PROFIS Design Guide - AC 318-19 July 2022 | Page 153

1.6 Sustained Load Failure Mode

Equations N _ba

Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering

N _ba

= λ _a т _cr π _da h _ef

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

Moisture content of concrete at time of anchor installation

Peak in-service temperature of concrete ° F т _cr psi

153 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions

т _uncr psi

Outdoor Dry to fully saturated 175 200 650 Indoor Dry 110 300 1000

( 1 ] If anchor design includes sustained tension , multiply values of Cr and Four by 0.4 . ( 2 ) If anchor design includes earthquake-induced forces for structures assigned to SDC C , D , E , or F , multiply values of т _cr

, by

0.8 and т _uncr by 0.4 .

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}

Example of a table in an ICC-ES evaluation report ( ESR ) showing characteristic bond stress values ( т _kcr and т _{k , uncr} ), the seismic reduction value α _{N , seis}

, and strength reduction factors ( ϕ-factors ) for bond strength . 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

Temperature Range A

Temperature Range B

Temperature Range C

Permissible installation conditions

Dry and water saturated concrete

Anchor Category

- ϕ _{d ,} ϕ _ws

- 0.65

Reduction for Seismic Tension α _{N , seis}

- 0.88 0.99 0.99 1.0 1.0 0.95 0.99

1

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 . 17.6.5.2.1 ; and is predicated on the following parameters :

• т _xxxx

— characteristic bond stress of the adhesive product ; designated in ACI 318-19 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-ES evaluation report ( 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 . The т-values given in ACI 318-19 Table 17.6.5.2.5 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 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 qualified for recognition 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 318-19 Eq . ( 17.6.5.2.1 ) does not reference α _{N , seis} . Since AC308 includes provisions for determining α _{N , seis} , adhesive anchor ESR ’ s derived from AC308 testing include α _{N , seis} as a parameter for calculating N _ba

. Therefore , PROFIS Engineering , which uses the adhesive anchor ESR data for calculating bond strength , likewise includes α _{N , seis} as a parameter for calculating N _ba

.

The provisions in Section 17.5.2.2 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 . ( 17.5.2.2 ). PROFIS Engineering divides out any α _{N , seis} -value when calculating

N _ba per Eq . ( 17.5.2.2 ).

Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :

λ _a

: lightweight concrete modification factor .

т _{k , xxxx}

: characteristic bond stress .

d _a

: anchor element diameter .

h _ef

: effective embedment depth .

Reference the Calculations section of the PROFIS Engineering report for more information on the parameter N _ba

.