since ACI 355.4 does not reference α N , seis , ACI
318-14 Eq . ( 17.4.5.2 ) does not reference α N , seis . Since AC308 includes provisions for determining α N , seis , adhesive anchor ICC-ESR derived from AC308 testing include α N , seis as a parameter for calculating N ba
. Therefore , PROFIS Engineering , which uses the adhesive anchor ICC-ESR data for calculating bond strength , likewise includes α N , seis as a parameter for calculating N ba
.
The provisions in Section 17.3.1.2 are relevant to sustained load conditions . Seismic loads are not considered sustained loads ; therefore , any seismic-specific parameters such as α N , seis do not need to be considered when calculating N ba per
Eq . ( 17.3.1.2 ). PROFIS Engineering divides out any α N , seis -value when calculating
N ba per Eq . ( 17.3.1.2 ).
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
λ a
:
т k , xxxx
:
d a
:
h ef
:
Lightweight concrete modification factor Characteristic bond stress Anchor element diameter Effective embedment depth
Reference the Equations and Calculations section of the PROFIS Engineering report for more information on the parameter N ba
.
153 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions