1.0 TENSION
1.5 Steel Failure Mode
Results N ua
Results ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
N ua
17.5 . 2 For each applicable factored load combination , design strength of anchors shall satisfy the criteria in Table 17.5.2 .
Excerpt from Table 17.5.2 showing the tension failure modes considered in ACI 318-19 anchoringto-concrete provisions .
Table 17.5.2 — Design strength requirements of anchors
Failure Mode Single Anchor
Individual anchor in a Group
Steel strength in tension ( 17.6.1 ) ϕN sa ≥ N ua ϕN sa
≥ N ua , i
Concrete breakout strength in tension ( 17.6 . 2 ) ϕN cb
≥ N ua
Pullout strength in tension ( 17.6.3 ) ϕN pn ≥ N ua ϕN pn
≥ N ua , i
Concrete side-face blowout strength in tension ( 17.6.4 )
Bond strength of adhesive anchor in tension ( 17.6.5 ) ϕN sb
≥ N ua
ϕN a
≥ N ua
Anchor Group
Anchors as a group
ϕN cbg
≥ N ua , g
ϕN sbg
≥ N ua , g
ϕN ag
≥ N ua , g
ACI 318-19 strength design provisions for steel failure in tension require calculation of a nominal steel strength ( N sa
). The nominal strength is multiplied by a strength reduction factor ( ϕ-factor ) to obtain a design strength ( ϕN sa
).
Design strength is checked against a factored tension load , defined by the parameter “ N ua
”. Chapter 2 in ACI 318-19 gives the following definitions for the factored tension load parameter “ N ua
”.
• N ua
= factored tensile force applied to anchor or individual anchor in a group of anchors ( lb )
• N ua , g
= total factored tensile force applied to anchor group ( lb )
• N ua , i
= factored tensile force applied to most highly stressed anchor in a group of anchors ( lb )
The design steel strength for a single anchor in tension ( ϕN sa
) calculated per Section 17.6.1 is checked against the factored tension load acting on the anchor , which is designated “ N ua
” in Table 17.5.2 . If ϕN sa ≥ N ua
, the provisions for considering steel failure in tension have been satisfied per Table 17.5.2 .
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 individually loaded anchor in tension , which is designated “ N ua , i
” in Table 17.5.2 .
If ϕN sa ≥ N ua , i
, the provisions for considering steel failure in tension have been satisfied per Table 17.5.2 .
The PROFIS Engineering report uses the generic designation “ N ua
” to reference either the only tension load acting on an anchor , or the highest tension load acting on an individual anchor within an anchor group . The PROFIS Engineering Load Engine permits users to input service loads that are factored per IBC factored load equations . Users can also import factored load combinations via a spreadsheet , or input factored load combinations directly on the main screen . PROFIS Engineering users are responsible for inputting tension loads . The software only performs tension load checks per Table 17.5.2 if tension loads have been input via one of the load input functionalities .
If a single anchor in tension is being modeled , PROFIS Engineering calculates the parameter ϕN sa
, and checks this value against either ( a ) the factored tension load acting on the anchor , which has been calculated using the loads input via the Load Engine , ( b ) the factored tension load acting on the anchor , which has been calculated using the loads imported from a spreadsheet or ( c ) the factored tension load acting on the anchor , which has been calculated using the loads input in the matrix on the main screen . The value for N ua shown in the report corresponds to the factored tension load determined to be acting on the anchor .
If a group of anchors in tension is being modeled , PROFIS Engineering calculates the parameter ϕN sa
, and checks this value against either ( a ) the highest factored tension load acting on an individual anchor , which has been calculated using the loads input via the Load Engine , ( b ) the highest factored tension load acting on an individual anchor , which has been calculated using the loads imported from a spreadsheet or ( c ) the highest factored tension load acting on an individual anchor , which has been calculated using the loads input in the matrix on the main screen . The value for N ua shown in the report corresponds to the highest factored tension load determined to be acting on an individual anchor within the anchor group .
Reference the Equations and Calculations section of the PROFIS Engineering report for more information on the parameter ϕN sa
151 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions