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Sustainableinterventions:Rehabilitationofoldtimberstructureswithtraditionalmaterials

TiagoIlharcoFacultyofEngineeringofPortoUniversity

tiagoid@fe.up.ptEsmeraldaPauprio

InstituteofConstructionFacultyofEngineeringofPortoUniversitypauperio@fe.up.pt

JooGuedesFacultyofEngineeringofPortoUniversity

jguedes@fe.up.ptAnbalCosta

DepartmentofCivilEngineeringofAveiroUniversityagc@ua.pt

ABSTRACT

Theinterventioninbuiltheritageisawayofpreservingculturalidentity.Therefore,itdemandsspecialcareandsensibility. Inparticular, therehabilitationofoldbuildingsconcernsnotonly faades,butallthestructuralelements,namelyfloors,roofs,and insidewalls,aspartofamoreglobalandconsistentheritage. However, most of the interventions on old buildings consist in the substitution of thestructuralelements insteadoftheirrehabilitation.Thissituationresultsmostlyofa lackofknowledgeandunderstandingoftheexistingmaterialsand(or)oftherehabilitation/strengtheningtechniques.Ingeneral,thepreservationofthestructuralelementsresultsinbenefits,notonlyintermsofheritagepreservation,butalso intheminimizationofthe interventionsandtheir impact.However,evenwhenthis strategy is followed, the rehabilitation/strengthening techniques using traditionalmaterials hasbeenoften ignoredand substitutedby techniqueswhichusemodernmaterials, frequentlyexpensiveandsometimeswithdoubtfulefficiency.Thissituation isparticularlycommon inoldtimberstructures,namelyroofsandfloors,whichexistallovertheWorld,insomecaseswithmanycenturies.Therefore,an effort should be done to invert this situation i.e., to show the community that it is possible topreservetimberstructuresand,atthesametime,tousetraditionalmaterialsandtechniques,leadingtomoresustainedactions.Inordertopromotesustainable interventions,contributingtoarealmaintenanceofthebuiltheritageand respecting the International chartsand ICOMOS (InternationalCouncilonMonumentsandSites)recommendations,NCREP (1) (Nucleus for theConservation andRehabilitationofBuildingsandBuiltHeritage,ateamwithinFEUPFacultyofEngineeringoftheUniversityofPorto)havebeenparticipatingin many rehabilitation projects, analyzing the state of conservation of buildings and designingrehabilitationsolutions,inparticularusingtraditionalmaterials,likewoodandsteel.ThepresentpaperwillfocusNCREPexperienceintheinterventionofoldtimberstructures,namelyatRodriguesdeFreitasschool,ValadaresPalace,andValongoandCorpusChristichurches.

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1. INTRODUCTIONMostofthebuildingsbuilttillthebeginningoftheXXcentury inPortugal ismadeofmasonry,mainlystone(exteriorandsomeinteriorwalls),andtimberelements(floors,roofs,ceilings,interiorandsomeexteriorwalls). Ifproperlyconnected, theseelementspromoteagoodglobalbehaviour: themasonrywalls support the floor beams and roof trusseswhich, on the other hand, act as horizontal braces,inducingamoreuniformdistributionofstiffnessandloadingthroughoutthestructure.Thus,ifproperlydesignedandingoodconditions,thesesystemsconstituteefficientstructures.Thistypeofconstructionisdisseminatedalloverthecountryandrepresentsmostofourbuiltheritage,justifyingthe increasing intereston itspreservationasmemoryofcultureand identity.Unfortunately,mostof it isdegradedandabandoned,demandingurgent intervention.However, the interventiononoldbuiltheritageisnotaconsensualissueandmayresultonlessconservativeapproaches.Inparticular,substituting structuralelements insteadof rehabilitating ithasbeenawidespreadpolicy that resultsmainly from the lack of knowledge on thematerials and on the techniques and their efficiency. Ingeneral, direct intervention on the elements, avoiding substitutions, not only results on heritagepreservation,but also on theminimization of the necessary actions and their impact. Though, evenwhen this option is considered, the intervener often prefers newmaterials, specially polymers andcomposites,sometimeswithhighercostsandnotalwayswithprovedefficiency, insteadoftraditionalmaterials.In this field, and particularly for old timber structures,NCREPs option has beenmostly oriented totechniquesusingtraditionalmaterials,likewoodandsteel.Thesetechniques,consisting,forinstance,intheadditionoftimberelementsandsteelplates,havebeenappliedintherehabilitationofoldbuildingswith very good results. Some exampleswill be analysed in this paper, namely: Rodrigues de FreitasSchool (Porto, beginning of XX century), Valadares Palace (Lisbon, reconstructed after the 1755earthquake),ValongoChurch(Valongo,XIXcentury)andCorpusChristiChurch(VilaNovadeGaia,XVIIcentury).At thesametime,and inorder tosupport the interventions,acampaignof laboratorial tests isbeingperformed inold timberbeams,notonlytounderstand themechanicalbehaviourof theseelements,butalso toassess theperformanceof techniques involving theuseof traditionalmaterials,analysingtheir efficiency, field of application, and evaluating advantages and disadvantages in comparison toother techniques. The tests are being done in LESE (Laboratory for Earthquake and StructuralEngineering)ofFEUP,intimberbeamsremovedfromoldbuildingsfloorsthat,foranumberofdifferentreasons,wouldbedemolished.Theresultsobtainedwillbesharedwiththescientificcommunityattheendofthecampaignandwill,hopefully,contributetomoresustainedinterventionsandinaccordancetointernationalchartersandrecommendations.

2. INTERVENTIONSINOLDTIMBERSTRUCTURESUSINGTRADITIONALMATERIALS

ThestructuralinterventionTheneed for the interventionon timber structures isusually related to theexistenceofdamagesoralterationsofusewith load increase.Between themostcommondamages,onecanrefer thenaturalones (knots,splits,etc.)and thoseresulting frombioticattacks (insectsand fungi)and from incorrectconstructivedetailsor structural interventions.These causesnotalwaysoriginate the collapseof thestructuralelementsorstructures,butareoftenassociatedtotheirdeficientbehaviour,withhighlevelsofvibrationsanddeformations.Consequently,inordertoensurethesafetyand,atthesametime,the

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properperformanceofthestructures, it isnecessaryto intervene inthedamagedstructuralelementsthroughrehabilitationactions.Thedecisionaboutthetypeofinterventionshouldbetakenonlyafterarigorousandcarefulsurveyofthe structure (3).According to the results obtained in the survey and to the circumstances of eachsituation, the intervention on a particular element or structure can take two different ways:Rehabilitation or Substitution. Rehabilitation can be seen as the natural solution that allows themaintenance of the element or the structure. This option may involve a strengthening action,particularlywhentheoriginalstructuresare improperlydesignedorwhenchangesofuse(withhigherloads)areexpected,demandingahigherstrength.Inalimitsituation,theinterventioncanconsistintheSubstitutionoftheelementorstructure,asolutionthatshouldbecarefullyanalysedtakingintoaccountthepercentageandintensityofthedamage.

ThechoiceofrehabilitationtechniquesThe rehabilitation of timber structures can be done using different techniques,with pros and consconcerningeffectiveness, compatibility, intrusiveness,etc. Someof them imply theuseof traditionalmaterials, such aswood and steel, andothers involve theuseofmore innovativematerials,namelycomposites (e.g.epoxy,FRPs).Theselectionof thebest techniquemust take intoconsideration theparticularities of the construction, namely the existence of constructive elements with particularinterest,e.g.ceilingswithdecorativeelements,or the increaseof loadoranycollateraleffect to thewalls, for instance. Besides of that,when choosing the techniques andmaterials to use, there are,amongothers, twocriteria linked toheritageprotection that shouldbe respected:CompatibilityandReversibility.Compatibilityislinkedtothephysicalandchemicalinteractionbetweentheexistingstructureandtheinterventionsolution.Inparticular,theelements,materialsand(or)techniquesimplementedshouldntreactwiththoseoftheexistingstructureorintroducehigherstiffnessinlocalizedstructuralareas.Thiscriterion avoids the introduction of new damage in the structure through the intervention. A goodexample of that are the glued or very rigid connections in timber elements that may induceconcentrationofstressesintheinterfacearea,i.e.theoccurrenceofnewdamage.Reversibilityislinkedtothewillthattheinterventionsbesubstitutablesothattheycangiveplacetomoreefficientand(or)protectiveinterventionsinthefuture.Generallyspeaking,thelessintrusivesolutionsareoftenthemorereversibleones.TheefforttakenbyNCREPintheuseanddevelopmentoftechniqueswithtraditionalmaterial,aswoodandsteel,isrelatedtotheabovementionedfactors.Ifcorrectlyanalysedandapplied,thesetechniquescanbeanexcellentsolution to rehabilitation interventions inold timberstructures.As (4) refers, theintervention shallbedone throughadetailedanalysisof the techniquesand the technologieswhichwereoriginallyusedintheconstruction.

TechniqueswithtraditionalmaterialsTherearemanydifferentwaysofusing traditional rehabilitation techniques inold timber structures,namely:(A)thefixationoftimberpiecesorthinsteelplates,withvariedconfigurations,tothesidesofthe element (themostly used byNCREP in the interventions, as it can be seen inpoint 3.); (B) theintroductionofthinsteelplatesintheinterioroftheelement;(C)theinstallationofsteelbeltsaroundtheelement; (D)the installationofnewstructuralelements (timberorsteel)paralleltotheexistents,amongothers(5).To increase knowledge on the efficiency of these techniques in order to give useful information todesignersandconstructorsaboutthesuitabilityofeachtechniquetosolvespecificsituations,NCREPisdevelopingalaboratorialtestingcampaign(seepoint4.).Asamatteroffact,theinformationrelatedto

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research on rehabilitation techniques on old timber structures using traditional materials is quitelimited. For instance, in the case of traditional carpentry joints, despite of being widely used, thenumberofstudiesontheirmechanicalperformanceandonpossiblestrengtheningtechniquesisscarce.With few exceptions, research on timber joints has been oriented towards new engineeringconfigurations. Simultaneously, only few studies were developed in elements subjected mainly tobending;someauthorsperformedbendingtestsinbeamsreinforcedwithsteelelements,butreachingcontradictoryresults.Themajorityofthestudieswasdoneinelementswithhighaxialorshearforces.Strengthening techniques on floors to improve the diaphragm behaviour have also been analysed,proving experimentally its efficiency, but advising that further refinement is still needed for thetechnologytobeapplied intheconstructionpractice(6).Concerningtheconnectionsbetweentimberstructures(roof,wallsandfloors)andmasonrywalls,althoughitisusuallyappointedasakeyelementtotheoverallbehaviourofabuilding(7),inparticularunderseismicevents,nosignificanteffortshavebeenspentontheirstudy.

3. INTERVENTIONSWITHTIMBERANDSTEELELEMENTS

IntroductionTheuseof timberelements in the rehabilitationofold timber structures isaverycommon solution.However,intheseinterventionsitsimportanttohavetimberelementsofthesamewoodspeciesandwithsimilarcharacteristics:density,strengthandstiffness,tothoseoftheoriginalstructure.(8)referstheconvenienceofusingoldtimberelements,withthedryingprocesscompleted,andtheimportanceof having compatible moisture contents between new and old elements to avoid physicalincompatibilities.When itsnotpossible toobtain similarwood, timberelements retrieved from thedemolition of old buildings can be used or, as alternative, the new elements, already dry, can bepreviously placed in the constructionswhere theywill be installed to acquire amoisture content inequilibriumwiththeconstructionenvironment.On theotherhand, solutionswith steelelementsarecommonlyused in interventionsonold timberstructures,particularlyontimberfloors, leadingtoan increaseofstrengthandstiffness.Eventhough,when using these elements, two questions should be analysed: the compatibility with the timberelements (the behaviour ofwood and steel is considerably different) and the fire resistance of themetallicelements.Infact,timberstructuressupporttemperaturesforwhichsteelstructureswouldhavealreadyfailed.Therefore,toavoidthesteelelementstobecometheweakestpointofthestrengthenedstructure its important to improvement their fire resistance, which can be done through physicalbarriers or fire retardant products. Simultaneously, steel elements should be protected againstcorrosion.ThefollowingsectionsdescribefourrehabilitationinterventionsofNCREPonoldtimberstructures:thefirsttwousingmainlytimberelementsandtheothertwousingmainlysteelelements.

RodriguesdeFreitasSchool,PortoThesurveyofthestructuresofRodriguesdeFreitasSchoolevidencedaprecariousstateofconservationof the timber roofs, involving an area of about 4000m2. The choice of the type of interventionwascarefullyanalysed;theglobalsubstitutionwasanoption,althoughthepreferredsolutionwas,sincethebeginning,therehabilitationwith localizedsubstitutionofstructuralelements.AdetailedstudyontheexistingstructuralelementswasperformedbyNCREP todefine thephilosophyof the intervention,namelytheapprovalandrejectioncriteria,allowingestimatingtheareaswhererehabilitationandsubstitutionswereexpected (9).Thisstudyconfirmed that therehabilitationwas thebestoptionandthefollowingtechniqueswererecommended:

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a)Additionofnewelementstothesidesofthedamagedelements

Thisoperationconsisted inthefixationofnewtimberpiecesonbothsidesofthedamagedstructuralelements,withM16stainlesssteelthreadedrodswithhexagonalnutandbroadbrimmedwashers(toincrease the tensiondistribution),endowing itofanhigher inertia,Fig.1andFig.2.Thenew timberpieces had physical andmechanical characteristics similar to the in situ elements andwere treatedagainstbioticattacks;thesteelrodsweresubmittedtoatreatmenttoincreasetheirfireresistance.

Existent timberelement

New timberelements(5cm thick)

Threadedrod M16

Damagedarea

Hexagonalnut M16

Broad-brimmedwashers

Fig.1Strengtheningofthedamagedstructuralelementswithtimberpieces.

Fig. 2 Strengthening of a damaged tie beam with timberpieces.

b)Introductionofbracingelements

Theintroductionofnewtimberbracingelementswassuggestedtoreducethelengthofthecompressedelements(raftersandstruts),decreasingthepossibilityofbuckling.Thesenewbracingelementswereinstalledinbothsidesofthereinforcedelementandadequatelyscrewedtothebattensortotheridges,Fig.3andFig.4.

Fig.3 Introductionofbracingstoreducethebuckling lengthofthecompressedelements(rafters).

Fig.4 Introductionofbracingstoreducethebuckling lengthofthecompressedelements(struts).

c)Partialsubstitutionofthestructuralelements

Incertainsituationsitwasnecessarytosubstitute(globallyorpartially)thedamagedelementsbynewones.Whileinthecaseofthestrutsandridgesitwasconsideredconvenienttosubstitutethecompletelengthoftheelement,inthecaseofraftersandtiebeamsitwaspossibletosubstituteonlyapartofit,withtheconnectionbetweenthenewandtheexistentbeingdonewithnewtimberpiecesineachsideoftheelements,fixedwithM16threadedrodsandscrews,Fig.5andFig.6.

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Existentstrut

New timber element(section similar tothe existent one)

Screw M14

New timberelement 3cm thick

Existing timberelement

Threaded rod M16with hexagonal nutand broad-brimmedwashers

Fig.5Substitutionofapartofastructuralelement. Fig.6Substitutionofapartofsecondarytiebeam.

ValadaresPalace,LisbonTheinterventioninValadaresPalaceconcernedtherehabilitationofthevaultedceilings,supportedbytimber beamswith a length of approximately 8,0m. After the survey of these beamswith the nondestructiveequipmentcalledResistograph,itwaspossibletoconcludeabouttheintensedegradationofthebeamssupportsduetobioticattacks:insectsandfungi.Itwasalsonoticedaconsiderabledeflectionatthemidspanofthebeams(about20,0cm),causedbytheloadofaheavysupportsystemofalamplocated at the top of themain stairs (10). Therefore it was recommended a local intervention torehabilitatethebeamssupportsandaglobalinterventiontocorrectthebeamsdeformations.a)Supportsrehabilitation

Therehabilitationofthetimberbeamssupportswasperformedthroughthefixation(withscrews),totheirsides,ofnewtimberelements.Thesenewelements,madeofthesamewoodspeciesoftheinsituelements,createdthenewsupportofthedamagedbeams inthewalls.Afterwardsthenewelementswereconnectedtoamudsill installedatthetopofthewall,toguaranteetheglobalbehaviourofthebuilding and their correct connection to the stone masonry wall, Fig. 7 and Fig. 8. The damagedextremitiesofthebeamswerecutandtheremainingwoodwastreatedagainstbioticattacks,Fig.9.

Fig. 7 Strengthening of the damagedstructuralelementswithtimberelements.

Fig.8Strengtheningofthedamagedstructuralelementswithtimberpiecesandasteelbracket.

Fig. 9 Cut of the damagedpartsofthebeams.

Ametallicbracket (L150x15)wasalso fixed to themasonrywall through threaded rods (crossing thewholethicknessofthewall)toimprovethebeamssupportsandtocontributetothewallstrengthening,particularlyinoutofplanactions,inaninterventionorientedtotheseismicprotectionofthebuilding,Fig.10.Allthenewtimberelementswerepreviouslytreatedinautoclavewithanantibioticproduct.Ontheotherhand,allthesteelelementsweresubmittedtoatreatmenttoincreasefireresistanceandto

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protect against corrosion. The structural design of the fasteners respected the recommendations ofEurocode5(11).

Mortar

ScrewHBS6180(6mm)

Fig.10Strengtheningofthedamagedstructuralelementswithtimberpiecesandasteelbracket.

b)Deformationcorrection

Aftertherehabilitationofthesupportsandtheremovaloftheheavy loadofthe lamp fromthemidspanofthebeams,theexistingdeflectionwasremovedthroughoutasystemofsteelcables.Beforetherestorationoftheplasters,theceilingsupportwasalso improvedwiththeuseofsmallthreadedrodsfixedtothetimberbeams,Fig.11andFig.12.

Fig.11 Improvementoftheceilingssupportwiththeuseofthreadedrods.

Fig. 12 Ceiling after the correction of the deformation andrestorationoftheplaster.

ValongoChurch,ValongoThe testsperformedwith theResistograph in the timber structural elementsof the roofofValongoChurch confirmed thedeepdegradationof someof the tiebeamsof the trusses,with lossesof thetransversalsectionexceeding,insomecases,50%.Someotherstructuralproblemswerealsoobservedinthetrusses,namelythefactthatsomehangerswereloadingthetiebeams,theexistenceofdeficientconnectionsbetweenstructuralelements,theintensedegradationoftheraftersandridgessupportsinthemasonrywallsandthedeformationofthesteelelementsthatperformtheconnectionbetweenthetiebeamsandthewalls(12).Sincethesubstitutionoftheroofstructurewasntanoption,notonlybyitspatrimonialvalue,butalsobecauseofthetechnicaldifficultyandcostsassociatedtoaninterventionofthattype,thesolutionconsistedinlocalizedstructuralinterventions,asitisdescribedinthefollowingpoints.

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a)Tiebeamssupportrehabilitation

The supportsof the tiebeamswere rehabilitatedwith steel plates, 6mm thick, inboth sides of theelement, through threaded rods (10mm),up toadistanceof1,0m from thewall toguarantee theconnectiontothesoundpartofthewood,Fig.13.Thesteelplateswereintroducedinexistentopeningsatthemasonrywalls,thedamagedpartsofthewoodwereremovedandthesoundpartsweretreatedagainstbioticattacksandseparatedfromthesealingmaterialwithaleadsheet.

Threaded rodM8 // 0.15

Stonemasonrywall

0.95 1.05

Trussrafter

Stainless steelplate 10mm

Trusstie-beam

Fig.13Strengtheningofasupportofatiebeamwithsteelplatesandthreadedrods.

b)Repositioningoftheconnectionsbetweenstructuralelements

Theconnectionsbetweenthetrusseselementswerereinforcedwithsteelplates,traditionallyused intheconstructionoftimbertrusses,Fig.14.

Fig.14Useoftraditionalsteelelementstoimprovetheconnectionbetweentimberelements.

c)Improvementoftheconnectionsbetweenraftersandtiebeams

Stretchedsteelcablesconnectingtheraftersofthetrusseswereplacedtoavoidtherafterstoslideonthetopofthetiebeams.Thesecablesactastiebeamsandcontributetotheproperfunctioningofthetrusses,Fig.15.

Fig.15Introductionofstretchedsteelcablestoconnectraftersoftrusses.

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d)Rehabilitationoftheconnectionsbetweenrafters/ridgesandwalls

Theconnectionsof the raftersand ridges to themasonrywallswere reinforcedwithsteelplatesandthreadedrods,solutionsimilartotheoneusedwiththetiebeams,Fig.16.

Fig.16Strengtheningofthesupportsofrafters/ridgesandthemasonrywalls.

CorpusChristichurch,VilaNovadeGaiaThesurveyperformed inCorpusChristichurchevidencedthe intensedegradationofthetimberroofs(UpperChoirandApse),astheresultofbioticattacks(13).In theUpperChoirsroof itwasobserved thewarpingofsome trusses tiebeamsandraftersand theruptureofsomeotherstructuralelements.Therehabilitationoftheroofinvolvedsomeparticularities,notlinkedtothedirectinterventiononthestructuralelements,butduetotheconstraintsassociatedtotheexistenceofawoodenceilingwithpaintedcoffersconnected to the trusses,Fig.17.Thisceiling,withhighpatrimonialvalue,wasrestoredinsituinordertoavoiditsdeterioration,factthatobligedthestructural intervention to be developed by the upper side of the ceiling. The care needed to avoiddamagingthecoffersimpliedsomeadditionalprecautions,suchastheprotectionwithgeotextilesandthemaintenanceoftemporarystrutstosupporttheceiling.The intervention in the roof consisted in the strengthening of the structural elements showinginsufficient transversal section, mainly in the supports, through the introduction of steel platesconnectedtothesidesand,insomecases,tothebottomoftheelementsthroughthreadedrods,andfixed to themasonrywalls,Fig.18andFig.19.Theconnectionsbetween thesupportbeamsand theceilingswere reinforcedwith new timber elements, inorder to avoid the ceiling to deform. In veryspecific situations,new timber structuralelementswere introduced to substitute thedamagedones,Fig.20.

Fig.17Existentwoodenceilingwithpaintedcoffers. Fig.18Strengtheningof the supportsof ceilingbeamswith

steelplatesandthreadedrods.

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Fig.19Strengtheningofthesupportsoftiebeamswithsteelplatesandthreadedrods.

Fig.20Substitutionofarafterbyanewelement.

InthecaseoftheApsetimberroof,exclusivelyconstitutedbyraftersandwith intensedegradation, itwasobservedthecrackingofthesubjacentvaultedceiling.Asthesecrackscouldbestabilizedthroughanefficientbracingofthesupportmasonrywalls,itwasdecidedtocreateanewandstiffertimberroof,Fig.21andFig.22.Thisnewroofwasidenticaltotheoldone,butwithreinforcedconnectionsbetweenstructural elements by means of traditional carpentry joints and steel elements, Fig. 23, whichcontributedtoan increaseofthetrussesstiffnessand,consequently,tothe improvementofthewallsstructural behaviour.Additionally, theconnectionbetween the rafters,and themudsillandbetweenthisoneandthewalls,werereinforcedtomobilizetheglobalstructuralbehaviourofthebuilding.

Fig.21OriginalroofoftheApse. Fig.22NewtimberroofoftheApse. Fig. 23 Steel elements introduced to

increasethestiffnessoftheroof

4. LABORATORIALTESTSINREALSIZESPECIMENSInordertosupporttheoptionstakeninoldbuildingsinterventions,acampaignoflaboratorialtestsinold timber beams is being performed. This campaign aims not only understanding themechanicalbehaviouroftheelements,butalsoassessingtheperformanceofrehabilitationtechniquesinvolvingtheuseoftraditionalmaterials,suchaswoodandsteel,attesting itsefficiency, itsfieldofapplicationandevaluating advantages and disadvantages in comparison to other techniques. The campaign focusmainlyontheexperimentalassessmentoftechniquesappliedto fullscaletimberstructuresretrievedfromoldbuildingsinPortugal.Thetestsarecarriedoutaccordingto(2),withtheapplicationofaseriesofcyclesof increasingdisplacementtothebeamsuptoa levelofdisplacementbeyondthemaximumpeak load, Fig. 24. Displacement transducers and a load cell measure the beam global and localdeformationandtheappliedload.Thebeams,withaveragediametersandspansofabout0,20and4,0mrespectively,weretestedfirstintheiractualstatetoassesstheoriginalmechanicalcharacteristics,stiffness,strengthandfailuremodes.Afterwards,accordingtothefailuremode,differentrehabilitationtechniquesusingtraditionalmaterialswillbe applied,namely the linkofnew timber elements to the existingones throughwooddowels,

Substituted rafter

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screwsandtraditionaljointsandtheuseofinternalorexternalsteelconnectors/plates/belts.Then,thebeamswill be tested again, following the same setup and loading conditions of the first test. Thecomparison of the resultswill give a goodmeasure of the techniques efficiency. The choice of theinterventionprocedurewill depend on the conservation state and on the behaviour of the elementduringthetestpriortotheintervention.Thebehaviouroftheoriginalbeams(firsttest)waslinearelasticuntilafragilerupture,whichhadplaceathalfspan,nearknotsorotherdefectssituated inthetensionedside,showingtheirstrongeffect inthe structural behaviour of the timber elements, in particular in the bending strength. This rupturehappened forvaluesclose to40,0kNand forhalfspandisplacementsof60,0mm,Fig.24.Afterwards,the beams responded with a small plastic plateau until higher displacements (about 90,0mm),followedbyasecond sudden ruptureandagradualdecreaseof strength.The loadingandunloadingcycles were applied to the beams after the first rupture until maximum displacements of about130,0mm.Thefinalresidualdisplacementswereof70,0mm.Theaveragemechanicalpropertiesofthebeamswere calculated according to EC5 (11) and are in the range of expected values:modulus ofelasticity,Em,g=7,5GPaandbendingstrength,fm=36,2MPa.Theresultofthemodulusofelasticitywasclosetothevaluesobtainedinaninsituloadtestperformedonbeamsofthesametimberfloor(5).

-505

1015202530354045

-10 10 30 50 70 90 110 130 150Displacement (mm)

Load

(kN

)

Beam VABeam VBBeam VC

Fig.24Testsontimberspecimensaccordingto(2)SetupandLoadvsdisplacementdiagrams.

Thetestingcampaignwillallowtheassessmentofthemechanicalcharacteristicsandbehaviourofrealstructures,inparticular:thebendingstiffness,strengthandfailuremodesofthebeams.Itwillbeshownthat timber structures canbe rehabilitatedusing traditionalmaterials at low cost, sustaining thenoneed for replacement under partial damage conditions. Hopefully, the testswill confirm that thesetechniquescanbeappliedwithsuccess,allowingmorecompatible interventions, inbetteragreementwithinternationalchartsandrecommendations.

5. CONCLUSIONSIn general, thepreservationof the structural elements results inbenefits,notonly in termsofbuiltheritage preservation, but also inminimization of the interventions and their impact. Even though,when this strategy is followed, the implementationof traditional rehabilitation techniques hasbeencommonly passed over by techniques which usemodernmaterials, frequently expensive and withdoubtful efficiency. This situation is particularly common in old timber structures,namely roofs andfloors,whichexistallovertheWorld,insomecaseswithmanycenturies.Therefore,aneffortshouldbedone to change this situation i.e., to show the community that it is possible to preserve timberstructuresand,atthesametime,tousetraditionalmaterialsandtechniques,leadingtomoresustainedinterventions.Inthisfield,NCREPsoptionhasbeenmostlyorientedtotechniquesusingtraditionalmaterials,suchaswoodandsteel.Thesetechniquesconsist,forinstance,intheadditionofnewtimberelementsandsteel

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plates, and have been applied in the rehabilitation of old buildings with very good results. Someexamplesaredescribed inthispaper,namelywithRodriguesdeFreitasSchool,ValadaresPalace,andValongo and Corpus Christi Churches. At the same time, a campaign of laboratorial tests is beingperformedinoldtimberbeamstoassesstheperformanceoftechniquesinvolvingtheuseoftraditionalmaterials,evaluatingadvantagesanddisadvantages incomparison toother techniques.The testsarebeingdone inLESE intimberbeamsremovedfromoldbuildingsfloorsthat,foranumberofdifferentreasons,wouldbedemolished.Theresultsobtainedwillbesharedwiththescientificcommunityintheendofthecampaign,andwillhopefullycontributetomoresustainableinterventionsandinaccordancetointernationalchartersandrecommendations.

REFERENCES

(1) NCREP 2007, Ncleo de Conservao e Reabilitao de Edifcios e Patrimnio, Faculdade deEngenhariadaUniversidadedoPorto,http://ncrep.fe.up.pt/.

(2). EN 408 Timber structures Structural timber and glued laminated timber Determinationofsome physical and mechanical properties". CEN. Office for Official Publications of the EuropeanCommunities.Brussels,Belgium,2003.

(3) Ilharco, T, Romo, X., Pauprio, E., Guedes, J., Costa, A., "Organization of information on builtheritageusingmultimediatechnologies,FirstEuromediterranenregionalconference,Barcelona,Spain,2007.

(4)Costa,A.,Arde,A.,Guedes,J.,Pauprio,E."MetodologiadeIntervenonoPatrimnioEdificado".2Seminrio.AIntervenonoPatrimnio,PrticasdeConservaoeReabilitao,Porto,2005.

(5) Ilharco, T. "Pavimentos demadeira em edifcios antigos. Diagnstico e interveno estrutural".MestradoemReabilitaodoPatrimnioEdificado.FEUP,Porto,2008.

(6)Marini,A.andE.Giuriani.TransformationofWoodenRoofPitchesintoAntiseismicShearResistanceDiaphragms.StructuralAnalysisofHistoricalConstructions,NewDelhi,2006.

(7)Ilharco,T.,Guedes,J.,Pauprio,E.,Arde,A.,Costa,A.Ensaiosinsituelaboratoriaisempavimentosdemadeira.Ocasodeumedifciodoinciodosc.XXdacidadedoPorto.Patorreb20093EncontrosobrePatologiaeReabilitaodeEdifcios,FEUP,Porto,2009.

(8) Appleton, J. Reabilitao de Edifcios Antigos Patologias e tecnologias de interveno, EdiesOrion,Amadora,2003.

(9)Costa,A.,Guedes,J.,Pauprio,E.,Ilharco,T."RelatriodeInspecoeDiagnsticoCoberturasdaEscolaSecundriaRodriguesdeFreitas."ICFEUP,Porto,2007.

(10) Costa, A., Pauprio, E., Ilharco, T. Costa, A. "Palcio de Valadares Avaliao do Estado deConservaodasCoberturas".ICFEUP,Porto,2009.

(11)EN199511:EUROPEANSTANDARD.Eurocode5:Design iftimberstructuresPart11:GeneralCommonrulesandrulesforbuildings.CEN,2004.

(12)Costa,A.,Pauprio,E.,Guedes,J.,Ilharco,T.,Lopes,V."IgrejadeValongoAvaliaodoestadodeconservaodascoberturas."ICFEUP,Valongo,2008.

(13)Costa,A.,Pauprio,E.,Ilharco,T.,Lopes,V."RelatriodeInspecoeDiagnsticoIgrejadeCorpusChristi."ICFEUP,VilaNovadeGaia,2007.