PROFIS Design Guide: US-EN Summer 2021 | Page 149

Sustained Tension Load — Bond Strength

Variables т _{k , c}

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

т _{k , c}

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 . 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 )

Table 17.4.5.2 — Minimum characteristic bond stresses ^{[ 1 ] [ 2 ]}

Installation and service environment

Outdoor

Moisture content of concrete at time of anchor installation

Dry to fully saturated

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

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 bond strength table in an ICC-ESR showing characteristic bond stress values ( т _{k , cr} and т _{k , uncr}

). 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 ²

Temperature Range B ²

Temperature

Range C ²

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

1 Bond strength values correspond to concrete compressive strength = 2500 psi . For concrete compressive strength between 2500 psi and 800 psi , the tabulated

_{f ́c f ́c} characteristic bond strength may be increased by a factor of ( / 2500 ) _{f ́c} ^{0 ,. 1} .

2 Temperature Range A : Maximum short term temperature = 130 ° F , Maximum long term temperature = 110 ° F . Temperature Range B : Maximum short term temperature = 176 ° F , Maximum long term temperature = 110 ° F . Temperature Range C : Maximum short term temperature = 248 ° F , Maximum long term temperature = 162 ° F .

The parameter “ т _{k , c}

” shown in the PROFIS Engineering report section for sustained tension load corresponds to the characteristic bond stress in either cracked or uncracked concrete . It is used to calculate the parameter “ N _ba

”, which is given in ACI 318-14 Equation ( 17.3.1.2 ), and defined in Equation ( 17.4.5.2 ).

ACI 318 anchoring-to-concrete provisions default to a design assumption that cracked concrete conditions exist ; however , N _ba can be calculated for either cracked or uncracked concrete conditions . PROFIS Engineering users can select either “ cracked ” or “ uncracked ” conditions when modeling an adhesive anchor system for sustained tension load . PROFIS Engineering calculates N _ba using the characteristic bond stress corresponding to the concrete condition selected , as 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 ACI 318 parameter

“ т _cr “ as “ т _{k , cr}

”. The PROFIS Engineering report section for sustained tension load designates the characteristic bond stress parameter as a generic “ т _{k , c}

” for either cracked or uncracked conditions .

т-values given 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-values for both cracked and uncracked concrete that are given in the ICC-ESR by this factor when concrete compressive strengths > 2500 psi are being modeled .

т-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-values corresponding to a particular temperature range are given in the bond strength table .

Reference the Variables section of the PROFIS Engineering report for Bond Strength for more information on :

т _{k , c , uncr}

:

т _{k , c}

:

Characteristic bond stress in uncracked concrete Characteristic bond stress in cracked concrete

Reference the Calculations section of the PROFIS Engineering report for Sustained Tension Load — Bond Strength for more information on :

N _ba

:

Basic bond strength for a single adhesive anchor

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