PROFIS Design Guide - AC 318-19 July 2022 | Page 150

1.5 Steel Failure Mode

Results ϕN _sa

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

ϕN _sa

17.5 . 2 For each applicable factored load combination , design strength of anchors shall satisfy the criteria in Table 17.5.2 .

ACI 318-19 strength design provisions for anchors in tension check a calculated design strength ( ϕN _N

) against a factored tension load ( N _ua

). The parameter “ design strength ” is defined as the product of a “ nominal strength ” ( N _N

) and one or more strength reduction factors ( ϕ-factors ). If ϕN _N ≥ N _ua for all relevant tension failure modes , the ACI 318-19 tension provisions are satisfied . When designing with ACI 318-19 anchoring-to-concrete provisions , nominal steel strength in tension ( N _sa

) is always calculated for a single anchor , and multiplied by the ϕ-factor for steel failure .

For applications consisting of only one anchor in tension , the design strength ( ϕN _sa

) is checked against the tension load acting on that anchor ( N _ua ). If ϕN _sa

≥ N _ua

, the ACI 318-19 provisions for steel failure in tension are satisfied . If an application consists of a group of anchors in tension , N _sa is calculated for a single anchor , and the design strength ( ϕN _sa ) is checked against the highest individual loaded anchor in tension ( N _{ua , i} ). If ϕN _sa

≥ N _{ua , i}

, the ACI 318-19 provisions for steel failure in tension are satisfied . The PROFIS Engineering report section for steel failure in tension uses the generic designation “ N _ua

” to reference either the only tension load acting on an anchor in tension , or the highest tension load acting on an individual anchor within an anchor group in tension .

PROFIS Engineering designates the strength reduction factor for steel failure

ϕ _steel

. ACI 318-08 anchoring-to-concrete provisions include an additional seismic reduction factor that is used to calculate anchor design strengths corresponding to brittle failure modes . Anchor elements can be defined in ACI 318 as “ ductile ” or “ brittle ” steel elements . Steel failure for a brittle steel anchor element is a “ brittle ”, i . e . “ nonductile ” failure mode ; therefore , design steel strengths calculated for a brittle steel anchor element using ACI 318-08 seismic provisions would include an additional strength reduction factor . PROFIS Engineering designates this seismic reduction factor “ ϕ _nonductile

”, and shows it in the results section of the report .

Since ϕ _nonductile is only relevant to seismic calculations with ACI 318-08 provisions , PROFIS Engineering always shows the parameter “ ϕ _nonductile

” equal to 1.0 in the

Results section of reports for ACI 318-19 provisions .

When modeling an anchor element in PROFIS Engineering using ACI 318-19 provisions , the calculated design steel strength in tension for both static and seismic load conditions equals ϕ _steel

N _sa

. No additional strength reduction factors are applied to the nominal steel strength .

Reference the Equations section of the PROFIS Engineering report for more information on :

ϕN _sa

: design steel strength in tension .

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

ϕ _steel

: strength reduction factor for steel failure

ϕ _nonductile

: seismic strength reduction factor

ϕN _sa

: nominal steel strength in tension

N _ua

: factored load acting on anchors in tension

A summary of calculated tension design strength versus the factored tension load for each tension failure mode relevant to the application is given in Part 3 Tension Load of the PROFIS Engineering report .

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