Today we sit down with our technical sales manager – Stevan Grkinic to discuss anchor installation, the British Standard BS 8539:2012, and its impact on M&E contractors.
“When we look at an assembly or bracket usually the weakest link is the anchor. In all my experience I have not seen that many true anchor failures, however, I have seen plenty of brackets and assemblies collapse”
This is mainly due to two reasons:
“Over 80% of the drop-in anchor (wedge anchor) are installed incorrectly” (Construction Fixings Association)
The BS 8539:2012 came into practice in the UK following a couple of potentially fatal accidents. The standard itself is aimed at anchor designers, specifiers, installers, and testers. The main points for the contractor are:
The BS 8539:2012 standard is focused upon four key areas:
“No matter the role you play within the supply chain, be it designer, project manager, the BS 8539:2012 standard states that whoever takes for responsibility for selecting anchor is assumed to be the supplier”. Before the specifier selects the correct anchor they need to have the due diligence and work through the following points.
Before any anchor can be put into service the following factors need to be considered:
Concrete is a fantastic material under compression but very poor under tension. You will often find a reinforcing bar to support the tension.
Anchors that are qualified to be used with cracked concrete are expected to function reliably in the expected widths of cracks developed. As a result of tensile stresses in concrete structures designed in accordance with BS EN 1992. In the region of an anchor, the concrete might be cracked or non-cracked.
The BS8539:2012: gives us an answer for that – if you don’t know, you have to assume its cracked unless you can prove otherwise and that’s usually via the structural engineer on-site.
This is why it is pivotal that the specifier understands if the concrete is cracked or uncracked and where they are making that actual installation.
The ETA also looks at cracked and non-cracked approvals with options 1 to 6 covering cracked and 7 to 12 non cracked.
Concrete is likely to be cracked from a variety of causes including:
Once again it is the responsibility of the specifier to understand the type of load that is being applied to the anchor. Different factors determine the choice of anchor.
The specifier needs to consider the environment in which the anchor is being asked to perform.
Most internal applications will be zinc plated, however, once we remove the walls for a multi-story car park for example the environment has altered. Therefore we need to be looking at alternative finishes such as hot dip galvanised (HDG) or Stainless Steel.
Certain applications such as swimming pools need very careful consideration as chlorine attacks the passive film on stainless and can cause internal cracking which can cause anchor failure.
Is it a flush fix or through fix or post-installed?
The type of installation will determine the suitability of different anchors.
This stage is very important for the specifier to understand. They will need to understand basic anchor principles in order to specify the right one. Here are the four main type of anchors:
Out of the four anchor types above two of them, the torque controlled through-bolt and the drop-ins, impose large stress into the substrate. This can cause issues if installed in the wrong locations. The undercut (concrete screw) and resin impose very little stress in the substrate and can be used closer together and closer to edges of slabs than the other two types.
BS 8539 specifies that whether it is possible it is important to use an ETA (European Technical Assessment) rated anchor. The ETA is a harmonised independent set of tests and standards adhered to by all reputable anchor manufacturers. The ETA test anchors in different substrates with varying loads and finally gives them the performance figures we use for the specifier to make the selection purposes. It is awarded following comprehensive testing to framework documents, which explore the functionality of the anchors in a wide range of site conditions.
The specifier needs to understand such issues as multiple-use and what this means as the majority of anchors are multiple-use, they also need to take into consideration other water and fire ratings.
Under BS 8539 the manufacturer and their agents should provide the specifier with:
Your supplier also has responsibilities:
BS 8539:2012 states that anchors should be installed and supervised by competent individuals. BS 8539 defines competent as:
“Suitably trained and qualified by knowledge and practical experience, and provided with the necessary instructions, to enable the required task(s) to be carried out correctly”.
BS 8539:2012 States that testing is not required if an ETA anchor has been used and installed and supervised by competent/trained individuals.
There are generally two different types of tests called for within M&E contracting:
The BS 8539 standard came into practice as due to the inability of specifiers on-site to go through the correct due diligence when installing an anchor. This led to two issues:
The BS 8539 puts the onus on the specifier - ensuring they follow due diligence and safely supply, install, and test all anchor fixings. The code of conduct is there to reduce the risk of any structural collapse and potentially fatal accidents.
MIDFIX are experts in onsite and offsite supports for the mechanical and electrical industries, delivered through design, engineering, fabrication, and industry training. For over 40 years MIDFIX has been supplying fixings and fasteners to support world-famous structures dotted across the UK’s landscape. It should come as no surprise that we have built up a deep level of knowledge and experience in specifying the right fixings for the correct application.