There is a growing requirement for bolt testing, anchor testing, fixing testing, scaffold testing, re-bar testing and many other variables in today’s market. This is not an all inclusive list. The testing itself is a relatively straight forward procedure, however it needs to be performed utilising the correct and properly maintained and certificated equipment.
The British standard BS8539 covers the majority of anchor testing scenarios. This includes testing for resistance determination and quality verification on base materials consisting of Standard Masonry, Non-Standard masonry, Standard concrete and non-standard concrete. The tests can be destructive (pull to failure), Non-destructive (Proof load) or Non-destructive (Test Load). Testing can be performed to Chemical anchors, mechanical anchors or plastic anchors.
Anchor bolt testing, design factors to consider
The loading required on a specific anchor should be determined by the required safety factors and the purpose for the test. (For example an eye bolt for fall arrest purposes). The length of time the load should be applied varies on the base material, the type of anchor and the purpose of the test. The number of specimens to be tested is dependent on the base material, the type of post-installed anchor and the purpose of the test.
At Hammond we get asked for this information all the time. Whilst we are happy to advise and recommend the correct equipment to perform the bolt testing we cannot advise of the safety critical information as listed in the paragraph above, that should be determined by the engineer (or other) responsible for the design.
Although the testing of pre-installed anchors is a relatively straight forward operation there are still factors to be considered. These are, but are not limited to the following:
- Fixing location
- Method of installation
- competency of installation
- base material
- test loading requirement
- load spread bridge suitability
- British standard methodology requirements
- Deflection measurement requirements
As briefly touched upon in our previous post, creep occurs when the pre-installed anchor bolt (or other) is slowly pulled from the material it is embedded in under load. This can cause the reading on the gauge to drop slowly.
Determination will be required as to whether it is creep (the fixing adjusting under load) and will stop within a few mm, or the method of adhesion has failed. This can be common in either mechanical or chemically fixed applications. Also bear in mind the type of base material. It could be that the load spread bridge is (digging in) if the substrate is a friable material or has a decorative coating applied. This can stop once the bridge has settled under load.
Another consideration here is the suitability of the load spread bridge. For example the model 2000 kit is usually supplied with a 150 rectangular bridge. Fitted with M10 stud legs. We don’t recommend using these for loading higher than 12kN. If there is a degree of settlement the test could be applying an uneven load to one side of the bridge. This can cause damage to the tester. There are stronger hex extension legs available, we can advise on the best test kit for the job if required.
A good rule of thumb regarding loading is to take the test slightly above the requirement. For example, if the test is to be conducted to 5 kN apply an even progressive load to 5.5 kN, just don’t go higher than 6 kN. This will help alleviate any settlement/creep issues potentially encountered and should give a settled reading on the gauge. When performing the test if you have to constantly top up the pull load you cannot achieve an acceptable result.
Please browse our site for information on specific test kits. The model 2000 can be found here.
Our post on class leading gauge accuracy is here.