Dissertation

I-Steel beams under tension: Lateral torsional buckling, behaviour and design Joo Toms Mello e Silva Thesis to obtain the Master of Science Degree in Civil Engineering Examination Committee Chairperson: Professor Doutor Fernando Manuel Fernandes Simes Supervisor: Professor Doutor Dinar Reis Zamith Camotim Supervisor: Professor Doutor Nicolas Boissonnade Member of the Committee: Professor Doutor Lus Manuel Calado de Oliveira Martins Member of the Committee: Professor Doutor Pedro Manuel de Castro Borges Dinis October 2013 0,0 0,2 0,4 0,6 0,8 1,0 1,2 0,000,501,001,502,002,503,00 !LT "LT

You must be the change you wish to see in the world. Mahatma Gandhi ii iii ACKNOWLEDGMENTS I would like to thank all the people who contributed in some way to the work described in this thesis. Firstandforemost,Ithankmyacademicandscientificsupervisor,ProfessorDinarCamotimforbeingan outstandingsupervisorandanexcellentprofessor.Hisconstantencouragement,supportandinvaluable suggestions made it possible to carry out the work presented in this dissertation successfully. I would like also to acknowledge all the opportunities given to me during the last year, which have broaden my personal and professionalhorizonsconsiderably. Lastly, I would like to thank him for sharing with me his revolutionary and perfectionist vision of the professional and academic/research work. Second,Iwouldliketothankmysupervisor,ProfessorNicolasBoissonnade,forhisconstantsupportandfor alwayspushingmetothelimitstomakethisdissertationabetterwork.Ialsowouldliketoexpressmy gratitude for receiving me so well in Switzerland and for always making me feel like it was my home. I would like also to thank Professor Pedro Borges Dinis for his full availability and for all the constructive advices given during the first part of this dissertation. I would like to express my deep gratitude and respect to my friend Joanna Nseir, for supporting me during last year and for the time devoted and constant contributions given to improve the quality of this dissertation. I would like to express my sincere appreciation, first to my friends, namely Joana and Maria Joo, as well as to my Suisse family, for their constant support in all my struggles and frustrations, as well as encouraging me in my decisions in my new life in Switzerland. Even from the distance, each one gave me force to overcome all kinds of obstacles, supported me to succeed in every new challenge and made me feel that they were always right there next to me. I would like to thank my family, especially my mother, father, sister and grandfather, for always believing in me, for their continuous love and their supports in my decisions. Without them I could not have made it here. iv v ABSTRACT Thisdissertationreportstheresultsofananalytical,numericalandexperimentalinvestigationdealingwith hot-rolledI-sectionsteelmembersactedbyacombinationofmajor-axisbendingandaxialtension(beams subjectedtotension),whichisrelativelyrareinpracticeand,therefore,hasreceivedlittleattentionfrom researchers in the past. In particular, there are no guidelines for the design against buckling ultimate limit states of such members (only their cross-section resistance is checked). This means that the axial tension favourable effect onlateral-torsionalbuckling/failureisneglected,thusleadingtoover-conservativedesigns!indeed,abeam subjected to axial tension is currently designed against lateral-torsional failure as a pure beam. In order to acquire scientific knowledge and provide design guidance on this topic, the lateral-torsional stability, failure and design of hot-rolled steel I-beams with fork-type end supports and acted by simple transverse loadings (mostly applied end moments) and various axial tension values are addressed in this work. After developing and validating an analytical expression to calculate critical buckling moments of beams under uniform bending and axial tension, numerical(beamfiniteelement)bucklingresultsarepresentedforthenon-uniformbendingcases.Then,twofull-scale tests involving a narrow and a wide flange beams under eccentric tension are described and their results are used to develop shell and beam finite element models!thelatter are subsequently employed to perform a parametric study aimed at gathering a fairly extensive ultimate strength/moment data bank. Finally, this data bank is used to assessthemeritsofadesignapproachproposedinthisworkforbeamssubjectedtotensionandcollapsingin lateral-torsionalmodes!thisdesignapproach,whichconsistsofslightlymodifyingthecurrentprocedure prescribed in Eurocode 3 to design beams against lateral-torsional failure, is shown to provide ultimate moment estimates that correlate very well with the values obtained from the numerical simulations. The predictions of the proposed design approach are also compared with those of the design procedure included in the ENV version of Eurocode 3 (but later removed). Keywords: Hot-rolled I-section steel beams, Combination of major-axis bending and tension, Lateral-torsional buckling, Failure governed by lateral-torsional buckling, Design approach vi vii RESUMO Esta dissertao apresenta os resultados de uma investigao analtica, numrica e experimental sobre vigas de ao laminadas a quente com seco em I, submetidos a uma combinao de flexo em torno do eixo de maior inrcia e traco (vigas traccionadas), a qual ocorre com pouca frequncia na prtica e, portanto, tem recebidopoucaatenodacomunidadecientfico-tcnica.Emparticular,noexistemdisposiesregulamentares relativasaodimensionamento,emrelaoaoestadolimiteltimodeencurvaduralateral,detaiselementos estruturais (apenas se efectua a verificao de seco). Isto significa que o efeito favorvel da traco no colapso por encurvadura lateral desprezado, conduzindo a um dimensionamento demasiado conservativo de facto, uma viga submetida a traco presentemente dimensionada como uma viga pura. Com o objectivo de adquirir conhecimento cientfico sobre o comportamento estrutural de vigas traccionadas, bem como contribuir para o seu dimensionamento eficaz, o presente trabalho aborda a estabilidade lateral (por flexo-toro), a resistncia ltima eodimensionamentodevigasmetlicaslaminadasaquente,comsecoemI,simplesmenteapoiadas(apoioem forquilha)esubmetidasacarregamentostransversaissimples(sobretudomomentosdeextremidade)e diferentesnveisdetracoaxial.Apsdesenvolverevalidarumaexpressoanalticaparacalcular momentoscrticosemvigassubmetidasaflexouniformeetraco,apresentam-seresultadosnumricos (elementofinitodeviga)relativosavigassubmetidasaflexono-uniforme.Emseguida,descrevem-sedois ensaiosexperimentais,efectuadosescalarealeenvolvendoduasvigas,umadebanzosestreitoseoutrade banzoslargo,submetidasatracoaplicadadeformaexcntrica,cujosresultadosobtidossousadospara desenvolver modelos de elementos finitos de casca e viga este ltimo modelo , posteriormente, utilizado para efectuar um estudo paramtrico destinado a reunir uma considervel base de dados de resistncias/momentos ltimosdevigastraccionadas.Finalmente,estesresultadossoutilizadosparaavaliaraqualidadedas estimativasfornecidasporumametodologiadedimensionamentopropostanestetrabalhoparavigas submetidasatracoecujocolapsoprovocadoporencurvaduralateralmostra-sequeestametodologiade dimensionamento,aqualconsistenumapequenamodificaodoprocedimentoprescritopelaactualversodo Eurocdigo 3 para calcular a resistncia de vigas encurvadura lateral, fornece estimativas da resistncia ltima queexibemumacorrelaomuitoboacomosvaloresobtidosatravsdassimulaesnumricas.As estimativas fornecidas pela metodologia de dimensionamento proposta so tambm comparadas com as que resultam da aplicao do procedimento preconizado na verso ENV (Pr-Norma Europeia) do Eurocdigo 3, o qual no figura na verso actual. Palavras-chave: VigasdeaolaminadasaquentecomsecoemI,Combinaodeflexoemtornodoeixodemaiorinrciae traco,Estabilidadelateral(porflexo-toro),Colapsoprovocadoencurvaduralateral,Metodologiade dimensionamento viii ix TABLE OF CONTENTS !"#$%&'()*+($,- ////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 000 !1-,2!", ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 3 2(-4+% //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 30000 ,!1'( %5 "%$,($,- /////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 06 '078 9: 50;7 /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 6000 '078 9: ,?@A>7 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 606 "B?C8>= D /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// D EF8=9GA0J0F?=K =>J?=L7 /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// M D/M/ +9803?809F ?FG 7H9C> 9: 8B> N9=L /////////////////////////////////////////////////////////////////////////////////////////////// O D/O/ %=;?F0P?809F 9: 8B> G077>=8?809F ////////////////////////////////////////////////////////////////////////////////////////////////// Q "B?C8>= M /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// R '?8>=?A ,9=709F?A 17= O ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// MO 4A80J?8> 1>B?309F;8B ! 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