CFA Guidance Note: ETAs & design methods for anchors used in construction.

Transcription

1 Ensuring best fixings practice CFA Guidance Nte: ETAs & design methds fr anchrs used in cnstructin. Cntents 1 Intrductin 2 Legal backgrund 3 Terminlgy 4 ETAs and ETAGs 5 Anchr Selectin 6 Design methds 7 Anchr Installatin in cmpliance with ETAs 8 Benefits f using anchrs with ETAs 9 References 1 INTRODUCTION ETA- 12/9999 ETA t ETAG 001 Optin 1 fr use in cracked r nn-cracked cncrete. This Guidance Nte has been written t cmplement BS 8539:2012 Cde f practice fr the selectin and installatin f pst-installed anchrs in cncrete and masnry published in Octber 2012 and which, by virtue f restrictins placed n the publicatin f British Standards, cannt be seen t endrse the use f independent endrsements such as Eurpean Technical Apprvals and which therefre refers t this Guidance Nte fr elabratin n the subject f ETAs. What BS 8539 des say with regard t ETAs is: Users f this British Standard are advised t cnsider the desirability f selecting anchrs with a relevant Eurpean Technical Apprval. It was the clear will f the BS drafting panel that, wherever pssible, i.e. fr any applicatin fr which a suitable anchr with an ETA exists n the market, then such an anchr shuld be chsen. ETAs (Eurpean Technical Apprvals), are the nly mechanism by which manufacturers can gain independently assessed apprvals fr anchrs t be used in safety critical applicatins thrughut Eurpe. They als facilitate the cmparisn f the perfrmance f similar prducts as they are based n tests carried ut t clsely cntrlled methds. The first ETAG was published, and the first ETAs granted in 1997, since which time additinal ETAGs have been published (as listed belw) t cver the vast majrity f drilled in anchr types in the mst cmmn structural materials. Many cmpanies large and small have since gained, between them, hundreds f ETAs fr their prducts and there are few applicatins which cannt be cvered using an anchr with an apprpriate ETA. The CFA has, via the CEO 1, actively participated in the relevant EOTA Wrking Grup and has strngly supprted the prcess. This Guidance Nte is intended t help the users f ETAs, i.e. the specifiers and installers f anchrs, t understand hw t select a prduct with an ETA t the mst apprpriate ETAG Part, t understand the basis f the design prcess and t ensure that installatin is carried ut t the requirements f the ETA. As indicated under legal backgrund the situatin is changing due t the implementatin f the Cnstructin Prducts Regulatin in July This Guidance Nte will be updated as and when necessary t keep all stakehlders up t date with the requirements. Readers wishing t be kept infrmed shuld lg n t the CFA website at and register fr the ccasinal newsletter. The full benefits t specifiers and users f using anchrs with ETAs are summarised in sectin LEGAL BACKGROUND One f the main aims f the Eurpean Unin is t avid barriers t trade between Member States. These barriers may be created by different natinal technical specificatins. The intentin f the EU was t harmnise the specificatins fr prducts in several Directives, which had t be transferred int natinal law in the Member States. Anchrs are cvered by the Cnstructin Prducts Directive [1,2] (CPD). This Directive describes in a general way hw t demnstrate fitness f a cnstructin prduct fr its intended use. This can be dne by fllwing a harmnised standard r if a prduct standard des nt exist - by gaining an ETA ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber 2012

2 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin based n a harmnised Eurpean Technical Apprval Guideline (e.g. ETAG 001 Metal anchrs fr use in cncrete). N natinal regulatins shall cntradict these technical specificatins. Frm 1 July 2013 the Cnstructin Prducts Directive will be replaced by the Cnstructin Prducts Regulatin (CPR). Under the CPR Eurpean Technical Apprvals will be replaced by Eurpean Technical Assessments (ETA) and ETAGs by Eurpean Assessment Dcuments (EAD). Existing Eurpean Technical Apprvals will remain valid until the end f their published validity perid at which time they are likely t be transfrmed t Eurpean Technical Assessments. Existing ETAGs will be transfrmed int EADs but new prducts nt cnfrming t existing ETAGs will have new EADs written fr them when requested by the manufacturer. 3.0 TERMINOLGY The basic terminlgy used in discussing ETAs is utlined belw. Much f the day t day terminlgy used in the business f cnstructin fixings is changing. A Guidance Nte: Anchr terminlgy and ntatin, detailing the crrespndence between ld and new terms is dwnladable frm the CFA website. In particular BS 8539 adpts terminlgy cmmn t Eurcdes s the term actin is used fr lads t be applied t the anchr via the fixture and resistance fr lads relating t the capability f the anchr t resist such actins. EOTA Eurpean Organisatin fr Technical Apprvals The rganisatin respnsible fr develping ETAGs in line with mandates issued by the Eurpean Cmmissin. Includes Apprval Bdies frm member states. CEO represents Eurpean manufacturers n the EOTA wrking grup. ETAG Guideline fr Eurpean Technical Apprval The Key dcument fr manufacturers, apprval bdies and test labratries. The framewrk fr test prcedures, assessments and design methds against which anchrs are tested and assessed. Prducts nt cvered by the exact scpe f a particular ETAG may be handled via a special prcedure by agreement amng the Apprval Bdies f EOTA. ETA Eurpean Technical Apprval The Key dcument fr specifiers. It cnfirms fitness fr the intended use and cntains details f the anchr specificatin, perfrmance characteristics, Design Methd and applicatin limits. It indicates which ETAG the anchr is apprved t and which Optin is cvered fr the categry f use (see sectin 5). Attestatin Of Cnfrmity The attestatin f cnfrmity prcedure requires initial type testing f the anchr prduct by an independent bdy. It als requires factry prductin cntrl and its supervisin by an independent labratry. This ensures that bth the prduct and its perfrmance remain unchanged in regular prductin frm that tested in the apprval prcedure. The ETAG 001 Metal Anchrs fr use in Cncrete requires attestatin t high levels as safety critical applicatins are cvered. CE marking An anchr prduct must have an ETA and have achieved the Attestatin f Cnfrmity befre the manufacturer may affix CE marking. It allws the cnstructin wrks t meet the relevant Essential Requirements f the Cnstructin Prducts Directive. CE marking enables prducts t be ffered fr sale thrughut the EU. It is nt intended as a quality mark but effectively the requirements are sufficiently strict that, in this case, it may be regarded as ne. Under the CPD CE marking is already mandatry in mst member states f the EU. Once the CPD has been replaced by the CPR CE marking will be mandatry fr cnstructin prducts which carry an ETA. Certain terms used in BS 8539 have meanings particular t that cde f practice: Specifier Persn respnsible fr the selectin f the anchr. (May be the designer.) Designer Persn with verall respnsibility f the design f a structure, including the anchrage, thrughut the whle design and cnstructin phase. (May be the specifier.) Selectin Overall prcess f selecting the type and size f an anchr r grup f anchrs (the design prcess is part f this). Design The prcess f determining the size f anchr in relatin t the lads t be transferred. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

3 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 4 ETAGs and ETAs As stated in the definitins abve ETAs are awarded fllwing tests and assessments carried ut t the apprpriate ETAG whse scpe is as utlined belw. The ETA is the frmal dcument carrying the perfrmance data against which the design prcess fr selecting the size f anchr is carried ut. When using manufacturer s published data users shuld check, by reference t the actual ETA, that quted perfrmance actually cmes frm the ETA. The chice f apprpriate ETAG is utlined in sequence charts in sectin Test regimes and assessment criteria ETAGs cntain cmprehensive test regimes with demanding requirements, this mean specifiers can have full cnfidence in the functining f the apprved anchr and in the published perfrmance characteristics. Requirements are laid dwn fr three key aspects: Suitability, Admissible Service Cnditins, Durability. Suitability tests These tests investigate the sensitivity f anchrs t varius influencing factrs, where apprpriate, such as lw and high cncrete strength, repeated lads, lcatin in cracks, repeated crack penings, sustained lads, elevated temperatures and aspects f installatin such as hle cleaning, drill diameter tlerance, installatin trque, humidity and temperature. Tests are nly required in cracked cncrete when the apprval cvers use in cracked cncrete. Admissible Service Cnditins tests These tests determine the characteristic resistances as well as apprpriate edge and spacing distances dependent n the ptin chsen by the manufacturer. Durability Varius envirnmental cnditins are cnsidered. Generally n tests are required if zinc plated anchrs are restricted t dry indr cnditins and stainless steel anchrs are used fr nrmal external atmspheric expsure r permanently damp internal cnditins. Fr harsh envirnments different materials r catings may be apprved fllwing special tests. Bnded anchr materials are subject t special accelerated ageing tests. Assessment criteria applied t test results Cmprehensive requirements fr all suitability tests include: - Lad/displacement curves are assessed t ensure smth curves with n uncntrlled slip. - Prducts must shw a limited scatter f results. - Cmparisn f ultimate values frm tests with varius influencing factrs against results frm a reference test. Special requirements are als set fr individual tests. Characteristic resistances fr sme anchrs may be higher r lwer than fr previusly published values due t the harmnised safety apprach f the ETAG. Resistances fr cracked cncrete are generally lwer than fr nncracked cncrete. 4.2 ETAGS issued t date. At the time f publicatin the fllwing ETAGs have been published. q q q q ETAG 001 Metal anchrs fr use in cncrete ETAG 014 Plastic anchrs fr fixing f external thermal insulatin cmpsite systems with rendering. ETAG 020 Plastic anchrs fr multiple use in cncrete r masnry fr nn-structural applicatins ETAG 029 Metal injectin anchrs fr use in masnry Alngside these main dcuments are a series f Technical Reprts cvering varius assciated aspects TR 018 Assessment f trque-cntrlled bnded anchrs TR 020 Evaluatin f Anchrages in Cncrete cncerning Resistance t Fire TR 023 Assessment f pst-installed rebar cnnectins TR 029 Design f bnded anchrs These are referred t in the mre detailed discussin f the scpe f each ETAG belw. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

4 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin The EOTA website lists ETAGs endrsed by the Cmmissin (dwnladable), alng with Technical Reprts and details f revisins t ETAGs cntained in Histry/Prgress Files and a full list f ETAs awarded t date. 4.3 Individual ETAGs in mre detail ETAG 001 Metal anchrs fr use in cncrete Parts 1-5 Part 1 General Part 2 Trque cntrlled expansin anchrs Part 3 Undercut anchrs Part 4 Defrmatin cntrlled anchrs Part 5 Bnded anchrs* Part 6 Anchrs fr multiple use in nn-structural applicatins Annex A Test requirements Annex B Tests fr admissible service cnditins Annex C Design methds** * Requirements fr Trque cntrlled bnded anchrs are cvered in an EOTA Technical Reprt: TR 018 Assessment f Trque cntrlled bnded anchrs, while Assessment f pst-installed rebar cnnectins is dealt with in TR 023. ** Design f bnded anchrs is cvered in TR 029. Part 2 Trque cntrlled Part 3 Undercut Part 4 Defrmatin cntrlled Part 5 Bnded anchrs These illustratins are general examples nly, ther cnfiguratins f anchrs als fall within these categries. Anchrs apprved t ETAG 001 Parts 1 5 are suitable fr single r multiple use in applicatins which are either statically determinate r statically indeterminate (see belw). They are qualified accrding t ne f 12 ptins which cver the varius applicatin parameters as shwn in Table 1 belw, including cncrete strength and cnditin (i.e. cracked r nn-cracked); lading directin and edge/spacing criteria. Critical amng these is that ptins 1-6 cver use in cracked r nn-cracked cncrete while ptins 7 12 cver use in nn-cracked cncrete nly. Lw numbered ptins, 1 and 7, are the mst cmprehensive while high numbered ptins, 6 and 12, invlve severe limitatins, see Table 1 and sectin 6.2. Currently the subjects f fatigue and seismic actins are nt cvered by ETAG parts specifically althugh manufacturers may have their wn data. EOTA are drafting the fllwing annexes t ETAG 001 which are expected t be published within the freseeable future and befre June Annex D Assessment f metal anchrs under dynamic (fatigue) actins Annex E Assessment f metal anchrs under seismic actins Annex F Evaluatin f anchrages in cncrete cncerning resistance t fire (T be based n TR 20). ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

5 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin Table 1 Optins fr ETAs qualified accrding t ETAG 001. Cncrete Characteristic resistance quted fr Optin N. Cracked & Nncracked Nncracked nly C20/25 nly C20/25 up t C50/60 One (lwest) value - any directin Tensile & Shear values Reduced Edge & Spacing Design Methd* 1 ü ü ü ü A 2 ü ü ü ü A 3 ü ü ü ü B 4 ü ü ü ü B 5 ü ü ü C 6 ü ü ü C 7 ü ü ü ü A 8 ü ü ü ü A 9 ü ü ü ü B 10 ü ü ü ü B 11 ü ü ü C 12 ü ü ü C * See sectin 6.2 fr a brief utline f the different Design Methds When selecting an anchr fr a particular applicatin care will be needed t check that the Optin f a particular ETA cvers the applicatin parameters ETAG 001 Metal anchrs fr use in cncrete Part 6: Anchrs fr multiple use in nn-structural applicatins. This ETAG Part is sufficiently different t the ther parts f ETAG 001 as t be regarded as a different ETAG. It is aimed primarily at fixings fr the tp fixing f suspended ceilings, see als 2. Anchrs apprved t this ETAG are suitable fr use in cncrete which may be cracked n nn-cracked and fr applicatins which are statically indeterminate nly i.e. are safety critical but where lad sharing can take place and the failure f an individual anchr will nt lead t the cllapse f the whle system. In rder t use anchrs with ETA t this ETAG part the precnditins f the definitin f Multiple use must be satisfied, if they are nt then anchrs t ETAG 001 Parts 1 5 shuld be used. The definitin f multiple use is as fllws fr anchrs t ETAG 001 Part 6*: <<The design f the fixture is such, that in the case f excessive slip r failure f ne anchr the lad can be transmitted t neighburing anchrs withut significantly vilating the requirements n the fixture in the serviceability and ultimate limit state. Fr example the design f the fixture may specify the number n 1 f fixing pints t fasten the fixture and the number n 2 f anchrs per fixing pint. Furthermre by specifying the design value f actins N Sd n a fixing pint t a value n 3 * (kn) up t which the strength and stiffness f the fixture are fulfilled and the lad transfer in the case f excessive slip r failure f ne anchr need nt t be taken int accunt in the design f the fixture. In the absence f a definitin by a Member State the fllwing default values may be taken: n 1 4; n 2 1 and n 3 3.0kN r n 1 3; n 2 1 and n 3 2.0kN * values fr n 3 are different fr ETAG 020 see belw. The value n 3 might be increased if in the design it is shwn that the requirements n the strength and stiffness f the fixture in the serviceability and ultimate states after the failure f ne anchr are fulfilled.>> The abve values fr n 1, n 2 and n 3 apply in the UK. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

6 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin The abve definitin f Multiple use means that when an applicatin fulfils the precnditins fr n 1, n 2 and n 3 the stiffness f the fixture des nt need t be cnsidered in the design. The first f the abve definitins is illustrated in the figure belw, the secnd is similar. n 1 - At least 4 fixing pints n 2 - At least 1 anchr per fixing pint n 3 < 3kN per fixing pint Fixture Figure 1 Illustratin f parameters qualifying an applicatin as Multiple use. Nte: Multiple use des nt mean r imply that an anchr can be re-used, mst cannt ETAG 014 Plastic anchrs fr fixing f external thermal insulatin cmpsite systems with rendering. Apprvals may be gained in a variety f base materials including cncrete (nrmal weight; lightweight aggregate r autclaved aerated) and/r masnry units f clay, calcium silicate, aggregate cncrete, autclaved aerated cncrete r ther similar materials. See als 4.4 belw ETAG 020 Plastic anchrs fr multiple use in cncrete r masnry fr nn-structural applicatins 5 parts cver 1) General requirements, use in 2) nrmal weight cncrete, 3) slid masnry, 4) hllw r perfrated masnry and 5) autclaved aerated cncrete. 3 annexes cver A) Details f tests, B) Recmmendatins fr tests t be carried ut n the cnstructin wrks and C) Design Methds fr anchrages. Anchrs apprved t ETAG 020 are suitable fr use in applicatins which are statically indeterminate nly and satisfy the definitin f Multiple use specific t this ETAG which is similar t that f ETAG 001 Part 6, see abve, with the fllwing values fr n 3. See als 4.4 belw. n 1 4; n 2 1 and n 3 4.5kN r n 1 3; n 2 1 and n 3 3.0kN ETAG 029 Metal injectin anchrs fr use in masnry 1 part cvers all test and assessment requirements 3 annexes cver A) Details f tests, B) Recmmendatins fr tests t be carried ut n the cnstructin wrks and C) Design Methds fr anchrages Anchrs apprved t ETAG 029 are suitable fr use in applicatins which are either statically determinate r statically indeterminate. See als 4.4 belw. 4.4 Qualificatin f the masnry f the jb. When anchrs with ETAs accrding t ETAG 014, ETAG 020 r ETAG 029 are specified fr use in masnry and the particular masnry f the jb in questin falls int the categry f masnry cvered by the ETA but the masnry units f the jb d nt meet r exceed the strength and dimensins f thse quted in the ETA then site tests are necessary t determine the allwable resistance. A prcedure fr carrying ut such jb site tests is called up in an annex f the relevant ETAG, hwever as the test requirements are particularly nerus (15 tests are t be carried ut t failure) BS 8539 als allws tests t be carried ut t an alternative prcedure in which as few as 5 tests may be carried ut and the results analysed t a statistical apprach. This test regime is utlined in BS 8539 Annex B and details f hw t carry ut the tests in CFA Guidance Nte Prcedure fr site testing cnstructin fixings ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

7 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 5 ANCHOR SELECTION. There are many factrs t be taken int accunt when selecting the mst apprpriate anchr, these are elabrated in BS 8538 sectin 5 and in a CFA Guidance Nte: Anchr Selectin. BS 8539 splits the selectin prcess int tw phases - the selectin f the anchr type and, nce that is determined, the chice f crrect size t satisfy the lading requirements f the applicatin. The latter prcess is referred t as Design and the methds by which it is carried ut are Design Methds, these are elabrated in sectin 6.0 f this Guidance Nte and Annex A f BS One aspect f vital imprtance t the first phase referred t abve, chsing the anchr type, is that, wherever pssible, anchrs qualified with an ETA t the mst apprpriate ETAG shuld be chsen. The fllwing sequence diagrams are intended t assist with the selectin f the mst apprpriate prduct, ne fr use in cncrete and ne fr anchrs t be used in masnry. Bth als indicate the apprach that shuld be fllwed if n anchr is available with an apprpriate ETAG. Sequence diagram fr the selectin f anchrs with the mst apprpriate ETAG fr use in cncrete. Is the lad applicatin statically determinate? N Is the cncrete cnsidered t be cracked? r unknwn N N Are the qualificatins fr Multiple use satisfied? Chse Anchrs with ETA t ETAG 001 Pts 1 5 Optin 1-6 Chse Anchrs with ETA t ETAG 001 Pts 1 5 Optin 7-12 Chse Anchrs with ETA t ETAG 001 Part 6 r ETAG 020 Pt 2 Are anchrs with apprpriate ETA available? N Design anchrage accrding t Design methd stated in ETA Is detailed perfrmance data available frm the manufacturer? N Determine Allwable Resistance frm site tests as BS 8539 Annex B.2.3. Design anchrage accrding t manufacturer s Design methd ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

8 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin Sequence diagram fr the selectin f anchrs with the mst apprpriate ETAG fr use in masnry. Is the lad applicatin statically determinate? N N Are the qualificatins fr Multiple use satisfied? Anchrs qualified fr Statically Determinate use e.g. ETAG 029 Anchrs qualified fr Multiple use e.g. ETAG 14 & 20 Are anchrs with apprpriate ETA available? N Are the qualificatins fr the base material satisfied? Chse an anchr allwed by the manufacturer t be used in this categry f masnry. N Is detailed perfrmance data available frm the manufacturer fr this categry f masnry? Determine Allwable Resistance frm site tests as per relevant ETAG r BS 8539 Annex B.2.2 N Determine Allwable Resistance frm site tests as BS 8539 Annex B.2.3 Design anchrage accrding t Design methd stated in ETA Design anchrage accrding t manufacturer s Design methd ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

9 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 5.1 Cmmentary n the sequence diagrams The use f anchrs with ETA is necessary nly fr applicatins regarded as being safety critical, ETAG 001 in particular refers t applicatins in which the failure f anchrs can: a) result in cllapse r partial cllapse f the structure; and/r b) cause risk t human life; and/r c) lead t significant ecnmic lss Is the applicatin relevant with respect t safety? T answer this questin requires engineering judgement and is the respnsibility f the specifier. In general safety relevance must be assumed when the failure f the anchrage wuld cmprmise the stability f the wrks, cause risk t human life and/r lead t cnsiderable ecnmic cnsequences. If this can be answered definitely with n the user can select and use anchrs withut ETA. If the reply is yes apprved prducts shuld be used r anchrs chsen which can demnstrate cmpliance with the Building Regulatins by sme ther means. It is always pssible t imagine a chain f events leading t the wrst cnsequences resulting frm the failure f any anchrage. This wuld suggest that all applicatins shuld be cnsidered t be safety relevant. Hwever the prbability f this chain f events arising shuld be taken int accunt. The recmmendatin f BS 8539 is clear that fr any safety critical applicatin anchrs with ETA shuld be used if there are such anchrs n the market. Is the part t be fixed part f the building structure? Simplified, the answer t the questin is easy: What happens if the fixed part is remved? If the clumn f a warehuse is remved the structure will cllapse (if the respective lads ccur). Therefre, the clumn is part f the lad bearing structure. Hwever, if a pipeline in a building is remved the lad bearing structure is preserved but the use f the building is restricted. Therefre, the pipeline is nt part f the lad bearing structure. Is the lad statically determinate r indeterminate? An applicatin is statically determinate if the stability f the fixture is dependent n every anchr supprting it and the failure f ne culd lead t cllapse f that element within the wrks. It is therefre indeterminate if the stability f the fixture is nt dependent n every anchr supprting it, i.e. there is a degree f redundancy. This means that if ne anchr fails, r mre likely suffers sme displacement, as a result f the applied lad, the fixture, be it a simple bracket r run f pipewrk r the grid f a suspended ceiling, will have sufficient stiffness t transfer the lad t adjacent anchrs. In the general case prving redundancy is difficult and requires sphisticated structural analysis. Fr mst cases therefre it is simpler and safer t assume the applicatin t be statically determinate and t select anchrs with ETA which satisfy that requirement e.g. t ETAG 001 Parts 1-5. In the case f suspended ceilings and similar light duty applicatins invlving multiple anchrs n such analysis is required if an anchr qualified t ETAG 001 Part 6 is used as lng as the applicatin satisfies the criterin fr Multiple use as defined in the ETAG and utlined in sectin Fr applicatins invlving Plastic anchrs t ETAG 020 Multiple use is defined in This issue is als elabrated in BS Is the cncrete cnsidered t be cracked? The respnsibility fr the decisin as t whether the cncrete in the area f an anchrage is cracked r nt rests slely with the specifying engineer. Cncrete may be cracked as a result f a variety f causes. ETAG 001 Annex C allws each Member State t give guidance n the distinctin between cracked and nn-cracked cncrete. In the absence f such guidance a methd is given fr determining whether a particular part f the structure is cracked r nt, by calculating the stress cnditin. If n such cnsideratin is made then cracked cncrete shuld be assumed. This means it is pssible t slve the prblem as there are numerus qualified prducts n the market. Hwever, the qualificatin class f the prduct makes the applicatin mre expensive. Verifying that cncrete is nt cracked can be required when the amunt f the lad ccurring and the gemetrical cnditins (small structures, clse spacing and edge distances f the anchrs) require detailed calculatin by explring all pssibilities. The capacity f anchrs suitable fr cracks given in the ETA can be at least 40% greater when they are anchred in cncrete which is nt cracked. The extra effrt in the calculatin can thus be justified. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

10 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 6.0 DESIGN METHODS Once the type f anchr has been determined the size can then be ascertained accrding t the relevant design methd. The design f anchrs with ETA is based n a cmmn safety cncept described belw. 6.1 Safety cncept The safety cncept can be simply stated as the requirement that the applied lad must be less than the ability f the anchr t supprt it with a suitable margin f safety. The precise safety margin depends n the design apprach. Anchrs with ETA use Design methds based n the Partial Safety Factr (PSF) apprach, see 6.2. Anchrs withut ETA r similar (usually natinal) apprvals will utilise the Glbal Safety Factr (GSF) apprach, see 6.3. The tw appraches are summarised belw in terms f the relatin between lads. Partial Safety Factr apprach Glbal Safety Factr apprach ETAG Annexes Currently design methds fr mst anchrs with ETA are published as an annex t the apprpriate ETAG e.g. ETAG 001 Annex C r in the case f bnded anchrs, an EOTA Technical Reprt TR 029 Design methds fr bnded anchrs. CEN Technical Specificatins t CEN/TS 1992 Since 2009 anchrs may have a design methd accrding t a CEN Technical Specificatin CEN/TS Parts 1 5 cvering the varius anchr types: Headed fasteners, Anchr channels, Pst-installed mechanical fasteners and Pst-installed chemical systems. The basis f the design methds enshrined in these TS is the same as ETAG 001 Annex etc. but varies in detail. As part f the preparatin fr the implementatin f the CPR it is expected that these five Technical Specificatins will be amalgamated int ne dcument and published as a Eurpean standard, prbably during Watch the CFA website (Apprvals etc.) fr details. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

11 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 6.2 Partial Safety Factr Apprach Ultimate limit state Nte: In the fllwing sectin the ntatin F is used t dente a frce (actin r resistance) in a directin unspecified. In practice F will usually be replaced by N fr tensile frces and V fr shear. The primary requirement fr safety is: F Sd < F Rd Where F Sd = Design Actin in accrdance with the relevant cde F Rd = Design Resistance F Sd is determined by the applicatin f a particle safety factr γ F t the characteristic actin F Sk F Sd = F Sk. γ F γ F is usually taken as 1.4 unless the permanent and variable cmpnents f the characteristic actin (G k and Q k ) are knwn, and they act in the same directin, in which case the fllwing applies: F Sd = G k. γ G + Q k. γ Q Where G k (Q k ) = Characteristic value f permanent (variable) actin γ G (γ Q ) = Partial safety factr fr permanent (variable) actin and are given in ETAG 001 as respectively 1.35 and 1.5. F Rd = F Rk /γ M Where F Rk = Characteristic resistance f the anchr γ M = Partial safety factrs fr the base material The characteristic resistances and partial safety factr fr the material are given in the ETA. Serviceability limit state Displacements at service lads are quted in the ETA fr use in the serviceability limit state design. Three design appraches are elabrated in ETAG 001 Annex C as indicated in Table 1 abve sectin These are related t the ptins. Design methd A being the mst cmprehensive and prvides a sphisticated design cncept in rder t gain ptimum perfrmance f the anchrs and at the same time an ecnmical design. The methd distinguishes between different lad directins (tensin, shear, cmbined tensin and shear), lw and high cncrete strengths plus characteristic and minimum edge and spacing distances. Methds B and C are simplified appraches ffering prgressively less flexibility f applicatin parameters as utlined in Table 1. In Design methd A the fllwing different failure mdes are cvered: Tensin actins: Shear actins: - steel failure - steel failure - cncrete cne failure - cncrete edge failure - pull-ut / pull-thrugh failure - pryut failure - splitting failure - cmbined cncrete and bnd failure in the case f bnded anchrs The design resistance F Rd is calculated fr every mde f failure cnsidering all influencing parameters, such as embedment depth, crss-sectinal area and steel strength f the anchr, axial and edge spacings, thickness f cncrete member, cncrete strength, reinfrcement, eccentricity f lad and cnditin f cncrete (cracked r uncracked). The design resistance is cmpared with the crrespnding design actin F Sd. The mst unfavurable mde f failure is decisive fr each lad directin. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

12 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin Subsequent t the prf fr separate tensin and shear lads an interactin requirement has t be fulfilled fr cmbined tensin and shear lads. In additin t the parameters which differentiate the 12 ptins, such as cncrete strength and cnditin (i.e. cracked r nn-cracked), lading directin, spacing centres and edge distances, there are many ther parameters which need t be cnsidered in arriving at a design that will satisfy all the necessary criteria and assumptins n which the ETA has been based. Sme f these parameters include:- cncrete member thickness, plate stiffness f the fixture, diameter f clearance hles in the fixture and eccentricity f lading in tensin, shear r bending and will be taken int accunt by the design methd. Design f the anchr is intended t be carried ut by a suitably qualified engineer. Mst manufacturers prvide sftware t assist in the selectin f fixings fr these safety critical applicatins. This is undubtedly the mst efficient way t ensure that all the necessary criteria have been taken int accunt althugh selectin using Technical Data sheets will still, in thery, be pssible. Manufacturers smetimes publish perfrmance characteristics based n criteria ther than ETA. The basis f data used in the design prcess shuld therefre be checked. 6.3 Glbal safety factr apprach. This design apprach is based n the use f a glbal safety factr, which is used t relate the perfrmance f the anchr in the base material t the recmmended resistance. The requirements fr the characteristic actin are: a) When manufacturer s data is used and site tests have nt been needed: characteristic actin recmmended resistance, i.e. F Sk F rec b) When the Allwable Resistance has been determined frm site tests: characteristic actin allwable resistance, i.e. F Sk F R,all 7.0 ANCHOR INSTALLATION IN COMPLIANCE WITH ETA 7.1. Anchrs All CFA manufacturers give the infrmatin n the specific cnditins fr installing their anchrs. This infrmatin respects the requirements f the crrespnding ETA and may be printed either directly n anchr bxes r n a leaflet within bxes. This infrmatin includes: drill bit diameter, thread diameter, maximum thickness f the fixture, minimum installatin depth, minimum hle depth, required trque mment, infrmatin n the installatin prcedure, including cleaning f the hle, preferably by means f an illustratin, reference t any special installatin equipment needed, identificatin f the manufacturing batch. ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber

13 CFA Guidance Nte ETAs & design methds fr anchrs used in cnstructin 7.2. Installatin f anchrs The fitness fr use f the anchr is assumed if the anchr is installed as fllws: anchr installatin carried ut by apprpriately qualified persnnel and under the supervisin f the persn respnsible fr technical matters n the jb site use f the anchr nly as supplied by the manufacturer withut exchanging the cmpnents f an anchr; anchr installatin in accrdance with the manufacturer s specificatins, including the use f a suitably qualified drill bit*; anchr psitining in accrdance with drawings prepared fr that purpse by an engineer; thickness f the fixture crrespnding t the range f required thickness values fr the type f anchr; check f cncrete being well cmpacted, e.g. withut significant vids; clearing the hle f drilling dust; anchr installatin ensuring the specified embedment depth, that is the apprpriate depth marking f the anchr nt exceeding the cncrete surface r embedment depth cntrl; keeping f the edge distance and spacing t the specified values withut minus tlerances; psitining f the drill hles withut damaging the reinfrcement; in case f an abrted hle: either the new hle shuld be drilled at a minimum distance away f twice the depth f the abrted hle r at a smaller distance if the abrted drill hle is filled with high strength mrtar. If under shear r blique tensin lad the abrted hle must be filled if it is in the directin f the lad; applicatin f the recmmended trque mment using a calibrated trque wrench. * Drill bits carrying the inspectin mark will satisfy this requirement, Inspectin mark (g t fr mre infrmatin) 8 BENEFITS OF USING ANCHORS WITH ETA The use f CE-marked anchrs with a Eurpean Technical Apprval has numerus benefits fr specifiers and installers quite apart frm cmplying with the recmmendatins f BS Anchrs apprved in accrdance with the cmprehensive test regimes and assessment criteria f ETAG 001 will necessarily crrespnd t state-f-the-art anchring technlgy. The liabilities f bth specifiers and installers are safeguarded. The thrugh investigatin f anchr functining in the suitability tests means that installatin safety is assured and anchrs will nt be sensitive t reasnable variatins frm the manufacturer s installatin instructins which may ccur in the cnstructin prcess. Perfrmance values may be relied upn. Design accrding t the relevant design methd, alng with sftware t guide the selectin prcess, means that specifiers can be cnfident that the mst suitable anchr has been chsen. This ensures ecnmic design f anchrs with an apprpriate safety margin. Eurpean Technical Apprvals are accepted in all EU member states a benefit in the case f freign cntracts. CE marking f anchrs demnstrates a permanent internal factry prductin cntrl f the manufacturing prcess which is regularly mnitred by an independent bdy, s the specifier can be cnfident that the prduct supplied t the jb site has the same perfrmance as that tested in the apprval prcess. Installers benefit frm clear installatin instructins, which manufacturers are bliged t prvide, while site engineers can identify the installed prduct frm bligatry markings. Overall this cmbinatin f benefits means that all parties t the cnstructin prcess and the resulting building can be cnfident in the lng term security f the anchrages used, including the user f the building wh will never even be aware f the existence f the anchrs. This is ne f a series f Guidance Ntes dwnladable free frm the CFA website at Fr mre infrmatin cntact: Cnstructin Fixings Assciatin Tel ms@the-cfa.c.uk Cntact us via the website: 1 CEO Cmitè Eurpèen de L Outillage (Eurpean Tls Cmmittee) represented n EOTA Wrking Grup by the CEO Technical Wrking Grup f which the CFA has held the Chairmanship since Best practice guide t the selectin and installatin f tp fixings fr suspended ceilings. Published jintly by the CFA and Assciatin f Interir Specialists ETAs & DESIGN METHODS FOR ANCHORS USED IN CONSTRUCTION - Issue 1. Octber