PROFIS ENGINEERING REPORT TENSION LOAD
Bond Failure Mode
Variables т k , c , uncr
Variables ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
т k , c , uncr
17.4 . 5.1 ………………………….. where
and the constant 1100 carries the unit of lb / in 2 .
c Na
= 10d a т uncr ( 17 . 4 . 5 . 1d ) 1100
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 )
The characteristic bond stress т cr shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4 .
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 . ( 17.4.5.2 ) and shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4 .
It shall be permitted to use the minimum characteristic bond stress values in Table 17.4.5.2 provided ( a ) through ( e ) are satisfied : ( a ) Anchors shall meet the requirements of ACI 355.4 ( b ) Anchors shall be installed in holes drilled with a rotary impact drill or rock drill ( c ) Concrete at time of anchor installation shall have a minimum compressive strength of 2500 psi ( d ) Concrete at time of anchor installation shall have a minimum age of 21 days ( e ) Concrete temperature at time of installation shall be at least 50 ° F
Table 17.4.5.2 — Minimum characteristic bond stresses [ 1 ] [ 2 ]
Installation and service environment
Moisture content of concrete at time of anchor installation
Peak in-service temperature of concrete ° F
Outdoor Dry to fully saturated 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 . т cr psi т uncr psi
The parameter “ т uncr
” corresponds to the characteristic bond stress in uncracked concrete . It is used to calculate the parameter “ c Na
”, which is defined in ACI 318- 14 Equation ( 17.4.5.1d ). If uncracked concrete conditions are assumed , т uncr is also used to calculate the parameter “ N ba
”, which is defined in ACI 318-14 Equation
( 17.4.5.2 ).
ACI 318 anchoring-to-concrete provisions default to a design assumption that cracked concrete conditions exist ; however , c Na is always calculated using т uncr regardless of whether cracked or uncracked concrete conditions are assumed .
N ba can be calculated for either cracked or uncracked concrete conditions . PROFIS Engineering calculates c Na and N ba using the characteristic bond stress values given in the ICC-ESR for the adhesive anchor system . The ICC-ESR designates the ACI 318 parameter “ т uncr
” as “ т k , uncr ” and the PROFIS Engineering report designates “ т uncr ” as “ т k , c , uncr
”.
Testing per the ICC-ES acceptance criteria AC308 and the ACI test standard ACI 355.4 is used to derive characteristic bond stress values for adhesive anchor systems . Values derived from this testing are provided in an ICC-ESR . Values designated “ т k , uncr
” in the ICC-ESR correspond to the characteristic bond stress in uncracked concrete . The values designated “ т uncr
” in ACI 318-14 Table 17.4.5.2 are intended to be used as guide values in the absence of product-specific data . When uncracked concrete conditions are assumed , PROFIS Engineering uses the
т k , uncr values given in the ICC-ESR for adhesive anchor bond strength calculations . Although noted in the ICC-ESR as a “ strength ”, т k , uncr is stress parameter having units of psi .
т k , uncr
-values in the ICC-ESR are relevant to testing in concrete having a compressive strength of 2500 psi . These values can be increased for compressive strengths 2500 psi < f ́c < 8000 psi using the factor noted in the bond strength table footnotes . PROFIS Engineering increases the т k , uncr
-values by this factor when concrete compressive strengths > 2500 psi are being modeled .
18 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions