Check pry-out failure of an anchor or anchor group in shear to AS 5216:2021 Clause 7.2.4, with k8 and the cone resistance. Run the template now.
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About this AS 5216 Pry-out Failure Calculator
This calculator checks the design pry-out resistance of a single anchor or a rectangular anchor group in shear to AS 5216:2021 Clause 7.2.4. A short, stiff anchor loaded in shear levers about a point near the surface, and its embedded end pushes out a body of concrete on the side away from the load. The standard ties this resistance to the concrete cone resistance in tension, so the page calls CalcTree's concrete cone template with its own anchors and applies the pry-out factor k8.
- Structural engineer. Checking shallow anchors under base plates, brackets and ledger fixings, where short embedment makes pry-out govern ahead of steel failure.
- Bonded anchor specifier. Comparing the concrete cone with the combined pull-out and bond resistance, since the smaller of the two drives pry-out for a bonded anchor.
- Checking engineer. Tracing the pry-out number back through the projected areas and cone factors, all shown on the page.
The cone calculation sits on the page as a live card with this page's inputs, so nothing is copied by hand. It is an engineering-grade calculator on CalcTree, ready to duplicate into your project.
More info on AS 5216 Pry-out Failure
Inputs
You enter the grid of anchors loaded in shear and their spacings, the four edge distances, the effective embedment depth, f′c, the cone factor k1, the reinforcement spacing condition, the pry-out factor k8, the anchor type, the capacity factor φMc and the design shear on the group. For bonded anchors you also enter the characteristic combined pull-out and bond resistance N_Rk,p, and the eccentricities of the shear resultant can be set in each direction.
Cone resistance over the shear-loaded anchors
N_Rk,c is computed by the concrete cone template (Eq. 6.2.3.1) with the shear's eccentricities, no compression force under the fixture and no applied tension. The page brings back the embedment depth used, the projected areas, the edge, shell spalling and eccentricity factors, and the cone resistance itself. The reduced embedment depth for narrow members (Clause 6.2.3.8) is applied inside the cone template.
Pry-out resistance and design check
Clause 7.2.4 gives V_Rk,cp as k8 times the tension resistance used. For mechanical and cast-in anchors that is N_Rk,c; for bonded anchors it is the smaller of N_Rk,c and N_Rk,p. The capacity factor φMc from Table 3.2.4 gives the design resistance, checked against the design shear under Clause 3.4.3, with a utilisation and a pass or fail result.
Common Calculation Errors to Avoid
- Leaving k8 at the default without checking. Many approvals give a higher pry-out factor. The default is conservative but can under-rate the anchor, so read k8 from the approval.
- Ignoring bond for bonded anchors. A bonded anchor can be limited by combined pull-out and bond rather than the cone. Select the bonded anchor type and enter N_Rk,p so the smaller resistance governs.
- Using the tension eccentricity. For pry-out the cone factors take the eccentricity of the shear resultant from the centroid of the anchors loaded in shear, not the tension resultant.
- Including anchors that carry no shear. Where only some anchors of a group take shear, enter only those anchors as the grid.
- Treating pry-out as the only shear check. Steel failure with and without a lever arm and concrete edge failure are separate checks under AS 5216:2021 Section 7.2.
Engineering templates
Common calculators
Design guides
FAQs
What is pry-out failure?
Pry-out is a shear failure mode of short, stiff anchors. Under shear the anchor rotates about a point near the surface, and its embedded end breaks out concrete on the side away from the load. It typically governs for shallow embedment away from edges.
Why does a shear check need the concrete cone resistance?
AS 5216:2021 Clause 7.2.4 expresses pry-out resistance as the pry-out factor k8 times the concrete cone resistance of the anchors loaded in shear. The page calls CalcTree's concrete cone template with the same anchors, so both calculations stay consistent.
What k8 should I use?
Use the value in the anchor's approval. If the approval gives none, the page's default is the conservative value, but many products are approved for a higher k8.
How are bonded anchors treated differently?
For a bonded anchor the page takes the smaller of the concrete cone resistance and the combined pull-out and bond resistance N_Rk,p of the same anchors, then multiplies by k8.
Does this include concrete edge failure?
No. Concrete edge failure, and steel failure with or without a lever arm, are separate AS 5216:2021 checks with their own CalcTree templates. The interaction of tension and shear is also checked separately.
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