COMBINED TENSION AND SHEAR LOAD
Parabolic
Results Utilization Status
Results 318-14 Chapter 17 Provision Comments for PROFIS Engineering Status
R17.6 – Interaction of tensile and shear forces The shear-tension interaction expression has traditionally been expressed as
N ua
N n
E
+
V ua
V n
E
≤ 1.0
……………………………………
The PROFIS Engineering anchor portfolio includes post-installed mechanical anchors , postinstalled adhesive anchors , and cast-anchors . The following tension failure modes are considered for each type of anchor :
post-installed mechanical anchor steel strength : pullout strength : concrete breakout strength :
post-installed adhesive anchor steel strength : bond strength : sustained tension load β N
= N ua ( i ) / ϕ steel
N sa β N
= N ua ( i ) / ϕ concrete
N pn , f ́c β N
= N ua ( i ) / ϕ concrete
N cb or β N = N ua ( g )
/ ϕ concrete
N cbg β N
= N ua ( i ) / ϕ steel
N sa β N
= N ua ( i ) / ϕ bond
N a or β N = N ua ( g )
/ ϕ bond
N ag
( for bond strength ): β N = N ua ( i )
/ 0.55ϕ bond
N ba concrete breakout strength :
cast-in anchor steel strength : pullout strength : concrete breakout strength :
β N
= N ua ( i ) / ϕ concrete
N cb or β N = N ua ( g )
/ ϕ concrete
N cbg β N
= N ua ( i ) / ϕ steel
N sa β N
= N ua ( i ) / ϕ concrete
N pn , f ́c β N
= N ua ( i ) / ϕ concrete
N cb or β N = N ua ( g )
/ ϕ concrete
N cbg side-face blowout strength : β N = N ua ( i )
/ ϕ concrete
N sb or β N = N ua ( g ) where N ua ( i ) corresponds to the highest factored tension load acting on an individual anchor and
N ua ( g ) corresponds to the total factored tension load acting on a group of anchors .
PROFIS Engineering designates the parameter ( N ua / ϕN n
) as ” β N
”, and shows it as a percentage (%) in the report under the heading “ Status ”. ACI 318-14 anchoringto-concrete provisions for tension are satisfied if all the β N
-values for the tension failure modes being considered are ≤ 100 %. The highest β N
-value corresponds to the “ controlling ” or “ governing ” failure mode in tension , and is used as the tension component in the parabolic equation given in the commentary R17.6 .
PROFIS Engineering designates the parameter ( V ua / ϕV n
) as ” β V
”, and shows it as a percentage (%) in the report under the heading “ Status ”. ACI 318-14 anchoringto-concrete provisions for shear are satisfied if all the β V
-values for the shear failure modes being considered are ≤ 100 %. The highest β V
-value corresponds to the “ controlling ” or “ governing ” failure mode in shear , and is used as the shear component in the parabolic equation given in the commentary R17.6 .
For the example below , all the β N
-values are ≤ 100 %; therefore , PROFIS Engineering shows the “ Status ” for each value as “ OK ” since ACI 318 anchoringto-concrete provisions are satisfied . Concrete Breakout Failure is the governing failure mode for tension because it has the highest utilization ( β N
= 51 %). This value is used as the tension component in the parabolic equation . However , the β V
-value for Concrete Edge Failure in direction x + is > 100 % ( β V = 130 %); therefore , PROFIS Engineering shows the “ Status ” for this β V
-value as “ not recommended ” since ACI 318 anchoring-to-concrete provisions are not satisfied .
βˆ
= 130 % is also the governing failure mode for shear because it has the highest utilization . This value is used as the shear component in the parabolic equation .
3 Tension load
Load N ua [ lb ]
Capacity
ϕN n
[ lb ]
Utilization
β N
= N ua / ϕN n
Status
Steel strength * 5,000 14,550 35 OK Bond strength ** 10,000 31,564 32 OK Sustained tension load bond strength * 3,450 16,800 21 OK Concrete breakout Failure ** 10,000 19,971 51 OK
* highest loaded anchor ** Anchor group ( anchors in tension )
4 Shear load Load V ua
[ lb ]
Capacity ϕV n [ lb ]
Utilization
β N
= V ua / ϕV n
Status
Steel strength * 3,750 8,221 46 OK
Steel failure with lever arm *
Pryout ( bond strength controls )*
Concrete edge failure in direction x + **
* highest loaded anchor ** Anchor group ( relevant anchors )
N / A N / A N / A N / A
15,000 76,400 20 OK
15,000 11,592 130 not recommended
356 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions