COMBINED TENSION AND SHEAR LOAD
Tri-Linear
Equations Utilization β NV = ( β N
+ β V
)/ 1.2 ≤ 1 ( continued )
Equations 318-14 Chapter 17 Provision Comments for PROFIS Engineering β NV
= ( β N + β V
)/ 1.2 ≤ 1 Excerpt from Table 17.3.1.1 showing the shear failure modes considered in ACI 318-14 anchoring-to-concrete provisions .
Table 17.3.1.1 — Required strength of anchors , except as noted in 17.2.3
Failure Mode Single Anchor
Individual anchor in a Group
Steel strength in shear ( 17.5.1 ) ϕ steel
V sa
≥ V ua ϕ steel
V sa
≥ V ua , i
Concrete breakout strength in shear ( 17.5 . 2 )
Concrete pryout strength in shear ( 17.5.3 ) ϕ concrete
V cb
≥ V ua ϕ concrete
V cp
≥ V ua
Anchor Group
Anchors as a group
ϕ concrete
V cbg
≥ V ua , g ϕ concrete
V ag
≥ V ua , g
17.3.1.3 When both N ua and V ua are present , interaction effects shall be considered using an interaction expression that results in computation of strength in substantial agreement with results of comprehensive tests . This requirement shall be considered satisfied by 17.6
Part 4 of the PROFIS Engineering report shows the ratio of factored shear load ( V ua
) to shear design strength ( ϕV N ) via the parameter β V
. For the example below , concrete edge failure in direction x + is the governing failure mode for shear because it has the highest utilization ( β V
= 60 %).
Example : 4 Shear load
Load V ua [ lb ]
Capacity
ϕV n
[ lb ]
Utilization
β N
= V ua / ϕV n
Status
Steel strength * 1,500 4,540 33 OK Steel failure with lever arm * N / A N / A N / A N / A Pryout ( bond strength controls )* 6,000 52,765 12 OK Concrete edge failure in direction x + ** 6,000 10,080 60 OK
* highest loaded anchor ** Anchor group ( relevant anchors )
For the examples above , both the governing tension failure mode ( β N = 51 %) and the governing shear failure mode ( β V
= 60 %) are greater than 20 %; therefore , PROFIS Engineering would perform the combined interaction check per Eq . ( 17.6.3 ) as follows :
β NV
= ( β N + β V
)/ 1.2 check : β NV
≤ 1.0
= ( 0.51 + 0.6 )/ 1.2 = 0.925 check : 0.925 ≤ 1.0 OK
Reference the PROFIS Engineering design guide section on the parabolic interaction equation for additional information about PROFIS Engineering interaction calculations .
359 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions