PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Variables т k , c
Variables 318-14 Chapter 17 Provision Comments for PROFIS Engineering
т k , c
17.4.5 . 2 The basic bond strength of a single adhesive anchor in tension in cracked concrete , N ba
, shall not exceed 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 cr
” corresponds to the characteristic bond stress in cracked concrete . If cracked concrete conditions are assumed , т cr is 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 . N ba can be calculated for either cracked or uncracked concrete conditions . PROFIS Engineering calculates 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 cr
“ as “ т k , cr ” and the
PROFIS Engineering report designates “ т cr “ as “ т k , c
”.
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 , cr
” in the ICC-ESR correspond to the characteristic bond stress in cracked concrete . The values designated ” т cr
“ 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 cracked concrete conditions are assumed , PROFIS Engineering uses the
т k , cr values given in the ICC-ESR for adhesive anchor bond strength calculations . Although noted in the ICC-ESR as a “ strength ”, т k , cr is stress parameter having units of psi .
т k , cr
-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 , cr
-values by this factor when concrete compressive strengths > 2500 psi are being modeled .
т k , cr
-values in the ICC-ESR are also dependent on the “ temperature range ” corresponding to “ long term ” and “ short term ” concrete temperatures . The ICC-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 ICC-ESR .
т k , cr
-values corresponding to a particular temperature range are given in the bond strength table .
Reference the Variables section of the PROFIS Engineering report for more information on :
т k , c , uncr
: Characteristic bond stress in uncracked concrete
Reference the Calculations section of the PROFIS Engineering report for more information on :
N ba
: Basic bond strength for a single adhesive anchor
221 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions