Check splitting failure of anchors in tension to AS 5216:2021 Clause 6.2.6, including when the check is waived and the narrow-member rule. Try it free.
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About this Anchor Splitting Failure Calculator
This calculator works out the design splitting resistance of a single anchor or a rectangular group of anchors in tension, to AS 5216:2021 Clause 6.2.6, and first decides whether the check is required at all. Splitting is the concrete cracking apart under the wedging forces an anchor exerts, and it is most likely in a thin member or close to an edge. The resistance takes the same form as the concrete cone, on the splitting distances from the approval, with a further factor for the member thickness.
- Structural engineer checks expansion and bonded anchors in thin slabs, upstands and narrow beams where splitting can govern.
- Precast designer confirms anchor layouts near the edges of panels and nibs, and sees which waiver, if any, removes the check.
- Design checker traces the waiver conditions and the narrow-member reductions step by step instead of taking a single number on trust.
The page is an engineering-grade CalcTree calculation: every equation is visible and live, and it can be saved alongside the other anchor checks for the same connection.
More info on Anchor Splitting Failure
When the check is required
Clause 6.2.6 waives the splitting check in two cases: when every edge is at least 1.2 c_cr,sp from the anchors in a member at least h_min thick, or when the cone and pull-out design is for cracked concrete and reinforcement limits the splitting crack width. The page evaluates both conditions as booleans and reports whether the check applies. Where it does not, the check passes whatever the utilisation.
Narrow members
Where three or more edges are closer than c_cr,sp, the splitting distances are scaled down in proportion to a reduced depth, following Clause 6.2.3.8. The cone term of the splitting resistance uses the cone's own narrow-member rule on 1.5 h_ef, so the page tracks both reductions separately and shows the close edge distances that drive each one.
Projected areas and factors
Each anchor projects a square of side s_cr,sp. The actual projected area A_c,N is the group's extent in each direction with edges and spacings capped at the splitting distances used, and a plan view shows it with each anchor's square and the line 1.2 c_cr,sp from the anchors. The edge, shell spalling and eccentricity factors take the concrete cone's forms on the splitting distances. The thickness factor ψh,sp of Eq. 6.2.6.2(3) raises the resistance for a member thicker than the approval's minimum h_min, within two limits: one set by the embedment depth and the smallest edge distance, and an absolute cap.
Splitting resistance and result
One anchor resists the lesser of its pull-out resistance at f′c and the cone resistance of one anchor, Eq. 6.2.3.2, on the cone's depth (Eq. 6.2.6.2(4)). Eq. 6.2.6.2(2) scales that by the area ratio and the combined factor, and the capacity factor φMsp gives the design resistance for the verification of Clause 3.4.2. The c_cr,sp, h_min, k1 and φMsp values come from the anchor's approval. The result passes when the check is not required, or when the design splitting resistance is at least N*.
Common Calculation Errors to Avoid
- Claiming the reinforcement waiver without designed reinforcement is not allowed. Splitting reinforcement counts only where it is designed to resist the splitting forces and limit the crack width.
- Applying the waiver in uncracked concrete misreads the rule: the reinforcement waiver needs the cone and pull-out design to be for cracked concrete.
- Skipping the narrow-member reduction overstates the resistance where three or more edges are close to the anchors.
- Using the wrong pull-out value mixes anchor types. Use the mechanical anchor's pull-out resistance at f′c, or the bond resistance of one bonded anchor.
- Treating a member thinner than h_min as a lower thickness factor misreads the approval. A thinner member is outside the approval altogether, not merely a smaller ψh,sp.
- Building the area from every anchor when only some are in tension overstates the resistance. For an irregular layout or partial tension, use the anchors actually in tension.
Engineering templates
Common calculators
Design guides
FAQs
What causes splitting failure in anchors?
An anchor loaded in tension pushes outwards on the surrounding concrete. In a thin member or close to an edge those wedging forces can crack the concrete apart before the cone or pull-out capacity is reached.
When can I skip the splitting check?
AS 5216:2021 Clause 6.2.6 waives it when every edge is at least 1.2 c_cr,sp away and the member is at least h_min thick, or when the design is for cracked concrete and reinforcement limits the splitting crack. The page tests both and states the result.
Where do c_cr,sp and h_min come from?
Both come from the anchor's approval, together with the cone factor k1 and the capacity factor for splitting. The page does not assume them.
How is a far edge entered?
Enter any distance of 1.2 c_cr,sp or more. Edges beyond that distance do not reduce the splitting area or trigger the narrow-member rule.
Does a thicker member help?
Yes. The thickness factor ψh,sp raises the resistance as the member gets thicker than the approval's minimum, up to its limits. A member thinner than h_min is outside the approval.
Does it cover splitting during installation?
No. Splitting during installation is controlled by the approval's minimum edge distance, spacing and member thickness. For a bonded anchor, enter the bond resistance of one anchor in place of the pull-out resistance.
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