PART 4 SHEAR LOAD
Steel Failure Mode
Results ϕV sa , eq
Results 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ϕV sa , eq
17.2.3.5.3 Anchors and their attachments shall be designed using one of options ( a ) through ( c ):
( a ) The anchor or group of anchors shall be designed for the maximum shear that can be transmitted to the anchor or group of anchors based on the development of a ductile yield mechanism in the attachment in flexure , shear , or bearing , or a combination of those conditions , and considering both material overstrength and strain hardening effects in the attachment .
( b ) The anchor or group of anchors shall be designed for the maximum shear that can be transmitted to the anchors by a non-yielding attachment .
( c ) The anchor or group of anchors shall be designed for the maximum shear obtained from design load combinations that include E , with E increased by Ω 0
. The anchor design shear strength shall satisfy the shear strength requirements of 17.3.1.1 .
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 .
Excerpt from ACI 318-14 Table 17.3.1.1 showing provisions for shear calculations . Table 17.3.1.1 — Required strength of anchors , except as noted in 17.2.3
Failure Mode
Steel strength in shear ( 17.5.1 )
Concrete breakout strength in shear ( 17.5 . 2 )
Concrete pryout strength in shear ( 17.5.3 )
Single Anchor
ϕ steel
V sa
≥ V ua ϕ concrete
V cb
≥ V ua ϕ concrete
V cp
≥ V ua
Individual anchor in a group
ϕ steel
V sa
≥ V ua , i
Table 17.3.1.1 |
|
|
Failure Mode |
Single Anchor |
Individual Anchor in a Group |
Steel Strength in Shear |
ϕ V Vsa , eq ≥ V ua
|
ϕ V Vsa , eq ≥ V ua , i
|
Anchor Group
Anchors as a group
ϕ concrete
V cbg
≥ V ua , g ϕ concrete
V cng
≥ V ua , g
ACI 318-14 strength design provisions for anchors in shear check a calculated design strength ( ϕV N
) against a factored shear load ( V ua
). When designing with ACI 318-14 anchoring-to-concrete provisions , nominal steel strength in shear ( V sa
) is always calculated for a single anchor , and multiplied by the ϕ-factor for steel failure . If the anchorage design is based on seismic load conditions , PROFIS Engineering designates “ V sa
” as “ V sa , eq ” because V sa
-values for some post-installed anchors in the PROFIS Engineering portfolio are specific to seismic loading .
For applications consisting of only one anchor in shear , the design strength ( ϕV sa , eq
) is checked against the shear load acting on that anchor ( V ua ). If an application consists of a group of anchors in shear , V sa , eq is calculated for a single anchor , and the design strength ( ϕV sa , eq ) is checked against the highest individual loaded anchor in shear ( V ua , i
). The PROFIS Engineering report section for steel failure in shear uses the generic designation “ V ua
” to reference either the only shear load acting on an anchor in shear , or the highest shear load acting on an individual anchor within an anchor group in shear .
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 corresponding to brittle failure modes . Design steel strengths calculated for a brittle steel anchor element using ACI 318-08 seismic provisions include an additional strength reduction factor , which PROFIS Engineering designates “ ϕ nonductile
”. Since ϕ nonductile is only relevant to seismic calculations with ACI 318-08 provisions , PROFIS Engineering shows “ 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 for a grouted standoff , an additional reduction factor (= 0.80 ) is applied to the nominal steel strength per Section 17.5.1.3 . PROFIS Engineering designates this parameter “ ϕ eb
” and shows it in the Results section of the report . The calculated design steel strength in shear for seismic load conditions and a grouted stand-off equals ϕ steel ϕ eb
V sa , eq
Reference the Results section of the PROFIS Engineering report for more information on the following parameters :
ϕ steel
: Strength reduction factor for steel failure
ϕ eb
: Strength reduction factor for grouted standoffs
ϕ nonductile
: Seismic strength reduction factor
V sa , eq
: Nominal steel strength in shear ( seismic load conditions )
V ua
: Factored load acting on anchors in shear
A summary of calculated shear design strength versus the factored shear load for each shear failure mode relevant to the application is given in Part 4 Shear Load of the PROFIS Engineering report .
315 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions