«CFA Guidance Note: ETAs & design methods for anchors used in construction. Contents 1 Introduction 2 Legal background 3 Terminology 4 ETAs and ETAGs ...»
Ensuring best fixings practice
CFA Guidance Note:
ETAs & design methods for anchors used in construction.
2 Legal background
4 ETAs and ETAGs (EADs)
5 Anchor Selection
6 Design methods
7 Anchor Installation in compliance with ETAs
8 Benefits of using anchors with ETAs
9 References ETA to ETAG 001 Option 1 for use in cracked or non-cracked concrete.
1 INTRODUCTIONThis Guidance Note has been written to complement BS 8539:2012 Code of practice for the selection and installation of post-installed anchors in concrete and masonry published in October 2012 and which, by virtue of restrictions placed on the publication of British Standards, cannot be seen to endorse the use of independent endorsements such as European Technical Approvals/Assessments (ETAs) and which therefore
refers to this Guidance Note for elaboration on the subject. What BS 8539 does say with regard to ETAs is:
“Users of this British Standard are advised to consider the desirability of selecting anchors with a relevant European Technical Approval.” It was the clear will of the BS drafting panel that, wherever possible, i.e. for any application for which a suitable anchor with an ETA exists on the market, then such an anchor should be chosen.
ETAs (European Technical Approvals/Assessments), are the only mechanism by which manufacturers can gain independently assessed approvals for anchors to be used in safety critical applications throughout Europe. They also facilitate the comparison of the performance of similar products as they are based on tests carried out to closely controlled methods.
ETAs have, until recently, been awarded after rigorous testing to the requirements of European Technical Approval Guidelines (ETAGs) which are eventually to be replaced by European Assessment Documents (EAD) following implementation of the Construction Products Regulation on 1 July 2013. The first ETAG was published, and the first ETAs granted, in 1997 since which time additional ETAGs have been published (as listed below) to cover the vast majority of drilled in anchor types in the most common structural materials.
Many companies large and small have since gained, between them, hundreds of ETAs for their products and there are few applications which cannot be covered using an anchor with an appropriate ETA.
This Guidance Note is intended to help the users of ETAs, i.e. the specifiers and installers of anchors, to understand how to select a product with an ETA to the most appropriate ETAG Part, tounderstand the basis of the design process and to ensure that installation is carried out to the requirements of the ETA & BS 8539.
As indicated under legal background the situation has changed since the implementation of the Construction Products Regulation in July 2013. This Guidance Note will be updated as and when necessary to keep all stakeholders up to date with the requirements. Readers wishing to be kept informed should log on to the CFA website at www.the-cfa.co.uk and register for the occasional newsletter.
The full benefits to specifiers and users of using anchors with ETAs are summarised in section 9.0.
2 LEGAL BACKGROUNDOne of the main aims of the European Union is to avoid barriers to trade between Member States. It also aims to harmonise the rules by which the performance of construction products is expressed, by means of the Construction Products Regulation (CPR) which, on 1 July 2013, replaced the Construction Products Directive.
The CPR requires that manufacturers of all Construction Products that fall within the scope of a harmonised European Standard (hEN) or have been awarded an ETA shall draw up a Declaration of Performance (DoP) and all such products must carry CE marking.
Under the CPR European Technical Approvals will remain valid during their period of validity (up to 5 years) and will gradually be replaced by European Technical Assessments (ETA). ETAGs existing before 1 July ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 2. July 2013 CFA Guidance Note ETAs & design methods for anchors used in construction 2013 may, for the time being, be used as the basis for awarding ETA but will eventually be transformed into EAD. New products not conforming to existing ETAGs will have new EADs written for them when requested by the manufacturers. A listing of all existing ETAGs is published on the EOTA website (www.eota.eu) under the heading “Publications” use the link: http://www.eota.eu/en-GB/content/etags-used-as-ead/26/
3.0 TERMINOLGY The basic terminology used in discussing ETAs is outlined below. Much of the day to day terminology used in the business of construction fixings is changing. A Guidance Note: Anchor terminology and notation, detailing the correspondence between old and new terms is downloadable from the CFA website.
In particular BS 8539 adopts terminology common to Eurocodes so the term “action” is used for loads to be applied to the anchor via the fixture and “resistance” for the capability of the anchor to resist such actions.
EOTA European Organisation for Technical Assessment – was European Organisation for Technical Approvals The organisation responsible for developing EADs in line with mandates issued by the European Commission. Includes Assessment Bodies from member states. CEO represents European manufacturers on the relevant EOTA working group.
ETAG Guideline European Technical Approval – being replaced by EAD European Assessment Document The Key document for manufacturers, approval bodies and test laboratories. The framework for test procedures against which anchors are tested and assessed. ETAGs also carry design methods but newly written EADs will not. In future design methods will be enshrined in a European Standard EN 1992-4 Design of fastenings for use in concrete.
ETA European Technical Approval – being replaced by ETA European Technical Assessment The Key document for specifiers. It contains details of the anchor specification, application limits, performance characteristics, and installation method. It indicates which ETAG/EAD the anchor is approved/assessed to, which design method is to be used and, in the case of anchors with ETA to ETAG 001, which Option is covered for the category of use (see section 5). Existing ETApprovals are valid for no more than five years. ETAssessments will have no limit to their validity as long as the AVCP is maintained and hence the DoP.
DoP Declaration of Performance
The document in which the manufacturer assumes legal responsibility for maintaining the conformity of the product against the declared performance. Requirements for the DoP are contained in Annex III of the CPR. See also. Before the DoP can be completed the AVCP assessment must be established.
Any construction product for which the manufacturer has drawn up a DoP must carry CE marking and, generally speaking – as there are very few harmonised European Standards covering anchoring products
- this means it must have an ETA and have achieved the AVCP (see below) before the manufacturer may affix CE marking. CE marking enables products to be offered for sale throughout the EU. It is not intended as a quality mark but effectively the requirements are sufficiently strict that, in this case, it may be regarded as one. Under the CPR CE marking is mandatory for construction products which carry an ETA.
AVCP system of Assessment and Verification of Constancy of Performance – replaces Attestation Of Conformity The system of AVCP determines the conformity of the product against its technical specification as contained in the hEN or ETA to ensure that both the product and its performance remain unchanged in regular production from that tested in the ETA procedure. AVCPs may have different levels dependent on the implications for the product on health and safety. The manufacturer is required to have a fully documented factory production control system. The ETAGs/EADs for anchors require AVCP to high levels as safety critical applications are covered.
Certain terms used in BS 8539 have meanings particular to that code of practice:
Specifier Person responsible for the selection of the anchor. (May be the designer.) Designer Person with overall responsibility of the design of a structure, including the anchorage, throughout the whole design and construction phase. (May be the specifier.) Selection Overall process of selecting the type and size of an anchor or group of anchors (the design process is part of this).
Design The process of determining the size of anchor in relation to the loads to be transferred.
4 ETAGs and ETAs As stated in the definitions above ETAs are awarded following tests and assessments carried out to the appropriate ETAG whose scope is as outlined below. The ETA is the formal document carrying the performance data against which the design process for selecting the size of anchor is carried out. When using manufacturer’s published data users should check, by reference to the actual ETA, that quoted performance actually comes from the ETA.
The choice of appropriate ETAG is outlined in sequence charts in section 5.
4.1 Test regimes and assessment criteria ETAGs contain comprehensive test regimes with demanding requirements, this mean specifiers can have full confidence in the functioning of the approved anchor and in the published performance characteristics.
Requirements are laid down for three key aspects:
Suitability, Admissible Service Conditions, Durability.
Suitability tests These tests investigate the sensitivity of anchors to various influencing factors, where appropriate, such as low and high concrete strength, repeated loads, location in cracks, repeated crack openings, sustained loads, elevated temperatures and aspects of installation such as hole cleaning, drill diameter tolerance, installation torque, humidity and temperature. Tests are only required in cracked concrete when the approval covers use in cracked concrete.
Admissible Service Conditions tests These tests determine the characteristic resistances as well as appropriate edge and spacing distances dependent on the option chosen by the manufacturer.
Durability Various environmental conditions are considered. Generally no tests are required if zinc plated anchors are restricted to dry indoor conditions and stainless steel anchors are used for normal external atmospheric exposure or permanently damp internal conditions. For harsh environments different materials or coatings may be approved following special tests. Bonded anchor materials are subject to special accelerated ageing tests.
Assessment criteria applied to test results
Comprehensive requirements for all suitability tests include:
- Load/displacement curves are assessed to ensure smooth curves with no uncontrolled slip.
- Products must show a limited scatter of results.
- Comparison of ultimate values from tests with various influencing factors against results from a reference test.
Special requirements are also set for individual tests.
Characteristic resistances for some anchors may be higher or lower than for previously published values due to the harmonised safety approach of the ETAG. Resistances for cracked concrete are generally lower than for noncracked concrete.
4.2 ETAGS issued to date.
At the time of publication the following ETAGs have been published.
ETAG 001 Metal anchors for use in concrete ETAG 014 Plastic anchors for fixing of external thermal insulation composite systems with rendering.
ETAG 020 Plastic anchors for multiple use in concrete or masonry for non-structural applications ETAG 029 Metal injection anchors for use in masonry
These illustrations are general examples only, other configurations of anchors also fall within these categories.
Anchors approved to ETAG 001 Parts 1 – 5 are suitable for single or multiple use in applications which are either statically determinate or statically indeterminate (see 4.3.2. below). They are qualified according to one of 12 options which cover the various application parameters as shown in Table 1 below, including concrete strength and condition (i.e. cracked or non-cracked); loading direction and edge/spacing criteria. Critical among these is that options 1- 6 cover use in cracked or non-cracked concrete while options 7 – 12 cover use in non-cracked concrete only. Low numbered options, 1 and 7, are the most comprehensive while high numbered options, 6 and 12, involve severe limitations, see Table 1 and section 6.2.
Currently the subject of fatigue is not covered by ETAG parts specifically although manufacturers may have their own data. EOTA are drafting the following annexes to ETAG 001 which are expected to be published within the foreseeable future.
Annex D Assessment of metal anchors under dynamic (fatigue) actions o Annex F Evaluation of anchorages in concrete concerning resistance to fire (To be based on o TR 20).
When selecting an anchor for a particular application care will be needed to check that the Option of a particular ETA covers the application parameters.
4.3.2 ETAG 001 Metal anchors for use in concrete Part 6: Anchors for multiple use in non-structural applications.
This ETAG Part is sufficiently different to the other parts of ETAG 001 as to be regarded as a different ETAG. It is aimed primarily at fixings for the top fixing of suspended ceilings, see also.
Anchors approved to this ETAG are suitable for use in concrete which may be cracked on non-cracked and for applications which are statically indeterminate only i.e. are safety critical but where load sharing can take place and the failure of an individual anchor will not lead to the collapse of the whole system. In order to use anchors with ETA to this ETAG part the preconditions of the definition of “Multiple use” must be satisfied, if they are not then anchors to ETAG 001 Parts 1 – 5 should be used.