PROFIS ENGINEERING REPORT SHEAR LOAD
Concrete Breakout Failure Mode
Results ϕ seismic
Results 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ϕ seismic
17.2.3.4.4 The anchor design tensile strength for resisting earthquake forces shall be determined from consideration of ( a ) through ( e ) for the failure modes given in Table 17.3.1.1 assuming the concrete is cracked unless it can be demonstrated that the concrete remains uncracked :
( a ) ϕN sa for a single anchor or for the most highly stressed individual anchor in a group of anchors ϕN sa corresponds to steel failure ( tension ) in Table 17.3.1.1 ] ( b ) 0.75ϕN cb or 0.75ϕN cbg except that N cb or N cbg need not be calculated where anchor reinforcement satisfying 17.4.2.9 is provided [ ϕN cb or ϕN cbg correspond to concrete breakout failure ( tension ) in Table 17.3.1.1 ]
( c ) 0.75ϕN pn for a single anchor or for the most highly stressed individual anchor in a group of anchors [ ϕN pn corresponds to pullout failure ( tension ) in Table 17.3.1.1 ] ( d ) 0.75ϕN sb or 0.75ϕN sbg
[ ϕN sb or ϕN sbg correspond to side-face blowout failure ( tension ) in Table 17.3.1.1 ]
( e ) 0.75ϕN a or 0.75ϕN ag ϕN a or ϕN ag correspond to bond failure ( tension ) in Table 17.3.1.1 ] where ϕ is in accordance with 17.3.3 .
17.3.3 Strength reduction factor ϕ for anchors in concrete shall be as follows when the load combinations of 5.3 are used :
……………………………………………………………………………………………………
( c ) Anchor governed by concrete breakout , side-face blowout , pullout , or pryout strength Condition A
Condition B ( i ) Shear loads 0.75 0.70
PROFIS Engineering calculations for concrete breakout failure in tension when seismic load conditions are being modeled :
single anchor : design concrete breakout strength = ϕ seismic ϕ concrete
N cb
. anchor group : design concrete breakout strength = ϕ seismic ϕ concrete
N cbg
.
PROFIS Engineering calculations for concrete breakout failure in shear when seismic load conditions are being modeled :
When designing an anchorage for seismic tension load conditions , ACI 318-14 provisions for concrete breakout failure in tension require calculation of a nominal concrete breakout strength ( N cb or N cbg
). The nominal strength is multiplied by two strength reduction factors ( ϕ-factors ): one ϕ-factor for concrete breakout failure in tension , and one ϕ-factor for seismic tension load conditions , to obtain a design strength ( 0.75ϕN cb or 0.75ϕN cbg
).
PROFIS Engineering designates the 0.75 seismic tension reduction factor noted in ACI 318-14 Section 17.2.3.4.4 “ ϕ seismic
”. This reduction is only considered with respect to non-steel tension failure modes when calculating tension design strengths for both cast-in-place and post-installed anchors subjected to seismic tension loads .
When designing an anchorage for seismic shear load conditions , ACI 318- 14 strength design provisions for concrete breakout failure in shear require calculation of a nominal concrete breakout strength ( V cb or V cbg
) that is only multiplied by one ϕ-factor to obtain a shear design strength ( ϕV cb or ϕV cbg ).
PROFIS Engineering designates this ϕ-factor “ ϕ concrete ”. The 0.75 seismic strength reduction factor ( ϕ seismic
) required per Section 17.2.3.4.4 is only relevant to tension calculations , and is therefore not applied to V cb or V cbg when the anchorage is being designed for seismic shear load conditions . The PROFIS Engineering report always shows ϕ seismic equal to 1.0 for shear concrete breakout calculations when seismic shear load conditions are being modeled .
When calculating the design concrete breakout strength in shear for cast-in-place anchors , the parameter “ ϕ concrete
” in the PROFIS Engineering report is taken from
Section 17.3.3 ( c )( i ).
When calculating the design concrete breakout strength in shear for post-installed anchors , the parameter “ ϕ concrete
” in the PROFIS Engineering report is taken as follows :
• If “ Condition B ” is selected as a design parameter , “ ϕ concrete
” is taken from the ϕ-factor for shear given in the ICC-ESR for the anchor
• If “ Condition A ” is selected as a design parameter , “ ϕ concrete ” is taken from
Section 17.3.3 ( c )( i )
Reference the Results section of the PROFIS Engineering report for more information on the following parameters :
V cb or V cbg : Nominal concrete breakout strength in shear ϕV cb or ϕV cbg
: Design concrete breakout strength in shear
ϕ concrete
: Strength reduction factor for shear concrete failure single anchor : Design concrete breakout strength = ϕ concrete
V cb anchor group : Design concrete breakout strength = ϕ concrete
V cbg
201 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions