PART 3 TENSION LOAD
Steel Failure
Equation ϕN sa
Equation ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ϕN sa
≥ N ua
17.3.1.1 The design of anchors shall be in accordance with Table 17.3.1.1 . In addition , the design of anchors shall satisfy 17.2.3 for earthquake loading and 17.3.1.2 for adhesive anchors subject to sustained tensile loading .
Table 17.3.1.1
Failure Mode |
Single Anchor |
Individual Anchor in a Group |
Steel Strength in Tension |
ϕN sa
≥ N ua
|
ϕN sa
≥ N ua , i
|
ACI 318-14 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 318-14 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 318-14 . 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 .
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 318-14 provisions .
When modeling an anchor element in PROFIS Engineering using ACI 318-14 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 .
132 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions