COMBINED TENSION AND SHEAR LOAD
Parabolic
Variables β N
Variables 318-14 Chapter 17 Provision Comments for PROFIS Engineering
β N
R17.6 – Interaction of tensile and shear forces The shear-tension interaction expression has traditionally been expressed as
N ua
N n
E
+
where E varies from 1 to 2 . The current trilinear recommendation is a simplification of the expression where E = 5 / 3 . The limits were chosen to eliminate the requirement for computation of interaction effects where very small values of the second force are present . Any other interaction expression that is verified by test data , however , can be used to satisfy 17.3.1.3 .
V ua
V n
E
≤ 1.0
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 tension ( 17.4.1 ) ϕN sa ≥ N ua ϕN sa
≥ N ua , i
Concrete breakout strength in tension ( 17.4.2 ) ϕN cb
≥ N ua
Pullout strength in tension ( 17.4.3 ) ϕN pn ≥ N ua ϕN pn
≥ N ua , i
Concrete side-face blowout strength in tension ( 17.4.4 )
Bond strengh of adhesive anchor in tension ( 17.4.5 ) 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
Part 3 of the PROFIS Engineering report shows the ratio of factored tension load ( N ua
) to tension design strength ( ϕN N ) via the parameter β N
. PROFIS Engineering calculates β N for each tension failure mode relevant to a particular anchor type .
Per ACI 318-14 Table 17.3.1.1 , the tension provisions of Chapter 17 are satisfied if all the calculated design strengths for tension failure modes are greater than or equal to the corresponding factored load . When PROFIS Engineering calculates
β N
, it rounds up the result to the nearest whole number . The β N
-values given in Part 3 of the report correspond to a percentage . The PROFIS Engineering report shows “ OK ” under the Status heading if the β N
-value is ≤ 100 %.
The highest β N
-value corresponds to the “ controlling ” or “ governing ” failure mode in tension . This value is used as the tension component in the interaction equation . For the example below , all the calculated β N
-values are ≤ 100 %, and concrete breakout failure is the governing failure mode for tension because it has the highest utilization ( β N
= 51 %). The tension provisions of Chapter 17 have been satisfied . 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 *
Concrete breakout Failure **
* highest loaded anchor ** Anchor group ( anchors in tension )
3,450 16,800 21 OK
10,000 19,971 51 OK
When N ua is greater than ϕN n
, the β N
-value will be greater than 100 %. The tension provisions of Chapter 17 are not satisfied when N ua is greater than ϕN n
. The PROFIS Engineering report shows “ not recommended ” under the Status heading if the β N
-value is ≥ 100 %. For the example below , the β N
-values for bond strength and concrete breakout failure are > 100 %; therefore , the PROFIS Engineering report shows “ not recommended ” under the Status heading for these failure modes to indicate that the Chapter 17 provisions have not been satisfied .
3 Tension load Load N ua
[ lb ]
Capacity ϕN n [ lb ]
Utilization
β N
= N ua / ϕN n
Status
Steel strength * 10,000 26,347 38 OK Bond strength **
Sustained tension load bond strength *
Concrete breakout Failure **
* highest loaded anchor ** Anchor group ( anchors in tension )
40,000 33,922 118 not recommended
5,000 11,495 44 OK
40,000 26,603 151 not recommended
Reference the PROFIS Engineering design guide section on β V for additional information about PROFIS Engineering interaction calculations .
350 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions