OvidiusUniversityAnnalsofConstructionsVolume1,Number3,4,April2002StrengtheningoftheSteelPlateGirdersbyPrestressingwithRigidTieRodsPetruMOGAStefanGUTIUTechnicalUniversityofCluj-Napoca,Cluj-Napoca,3400,RomaniaAbstract:Twomethodsofstrengtheningofthesteelplategirdersarepresentedinthispaperwiththeaimofcarryingcapacityincrease:onebasedontensionflangecrosssectionincreaseandtheotherusingrigidprestressedorunprestressedtierodsaddedunderthebottomflange.Keywords:steelplategirders,strengthening,prestressing,carryingcapacityincrease,rigidtierods1.IntroductionStaticanddynamicphysicalwear,accidentalwearandtrafficconditionschangescandeterminethenecessityofsomestrengtheningworkswhichhavetobeabletoensurethefunctionalityandasafefutureuseofthebridgestructure.Thecarryingcapacityincreaseofthesteelplategirders,concomitantlywiththeirrigidityincreasecanbeefficientlymaterializedthroughthecrossflangessectionincreaseorthroughtherigidprestressedorunprestressedtierodslayedundertheFig.1.Stresspatternsofthestrengthenedgirdertensionflange.ThestressespatternsofthestrengthenedThestateofstressesistheextremecrossgirderarepresentedinthispaperandanumericalsectionfibersofthesteelgirderandintheaddedexampleisgivenhere.elementtothebottomflangewillbe:MψM2.StresspatternsanddeflectionsizeofthegP'σs=ys+ys(1a)strengthenedsteelplategirdersIIcMgψMP'2.1.Strengtheningbyflangecrosssectionσi=yi+yi(1b)IIincreasingcψMσ=Py(1c)AddingstrengtheningelementsononeoronccIcbothgirderflanges,theincreaseofthemomentofwhere:inertiaisobtainedandimplicitlythestressesandIc-momentofinertiaofthestrengthenedsection;deflectionsundertheliveloadswilldiminish.ψ-dynamiccoefficientoftheliveloads.ThestresspatternsofthestrengthenedsteelplategirderthroughaTshapeweldedelementThefavorableeffectsarealsoobtainedwithaddedonthebottomflangearepresentedinFig.1.regardtotheelasticgirderdeflection.Foragirderwithavariablecrosssectionthedeflectioncanbeevaluatedbytherelation:ISSN-12223-7221©2000OvidiusUni