Recommendations for the improvement of existing …...Christof Haberacker, WTD 52 Recommendations...

Recommendations for the improvement of existing European norms for testing the resistance of windows and glazed façades to explosive effects

2015

Editors: Alexander Stolz, Fraunhofer Institute Oliver Millon, Fraunhofer Institute Authors: Chiara Bedon, University of Trieste Kevin C. Ans van Doormaal, TNO Christof Haberacker, WTD 52 Götz Husken, BAM Martin Larcher, European Commission Oliver Millon, Fraunhofer Institute Arja Saarenheimo, VTT George Solomos, European Commission Alexander Stolz, Fraunhofer Institute Laurent Thamie, CEA Georgios Valsamos, European Commission Andy Williams, CAST

The research leading to these results has received funding from the European Union as part of the European Reference Network for Critical Infrastructure Protection project.

ERNCIP thematic group Resistance of structures to explosion effects

EUR 27554 EN

Recommendations for the improvement of existing European norms for testing the resistance of windows and glazed façades to explosive effects

This publication is a Technical report by the Joint Research Centre, the European Commission’s in-house science service. It aims to provide evidence-based scientific support to the European policy-making process. The scientific output expressed does not imply a policy position of the European Commission. Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of this publication. Contact information European Commission Joint Research Centre Institute for the Protection and Security of the Citizen Georgios Giannopoulos Address: Joint Research Centre, Via Enrico Fermi 2749, TP 721, 21027 Ispra (VA), Italy E-mail: [email protected] Tel.: +39 0332 78 6211 Fax: +39 0332 78 5469 JRC Science Hub https://ec.europa.eu/jrc JRC98372 EUR 27554 EN ISBN 978-92-79-53394-5 ISSN 1831-9424 doi:10.2788/319252 © European Union, 2015 Reproduction is authorised provided the source is acknowledged. All images © European Union 2015.

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TRAFFICLIGHTPROTOCOL‘White’

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1ReviewreportoftestingmethodsTG:Resistanceofstructurestoexplosioneffects

European Reference Network for Critical Infrastructure Protection (ERNCIP) thematic group

Recommendationsforthe

improvementofexistingEuropeannormsfortestingtheresistanceofwindowsandglazedfaçadesto

explosiveeffects

Thematic group:

Resistance of structures to explosion effects

Coordinator: Dr. Alexander Stolz, Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut (EMI) Deputy coordinator: Dr. Oliver Millon, Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut (EMI)

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Editors: Alexander Stolz Oliver Millon Authors (in alphabetical order): Chiara Bedon Kevin C. Ans van Doormaal Christof Haberacker Götz Hüsken Martin Larcher Oliver Millon Arja Saarenheimo George Solomos Alexander Stolz Laurent Thamie Georgios Valsamos Andy Williams Acknowledgements: The research leading to these results received funding from the European Union within the European Reference Network for the Critical Infrastructure Protection project hosted at the Joint Research Centre (JRC) — European Commission — Via E. Fermi 2749 — Ispra, Varese (VA), Italy.

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Abstract:Itisimportanttoprotectcriticalbuildings(shoppingcentres,governmentbuildingsandembassies),infrastructureandutilitiesandtrainandundergroundstationsfromgettingdamaged,destroyedordisrupted by deliberate acts of terrorism, criminal activity and malicious behaviour. Normalregulationsandbuildingguidelinesdonotgenerallytakethesethreatsintoaccount.Theintroductionofappropriateregulationsorguidelines,wheredeemednecessary,shouldenhancetheresilienceofbuildingsandinfrastructuresagainstexplosionincidents.Inordertoprotecttheinfrastructure,testingmethodswhichcananswerthequestionastowhethercertainbuildingelementscanwithstandcertainloadingconditionscreatedbyanexplosiveeventarerequired.Theapplicablestate-of-the-arttechniquesmayincludeeitherexperimentalornumericalmethods,oracombinationofboth.Therefore,thethematicgroup(TG)ontheresistanceofstructurestoexplosioneffectswasformedinordertobringtherequiredexpertisetogether,tomakeitcommonlyavailableandtofindanddefineharmonisedmethods and solutionswhich can be provided to the decision-makers responsible forcriticalinfrastructureprotection.TheTGdescribedinafirstreport(JPC87202)thephysicalphenomenawhichhavetobeunderstoodinordertoensureapropertestingoftheelementsandacorrect interpretationoftheresults. Inasecondstage, thedifferencesbetweentheexistingstandards for testingblast-resistantglazingandwindows have been derived, and a basis for fundamental recommendations for the futuredevelopmentofthesuiteofEuropeanstandardshasbeenaddressed(JRC94930).Based on the prior findings, this report now formulates the proper enhancements of the existingstandardsintermsofactualrecommendationsfortheimprovementoftheteststandards.

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Contents1. Introduction............................................................................................................................6

2. Scopeofthereport.................................................................................................................7

2.1.Terminologyonglazing..........................................................................................................8

2.2.Availableteststandards.........................................................................................................8

3. Mountingofelements...........................................................................................................11

3.1.Requirements......................................................................................................................11

3.2.Remarksandcomments......................................................................................................12

3.3.Recommendationsforimprovement..................................................................................15

4. Loadingconditionsforblasttesting......................................................................................17

4.1.Requirements......................................................................................................................18



5. Measurementtechnique.......................................................................................................26

5.1.Requirements......................................................................................................................26



6. Interpretationofresults........................................................................................................31

6.1.Requirements......................................................................................................................31

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7. Listofreferences...................................................................................................................35

7.1.Standards.............................................................................................................................35

7.2.Literature.............................................................................................................................35

8. Listoftables..........................................................................................................................36

9. Listoffigures.........................................................................................................................37

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1. IntroductionThe standardisation of building products is an essential point of the building products. If thebehaviourofmaterialsandsystemsisknown,theirsafeusageinbuildingscanbeassured.Therefore,product standards define the required performance properties of components which have to befulfilled. The related test standards describe methods and processes to analyse the behaviour ofmaterialsandsystemsfordefinedloadingsinordertobeconformtotheregulationsoftheproductstandards.Extremedynamicloadingscenariosarerarelyconsideredinthebuildingindustry.Suchloadingsarecharacterised by high loading pressures which act in small loading times. Stress-wave and shock-wave loadingscomingfromdetonationand impacteventsbelongtosuch loadingscenarios.There,thebehaviourof the loadedmaterialsdiffers fromthebehaviourunderquasi-static loading,whichcan lead (in the case of dynamic loading) to an increase of strength and stiffness. However, theloading time is essential. Thus, for considering strengthening effects and in order to know thebehaviourofmaterialsandsystemsundersuchloadings,theloadingprocesshastobestandardisedand ideally internationally harmonised. Therefore, the physical background is described in(JRC87202).For safety glazing and safety windows, doors and shutters, international standards do exist,describingtestproceduressuchastheshock-tubetestandthearenatest.Basedon thedescribed testprocedures, thestandardsproposeaclassificationwith respect to theblast properties and the damage status of the sample. Different classification levels are definedwhichshowdifferencesincomparisontoeachother(JRC94930).The European standard lacks, which were investigated and analysed by the European referencenetwork for critical infrastructureprotection (ERNCIP) group in thepast (JRC94930), are especiallyidentified. These lacks were considered in this report and recommendations for improvement ofEuropean standards for both, safety glazing and safety windows, doors and shutters will beformulated.This report is structured as follows: Chapter 2 defines theboundary conditions for the report anddocumentsthescopeandtheterminology.Furthermore, itgivesanoverviewabout internationallyexistingstandardswithrespecttotheconsideredtopic.Chapters3,4,5and6focusonspecialdetailsto be addressed in the tests standards. Of these, Chapter 3 describes the mounting of the testsamples,Chapter4definesimprovementswithrespecttotheloadingconditions,Chapter5focuseson the measurement technique which has to be applied in the tests for an exact and reliableevaluationofthetests,andChapter6considerstheinterpretationoftheresults.

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2. ScopeofthereportTheclassificationofsecurityglazingpanes,securitywindowanddoorsystemswithrespecttotheirblast resistance is an important issue. Their loading can result from accidental or deliberatedincidents.Today,thefollowingmainstandardsareavailabledescribingthetestingprocessbyusingshock-tubefacilitiesandarenatestsapplicableintheEU.

• EN13123-1:2001‘Windows,doorsandshutters—Explosionresistance—Requirementsandclassification—Part1:shocktube’.

• EN13123-2:2004‘Windows,doorsandshutters—Explosionresistance—Requirementsandclassification—Part2:rangetest’.

• EN 13124-1:2001 ‘Windows, doors and shutters— Explosion resistance— Testmethod—Part1:shocktube’.

• EN 13124-2:2004 ‘Windows, doors and shutters— Explosion resistance— Testmethod—Part2:rangetest’.

• EN 13541:2012-06 ‘Glass in building — Security glazing — Testing and classification ofresistanceagainstexplosionpressure’.

• ISO 16933:2007 ‘Glass in building — Explosion-resistant security glazing — Test andclassificationforarenaair-blastloading’.

• ISO 16934:2007 ‘Glass in building — Explosion-resistant security glazing — Test andclassificationbyshock-tubeloading’.

The practical application of testing and classifying security glazing products reveals existinglimitations.Theselimitationsandidentifiedgapsintheexistingstandardisationhavebeencollectedandreported in (JRC94930)andarebasedonthegainedexperienceofthecombinedexpertteam.Eachmember of the expert team has broad experience in the practical application of the testingstandards.Thus,thisknowledgeandpracticalexperiencewillagainbeincorporated.In(JRC94930),acomplexcomparisonofinternationallyavailablestandardswaspreparedresultinginthe identification of gaps in the European standards. The results of this former report are nowaddressedinthisdocumentandimprovementsareformulated.TheaimistoessentiallyimprovetheexistingEuropeanstandardsforthetestingandclassificationofsecurity-glazingproducts.Hence, this report presents recommendations for the future development of one combinedimprovedEuropean standard in this area.Bypublishing this report andmaking it available for theresponsiblenationalstandardisationbodies,astimulationofthediscussionfortheimprovementoftheEuropeanstandardsisintendedwithrespectto:

• applicabilitytoglazingproducts;• mountingofelements;• loadingconditions;• measurementtechnique;• interpretationofresults.

Ingeneral,thereportwillgiverecommendationsforglazingandwindowstestedtoexplosioneffects.Therecommendationswilladdressthefollowingspecificareasoftheexperimentaltestprocedures:

• shock-tubetests;• arenatests.

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2.3.TerminologyonglazingSince this document is a reportwhich is basedonearlier reports (JRC87202, JRC94930), the sameterminologyisusedforreasonsofconsistency.Inthisreport,securityglazingisdefinedforboth:

• securitywindowsandsecuritydoorsystems;and• security-glazedfaçadesystems.

Itisimportanttoconsiderthewindow(ordoor)orthefaçadeasasystem,consistingofthesecurityglass,thegasketorsealant,theframe,thefixingoftheframe,andthesupportsystem.Theblastpressure istheloadingpressurewhichactsasreflectedpressureonthetestsample.Theloading is applied to thewhole areaof thewindowor façadewithequalpressure-timehistoryoneachpointofthetestsampleunderpermissionofacertainscattering.Thebehaviourof theglass isdependenton thepanesize.The loadon the support systemand itsperformancearealsodependentonthesizeoftheglasspane(s).If glass is tested in a rigid frame, the stresses in the glass aremaximised as are the loads in theframe’s fixings.However, if theglass ismounted ina framewithgasketsor sealants, the system’sflexibilitytendstoreducestressesintheglassandthefixings.

2.4.AvailableteststandardsIntroducingthethemeoftesting,classifyingandcertifyingsecurity-glazingproducts,thissectionwillgiveashortoverviewaboutexistingstandards,theiravailabilityandthecontentsaddressedinthem.Generally speaking, in European standards, extreme loading on building components is limited toglazingproducts.Althoughthestandardfor loadingconditionsEC1DINEN1055pointsoutthattheconsideration of extreme loading events has to be taken into account (DIN EN1055-100), cleardefinitionsofloadingsareonlyavailableforsecurityglazingandsecurity-glazingproducts.The EuropeanCommittee for Standardisation (CEN) published the first standards for testing blast-resistantglazing in2001.These includeaEuropeanstandard(EN)fortestingsecurity-glazingpanes(newestversion:EN13541:2012)andasuiteofstandardsfortestingcompletesystemslikewindows,doors and shutters (EN 13123-1:2001, EN 13123-2:2004, EN 13124-1:2001 and EN 13124-2:2004).Currently,therearenostandardsfortestingglazedfaçades.Allthesestandardsdescribeproceduresforblastclassificationusingshock-tubetestsorarenatests.EN13541:2012onlyconsidersasinglepaneoflaminatedglasswithasinglefixedsizeinarigidframeunderexactlyprescribedtest-andboundaryconditions.Duetotheimportanceofthepanesizeandthesystem’sflexibility(asnotedabove),thisstandardhaslimitedpracticalutility.Thestandardcouldbeamended topermit anypane size tobe tested. It shouldbenoted that this standardproducesconservative results but may provide a usual limit case for the glass. This standard only makesprovisionfortestingwithashocktube. Inthescopeofthisreport,onlysecuritywindow,doorandfaçadesystemsare focusedon.Standardsdescribing testingproceduresandclassification levelsofpuresecurityglazing,liketheEN13541:2012,arenolongertakenintoaccount.EN13123-1:2001andEN13123-2:2004considerthewholeopeningsystemforwindows,doorsandshutters. Thementioned standards allow tests at the element’s real size and with its real frame,producing realistic results. Inaddition,no limitationsaredefined for thegeometryof thesamples.Withrespecttothefixationofthesecurity-glazingproductonthesubstructure,ithastoberealised

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asrealisticallyaspossible.Thisincludesthekindoffixation,thenumberoffixationelementsandthedirectionofthefixationelementsinthesubstructure.Thesestandardsmakeprovisionforshock-tubetestingandarenatestingwithsmallcharges.TheUnited States government General Service Administration (GSA) published a test protocol forglazingin2003(GSA-TS01:2003),whichpermitstestingbyshocktubeorarena.Theactualtestloadsarenotincludedsincetheyareclassified.The InternationalOrganisation for Standardisation (ISO)published the standard ISO16933:2007 in2007. Itwas largelybasedontheENstandards. Itextendedthetestconditionstoallowtheuseoflarge charges in arena tests. It also included additional small charges to encompass the GSA testrequirements.Aparallelstandard(ISO16934:2007)coversshock-tubetesting.The American Society for Testing and Materials standard ASTM F 1642:2004 was developed inparallelwiththeISOstandards.The available test standards describe procedures to investigate the blast resistance of security-glazingsystems.Guidelinesaremadewithrespectto:

• boundaryconditionsandmountingofelements;• loadingconditions;• measurementtechnique;• interpretationofresults.

The comparison of the abovementioned standards identifies gaps and limitations of Europeanstandards. The result of the comparison is that the ISO 16934:2007 gives the best definitions andregularitiesandthecleareststatements.TheISOstandarddefineshazardcriteria,especiallyfortheinterpretationofthedamage.In improving the practicability of the existing European standards for shock-tube testing, the nextchapterswillrefertoeachoftheabovementionedpointsandproviderecommendationstoincreasethepracticability.It is worth documenting one improvement here: the European test standards for security-glazingsystems refer only to windows, doors and shutters. Since glazing façade systems with differentmounting and boundary conditions with increasing trend are integrated into today’s and futurebuildingstructures,theconsiderationofsuchglazingsystemsassecurity-glazingsystems,whicharealreadyavailableonthemarket,isstronglyrecommended.Uptothepresentday,suchelementsaretestedonlyreferringtoEN13123-1:2001andEN13124-1:2001—however,withoutthepermissionofacertification.Table2.1summarisesthegeneralitemsofthecurrentstandards.

Table2.1:Generalitemsofallcurrentstandardsdescribingblastloadsonsecurity-glazingproducts.

Standard/Item Application Test method Sample

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EN 13541:2012 Glass

Shock-tube test Fixed, vision size 1 100 mm × 900 mm

EN 13123-1:2001/ EN 13124-1:2001

Windows, doors, shutters Shock-tube test User defined

EN 13123-2:2004/ EN 13124-2:2004

Windows, doors, shutters Arena test User defined

GSA-TS01:2003 Windows Shock-tube or arena test 1 650 mm × 1 200 mm, specified other sizes are permitted

ASTM F 1642:2004 Glass, windows Shock-tube or arena test User defined ISO 16933:2007 Glass, windows Arena test Fixed, vision size

1 100 mm × 900 mm ISO 16934:2007 Glass, windows Shock-tube test Fixed, vision size

1 100 mm × 900 mm

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3. MountingofelementsThischapterconsiders theboundaryconditionswithrespect to the integrationof thetestsamplesintotheshock-tube,herecalledmountingofelements.Sincebuildingcomponentsshouldbetestedwiththegoalofgettingacertificateindicatingacertainresistancetoaspecificblastloadingandthelatterusageofsuchelementsinbuildingconstructions,the aimmust be to realise the fixation of the test samples on the substructure as realistically aspossible.Based on the existing test standards, this chapter will document the status quo shortly and willderive recommendations resulting from remarks of the expert team of the ERNCIP group. Thissectionconsidersdifferenttestarrangementsfortheaccomplishmentofblasttests.3.1.Requirements

The requirements of the current test standards regarding the mounting of test samples in testfacilities (shock-tube tests and arena tests) are quite different. The deliverable D1 (JRC87202)documentsthestatusquooftheexistingteststandards.Generallyspeaking,themorethespecimenispurpose-builtforaspecificbuilding,theharderitistocomplywithcommon,complexregulationsin standards for the testing institute. For example, EN 13123-1:2001 and EN 13123-2:2004 or ISO16933:2007 and ISO 16934:2007 force a realisticmounting of the test elements,which should beveryclosetothelatterapplicationofthebuildingcomponent. It isclearlystatedtoaccomplishthetestasrealisticallyaspossibletogetrepresentativeandcomparableresultswithrespecttothetestsamplebehaviourunderacertain loading.However, this requirementdemandsahigh flexibilityofthetestsite.Thespecifications for testing laminatedglazingpanes (e.g.EN13541:2012)aremuchmoreprecisethan the requirements for windows, doors or shutters [EN 13123-1:2001, EN 13123-2:2004, EN13124-1:2001, EN 13124-2:2004], which is likely to be a result of theminor size of the specimenbecausethetechnicalrequirementsarenormallyeasiertoachieve inthatcase. Inadditiontothat,thelaterassemblyconditionsinthebuildingareoftennotthatclearlydefinedbecausetheelementtobetestedisnotdesignedforaspecificbuildingbutasastandardproductformanyapplicationsinthefuture.However,forbettercomparability,certainspecificationsarenecessaryeveniftheloadingvarietyislarge.Table3.1documentsasummaryofallcurrentstandardsconsideringblastloadingonsecurity-glazingproductswithrespecttomountingofthesamples.

Table3.1:Mountingoftestsamplesofallcurrentstandardsdescribingblastloadsonsecurity-glazingproducts.

Standard/Item Test of partially opened systems

Mounting of samples

EN 13541:2012 No Well defined EN 13123-1:2001/ EN 13124-1:2001

No General description only

EN 13123-2:2004/ EN 13124-2:2004

No General description only

GSA-TS01:2003 No Outline description only ASTM F 1642:2004 No Outline description only ISO 16933:2007 No Well defined for glass; general

description for windows ISO 16934:2007 No Well defined for glass; general

description for windows

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3.2.Remarksandcomments

Based on the review report of testing methods — deliverable D2 (JRC94930) — indicating therequirements of the boundary conditions of blast tests needed today, the following remarks aregivenbytheexpertteamtobeconsideredformountingthespecimensproperly.Sincethemountingofthetestsamplesisacriticalpointinanytestarrangement,thegivenremarksapplytobothshock-tubetestsandarenatests.— Stiffnessofthesubstructure:inmostteststandards,astiffsubstructureisdemandedtoresist

the expected loading levelwithout significant deformations,which can have an influence onthe test sample responseand thusan influenceon the test result. This isnotanappropriateapproachinanycase,forinstanceiftherealsubstructureisactuallyamoreflexibleorweakerbuildingfaçade.

— Tightnessofthetestsetup:aclosedsubstructureisrequiredtopreventtheexplosionpressurefromescapingor, in thecaseofa test sample integrated intoaclosedstiff container/box, toprevent the air blast fromwrapping around the sample. The existing test standards demandthattheblastpressureshouldonlyhittheattackfaceofthetestsample.Air-floweffects,whichcanleadtoasupportofthetestsampleonitsprotectiveface,havetobeavoided.Acompleteairtight sealingof the jointbetween the test specimenand thesubstructureoracompletelyairtightenclosedsubstructurecanonlybeachievedwithgreatmechanicalefforts.Nevertheless,ithastobeassuredbythetestinstitutethattheresultingleakingpressuredoesnotinfluencetheloadingconditionsandtheresponseofthespecimen.Furthermore, incaseofusinganopen testarrangementwitha test sample integrated intoacontainer, ithastobeguaranteedthatthepressurecompensationbetweenthe insideofthecontainer and the outside (pressure on the attack face of the test sample) should not occurbeforethetestobjecthasreacheditsmaximumdeflection.Thiswouldresultinanunderloadofthe specimen and would positively influence the test sample behaviour. The next figureexplainsitgraphically.Itshowsanexemplarypressure-timehistorywithacomparisonbetweenthepressureinside(protectiveface)andthepressureoutside(attackface)ofatestspecimenusinganenclosedtestbox.Theexamplevisualisesthatonlytheblastloadingissignificantforthetargetresponseonlyduringthefirst34ms.Afterthat,pressurecompensationbetweentheinterior and the exterior of the test container occurs, resulting in similar pressure-timehistories.

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Figure3.1:Comparisonofexteriorandinterioroverpressure

— Connections:accordingtoEN13124-1andEN13124-2,window,doorandshuttersystemsaretested, and these systems consist of the glazing, the frame and the fixation elements forintegration into the substructure. The standards demand that the substructure of the testfacilityshouldbeabletoprovidearealisticintegrationofthetestsampleaccordingtoitslatermounting situation. The connections between the test specimen and the supportingsubstructure,andhereespeciallytheinteractionbetweenfixationelementsandsubstructure,arenotwithinthefocusofthetest.However,theyshouldbefabricatedinsuchawaythattheyrepresentarealisticscenarioandtheexpectedfailuremode.In practice, the assembly of specimens depends on the connections to the test sitesubstructure.Betweenthespecimenandthewallsorthebottomofthetestsite,asupportingsubstructurewhicheithersimulatesawindowordoorframe,afaçadeoranotherload-bearingstructure of a building is erected. The following Figure 3.2 should indicate exemplary testsetupswiththeirconnectionlinesorjoints.

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Figure3.2:Exemplarytestsetupsandtheirconnectionlines;a)testofaglazing,b)testofawindow/door,c)testofafaçadeelementwithdampingelements.

The constructivedesignof the supporting substructureand the connections to the specimen(redlines)arecriticalforthesuccessofthetest.Thesupportingstructureandtheirconnectionsarenottobetested.Ifglazingelementsaretobetested,theconnectionsaremostlymadebyscrewedjoints.Ifwholewindowsordoorsaretobetested,thejointisoftenwelded,eventoensureasealedconnection.Ifthespecimenincludesdamperelements,it isalsopossiblethattheconnectionshavetosimulateacablefaçadeinsteadofareinforcedconcretewall. Inthatcase,thedesignactsinaccordancewiththeactualprincipleofthemounting,whichisintendedfor the building. The tightness of the connection for movable parts is hard to consider ingeneral.

a) b)

c)

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— Clampingpressureforglass:fortestingglazingpanesonly,theclampingpressureoftheline-supportsurroundingthewholetestsamplecanhaveasignificanteffectonthetestresultsandshouldbespecifiedaccordingtoISO16933:2007,ISO16934:2007andEN13541:2012.

— Area of the substructure: as mentioned in the previous report (JRC87202‘Review report oftestingmethods’, Figure 24), themeasured reflected peak pressures depend on the surfaceareaofthesurroundingsubstructure.Thetest institutehastoguaranteeaplaneshock-front.The substructure should be large enough so that the impulse acting on the test specimen isuniformlydistributed.Thisuniformityhastobeprovenbycalibrationmeasures.

3.3.RecommendationsforimprovementBased on the above documented remarks and comments, the following recommendations for theimprovementoftheexistingEuropeanstandardsareproposedbytheexpertteam.

1. Stiffnessofthesubstructure

Theactualassemblyconditionsshouldbeconsideredasrealisticaspossibleduringthecertificationprocess. That means it is recommended to adapt the integration of the test samples into thesubstructureofthetestfacilitytoachievearealisticmountingofthesamplewhichiscomparabletotheexpectedmountingsituationinthelaterusageofthetestedbuildingcomponent.Inanycase,itisrecommendedtodocumentthemountingofthetestsampleinthetestreport.Nevertheless, since the knowledge about the real mounting of the structural elements into thebuildingisofteninadequateortheeffortstoachievetheseconditionsthroughconstructivemeasureswouldresultinexpensesbeingtoohigh,simplificationsshouldbepossiblewherebythespecimeniserectedinastiffersubstructurethaninreality.Thisisinagreementwiththecurrentteststandards.Onlythewindow,doorandshuttersystemistested,notthesystemincludingthesubstructure.Thiswould avoid a positive influence of the substructure on the behaviour of the tested system. Theresultofthisprocedureisalittlehigherloadingofthetestsample.Forexample,asetupwithawholecablefaçadeisusuallynotaffordable.Thesolutionwouldbetosimplifythecablewithasteelbartotestasingleelement.Furthermore, future standards shoulddetermine that thedeflectionof the substructure shouldbemeasured during the test. The result of the measurement will quantify the stiffness of the sub-structureandwillbepartofthetestreportandthetestcertificateasadescriptionoftheboundaryconditionsofthetestarrangement.Thisisespeciallyrecommendedifthetestspecimenistestedasaproductforunknowninfrastructureprojectsinthefuture.

2. Tightnessofthetestsetup

Aclosedsubstructureisrequiredtopreventtheexplosionpressurefromescaping(shocktube)or,inthe caseof a closed container/box, toprevent theair blast fromwrappingaround the sample. Toensurethatthe leakingpressurebehindthetestspecimendoesnot influencethebehaviourofthetestsampleandeventhetestresult,theimprovedteststandardsshouldspecify:

• whichdegreeoftightnessofthetestarrangements(substructure)isrequired;• whichmethodscouldbeusedforclosingthesubstructure.

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Furthermore,thereisaneedforadditionalmeasurementsofthepressureontheprotectivefacetoensurethatnorelevantairblastintrudesthetestchamberorwrapsaroundthetestspecimen.Somespecimendesignsallowopeningsduringtheloading.Inthiscase,especiallywhenlongpositivephasedurations are requested, regulations should require pressure transducers on the back side orprotectionsideofthetestobject.

3. Connections

Forfutureregulations,itisrecommendedtoconsiderarequirementfortheconnections.Iftherealconditions are known or achievable, the connections should not be more ductile, weak or evenunnecessarilystifferorstrongerthanintherealapplication.However,iftheyare,consciousductileconnectionsshouldbetestedaspartofthespecimen.

4. Clampingpressureforglass

ThespecificationsofthekindofclampingrealisingthelinesupportanditsclampingpressureinISO16933:2007,ISO16934:2007andEN13541:2012shouldbeincludedinallrelevantteststandardsfortestingglazingpanesonly.

5. Areaofthesubstructure

For the improvement of current standards, the expert team recommends indicating a minimalnominal value for the area surrounding the specimen. The test institute has to guarantee a planeshock-front acting on the test specimen. Thepressure and the positive specific impulse should beuniformly distributed on the test sample. This has to be proven by providing calibrationmeasurements.Inthecasethisuniformityisnotgiven,theinstitutehastotakemeasuresinordertomeetthisrequirement.

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4. LoadingconditionsforblasttestingTheloadingoftheelementisthemostimportantboundaryconditioninaclassificationtest,whichisaddressed in this chapter. The definition of the blast load and its generation is a basis for aclassification of glazing products used in building constructions. In this scope, the chapter firstcompactly describes the status quo of existing standards (EN 13123-1:2001, EN 13123-2:2004, EN13124-1:2001andEN13124-2:2004)(Section4.1.).InSection4.2.,thestatusquowillbeanalysedandevaluated.Commentswillbegivenwithrespectto identified gaps. Finally, in Section 4.3., recommendations for the improvement of the existingstandardswillbeformulated.The source of an explosion, for example, can be a chemical reaction (or detonation of highexplosives).Thisreactionresultsinarapidriseoftemperatureandpressureinaveryshorttime.Inparticular, the very high pressures can cause considerable damage to building structures.Furthermore,thetypeofexplosionscandiffer,startingfromdeflagrationtofastdeflagrationandupto detonations. The actual type of the regarded explosion also determines the significant loadingparameters pressure amplitude, shape and increase of pressure profile and the loading duration.Phenomenawhichcouldcausethedifferenttypeofexplosivesaredetonationofhighexplosives,gasanddustexplosionscausedbyaccidents,sabotageorterrorism.

Anexplosionisaphysicalprocessinwhichsuddenlylargeamountsofenergyarereleasedthatwaspreviouslyconcentrated inasmallspace.This leadstoasuddenvolumeexpansionofgases,whichfinally creates blast waves travelling through the surrounding medium air emanating from anidealisedpointsource.

Figure4.1:Characterisationofablastwavedescribedbythethreeproperties:peakoverpressure(loadingpressure),positivedurationandpositivespecificimpulse.

Blast waves spherically propagate in the medium air with strongly decreasing peak pressures byincreasing thedistance to thedetonation source. If ablastwavehits a structure, it is loadedbyaspecificpressure-timehistory,ideallyshowninFigure4.1.Ingeneral,ablastwaveischaracterisedbyashockfront,whichisinturncharacterisedbyasuddenstrongincreaseoftheloadingpressureup

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totheultimateloadingpressure(pmax),adecayofthepressureoverthetimewithapositivephase(periodofoverpressure)andafollowingnegativephase(undertowphase).Theloadingpressureonthestructureisthereflectedpressure(pmax).Thedecayphaseiscontrolledbythepositiveduration(t+)— the time of an existing overpressure. The third describing property is the positive specificimpulse (i+),mathematically describedby the area under the pressure-timehistory of the positivephase.Thenegativespecificimpulseduetotheundertowphase(i-)ismostlynotconsidered.

Dependingonthescenario(explosivetype,explosivesubstance,mass,stand-off),thepressure-timehistorycansignificantlydiffer.Thus,pressure,positivedurationandpositivespecific impulseare indirectcorrelationwithchargemassanddistance,aswellastheexplosiontype.

4.1.RequirementsThissectionprovidesacomprehensiveoverviewaboutcurrentEuropeanandISOstandardsforblasttesting on security-glazing products. Here, the loading conditions for both methods of blastresistanceanalysis—arenatestsandshock-tubetests—aresummarised.Table4.1summarisestheroughloadingconditionsofallcurrentstandardsusedforacertificationofglazingproductsagainstblastloading.

Table4.1:Summaryofthegeneraldescriptionoftheloadingconditionsofallcurrentstandardsdescribingblastloadsonsecurity-glazingproducts.

Standard/Item Standard loading User defined loading Petrochemical loading and gas explosion

EN 13541:2012 Large charge VBIED No No EN 13123-1:2001/ EN 13124-1:2001

Large charge VBIED No No

EN 13123-2:2004/ EN 13124-2:2004

Small charge PBIED No No

GSA-TS01:2003 Large charge VBIED Yes No ASTM F 1642:2004 Small PBIED and large

charge VBIED Yes No

ISO 16933:2007 Small PBIED and large charge VBIED

No No

ISO 16934:2007 Large charge VBIED Yes, without certification No In the current standards applicable for shock-tube tests (EN13541, EN13123-1, EN13124-1 andISO16934), see Table 4.2 and Table 4.3, where four to six loading levels used for a productcertificationaredefined.These levelsaredescribedbythethreeabovementionedblastproperties:reflected pressure (pmax), positive duration (t+) and positive specific impulse (i+). In addition, thepositivedurationisproposedtobegreaterthan20ms.Furthermore,thecurrentstandardsdescribethe generation of the blast load (EN 13124-1:2001, EN 13124-2:2004, EN 13541:2012, ISO16933:2007andISO16934:2007).

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Table 4.2: Definition of loading levels in existing European standards (EN 13541:2012-06 and EN13123–1:2001-10)applicableforshock-tubetests.

EN 13541:2012-06, applicable for laminated glazing panes EN 13123–1:2001-10; applicable for windows, doors

and shutters Level pmax [kPa] i+ [kPa ms] Level pmax [kPa] i+ [kPa ms]

ER1 50 < pmax < 100 370 < i+ < 900 EPR1 50 < pmax < 100 370 < i+ < 900

ER2 100 < pmax < 150 900 < i+ < 1 500 EPR2 100 < pmax < 150 900 < i+ < 1 500

ER3 150 < pmax < 200 1 500 < i+ < 2 200 EPR3 150 < pmax < 200 1 500 < i+ < 2 200

ER4 200 < pmax < 250 2 200 < i+ < 3 200 EPR4 200 < pmax < 250 2 200 < i+ < 3 200

Table4.3:Definitionof the loading levelsaccordingto ISO19634:2007-07applicable forshock-tubetests.

ISO 16934:2007-07, applicable for laminated glazing panes, windows and doors

Level pmax [kPa] i+ [kPa ms] Mass [kg] Stand-off [m]

ER30 30 170 30 33

ER50 50 370 100 34

ER70 70 550 160 33

ER100 100 900 500 39

ER150 150 1 500 1 000 41

ER 200

200

200 2 200

2 000 46

For completeness, Table 4.4 and Table 4.5 summarise the loading conditions applicable for arenatests,describedbychargemassandstand-off.InTable4.5(ISO16933),theresultingblastparameterspmaxandi+aregivenaswell.

Table4.4:DefinitionofloadinglevelsaccordingtoEN13123-2:2004-05forapplicationinarenatests.

EN13123-2: 2004-05; applicable for windows, doors and shutters Level Mass [kg] Stand-off [m]

EXR1 3 5.0

EXR2 3 3.0

EXR3 12 5.5

EXR4 12 4.0

EXR5 20 4.0

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Table4.5:DefinitionofloadinglevelsaccordingtoISO16933:2007-07forapplicationinarenatests.

ISO 16933:2007-07, applicable for laminated glazing panes, windows and doors

Level pmax [kPa] i+ [kPa ms] Mass [kg] Stand-off [m]

EXV45 30 180 100 45

EXV33 50 250 100 33

EXV25 80 380 100 25

EXV19 140 600 100 19

EXV15 250 850 100 15

EXV12 450 1 200 100 12

EXV10 800 1 600 100 10

All values given for the loading levels are defined as minimal values. However, this leads to theassumptionthatthetestshavetobecarriedoutbyusingtheseminimalvalues.

4.2.RemarksandcommentsThe review report (Deliverable D2 (JRC94930)) and the comprehensive overview of Section 4.1.summarisetheresultingdefinitionofloadingconditionsbyapplicationofthecurrentteststandards.Thefollowingconclusionsaredrawn.

— AstrictdistinctionismadeinEuropeanandISOstandardswithrespecttothesimulatedloadingscenario—close-indetonationsandfar-fielddetonations.Shock-tubeexperimentsarecapableof representing far-field detonations and arena tests are applicable for close-in and far-fielddetonations.

— The European standards consider loading scenarios for vehicle borne improvised explosivedevices(VBIEDs)inarenatests,unliketheISOstandard.

— Theteststandardswhichareapplicableforshock-tubetestingshowastrongsimilarityintermsof loading levels. Thatmeans that all standards define loading levels expressed by reflectedoverpressureandpositivespecificimpulsewithadefinedrangeofscattering,whichareequalbetweenENandISO.OnlyISOdefinestwomoreloadinglevels.

— ThecurrentEuropeanstandardEN13123-1defines four loading levels (EPR1-EPR4).For theselevels, values for pressure and impulse are defined, which the products have to withstandwithinthetest.However, thesevaluesrepresentonlyminimalvaluesforbothparameters. Inthisscope,thestandardsprescribethatpressureandimpulseshouldnotbelowerthanthesevalues and shouldnot exceed the valuesof thenexthigher level. Taking this into account, arangeforpressureandimpulseisdefinedanditisencouragedtotesttheproductsattheclassrangeminimum.Aswell,EN13541definesforreflectedpressureandpositivespecific impulserangeswith the requirementof fulfillingat least theminimalvalues.Fromourpointofview,this procedure is not sufficient. The product has to be tested against the highest values forpressureandimpulsetorepresentallcombinationsofacertainloadinglevel.

— Theteststandardsapplicableforarenatestsareverysimilarintermsofloadinglevels.— The defined real-test scenarios, which are the basis of the definition of the loading levels

accordingtoreflectedoverpressureandpositivespecificimpulse,coveronlydetonationsfrom

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high-explosive events and do not define loading levels for gas explosions coming fromaccidentalevents.

4.3.RecommendationsforimprovementTakingtheremarksofSection4.2.intoaccount,thefollowingrecommendationsarederived.

— TheexpertteamfirstrecommendsaharmonisationoftheENandISOstandardswithregardtothe number and the definition of loading levels. Here, the classification levels of the ISOstandardsofferawider,morespecialisedclassificationofbuildingproductswithloadinglevelsbelowEPR1andbetweenEPR1andEPR3.

— Furthermore, it is proposed that the European standards will be extended to include arenatests to representVBIEDs.Thiswould lead toahigher flexibility in theapplicationof the testmethod.However,thetestinstitutehastoguaranteeandtoprovethattheconditionsofafar-field detonation, resulting from a VBIED in a large distance, are fulfilledwith respect to theplanarwave,onlyloadingontheattackfaceandnosupportingbystreamingeffects.There,thefollowingquestionshavetobediscussedanddefinitionshavetobemade,respectively.

o How should VBIED scenarios be characterised with reference to charge weight,explosivetypeanddistance?

o Taking into account the different substances that can cause explosive events, thequestion is how equivalent factors for the description of reflected overpressure andpositivespecificimpulsescanbedefinedforalltests?Especiallyforshock-tubetesting,it has to be guaranteed that the scenario-specific blast parameters represent thedecisiveloadingscenarios.

— Theexpertteamsuggeststheimplementationofanoptionforuser-definedloadingscenarios.Blast tests should be accomplished with respect to pressure-impulse combinations below,betweenorabovethedefinedloadinglevels.Sincecertificatescanbeissuedfortestsoutsidethe defined loading levels, a higher practicability will be reachedwith this option.With thisprocedure, the tendency of more individualised demands on building structures and theircomponents will be addressed. For building components like glazing façades, which areconstructed andmanufactured for a special single application, a certificationwith respect tospecificloadingscenariosshouldbepossible.

— With respect to the definition of loading levels and the related blast properties, animprovement is strongly recommended. New loading levels have to be defined with a newidentification (see Figure 4.2). However, it is still recommended to integrate the old loadinglevels.Inordertorepresenttheupperlimitsofreflectedpressureandpositivespecificimpulse,anewidentificationoftheloadinglevelsissuggested.Thenewfixedloadinglevelsaredefined,as documented in Table 4.6. There, the required parameters to be reached in the test areprintedinbold.

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Table 4.6: Recommendation for the definition of loading levels with respect to reflectedpressureandpositivespecificimpulseaccordingtothecurrentstandard(EN13123-1:2001).

Level pmax [kPa] i+ [kPa ms]

EPR1 0 < pmax ≤ 50 0 < i+ ≤ 370 EPR2 50 < pmax ≤ 100 370 < i+ ≤ 900 EPR3 100< pmax ≤ 150 900 < i+ ≤ 1 500 EPR4 150 < pmax ≤ 200 1 500 < i+ ≤ 2 200 EPR5 200 < pmax ≤ 250 2 200 < i+ ≤ 3200

— Additionally, inthescopeoftheimplementationforuser-definedloadingscenarios,therange

of loadingscenariosshouldbeextendedtogasexplosionsaswell.Forthispurpose,scenariosshould be specifiedwith respect to the transient loading profile consisting ofmaximum andminimumpressureandpositiveandnegativeimpulse.Furthermore,theshapeofpressureriseanddecreasehastobedefinedwithrespecttoapplicabilityinthetestfacility.

— Forarenatests,thetypeandshapeofthechargeshouldnotbespecifiedaslongasthecorrectblast parameters are applied to the test specimen. The use of spherical or hemisphericalchargesrepresentsanidealbutoftennotrealisticscenario.Furthermore,theuseofsphericalchargesmade of TNT is cost-intensive. Therefore, alternative explosives, such as ammoniumnitrate/fueloil(ANFO),shouldbeacceptedasalternativesinordertoconsiderrealisticloadingscenariosresultingfromaVBIEDorPBIED.

Suggestionsfortherealisationoftheimprovements

Below,therecommendationsarespecifiedanddescribedingreaterdetail.Here,adistinctionfortherecommendationsismade.Thefollowingpointswillbeaddressed:

• shock-tubetesting;• arenatesting.

Shock-tubetesting

Withrespecttotheloadinglevels,Europeanteststandardsforglazingandsecuritywindows,doorsand shutters show that equal blastproperties have tobe reachedwithin the tests.HarmonisationwiththeISOstandardsisstronglyrecommended.Thisstandarddefinessix loadinglevels insteadoffour fixed levels. Taking a higher flexibility and the requirement of loading levels of customers’demand into account, a new distinction into loading levels is proposed in this document. Startingfromapressure-impulsediagram, several loading levels canbe identified. There, lower andupperlimitsforreflectedoverpressureandpositivespecificimpulsearedefined.

• plow:0kPa• pup:400kPa• ilow:0kPams• iup:5200kPams

With this new classification, gas explosions are also addressed beside far-field detonations due tohigh explosives. With the distinction into loading levels, a similarity to the current standards is

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enabled allowing a comparison of products tested before ensuring a very high flexibility. Thus, acertificationof glazing productswith regard to the expectedblast loading for the specific buildingcomponent can be reached, resulting in a customer-defined product certification. For the testinstitutes,thenewclassificationoffersthepossibilitytoofferawideandfullrangeoftestswithintheperformancecapabilitiesoftheirtestfacility.

Furthermore,fortheapplicationofnewfixedloadinglevels,theexpertteamstronglyrecommendsdefining thehighestvalues foraspecific loading level forbothblastparameters-reflectedpressureandpositive specific impulse as standard.Hereby it canbe guaranteed that theworst case of theloadinglevelistested,andnotitsminimalrepresentation.Iftheproductwithstandsthisloading,itisassumed to also withstand all loading with p-i combinations with lower reflected pressure andpositivespecificimpulse.

Additionally, a new, more specific identification of the loading level is needed. The expert teamproposedan identification label (ID)consistingofthemaximalvaluesofthereflectedoverpressureand thepositivespecific impulse.Figure4.2 shows theproposednew loading levelsdefinition inageneral overview. The pressure-impulse diagram could be integrated into the standard. Anapplicationofthisdescriptioninarenatestswiththesameadvantagesisalsopossible.

Figure4.2:Proposeddefinitionofloadinglevelsbyusingapressure-impulsediagram.

Besidethe loading levelsof thecurrentEuropeanstandards, thegraphicshowsadistinction intoacertain number of loading levels within the proposed bounds for reflected pressure and positivespecific impulse defining the newadditional loading levels. The choice of the range for both blastparameters is taken with respect to the loading levels of the current standards. An increment of

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5kPaischosenonlyforthelowpressures.Figure4.3visualisesthep-idiagramapplicableforshock-tubetests.Thep-idiagramproposesvaluesfordetonationwithTNTaswellaschemicalsubstances.If in the underlying scenario the blast loading is caused by substances other than TNT, the blastpropertiesrequiredfortestinghavetobecalculatedbyusingtheTNTequivalentfactorsornumericalsimulations.

Figure4.3:Proposeddefinitionofloadinglevelsbyusingapressure-impulsediagramforapplicationinshock-tubetests.

However, tests with a specific customer requirement for a p-i combination, which lies within aspecific level, should be possible as well. In this case the combination of reflected pressure andimpulseof the test represents theupperbond forbothblastproperties. If theproductwithstandsthisloading,it isassumedthatitwithstandsloadingsoflowerp-icombinationsaswell.However,acleardocumentationinthetestcertificateandthetestreportisrequired.

Ifmorethanonesampleistested,theloadingcombinationwiththelowestreflectedpressureisthedecisive one. A graphical explanation in a p-i diagram indicating the experimental results andvisualisingthecoveredloadinglevelsisrecommended.

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Arenatests

TheexpertteamrecommendsaharmonisationoftheEuropeanstandardwiththeISOstandardwithrespecttothedefinitionof loadinglevels.Furthermore,thesameprocedureasthatforshock-tubetesting is applicable for close-in detonation scenarios. For arena tests, the same procedure withrespecttotheclassificationissuggested.

Consideringtherequestsforahigherflexibilityinthedefinitionofloadinglevelswithregardtothecustomers’ demand, a certification for levels not specified in the standards should be possible.Accordingtoshock-tubetests,theexpertteamproposestointegrateanequivalentflexibilityintheloading conditions for arena tests used for a product certification as well. In this scope, extremeloading scenarios characterised by detonations of high explosive substances can differ strongly intheir loading parameters (reflected pressure, positive and negative specific impulse, positive andnegativeduration,increaseanddecayoftheshockfront)andarecontrolledby:

• chargesubstance;• chargemass;• stand-off;• chargeshape.

The substance in particular has a strong influence on the loading properties that reflectedoverpressureandimpulse.Asthisisascloseaspossibletoarealisticscenario,alimitationtoTNTastheonlyappliedhighexplosivematerialseemstobetoostrict.Here,theimprovedstandardshouldallowtheuseofsubstancesotherthanTNTorsimilarhighexplosives,as longastheycouldensurereliableandreproducibleresults.Therealisationisnotcriticalinarenatestssincetheloadingcanbeachievedbyusingtherequiredchemicalsubstance.

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5. MeasurementtechniqueThis chapter considers the required measurement technique to be used in the blast test setups.Besides the required sensor-solutionsmeasuring loadingproperties and responseof the structuralelements, theirproperties and characteristics are summarisedaswell. Forexample, the sensitivityandthesamplingrateareimportantmeasurestobefulfilledinsuchfastrunningtests.

5.1.RequirementsThecertificationofbuildingproductsrequiresastandardisedtestsetupwithaspecificmeasurementtechnique to analyse the load. In high pressure experiments carried out by both shock-tube andarenatests,thecharacterisationoftheblastwaveis,besidetheevaluationofthedamage,themostessentialcriterion.Thus,fortheaccomplishmentofthetestspressure,transducersarerequiredforthe evaluation of the loading. The damage analysis is done optically. Adding deflection and strainmeasurementsystemswillgiveadditionalinformationabouttheelementbehaviour.However,suchsystems are not essential for the qualification of glazing products for a certification against blastloadingsandthusnotpartoftherequirements.

Beside the measurement characterising the loading, the climate properties and the storageproperties housing the test sample prior to the tests have to be recorded. There, beside thetemperatureandtherelativehumidity,theambientpressureisprescribedfordocumentationinthetestprotocolsaswell.

Table5.1:Measurementsystemsprescribedinallcurrentstandardsfortheaccomplishmentofblasttests.

Standard/Item Number of pressure transducers

Required parameters of climate condition

Storage conditions

EN 13541:2012 2 Ambient temperature, air pressure; surface temperature

Not specified

EN 13123-1:2001/ EN 13124-1:2001

Not specified; at least 1

Ambient temperature, air pressure; relative humidity; surface temperature

Not specified

EN 13123-2:2004/ EN 13124-2:2004

Not specified Ambient temperature, air pressure; relative humidity; surface temperature

Not specified

GSA-TS01:2003 ≥ 2 outside; 1 inside Not specified Not specified ASTM F 1642:2004 Shock-tube test: 3

Arena test: 4 Surface temperature Not specified

ISO 16933:2007 ≥ 3 Surface temperature Not specified ISO 16934:2007 ≥ 1; not specified Ambient temperature, air

pressure; relative humidity; shade temperature

Not specified

5.2.RemarksandcommentsCurrent standards (JRC94930)prescribe theuseof pressure transducers tomeasurepressure-timehistories.There, thebest locationon theattack facewouldbe in themiddleof the test specimen,because thehighest reflected impulseusuallyappears there. Inmost instances, this isnot feasiblebecauseofthreereasons:

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• first,theeigenfrequencyoftheglazingcanhaveasignificanteffectonthemeasurement;• second, pressure transducers are a considerable cost factor and could be destroyed during

thetest;• third,thepressuretransducerontheglazingwouldinfluencetheresponseoftheglazing.

Forthatreason,itisrecommendedtomeasurethesignalattheedgesofthetestobjectoronamorerigidpartofit.Nevertheless,statementsaboutthepressureconditionsinthemiddleofthepanearerequiredandpossibleifthetestisconductedinawell-known,calibratedtestbenchorif,incaseofarenatests,forexample,arigidcubiclehavingtransducers inthemiddleandthesamedimensionsandstand-offdistanceasthetestcubicleiserected.In the mentioned arena tests especially, calibration protocols or pressure-time histories fromadditionalrigidtestcubiclesshouldbeamandatorypartofthetestreportandresults.Additionally,thepressurehistory in themiddleof thetestsamplecanalsobecalculatedbynumericalmethodsbasedonavalidatednumericalmodelandthepressurerecordsattheedges.Currentstandardsprescribeshock-tubeandarenatestsfortheanalysisofsingleelements,likeonepane, one securitywindowor one security door, applicable to the integration in one story of thebuildingstructure.However,testsonsingleandmulti-storyfaçadesystemsoflargerdimensionsarenot foreseen in the current standards. In these cases in particular, a clear statement about thenumberandtheplacesofpressuretransducersseemstoberequired,takingintoaccountthelargedimensionsofsecurityglazingsystemswithrespecttotheshock-waveloading.

5.3.RecommendationsforimprovementFor both shock-tube tests and arena tests, the instrumentation of experimental setup and thesupportingstructureisnecessaryforanappropriateevaluationofthetestresultsintermsofcorrectloadinganddamageanalysis.Themeasuringsystemsshouldallowforthecompletedocumentationofall relevantdatafromtheresultingshockwaveandshock-wavepropagation,butalsoofclimatedata.Forthecharacterisationoftheload,theside-onpressureandthepeakoverpressureon—or,ifnotpossible, close to—thesample,arestrongly required.Furthermore, the interiorair-blastpressurebehindthetestsample(intheprotectivearea)hastoberecordedbyadditionaltransducers.Whenusingcubiclesinbothtestarrangements,thismeasurementbecomesrelevantinanalysingpossiblesupportingpressuresontheprotectivefaceofthetestsample(Chapter3).In the next subsections, the measurement systems are documented and recommendations areprovidedwithrespecttotheirpositionandtheirnumberwithinthetestsetup.

Air-blastpressuretransducers

Air-blast pressure transducers should be used to record themagnitude, above ambient pressures,and time development of the reflected shockwave impinging on the test specimen. The air-blastpressure transducers used should be capable of recording the anticipated air-blast pressure-timehistorywithinthelinearrangeofthetransducerandshouldbecalibratedproperlypriortotheblasttest. Each transducer shall have a rise/response time and resolution sufficient to capture thecompleteevent.Calibrationrecordsshouldbeprovidedsoastodemonstratethattheequipmentisabletomeasureairpressureintheexpectedrangewithatoleranceof±5%.

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Positioningofair-blastpressuretransducersinshock-tubetests

Theexpertteamrecommendstheuseofat leasttwopressuretransducers inonetestsetup.Theyshouldbemountedadjacenttothetestspecimentorecordthehistoryofthereflectedoverpressure.Thenumberandthepositionoftransducersdependonpossiblyoccurringclearingeffects.Thishasto be taken into account in the planning stage of the test series. The positions of all pressuretransducers have to be documented in both the test protocol and in the test report. There, thepositionsandthedistancestothetestsampleshouldclearlybeaddressed.Thepressuretransducersmountedadjacenttothetestspecimenshouldbecalibratedduringspecialpre-tests against pressure transducers set in the centre of rigid blanking plates fixed in the test-specimensupport.Thecalibrationrecordsshouldeitherdemonstratethatthereadingsareidenticalinthetwolocationsorprovidemeansofadjustingthereadingsofthepressuretransducersmountedadjacenttothetestspecimentovaluesthataccuratelyrepresentthereflectedpressure-timevaluesat the centre of the test specimen. The test institute should document a relevant pressure-timehistory indicating a planar shock-wave loading acting on the specimen, in terms of a calibrationexperiment. There, it is recommended to show the pressure-time histories of adjacent pressuretransducersandofonetransducerlocatedinthemiddleofthesampleposition.

Positioningofair-blastpressuretransducersinarenatests

Inordertocarryoutarenatests,theexpertteamrecommendsthreeair-blastpressuretransducerstobeplacedadjacent to the test specimensoron separate concreteblocks at the same stand-offdistance in order to avoid transducers on the test specimen itself, as in that case they wouldinfluencetheresponseofthespecimen.Furthermore,twopressuretransducersshouldbeplacedinthefreefieldatthesamedistanceasthetestspecimentoprovewhetheracompletedetonationofthe charge has been achieved. The installation of an additional pressure transducer inside theenclosed supporting structure is required to record the pressure-time history inside the enclosedsupporting structure. However, in case of an expected internal supporting pressure, an additionalpressuregaugehastobeinstalledinsidethesubstructureascloseaspossibletothetestsample.Ifthepressuretransducersareplacedadjacenttothetestspecimen,theactualblast loadactinginthecentreofthetestspecimencanbecalculatedviaappropriatenumericalsimulationsbasedontherecordeddataofthepressuretransducerslocatedatdefinedpointsaroundthetestspecimen.Usingthis approach, the clearing effect can also be considered. The numericalmodel is adjusted to theexperimentaldatathataredeterminedbythepressuretransducersmountedontheexteriorwallofthesupportingstructureaswellasthetransducersusedinthefreefield.DataacquisitionsystemThedataacquisitionsystemshouldrecordthesensordatacollectedbythepressuretransducersandtheadditionalmeasurementsystemsandhastobeusedinbothshock-tubetestsandarenatests.Itconsistsofeitherananalogueoradigitalrecordingsystemwithasufficientnumberofchannelstoaccommodate all pressure transducers and any other facultative chosen electronic measuringdevices(e.g.straingauges,etc.).Furthermore,thehighlydynamiccharacteristicsofdetonationsandtheresultingshockwaverequirea high sampling rate (at least >100kHz) and rise-time sensitivity response to a peak pressure of10μs.Ahigher sampling rate is recommendedby theexpert teamand should ideally reachabout

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1MHz. Filters to exclude alias frequency effects from the data should be incorporated (ISO16934:2007,GSA-TS01:2003).Thesystemusedforarenatestsshallbecapableofreliablyrecordingthepressure-timetraceofthehigh peak pressure (positive phase) and the following undertow phase (negative phase). The testinstitute has to guarantee that the chosen recording time of the data acquisition system is longenoughtoenableanevaluationoftheloadwithrespecttothetest-samplebehaviour.Therefore,therecordingofthepressure-timehistoryofashock-tubetestandanarenatestshouldstartbeforetheshock wave reaches the test specimen and should last for a time span of at least 10 times thedurationofthepositivephasefromthetimeofarrivalatthetestspecimen.ClimatedataTheclimateconditionsshouldberecordedwithin30minpriortothetest,astheyarenecessaryforaproperanalysisofarenaandshock-tubetests.Dependingonthetestconfiguration, the followingrequirementsarerecommendedforshock-tubetestsandarenatests.

• Shock-tube test: ambientair temperature, relativehumidity, ambientatmospheric pressureandsurfacetemperatureofthesample.

• Arenatest:ambientairtemperature,relativehumidity,ambientatmosphericpressure,windspeedanddirectionandsurfacetemperatureofthesample.

The ambient temperature should be measured on a shadow area close to the test sample in anappropriateway.Thesurfacetemperatureshouldbecapturedinthecentreofthetestspecimen.Ifthe test sample consists of different materials (e.g. glass and steel), the temperature of eachcomponent shouldbemeasured. The results of themeasurementshave tobedocumented in theexperimentalprotocolandshouldbestatedinthetestreport.The climate conditions of the storage of the test samples should be recorded with respect totemperatureandrelativehumidity.Theaveragevaluesofatimeof24hourspriortothetestshouldbedocumentedinthetestreport.AdditionalmeasurementsThetest reportshouldgiveacomprehensivebutcompleteoverviewof thetestand itsconditions.Photographic imagesandhigh-speedrecordingscansupport theanalysisof theelementbehaviouranditsevaluation.Photographsarestronglyrecommendedandthusrequiredfor:

• testsetup;• testconditionspriorandafterthetest;• statusofthetestsampleafterthetestonrelevantpositions(middleoftestspecimen,edges,

connectionsof the frameand theglazingwith the frame, space surrounding the test setupwithrespecttosplintersandfragments).

Theuseofahigh-speedcamerafortheanalysisofthedamageprocessisnotprescribed,buttheuseof such systems is useful for supporting the damage analysis if it can give information about thedamage stageswith respect to the loading. For testswith a hazard classification, awitness panelworkingasadebriscatcherisrequiredandstronglyrecommended.Furthermore,thebehaviourofthetestspecimenduringtheblastloadcanbeobservedusinglaser-optical deflectionmeasurement systems and strainmeasurement.With that, the damage process

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andtheelementbehaviourwithrespecttotheappliedloadisrealisedsupportingtheevaluationoftheblasttest.Suchfacultativesystemscanbearrangedonpointsofinterest.

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6. InterpretationofresultsThis chapter is focused on the interpretation of the results. Beside the evaluation of the loadingproperties,thebehaviourofthetestspecimensregardingcrackingandfragmentationisconsideredtoresult inaqualification into loading levelsandhazardclasses. Italsodescribesthecontentsofatest report according to the current standards and documents the experimental findings. Acomparisonismaderegardingtheevaluationofthedamageincurrentstandardsandthedefinitionofclassificationlevels.

6.1.RequirementsTheinterpretationoftheresultsisfocusedontheanalysisofthebehaviourofthetestsamplewithrespect to the applied loading. Current standards cover loading levels described by the blastpropertiesandreflectedoverpressureandpositivespecific impulse(seeChapter4)withrespecttotheobserveddamageafterthespecificexperiment.Thedamageisdescribedintermsofthedestructionoftheglassbysplinteringorfragmentation,orofthecompletesystembythedestructionoftheglassandthedestructionordamageoftheframeconstructionincaseofsecuritywindowsanddoors(EN13124-1:2001).Furthermore, the interpretation of the results contains the documentation of the results in a testcertificateandinatestreport.Thus,theessentialpointsofbothdocumentslikethewrittenresultofthetestleadingtoadefinedstructurewithallrequiredinformationareaddressedinthischapter.

Table6.1:Requirementsontheinterpretationofresultsincomparisontoallcurrentstandardsdescribingblastloadsonsecurity-glazingproducts.

Standard/Item Number of test samples

Damage assessment criteria

EN 13541:2012 3 No opening permitted EN 13123-1:2001/ EN 13124-1:2001

1 No opening permitted > 10 mm + splinter criteria

EN 13123-2:2004/ EN 13124-2:2004

1 No opening permitted > 10 mm + splinter criteria

GSA-TS01:2003 1 Hazard criteria ASTM F 1642:2004 Minimum 3 Hazard criteria + fragment

definition ISO 16933:2007 Minimum 3 Hazard criteria + fragment

definition ISO 16934:2007 Minimum 3 Hazard criteria + fragment

definition

6.2.RemarksandcommentsENstandardsdefinepass/failcriteriabasedondamagetotheglass(SorNS)andtheanchoring.Theapplicationof thedamageclassSorNSwith respect to theobservedglassdamage isqualitativelydescribed. Furthermore, the largest acceptable damage of the glazing and/or security-glazingproductsisdefinedquantitatively.

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In comparison to EN standards, ISOandASTMstandardsdefinea certainnumberof hazard levelsbased on the distribution and size of fragments behind the test sample. There, a more detailedqualifiedevaluationofthedamagecanbeachieved.Withrespecttothederivationofblastparametersfromablastexperiment,onlyISO16933:2007andISO 16934:2007 (AnnexA) describe a clearmethod for how to derive them froma pressure–timehistory. Ifmorethanonepressuretransducer isused,onlythe ISOstandardsdescribeaprocedureforhowtocalculatetherelevantvaluesandhowtoconsiderdeviationsfrommeanvalues.Allteststandardsprovideastructureandessentialpointsrequiredforatestcertificateandthetestreport.

6.3.RecommendationsforimprovementBasedonthegivenrequirementsandthecommentsresultingfromthereviewofcurrentEuropeanstandards, the following recommendations are given by the expert team. The current ISO16934:2007(E) ‘Glass inbuilding—Explosion-resistant securityglazing—Testandclassificationbyshock-tube loading’ has been considered as the basis and the recommended changes andamendmentsaresummarisedbelow.GeneralIngeneralithasbeennotedthatthestyleandcontentofISO16934:2007(E)andISO16933:2007(E)are noticeably different and any future review of the latter document should ensure consistentphrasingandterminology.LoadinglevelsAdditionalloadingrequirementsincludeVBIEDscenariosfor100kgto1000kgatrangesof15mto30m as well as PBIED scenarios of 3kg to 20kg at ranges of 3m to 10m. Thesemay not all beachievableinshock-tubestests.Forpetrochemicalandgasexplosionscenarios,otherrequirementsmayneedtobeconsidered.LoadingconditionsLoading conditions should generally be quoted as a combination of reflected pressure (peakoverpressure)and impulse (positivespecific impulse)witharepresentativeequivalentchargemassandrange.User-definedloadingconditionsshouldbeallowedfortestingandcertificationwithinputparametersbeyondthelistedexistingrange.TestandclassificationThe testmethodshouldbeaimedatclassifying ‘securitywindowsanddoors’butshouldalsohavethefacilitytocoverbothglassandfaçadeswherepossiblesothatthegeneralprinciplesofthetestmethodcanbeappliedtoglassorfaçades.

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Testingofframedwindowsystemsshouldbeallowedwith‘representativeandrealisticfixings’.Thisiscoveredinparagraph5.2(ISO16934:2007)‘Fenestrationassemblies’,butthesamplecanonlybeassessedandcannotbeclassified.Testingofaminimumofthreeidenticalsamples(asperISO16933:2007)isrecommendedinordertoestimatethestatisticalsignificance.Eachtesthastoleadtothesamecategorisation.Thelimitationsoftestingasinglesampleareclearlyexplainedinparagraph5.3(ISO16934:2007),butarequirementtotestmultiplesampleswouldbebeneficial.Theexplosionresistanceofthetestspecimensshouldcontinuetoberatedaccordingtothedefinedhazard levels and the corresponding analysis of the fragmentation of the sample. For this, thedamage on the protective face of the test sample (with respect to splintering, fragmentation,crackingandopenings)hastobeconsidered.Bytestingmultipleelements,thesampleshowingthehighestdamageistheessentialonewhichdefinesthehazardcriterionfortheproduct.The classification of fragmentation for glass and forwindows is considered satisfactory under theexistingA-Fsystemdefinedinparagraph8.2(ISO16934:2007).NOTE:forfaçadesitmaybepossibletousethesamesystemwithalimitofacceptableperformance,suchasA-Conlyfortallfaçades.A standardised method of deriving the blast parameters from the raw data is described in bothannexes of ISO 16934:2007 (paragraph A.4) and ISO 16933:2007 (paragraph A.4). Thesemethodsshouldbereviewedtoensurethattheyareconsistentwitheachother.NOTE:theprocessofdealingwithrawdatashouldbemoreorlessidenticalforbothshock-tubeandair-blastloading.The use of multiple pressure transducers (minimum two sensors) in a shock tube would providegreaterconfidenceinthedatarecorded.Themethodforassessingtolerancesofrecordedpressureand impulsevalues from ISO16933:2007 (paragraphB.3) shouldbe included in ISO16934:2007 tocoveruseofmultiplepressuretransducers.Theaveragemaximumpressureandstandarddeviationshouldbecalculatedandcomparedwiththeloadingscenario(maximumdeviationshouldnotexceed10%).Onlypressure transducersworking correctlyand thus showing reasonable results shouldbeconsideredinthecalculationoftheblastproperties.NOTE:EN13123-1:2001givesa ‘latitudeof -5%on thepressurevalue toallow forgauge-readingtolerance’.Table 6.2 gives an overall summary of the recommended requirements of a revised test andclassificationbyshock-tubeloadingstandardintermsoftheinterpretationofresults.

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Table6.2:Summaryofoverallrequirements.

No Item Recommendedrequirement

1 Application

Aimtocoverglass,windowsandfaçades.Façadesmaybe subject toa separate testmethodproposedat a later date, but test houses should be able to apply thegeneralprinciplesofarevisedtestmethod.

2 Testmethod Shock-tubetest(ISO16934).Arenatest(ISO16933)tofollow.

3 Standardloading Large(VBIED)andsmall(PBIED).

4 User-definedloading Yes(possiblywithoutcertification).

5 Petrochemicalloading Yes(possiblywithoutcertification).

6 Sampledimension User-defined.

7 Numberofsamples Minimum3.

8 Test of partially openedwindows/doors No.

9 Testofglazingfaçades Yes(initiallythroughapplicationofgeneralprinciples).

10 Mountingofsamples Welldefined forglass,windowsandfaçades (fixingsmustberepresentativeofoperationaluse).

11 Number of pressuretransducers Minimum2.

12 Damage assessmentcriteria Hazardcriteriaandfragmentdefinition.

Theserequirementswillalsoapplytothefuturerevisionofthetestandclassificationbyarenaair-blastloadingstandard.IdentificationofthetestsamplebyclassificationcodeTheidentificationoftheloadinglevelisrecommendedinordertointegratebothfixedloadinglevelsaccording to the current standards, but with a new label of the levels EPR1 to EPR5 and flexibleclasses. A certification should be possible for both. With respect to a higher flexibility, it isrecommended for theadditional (not fixed loading levels) touseanew identificationcode for thedistinctionof the classification level of securitywindows anddoors. There, the identification codeshouldcontain:

• averagereflectedoverpressure;• averagepositivespecificimpulse;• hazardclassreached;Example:securitywindowtestedat50kPaand400kPams,nodamage:EPR50/400A.

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7. Listofreferences

7.1.StandardsASTM F 1642:2004. Standard test method for glazing and glazing systems subject to air-blastloadings.ASTMInternational,2004.

EN 13123-1:2001-10. Windows, doors and shutters — Explosion resistance — Requirements andclassification—Part1:shocktube.CENEuropeanCommitteeforStandardisation,2001.

EN 13123-2:2004-05. Windows, doors and shutters — Explosion resistance — Requirements andclassification—Part2:rangetest.CENEuropeanCommitteeforStandardisation,2004.

EN13124-1:2001-10.Windows,doorsandshutters—Explosionresistance—Testmethod—Part1:shocktube.CENEuropeanCommitteeforStandardisation,2001.

EN13124-2:2004-05.Windows,doorsandshutters—Explosionresistance—Testmethod—Part2:Rangetest.CENEuropeanCommitteeforStandardisation,2004.

EN 13541:2012-06. Glass in building— Security glazing— Testing and classification of resistanceagainstexplosionpressure.CENEuropeanCommitteeforStandardisation,2012.

GSA-TS01:2003. Standard test method for glazing and window systems subject to dynamicoverpressureloadings.USGeneralServicesAdministration,2003.

ISO16933:2007-07.Glassinbuilding—Explosion-resistantsecurityglazing—Testandclassificationforarenaair-blastloading.InternationalOrganisationforStandardisation,2007.

ISO16934:2007-07.Glassinbuilding—Explosion-resistantsecurityglazing—Testandclassificationbyshock-tubeloading.InternationalOrganisationforStandardisation,2007.

7.2.LiteratureJRC87202. ERNCIP thematic area, ‘Resistance of structures to explosion effects’; review report oftestingmethods—DeliverableD1.EuropeanCommission—JointResearchCentre,2013.

JRC94930. ERNCIP thematic area, ‘A comparison of existing standards for testing blast-resistantglazing’—DeliverableD2.EuropeanCommission—JointResearchCentre,2014.

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8. ListoftablesTable2.1:Generalitemsofallcurrentstandardsdescribingblastloadsonsecurity-glazingproducts.9

Table3.1:Mountingoftestsamplesofallcurrentstandardsdescribingblastloadsonsecurity-glazing

products............................................................................................................................11

Table4.1:Summaryofthegeneraldescriptionoftheloadingconditionsofallcurrentstandards

describingblastloadsonsecurity-glazingproducts.........................................................18

Table4.2:DefinitionofloadinglevelsinexistingEuropeanstandards(EN13541:2012-06andEN

13123–1:2001-10)applicableforshock-tubetests..........................................................19

Table4.3:DefinitionoftheloadinglevelsaccordingtoISO19634:2007-07applicableforshock-tube

tests..................................................................................................................................19

Table4.4:DefinitionofloadinglevelsaccordingtoEN13123-2:2004-05forapplicationinarenatests.19

Table4.5:DefinitionofloadinglevelsaccordingtoISO16933:2007-07forapplicationinarenatests.20

Table4.6:Recommendationforthedefinitionofloadinglevelswithrespecttoreflectedpressureand

positivespecificimpulseaccordingtothecurrentstandard(EN13123-1:2001).............22

Table5.1:Measurementsystemsprescribedinallcurrentstandardsfortheaccomplishmentofblast

tests..................................................................................................................................26

Table6.1:Requirementsontheinterpretationofresultsincomparisontoallcurrentstandards

describingblastloadsonsecurity-glazingproducts.........................................................31

Table6.2:Summaryofoverallrequirements........................................................................................34

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9. ListoffiguresFigure3.1:Comparisonofexteriorandinterioroverpressure.............................................................13

Figure3.2:Exemplarytestsetupsandtheirconnectionlinesinprinciple;a)testofaglazing,b)testof

awindow/door,c)testofafaçadeelementwithdampingelements..............................14

Figure4.1:Characterisationofablastwavedescribedbythethreeproperties:peakoverpressure

(loadingpressure),positivedurationandpositivespecificimpulse.................................17

Figure4.2:Proposeddefinitionofloadinglevelsbyusingapressure-impulsediagram......................23

Figure4.3:Proposeddefinitionofloadinglevelsbyusingapressure-impulsediagramforapplication

inshock-tubetests............................................................................................................24

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doi:10.2788/319252 ISBN 978-92-79-53394-5

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