Structural Analysis of Historic Construction – D’Ayala & Fodde (eds) © 2008Taylor & Francis Group, London, ISBN 978-0-415-46872-5 Diagnosisandanalysisoftwoking-posttrusses J.M.Branco&P.J.S.Cruz Civil Engineering Department, ISISE, University of Minho, Portugal M.Piazza University of Trento, Trento, Italy ABSTRACT: An accurate geometric and mechanical evaluation of two king-post trusses, based in grading results with data gathered from NDT as well as from mechanical evaluation, followed by full-scale tests were performed.Thetrusseswerereassembledinlaboratoryandsubmittedtoaseriesofcyclictestsundersymmetric andasymmetricloading.Strengtheningtechniquesevaluatedinprecedentsresearchstepswereusedinasecond phaseofthecarryingtests. 1 INTRODUCTION The work presented here has been developed within ageneralresearchprogramdevotedtoinvestigatethe behavior of traditional timber trusses and to identify suitablestrengtheningstrategies.Thestudyaddresses theoverallbehavioroffull-scaletimbertrussesunder cyclic tests under symmetric and asymmetric load- ing.Thecarryingtestswereprecededbyanaccurate geometric and mechanical evaluation of each tim- ber elements of both trusses studied. Visual grading and non-destructive tests based on local and global evaluationwereperformed. After the carrying tests on the unstrengthened trusses, following a load procedure according to the Service and Ultimate Limit States, the trusses were strengthened. Strengthening techniques, based in the useofmetaldevices,wereevaluatedinprevioussteps of the research (Branco, 2005), through full-scale testsontraditionaltimberconnections.Strengthening aimedtoimprovethecarryingcapacityofthetrusses and to analyze the influence of the joint stiffness in the overall behavior, in particular, under asymmetric loads. 2 TRUSSESSTUDIED The trusses studied have been recover from an old buildinglocateatPergineValsugana(20kmEastfrom Trento) which will be transformed in a school. The constructionisnotveryancient,probablybuiltinthe firstpartofthelastcentury,anddidnotpresentsigns ofrehabilitationorstrengtheningactions.Thebuilding i = 1, Truss 1 i = 2, Truss 2 Tie-beam (Ti0) Rafter (Ri2) Strut (Si1) Strut (Si2) Rafter (Ri1) King post (Ki0) Figure1. Trussesgeometry. isatypicalruralconstructionwithgroundfloor,first levelandatticwithvisibletimberroofstructure.The changeintheuseofthebuildingresultsintheneces- sity to remove the timber trusses. The trusses with a king-post configuration have a span near to 10.5 meters. All members are composed by one single timber piece of Spruce (Picea Abies Karst.), presenting a meancross-sectionof20 × 23cm 2 .Allmemberswere marked before dismantling of the trusses necessary fortheirtransportationtotheMaterialsandStructural testingLaboratoryoftheUniversityofTrento. 3 DIAGNOSIS 3.1 Geometric assessment During the visual inspection, significant variation in cross-section geometric properties was founded. Becauseeachcomponentofthetrussesiscomposedby auniquetimberpiece,itisnormaltoverifysignificant variabilityinthecross-sectionareaoftheelements,in particularinthoselongerlikethetiebeams.Tohavean adequatereportofallthosevariabilitiesofthetrusses geometry, a geometric assessment was performed. 459