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Why test anchors on site?

Why test anchors?

The testing of anchors can be a crucial link in the chain of ensuring they fulfil their role in any safety critical application. Tests may be required for two distinct purposes:


Tests to determine suitability or Allowable Loads

These are done before the specification of anchors is finalised to ensure anchors are suitable for the base material concerned and have an adequate Allowable Load* - usually when the strength or precise nature of the base material is unknown and no Recommended Load* data is available from the manufacturer, e.g. in brickwork, blockwork or stonework. These tests will be done on anchors NOT to be used on the job. Two approaches are possible Preliminary Load tests*(this approach is recommended by the CFA) or Ultimate* Load testsprocedures for which are described in the CFA GN: Procedure for Site Testing Construction Fixings - 2012.

Tests to check correct installation

Carried out on anchors which are used on the job and after they have been installed to ensure they have been installed correctly. These tests are calledProof Tests.

For each of these purposes the requirements are different in terms of sample size, magnitude of load, rig dimensions etc. Full details of test procedures are given in the CFA Guidance Note - Procedure for Site Testing Construction Fixings -2012 

Tests are not needed -
If anchors are specified with a European Technical Approval and have been designed (selected) and installed fully in accordance with the requirements of the ETA.

Testing in shear

The shear performance of anchors in concrete is dependent primarily on the strength of the anchor rod and is little affected by installation quality. It therefore rarely justified to carry out site tests in shear in concrete. Shear tests may be justified for anchors to be used in masonry to determine allowable loads which will often be limited by displacement. See more under Testing categories. Procedures for shear testing are described in the CFA GN: Procedure for Site Testing Construction Fixings - 2012

*For the definition of the terms used to describe loads click on the heading Loads.