CONSTRUCTION FIXINGS
What does it cover? The clues are in the title. “Post-installed” anchors are those
set in drilled holes rather than cast-in channels or sockets. The Code does not cover so-called “direct fastenings” such as powered fasteners (shot fired or gas nailing). Concrete refers to both cracked and un-cracked structures.
Anchors may be qualified for use in either cracked concrete OR un-cracked concrete only but we should remember that effectively the vast majority of concrete structures are cracked – it’s the nature of concrete - and deciding whether the concrete on a particular job is cracked or not is the job of a structural engineer. To be on the safe side we should always point the customer in the direction of an anchor approved for use in cracked concrete.
“ The applications covered by the Code are all those which may be regarded as safety critical.”
Masonry covers brickwork, stonework and blockwork. The
Code tends to concentrate on brickwork but the principles apply to all types of masonry. While there are ETAGs covering the use of resin anchors and plastic anchors in several categories of masonry, their selection is not too straightforward. If the masonry units of a job are not at least as large and as strong as the masonry units referred to in the ETA then special tests must be carried out on-site to determine the allowable load. The Code allows two different test regimes to be used for this and a further two for the case of anchors without ETA. The applications covered by the Code are all those which may
be regarded as safety critical. If the failure of an anchor could lead to anyone getting hurt that application is covered by the Code and almost certainly warrants an anchor with an ETA. One of six annexes deals with the selection of anchors. It
contains two flow charts, one for concrete and one for masonry. In both charts the question is asked: “Is the application statically determinate or indeterminate?” Applications in which the failure of just one anchor might lead to the failure of the supported structure are statically determinate. Applications where there is a degree of redundancy, such that the failure of one anchor would be catered for by load sharing among its neighbours, are statically indeterminate. Anchors with ETA may be qualified to cater for one or both of these conditions. This is one of many reasons why the selection of the anchor is the responsibility of the specifier.
102 Fastener + Fixing Magazine • Issue 76 July 2012 Many other aspects of the selection process are covered, such
as anchor positioning, corrosion, the direction and nature of loading as well as practicalities such as the need for immediacy of loading, and catering (at the selection stage) for the installer hitting reinforcement during drilling.
How easy is it to understand? We have tried to make it as clear as possible but all British
Standards are written in “Standard” English, a language where everything is heavily qualified lest someone should interpret a phrase or sentence in the wrong way. The terminology used in the Code is therefore very specific and certain terms have very precise meanings. The Code makes a clear distinction between the “Selection” and the “Design” of a fixing, and between the role of the “Specifier” and that of the “Designer”. It is the subject of loads that will probably cause most
confusion among non-engineers. A load will now be either an “action” or a “resistance”. The action is the load coming from the fixture. The resistance is the capability of the anchor to resist the action. That may sound straightforward but once we start introducing partial safety factors and you realise that the ETA system has no equivalent to the “recommended load” you will see why the CFA intends to publish a series of guides to cover various aspects including terminology and loads, together with one for each of the key stakeholders – specifiers, distributors, contractors/installers and testers.
What are the key messages? Within its eighty or so pages there is a great deal of advice,
much aimed at the specifier and plenty for the installer, but the language used in writing standards means that some messages are somewhat hidden. For instance, the Code does not state, as the Irish Code does, that an anchor with an ETA MUST be used. This is for two reasons. The first is that sometimes, despite the large number of ETA anchors now available and the wide range of applications, base materials and anchor types they cover, there may be some special applications for which one does not exist. In those rare cases, anchors without ETA may be used. The second is that the BS Code is a standard and has to
follow international rules, which forbid the use of the word MUST together with any reference to third party endorsements such as approvals. You will therefore notice advice in the foreword stating, “Users of this British Standard are advised to consider the desirability of selecting anchors with a European Technical Approval (ETA).” Throughout the text reference is made to “Anchors qualified according to ETAG” instead of “Anchors with an ETA”. But the message we hope is clear. If available, an anchor with an ETA SHOULD be used. That way everyone’s interests are much better covered: be they seller, specifier, contractor, installer or, most importantly, building user. Another strong message is aimed at preventing accidents
such as the fatal one in Dublin, which saw several parties taken to court. The message is that an anchor specification may be changed but only if the proper procedure is followed. All too often contractors use a different anchor to the one specified, either to save money or because getting hold of the specified anchor is a bit awkward. If an anchor is properly specified this will be the result of a thorough consideration of all the relevant influencing factors and a design process to select the correct size, using
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