COMBINED TENSION AND SHEAR LOAD
Parabolic
Equations β NV
= β ζ N + βζ V ≤ 1 . 0
Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
β NV
= β ζ N + βζ V ≤ 1 . 0
R17 . 8 — Tension and Shear Interaction The tension-shear interaction expression has traditionally been expressed as
N ua
N n ζ
+
where ζ varies from 1 to 2 . The current trilinear recommendation is a simplification of the expression where ζ = 5 / 3 . The limits were chosen to eliminate the requirement for calculation 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 17.5.2.3 .
V ua
V n ζ
≤ 1.0
ACI 318-19 anchoring-to-concrete provisions default to what is known as a trilinear interaction equation , which is given in Eq . ( 17.8.3 ). PROFIS Engineering checks both Eq . ( 17.8.3 ) and the parabolic interaction equation given in the ACI 318-19 commentary R17.8 . The PROFIS Engineering report shows the most favorable results .
The failure mode for a given tension or shear load condition can be expressed as a ratio of factored load to design strength :
• factored tension load / tension design strength = ( N ua / ϕN N
)
• factored shear load / shear design strength = ( V ua / ϕV N
).
The “ governing ” failure mode can be defined as the highest ( factored load / design strength ) ratio for the failure modes being considered . PROFIS Engineering defines the calculated results using the parabolic interaction equation via the parameter “ β NV
”.
Part 3 of the PROFIS Engineering report shows the ratio of factored tension load ( Nua ) to tension design strength ( ϕN N
) via the parameter β N
. For the example below , concrete breakout failure is the governing failure mode for tension because it has the highest utilization ( β N
= 51 %).
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
17.5 . 2.3 If both N ua and V ua are present , interaction effects shall be considered using an interaction expression that results in calculated strengths in substantial agreement with results of comprehensive tests . This requirement shall be considered satisfied by 17.8
339 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions