PROFIS ENGINEERING REPORT TENSION LOAD
Bond Failure Mode
Calculations N ba
Calculations ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
N ba
= λ a т k , c α N , seis π da h ef
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 .
Where analysis indicates cracking at service load levels , adhesive anchors shall be shown compliance for use in cracked concrete in accordance with 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 .
Example : Example of a table in an ICC-ESR showing characteristic bond stress values ( т kcr and т k , uncr ) and the seismic reduction value α N , seis т cr psi т uncr psi
The parameter N ba corresponds to a calculated bond strength for a single adhesive anchor element without any fixed edge or spacing influences . It is used to calculate the nominal bond strength in tension ( N a or N ag ).
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 .
If cracked concrete conditions are being modeled , PROFIS Engineering uses the characteristic bond stress for cracked concrete ( т cr
) to calculate N ba
.
If uncracked concrete conditions are being modeled , PROFIS Engineering uses the characteristic bond stress for uncracked concrete ( т uncr
) to calculate N ba
.
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 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 . The values given in ACI 318-14 Table 17.4.5.2 for “ т cr
” or
” т uncr
” are intended to be used as guide values in the absence of product-specific data . PROFIS Engineering calculates N ba with the т k , cr and т k , uncr values given in the adhesive anchor ICC-ESR Although noted in the ICC-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 reduction factor derived from testing per AC308 / ACI 354 . It is used to calculate N ba when seismic load conditions are assumed . PROFIS Engineering uses the α N , seis
-values given in the adhesive anchor ICC-ESR to calculate N ba
. The parameter “ λ a
” is a lightweight concrete modification factor . Provisions for determining λ a are given in the adhesive anchor ICC-ESR . PROFIS Engineering uses the λ a -provisions given in the adhesive anchor ICC-ESR to calculate N ba
.
39 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions