1.0 TENSION
1.5 Steel Failure Mode
Equations ϕN sa
Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
ϕN sa
≥ N ua
17.5 . 2 For each applicable factored load combination , design strength of anchors shall satisfy the criteria in Table 17.5.2 .
Table 17.5.2 |
|
|
Failure Mode |
Single Anchor |
Individual Anchor in a Group |
Steel Strength in Tension |
ϕN sa
≥ N ua
|
ϕN sa
≥ N ua , i
|
ACI 318-19 strength design provisions for 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 .
Nominal steel strength in tension ( N sa
) is always calculated for a single anchor when designing with the provisions of ACI 318-19 . If an application consists of a group of anchors in tension , N sa is calculated for a single anchor , and the design strength is checked against the highest loaded anchor in tension ( N ua , i
). 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 strength calculated for a brittle steel anchor element using ACI 318-08 seismic provisions includes 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 for both static and seismic load conditions equals ϕ steel
N sa
, regardless of whether the anchor element is , by ACI 318 definition , “ brittle ” or “ ductile ”.
Reference the Calculations and Results section of the PROFIS Engineering report for more information on :
N sa
: nominal 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
ϕN sa
: design 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 .
138 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions