PROFIS Design Guide: US-EN Summer 2021 | Page 147

Sustained Tension Load — Bond Strength

Equations N _ba

Equations ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering

N _ba

= λ _a т _cr π _da h _ef

17.3.1.2 For the design of adhesive anchors to resist sustained tension loads , in addition to 17.3.1.1 , Eq . ( 17.3.1.2 ) shall be satisfied .

0.55 ϕN _ba ≥ ^N ua , s

( 17.3.1.2 )

Where N _ba is determined in accordance with 17.4.5.2 .

N _ba

= λ _a т _cr π _da h _ef

( 17.4.5 . 2 ) 17.4.5 . 2 The basic bond strength of a single adhesive anchor in tension in cracked concrete , N _ba

, shall not exceed 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 т _cr psi т _uncr psi

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 .

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

:

Example :

N _ba

=

( λ _a т _xxxx α _{N , seis} πd _a h _ef

) α _{N , seis}

Example of a table in an ICC-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-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

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

Dry and water saturated concrete

ϕ _d

, ϕ _ws - 0.65

Reduction for Seismic Tension α _{n , seis} - 0.88 1.0 1.0 1.0 1.0 0.97 1.0

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 . 17.4.5.2 ; and is predicated on the following parameters :

• т _xxxx

— characteristic bond stress of the adhesive product ; designated in ACI 318-14 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-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 318-14 Table 17.4.5.2 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 . 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 shown compliance 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

318-14 Eq . ( 17.4.5.2 ) does not reference α _{N , seis} . Since AC308 includes provisions for determining α _{N , seis} , adhesive anchor ICC-ESR derived from AC308 testing include α _{N , seis} as a parameter for calculating N _ba

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

.

The provisions in Section 17.3.1.2 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 . ( 17.3.1.2 ). PROFIS Engineering divides out any α _{N , seis} -value when calculating

N _ba per Eq . ( 17.3.1.2 ).

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

λ _a

:

т _{k , xxxx}

:

d _a

:

h _ef

:

Lightweight concrete modification factor Characteristic bond stress Anchor element diameter Effective embedment depth

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

.

147 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions