1.0 TENSION
1.1 Bond Failure Mode
Results ϕ seismic
Results ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
ϕ seismic
17.10.5.4 The anchor design tensile strength shall be calculated from ( a ) through ( e ) for the failure modes given in Table 17.5.2 assuming the concrete is cracked unless it can be demonstrated that the concrete remains uncracked :
………………………………..
( b ) 0.75 ϕN cb or 0.75 ϕN cbg except that N cb or N cbg need not be calculated if anchor reinforcement satisfying 17.5.2.1 ( a ) is provided [ ϕN cb or ϕN cbg correspond to concrete breakout failure ( tension ) in Table 17.5.2 ] ………………………………..
( e ) 0.75 ϕ Na or 0.75 ϕN ag
[ ϕN a or ϕN ag correspond to bond failure ( tension ) in Table 17.5.2 ]
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 — 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 bond failure in tension require calculation of a nominal bond strength ( N a or N ag
). The nominal strength is multiplied by one or more strength reduction factors ( ϕ – factors ) to obtain a design strength ( ϕN a or ϕN ag
). ϕ – factors are relevant to static and seismic load conditions .
ACI 318-19 Section 17.10.5.4 contains provisions to calculate tension design strengths for seismic load conditions . PROFIS Engineering designates the 0.75 reduction factor noted in this section as “ ϕ seismic
”. This reduction is applied to non-steel tension failure modes . When calculating tension design strengths for adhesive anchors , the relevant non-steel tension failure modes to which this reduction is applied include concrete breakout failure ( 0.75 ϕN cb or 0.75 ϕN cbg ) and bond failure ( 0.75 ϕN a or 0.75 ϕN ag
), as referenced in the excerpt to the left .
The ϕ – factors referenced in Table 17.5.2 correspond to tension design strengths calculated for static load conditions . The PROFIS Engineering report designates the ϕ – factor corresponding to bond failure for static load conditions “ ϕ bond
”. PROFIS Engineering uses the ϕ – factors derived from AC308 / ACI 355.4 testing , as given in the ICC-ES evaluation report ( ESR ) for the adhesive anchor system , for the parameter “ ϕ bond
”.
When seismic load conditions are modeled in PROFIS Engineering for an adhesive anchor system , the software calculates a design bond strength corresponding to ( 0.75 ϕ bond
N a or 0.75 ϕ bond
N ag
).
Reference the Results section of the PROFIS Engineering report for more information on the following parameters :
N a or N ag : nominal bond strength ϕN a or ϕN ag
: design bond strength
ϕ bond
: strength reduction factor for concrete failure
PROFIS Engineering calculations for bond failure in tension when seismic load conditions are being modeled :
single anchor : design bond strength = ϕ seismic ϕ bond
N a
. anchor group : design bond strength = ϕ seismic ϕ bond
N ag
.
45 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions