1.0 TENSION
1.6 Sustained Load Failure Mode
Variables т k , c
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
т k , c
17.5.2.2 Design of adhesive anchors to resist sustained tension shall satisfy Eq . ( 17.5.2.2 ) 0.55 ϕN ba
≥ N ua , s ( 17.5.2.2 ) where N ba is the basic bond strength in tension of a single adhesive anchor and is N ua , s the factored sustained tensile load .
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 π da h ef
( 17.6.5.2.1 )
Table 17.6.5.2.5 — Minimum characteristic bond stresses [ 1 ] [ 2 ]
Installation and service environment
Outdoor
Moisture content of concrete at time of anchor installation
Dry to fully saturated
Peak in-service temperature of concrete ° F т cr psi т uncr psi
175 200 650
Indoor Dry 110 300 1000 [ 1 ] Where anchor design includes sustained tension loading , multiply values of т cr and т uncr by 0.4 . [ 2 ] Where design includes earthquake loads for structures assigned to SDC C , D , E , or F , multiply values of т cr by 0.8 and т uncr by
0.4 .
Example of a bond strength table in an ICC-ES evaluation report ( ESR ) showing characteristic bond stress values ( т k , cr and т k , uncr ).
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 2
Temperature Range B 2
Temperature
Range C 2
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 т k , cr psi 1045 1135 1170 1260 1290 1325 1380 ( Mpa ) ( 7.2 ) ( 7.8 ) ( 8.1 ) ( 8.7 ) ( 8.9 ) ( 9.1 ) ( 9.5 ) т k , uncr psi 2220 2220 2220 2220 2220 2220 2220 ( Mpa ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) т k , cr psi 1045 1135 1170 1260 1290 1325 1380 ( Mpa ) ( 7.20 ) ( 7.80 ) ( 8.00 ) ( 8.67 ) ( 9.00 ) ( 9.00 ) ( 9.50 ) т k , uncr psi 2220 2220 2220 2220 2220 2220 2220 ( Mpa ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) ( 15.3 ) т k , cr psi 855 930 960 1035 1055 1085 1130 ( Mpa ) ( 5.9 ) ( 6.4 ) ( 6.6 ) ( 7.1 ) ( 7.3 ) ( 7.5 ) ( 7.8 ) т k , uncr psi 1820 1820 1820 1820 1820 1820 1820 ( Mpa ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 ) ( 12.6 )
The parameter “ т k , c
” shown in the PROFIS Engineering report section for sustained tension load corresponds to the characteristic bond stress in either cracked or uncracked concrete . It is used to calculate the parameter “ N ba
”, which is given in ACI 318-19 Equation ( 17.5.2.2 ), and defined in Equation ( 17.6.5.2.1 ).
ACI 318 anchoring-to-concrete provisions default to a design assumption that cracked concrete conditions exist ; however , N ba can be calculated for either cracked or uncracked concrete conditions . PROFIS Engineering users can select either “ cracked ” or “ uncracked ” conditions when modeling an adhesive anchor system for sustained tension load . PROFIS Engineering calculates N ba using the characteristic bond stress corresponding to the concrete condition selected , as given in the ICC-ES evaluation report ( ESR ) for the adhesive anchor system . The ESR designates the ACI 318 parameter “ т uncr
“ as “ т k , uncr ”, and the ACI 318 parameter “ т cr ” as “ т k , cr
”. The PROFIS Engineering report section for sustained tension load designates the characteristic bond stress parameter as a generic “ т k , c
” for either cracked or uncracked conditions .
т-values given in the ESR are relevant to testing in concrete having a compressive strength of 2500 psi . These values can be increased for compressive strengths 2500 psi < ƒ ́c ≤ 8000 psi using the factor noted in the bond strength table footnotes . PROFIS Engineering increases the т-values for both cracked and uncracked concrete that are given in the ESR by this factor when concrete compressive strengths > 2500 psi are being modeled .
т-values in the ESR are also dependent on the “ temperature range ” corresponding to “ long term ” and “ short term ” concrete temperatures . The ESR defines “ long term ” concrete temperatures as being “ roughly constant ” over time . “ Short term ” concrete temperatures are elevated temperatures “ that occur over brief intervals ”. Both types of temperature are relevant to the concrete temperature during the service life of the anchor , not the concrete temperature at the time anchors are installed . Long term and short term temperature ranges are defined in footnotes for the bond strength tables of an adhesive anchor ESR . т-values corresponding to a particular temperature range are given in the bond strength table .
Reference the Variables section of the PROFIS Engineering report for Bond Strength for more information on :
т k , c , uncr
: characteristic bond stress in uncracked concrete
т k , c
: characteristic bond stress in cracked concrete
Reference the Calculations section of the PROFIS Engineering report for Sustained Tension Load — Bond Strength for more information on :
N ba
: basic bond strength for a single adhesive anchor
1 Bond strength values correspond to concrete compressive strength f ́c = 2500 psi . For concrete compressive strength , f ́c between 2500 psi and 8000 psi , the tabulated characteristic bond strength may be increased by a factor of ( f ́c / 2500 ) 0 . 1 .
2 Temperature range A : Maximum short term temperature = 130 ° F , Maximum long term temperature = 110 ° F Temperature range B : Maximum short term temperature = 176 ° F , Maximum long term temperature = 110 ° F . Temperature range C . Maximum short term temperature = 248 ° F , Maximum long term temperature = 162 ° F Short term elevated concrete temperatures are those that occur over brief intervals , e . g . as a result of diurnal cycling . Long term concrete temperatures are roughly constant over significant periods of time .
155 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions