What Is Proof Load Testing and When Is It Required?

Definition

A proof load test applies a controlled tensile or shear force to a post-installed anchor to verify that the installation can sustain a predetermined load without failure, excessive displacement, or load decay. The anchor remains serviceable after the test. This distinguishes proof testing from ultimate testing, where the anchor is loaded to failure and cannot be reused.

When proof testing is required

BS 8539:2012+A1:2021 and AEFAC TN05 recommend that a sample of all project anchors used in safety-critical applications be subject to proof testing. Safety-critical anchors are those where failure could cause:

• Human injury or death
• Partial or full structural collapse
• Significant economic loss

Safety-critical applications include structural connections, facade fixings, overhead installations, fall arrest anchor points, and any anchor supporting loads where the consequence of failure is significant.

How the proof load is derived

The proof load is not a fixed number, it is derived from the design loads for the specific application. Three standards provide guidance:

VicRoads Section 680 specifies the proof load as 1.5 times the maximum serviceability design load for bonded anchors. For anchors in cracked concrete, the multiplier increases to 2.0 times the serviceability load.

BS 8539 Annex B.3 calculates the proof load as the characteristic action multiplied by a proof test factor. The factor is 1.5 when 2.5% of anchors are tested and 1.25 when 5% are tested.

AEFAC TN05 Volume 2 specifies that the proof load should not exceed the lesser of the ultimate limit state design capacity or 0.7 times the yield capacity of the fastener, whichever prevents damage to the anchor during testing.

The hold period and load decay criterion

The proof load must be held for a minimum of 30 seconds. During this hold period, the load must not drop by more than 10% of the peak value. A load drop exceeding 10% indicates a potential bond failure, progressive displacement, or substrate inadequacy that requires investigation.

These are the minimum requirements. The specifying engineer may require longer hold periods or tighter load decay limits for high-consequence applications.

What a proof test does not tell you

A proof test confirms that the installed anchor can sustain a specific load at the time of testing. It does not:

• Establish the ultimate capacity of the anchor-substrate system
• Guarantee long-term performance under sustained or cyclic loads
• Detect all failure modes (some require displacement monitoring)
• Replace the need for correct design and specification

For substrates where no published design data exists, such as masonry or rock, ultimate testing must be conducted first to establish the anchor capacity, and proof testing then verifies installation quality.

References

• BS 8539:2012+A1:2021, Section 9.3 and Annex B.3
• AEFAC TN05 Volume 2, Guidelines for Site Testing of Anchors: Proof Tests
• VicRoads Section 680, Bonded Anchors (September 2022)