How well do calculations methods prescribed in today's design codes and standards represent conditions in natural fires? Can the temperature and behavior of a steel member in fire be predicted from these calculations? A literature review of structural fire codes, full scale fire tests, published fire test data, the function and selection of design fires, mechanical and thermal behaviors of structural steel, and numerical calculation methods for the temperature of steel members was conducted as a foundation to analyze whether a not a structural fire engineer can answer these questions. Through comparisons of published data from four natural fires tests performed at the Cardington test facility in the United Kingdom to numerical calculations based upon prescribed methods from Eurocode 3 and the Swedish Design Manual, time-temperature curves were developed to demonstrate the variation in temperature of the recorded data in the natural fire tests at Cardington to the equivalent members being analyzed with numerical calculation methods. When available, fire compartment characteristics were replicated during numerical calculations to ensure the highest correlation between the recorded and calculated results. An Excel tool was created to rapidly calculate and produce the resulting time-temperature curves as well as yield strength, modulus of elasticity, and load carrying capacity using a variety of input parameters including design fire data and steel member selection. The goal of the Cardington fires study was to provide comparisons of published natural fire data to results of numerical calculation methods from the codes. Additional comparisons were developed using a US Office design to show the effects of changing compartment and design parameters on the steel temperature, yield strength, elastic modulus and load carrying capacity. Differences found in temperature of steel members between the published Cardington data and numerical calculations proved the difficulty of predicting the behavior of a structural steel beam throughout an entire length of a fire or even until failure. Discussion of results addressed the selection of design fires, input parameters, structural layouts of office buildings, heating and cooling phases of steel members, and failure criteria.

Sistemas mistos de aço e concreto são aqueles em que o elemento de aço trabalha estruturalmente em conjunto com o concreto. Essa associação dos materiais resulta numa melhor utilização de ambos os materiais tanto quanto à capacidade resistente, quanto em caráter construtivo, funcional e estético. O presente trabalho tem como finalidade a análise de vigas de aço e mistas de aço e concreto parcialmente revestidas em situação de incêndio. Esse estudo tem grande importância tendo em vista os incidentes com altas temperaturas em edificações ocorridos ao longo dos anos. O aumento de temperatura nas estruturas é um efeito nocivo, pois prejudica a rigidez e a resistência dos materiais, podendo levar estruturas ao colapso. As análises das vigas mistas aço e concreto parcialmente revestidas em situação de incêndio foram feitas através de análises experimentais que foram realizadas no forno horizontal à gás do Laboratório de Engenharia de Estruturas da EESC/USP. Foram realizados ensaios de flexão em pontos em altas temperaturas e a variável nos ensaios foi o fator de carga aplicado no meio do vão das vigas. Foi possível comparar o comportamento das vigas metálica e mistas, bem como as temperaturas em vários pontos ao longo do elemento por meio de termopares colocados em pontos estratégicos. Transdutores de deslocamento também foram usados para saber o valor de deslocamento nos apoios e no meio do vão das vigas. Uma análise térmica bidimensional através do ABAQUS também foi feita para comparação de resultados. Conclui-se que para uma mesma carga aplicada os deslocamentos foram mais expressivos nos ensaios das vigas em situação de incêndio se comparados aos valores obtidos nos ensaios à temperatura ambiente, observou-se o efeito benéfico do revestimento de concreto ao perfil metálico, responsável por um ganho expressivo de resistência ao fogo quando comparado aos elementos puramente metálicos e por fim obteve-se boa concordância entre as temperaturas encontradas por modelagem numérica através do ABAQUS e dos ensaios experimentais realizados. / Composite steel and concrete systems are those in which the steel element works structurally in conjunction with the concrete. This association of the materials results in a better use of both materials as much as the resistant capacity, as well as in a constructive, functional and aesthetic character. The present work has the purpose of analyzing steel beams and mixed steel and concrete partially coated in a fire situation. This study has great importance in view of the incidents with high temperatures in buildings that have occurred over the years. The increase in temperature in the structures is a harmful effect, as it impairs the rigidity and the resistance of the materials, which can lead to collapse structures. The analyzes of the composite steel and concrete composite beams in a fire situation were made through experimental analyzes that were carried out in the horizontal gas furnace of the Laboratory of Structural Engineering of EESC/USP. Bending tests were performed on points at high temperatures and the variable in the tests was the load factor applied in the middle of the span of the beams. It was possible to compare the behavior of the metallic and composite beams as well as the temperatures at various points along the element by means of thermocouples placed at strategic points. Displacement transducers were also used to know the displacement value in the supports and in the middle of the span of the beams. A two-dimensional thermal analysis through ABAQUS was also done for comparison of results. It was concluded that for the same applied load the displacements were more expressive in the tests of the beams in the fire situation compared to the values obtained in the tests at room temperature, the beneficial effect of the concrete coating was observed on the metallic profile, responsible for a an expressive gain of fire resistance when compared to the purely metallic elements and finally a good agreement was obtained between the temperatures found by numerical modeling through ABAQUS and the experimental tests performed.

Planet Earth's climate naturally varies over time, however the rapid change that is now takingplace is due mainly to human influence. Buildings and real estate sector's emissions ofgreenhouse gases is responsible for approximately 20,6% of Sweden’s total emissions ofgreenhouse and 33% of energy used 2018. Therefore, energy efficiency, a reduction in energyand energy supply with a low effect on the environment are necessary to manage environmentalquality objectives. Steel production requires high temperatures, and thus high energy consumption, both for meltingand processing, which in turn produces carbon dioxide emission into the air. Steel recycling isa much-needed innovation to save energy and reduce the amount of emission of carbon dioxide.However, even greater energy savings, and a reduction in the effect on the environment, can beachieved by reusing steel components instead of recycling or producing new steel. Despite thelarge environmental incentive, only a very small proportion of Sweden's total structural steel isreused. To date the process for reusing steel components has been unclear and needs to be clarified. Amajor challenge in the process is to create a marketplace where suppliers and buyers can meet.The purpose of this report is to investigate the possibility of parametric design to develop a toolthat selects suitable reusable steel beams from hundreds of beams which fit into new contextsin accordance with certain desired conditions. This work results in a program or script, where the user specifies his/her values and requirementsthat will apply to the selected beam. Furthermore, the program shows the beams that meet therequirements of users and sorts them in an environmentally friendly order. This program isexpected to help designers select the right reusable beam in the right place in a new project. The script was created to handle I- and H-beams using the program Rhinoceros-Grasshopper asa platform for parametric design and calculation. The program includes calculations for crosssectionalclasses, uniaxial and multi-axial bending without regard to the phenomena of lateraltorsional buckling, and transverse force where shear buckling is considered. However, the scriptdoes not handle beams with cross-section class 4. In conclusion the result of this study, which is the script, shows that it is possible to develop aparametric tool that calculates, analyzes and selects the beams that best suit the user's needs andwhere the selected beams are displayed in an environmentally friendly order. Such a tool canalso facilitate the process of reusing steel beams. It saves time and money as compared toperforming the selection manually. In addition, it opens people’s eyes to new efficient methodsand ways of thinking in the field of reusing. It can also be considered as an incentive forincreased reuse of steel beams while reducing the negative effect on the environment and whilesaving energy and natural resources. / Världens utsläpp av växthusgaser har under en lång period ökat mycket och detta ställer ossinför en global utmaning. Bygg- och fastighetssektorns utsläpp står för cirka 20,6% av Sverigestotala utsläpp av växthusgaser och 33% av energianvändningen år 2018. Därför ärenergieffektivisering, minskad energiförbrukning och energitillförsel med låg påverkan påmiljön nödvändiga för att klara miljökvalitetsmålen. Ståltillverkning kräver höga temperaturer, och därmed hög energiförbrukning, både försmältning och bearbetning, vilket i sin tur ger en del utsläpp i luften. Återvinning av stål är enbra strategi för att spara energi och minska mängden utsläpp av växthusgaser. Men ännu störreenergibesparingar, och minskning av miljöpåverkan, kan uppnås om stålkomponenteråteranvänds i stället för att återvinna eller tillverka nytt stål. Trots det stora miljöincitamentetåterbrukas väldigt liten andel av Sveriges totala konstruktionsstål. Processen för återbruk av stålkomponenter ser otydlig ut och den behöver fastställas. En storutmaning i processen ligger i att skapa en marknadsplats där säljare och köpare kan mötas. Dettahar en stark koppling till syftet med rapporten som är att utreda möjligheten med parametriskdesign att ta fram ett verktyg som väljer ut lämpliga återbrukbara stålbalkar av en databas nedett stort antal balkar, som passar in i nya sammanhang efter vissa önskade förutsättningar. Resultatet av arbetet blir ett verktyg eller skript, där användaren anger sina värden och krav somkommer att ställas på den utvalda balken. Vidare visar skriptet de balkar som klarar av kravenfrån användaren och sedan sorterar dem med avseende på minimal miljöpåverkan. Programmetförväntas hjälpa konstruktörerna att välja ut rätt återbrukbara balk till rätt plats i ett nyttsammanhang. Det framtagna verktyget är skapat för att hantera I- och H-balkar med hjälp av programmenRhinoceros-Grasshopper som en plattform för en parametrisk design och beräkning. Iprogrammet ingår beräkningar för tvärsnittklasser, enaxlig och fleraxlig böjning utan hänsyn tillvippning samt tvärkraft där hänsyn tas till skjuvbuckling. Skriptet hanterar dock inte balkar medtvärsnittklass 4. Resultatet av denna studie, vilket är skriptet, visar att det är praktiskt möjligt att ta fram ettparametriskt verktyg som beräknar, analyserar och väljer ut de balkar som passar bäst föranvändarens behov. Verktyget kan även underlätta processen för återbruk av stålbalkar,eftersom det sparar tid och pengar jämfört med ett manuellt urval. Dessutom öppnar det ögonenför nya effektiva arbeten och tänkesätt inom området återbruk. Det kan även anses vara ettincitament för en ökad återanvändning av stålbalkar och minskning av miljöpåverkan, vilketbidrar till energi- och resursbesparingar.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Lateral-torsional buckling (LTB) is an important failure mode that needs to be taken into account during the design of steel beams. The fundamental equation for determining the elastic critical moment of a beam was derived with the assumption that the beam is subjected to a uniform bending moment distribution. Loads on steel structures generate a great variety of bending moment distributions. The effect of the bending moment distribution is taken into account by a parameter known as the equivalent moment factor. The procedure outlined in the South African National Standard for limit-states design of hot-rolled steel work, SANS 10162-1:2011, for determining the equivalent moment factor was originally developed for a bending moment that is uniformly or linearly distributed, however it is currently used for all bending moment distributions. A Finite Element (FE) model was developed in this investigation for determining the equivalent moment factor. The numerical model included residual stresses and initial geometric imperfections commonly found in hot-rolled steel beams. To validate the assumptions made during the development of the FE model an in-depth experimental investigation was conducted on simply supported beams. Three different load configurations were considered in the experimental study in order to simulate various bending moment distributions. A comparison of the equivalent moment factor between the numerical results and the results obtained from various steel specifications, including SANS 10162-1:2011, was carried out in an attempt to quantify the positive and negative attributes of the various methods employed by steel design specifications. The experimental investigation concluded that the FE model is able to successfully represent a simply supported beam with realistic characteristics that include residual stresses and imperfections. The comparative study illustrated that for a bending moment distribution with a constant moment gradient, SANS 10162-1:2011 provides excellent results. However, for the other distributions considered in this investigation highly conservative results were obtained for the equivalent moment factor. The relevance of these findings were made clear by considering three design cases found in steel structures. The resistance moment of the beams in each of these cases was calculated according to each of the steel specifications. It was found that the use of a highly conservative procedure for determining the equivalent moment factor can lead to the uneconomical design of a structure. / AFRIKAANSE OPSOMMING: Laterale-torsie knik is ’n belangrike falings modus wat in ag geneem moet word tydens die ontwerp van staal balke. Die fundamentele vergelyking vir die bepaling van die elastiese kritieke moment van ’n balk is afgelei met die aanname dat die balk onderworpe is aan ’n eenvormige buigmoment verdeling. Belastings op staalstrukture genereer ’n groot verskeidenheid van buigmoment verdelings. Die effek van hierdie buigmoment verdelings word in ag geneem deur ’n parameter wat bekend staan as die ekwivalente moment faktor. Die prosedure uiteengesit in die Suid-Afrikaanse Nasionale Standaard vir die ontwerp van warm-gewalste staalwerk, SANS 10162-1:2011, vir die bepaling van hierdie faktor is oorspronklik ontwikkel vir ’n buigmoment wat uniform of linieêr verdeel is oor die lengte van die balk, maar dit word tans gebruik vir alle buigmoment verdelings. ’n Eindige Element (FE) model is ontwikkel in hierdie ondersoek vir die bepaling van die ekwivalente moment faktor. Die numeriese model sluit die residuele spannings en aanvanklike geometriese imperfeksies wat in die algemeen teenwoordig is in warm-gewalste profiele in. Die aannames wat gemaak is tydens die ontwikkeling van die FE model is bevestig met ’n in diepte eksperimentele ondersoek oor die gedrag van eenvoudig opgelegde balke. Drie verskillende las konfigurasies is oorweeg in die eksperimentele studie om verskeie buigmoment verspreidings na te boots. ’n Vergelyking van die ekwivalente moment faktor tussen die numeriese resultate en die resultate verkry van verskeie staal spesifikasies, insluitend SANS 10162-1:2011, is uitgevoer in ’n poging om die positiewe en negatiewe eienskappe van die verskillende metodes wat gebruik word in verskillende staal ontwerp spesifikasies, te kwantifiseer. Die eksperimentele ondersoek het tot die gevolgtrekking gelei dat die FE model in staat is om ’n eenvoudige opgelegte balk te verteenwoordig, met realistiese eienskappe wat residuele spannings en imperfekies insluit. Die vergelykende studie toon dat SANS 10162-1:2011 uitstekende resultate bied vir ’n buigmoment verdeling met ’n konstante moment gradiënt. Dit was egter gevind dat vir ander verdelings wat in hierdie ondersoek oorweeg is, SANS 10162-1:2011 hoogs konserwatiewe resultate bied. Die toepaslikheid van hierdie bevindinge is duidelik gemaak deur drie ontwerp gevalle wat algemeen in staalstrukture gevind word te bestudeer. Die weerstandsmoment is in elk van die gevalle bereken volgens elke staal spesifikasies. Daar is gevind dat die gebruik van ’n hoogs konserwatiewe prosedure vir die bepaling van die ekwivalente moment faktor kan lei tot die ontwerp van ’n onekonomiese struktuur.

Until recently, the hot-rolled steel members have been recognized as the most popular and widely used steel group, but in recent times, the use of cold-formed high strength steel members has rapidly increased. However, the structural behavior of light gauge high strength cold-formed steel members characterized by various buckling modes is not yet fully understood. The current cold-formed steel sections such as C- and Z-sections are commonly used because of their simple forming procedures and easy connections, but they suffer from certain buckling modes. It is therefore important that these buckling modes are either delayed or eliminated to increase the ultimate capacity of these members. This research is therefore aimed at developing a new cold-formed steel beam with two torsionally rigid rectangular hollow flanges and a slender web formed using intermittent screw fastening to enhance the flexural capacity while maintaining a minimum fabrication cost. This thesis describes a detailed investigation into the structural behavior of this new Rectangular Hollow Flange Beam (RHFB), subjected to flexural action The first phase of this research included experimental investigations using thirty full scale lateral buckling tests and twenty two section moment capacity tests using specially designed test rigs to simulate the required loading and support conditions. A detailed description of the experimental methods, RHFB failure modes including local, lateral distortional and lateral torsional buckling modes, and moment capacity results is presented. A comparison of experimental results with the predictions from the current design rules and other design methods is also given. The second phase of this research involved a methodical and comprehensive investigation aimed at widening the scope of finite element analysis to investigate the buckling and ultimate failure behaviours of RHFBs subjected to flexural actions. Accurate finite element models simulating the physical conditions of both lateral buckling and section moment capacity tests were developed. Comparison of experimental and finite element analysis results showed that the buckling and ultimate failure behaviour of RHFBs can be simulated well using appropriate finite element models. Finite element models simulating ideal simply supported boundary conditions and a uniform moment loading were also developed in order to use in a detailed parametric study. The parametric study results were used to review the current design rules and to develop new design formulae for RHFBs subjected to local, lateral distortional and lateral torsional buckling effects. Finite element analysis results indicate that the discontinuity due to screw fastening has a noticeable influence only for members in the intermediate slenderness region. Investigations into different combinations of thicknesses in the flange and web indicate that increasing the flange thickness is more effective than web thickness in enhancing the flexural capacity of RHFBs. The current steel design standards, AS 4100 (1998) and AS/NZS 4600 (1996) are found sufficient to predict the section moment capacity of RHFBs. However, the results indicate that the AS/NZS 4600 is more accurate for slender sections whereas AS 4100 is more accurate for compact sections. The finite element analysis results further indicate that the current design rules given in AS/NZS 4600 is adequate in predicting the member moment capacity of RHFBs subject to lateral torsional buckling effects. However, they were inadequate in predicting the capacities of RHFBs subject to lateral distortional buckling effects. This thesis has therefore developed a new design formula to predict the lateral distortional buckling strength of RHFBs. Overall, this thesis has demonstrated that the innovative RHFB sections can perform well as economically and structurally efficient flexural members. Structural engineers and designers should make use of the new design rules and the validated existing design rules to design the most optimum RHFB sections depending on the type of applications. Intermittent screw fastening method has also been shown to be structurally adequate that also minimises the fabrication cost. Product manufacturers and builders should be able to make use of this in their applications.

The concept of semi-rigid composite connection has been widely researched in the past; however, most of the researches are limited to composite joints with metal deck ¿ooring and solid concrete slabs. Composite construction incorporating precast concrete hollowcore slabs (HCU) is a recently developed composite ¿oor system for buildings. The research on the structural behaviour of the semi-rigid composite joints with HCU is new and without any previous experimental database. In this paper, eight full-scale tests of beam-to-column semi-rigid composite joints with steel beams and precast hollowcore slabs are reported. The variables are stud spacing, degree of the shear connections, area of the longitudinal reinforcement and slab thickness. The test set-up and instrumentation is described in detail. The experimental behaviour is analysed and based on the test data the structural behaviour of these semi-rigid composite joints is discussed. Based on the experimental data, a simpli¿ed method to predict rotation and moment capacity for this type of composite connection is proposed.

[pt] As cargas concentradas em vigas de aço são freqüentemente encontradas na prática. Nas situações onde o local de aplicação da carga é fixo, enrijecedores transversais de alma podem ser usados para aumentar a sua resistência, mas devem ser evitados por razões econômicas. Para cargas móveis, é fundamental conhecer a resistência última das almas não enrijecidas. Diversas teorias foram desenvolvidas para este problema, mas ainda assim, o erro das fórmulas de previsão é superior a 40%. Duas são as causas desta dificuldade de se encontrar uma equação mais precisa: o grande número de parâmetros que influenciam o comportamento de uma viga sujeita a cargas concentradas, e o número insuficiente de dados experimentais presentes na literatura. Por outro lado, o colapso da estrutura pode ocorrer por: plastificação, flambagem global da alma, enrugamento (crippling) ou uma combinação destes estados limites. Apesar disto, nenhum estudo foi desenvolvido para avaliar a participação total ou parcial de cada comportamento no colapso. As redes neurais são modelos computacionais inspirados na estrutura do cérebro, que apresentam características humanas como o aprendizado por experiência e a generalização do conhecimento a partir dos exemplos apresentados. Estas características permitiram, em estudos preliminares, a utilização das redes neurais na previsão da carga última de vigas de aço sujeitas a cargas concentradas. A Lógica Nebulosa tem como objetivo modelar o modo aproximado de raciocínio, tentando imitar a habilidade humana de tomar decisões racionais em um ambiente de incerteza e imprecisão. Deste modo, a Lógica Nebulosa é uma técnica inteligente que fornece um mecanismo para manipular informações imprecisas, como conceitos de esbeltez, compacidade, flexibilidade e rigidez, além de estabelecer limites mais graduais entre os fenômenos físicos do problema. Os Algoritmos Genéticos foram inspirados no princípio Darwiniano da evolução das espécies (sobrevivência dos mais aptos e mutações) e na genética. São algoritmos probabilísticos, que fornecem um mecanismo de busca paralela e adaptativa, e têm sido empregados em diversos problemas de otimização. Este trabalho é a continuação do estudo desenvolvido na dissertação de mestrado (Fonseca, 1999) e tem o objetivo de propor um sistema de avaliação do comportamento estrutural de cargas concentradas, através de uma identificação da influência dos diversos parâmetros na carga e nos tipos de comportamento resultantes (plastificação, enrugamento e flambagem global), estabelecendo limites mais flexíveis entre cada um destes. Esta análise será executada empregando um sistema neuro- fuzzy (híbrido de redes neurais e de lógica nebulosa). Para viabilizar esta análise, torna-se necessária a apresentação de dados de treinamento onde o comportamento estrutural é conhecido. Este trabalho também apresenta um estudo de otimização das fórmulas de projeto existentes empregando algoritmos genéticos. Os resultados obtidos neste trabalho contribuem para, no futuro, o desenvolvimento de uma fórmula de projeto mais precisa. De posse desta nova fórmula, uma sugestão para sua incorporação em normas de projeto de estruturas de aço poderá ser feita, garantindo, desta forma, um dimensionamento mais seguro e econômico. / [en] Concentrated loads on steel beams are frequently found in engineering practice. In situations where the load application point is fixed, transversal web stiffeners can be used to provide an adequate resistance, but for economic reasons should be avoided whenever possible. For moving loads, the knowledge of the unstiffened web resistance becomes imperative. Many theories were developed for a better understanding of the problem, however, a 40% error is still present in the current design formulas. A more accurate design formula for this structural problem is very difficult to be obtained, due to the influence of several interdependent parameters and to the insufficient number of experiments found in literature. On the other hand, the structural collapse can be associated to: web yielding, web buckling, web crippling or by their combined influence. Despite this fact, no investigations were found in literature to access their partial of global influence on the beam patch load resistance Neural networks were inspired in the brain structure in order to present human characteristics such as: learning from experience; and generalization of new data from a current set of standards. Preliminary studies used the neural networks potential to forecast the ultimate load of steel beams subjected to concentrated loads. The main aim of Fuzzy Logic is to model the complex approximated way of inference, trying to represent the human ability of making sensible decisions when facing uncertainties. Thus, fuzzy logic is an artificial intelligence technique capable of generating a mechanism for treating inaccurate and incomplete information such as: slenderness, flexibility and stiffness, still being capable of establishing gradual boundaries among the physical phenomena involved. Genetic algorithms are inspired on the Darwins principle of the species evolution and genetics. They are probabilistic algorithms that generate a mechanism of parallel and adaptive best fit survival principle and their reproduction and have been long used in several optimisation problems. This work extends the research developed in a previous MSc. program (Fonseca, 1999) and intends to evaluate and investigate the structural behaviour of steel beams subjected to concentrated loads, identifying the influence of several related parameters. This will be achieved by the use of a neuro-fuzzy system, able to model the intrinsic relationships between the related parameters. The proposed system aim is to relate the physical and geometrical variables that govern the ultimate load with its associated physical behaviour (web yielding, web crippling and web buckling), being capable of establishing gradual boundaries among the physical phenomena involved. This investigation was focused on the development of a neuro fuzzy system. The proposed neuro fuzzy system was trained with data where the collapse mechanism were properly identified validating its results. This investigation also presents a study of patch load design formulae optimization based on genetic algorithm principles. The obtained results may help the future development of a more accurate design formula, that could be incorporated in steel structures design codes, allowing a safer and economical design.

The contemporary imperative of sustainable development has established an unprecedented degree of urgency, in view of the intransigent challenges posed by the persistent and ever-increasing energy and climate crises. In 2019, the Swedish building industry accounted for 21% of the nation’s total greenhouse gas emissions, with the structural framework of a building contributing to 34% of its overall emissions. In response to climate change and the housing demand caused by a growing population, sustainable construction solutions are needed. By substituting steel beams with timber beams, the carbon emissions caused by the building industry can be reduced significantly. This study investigates whether timber based, or steel-reinforced timber beams can provide comparable load-bearing capacity to steel beams while reducing carbon. How this impacts the cross-sectional height of the beams is also taken into consideration. Different load-bearing properties were calculated according to Eurocode using Excel for all the surveyed beams. The carbon emissions were calculated based on the weight of each beam combined with climate data obtained from the Swedish National Board of Housing, Building and Planning. Findings suggest that timber-based beams made from glulam or laminated veneer lumber exhibit moment capacity and bending stiffness on par with those of steel beams while reducing the carbon emissions drastically, but at the cost of increased cross-section height. Steel beams were identified as the main source of carbon emissions. Consequently, also making steelreinforced timber beams only marginally successful in reducing carbon emissions if at all.

[pt] Estruturas cada vez mais esbeltas têm sido usadas para otimizar edifícios de grande porte e reduzir custos, inclui-se nisto o pé-direito das edificações e portanto a altura das vigas. Grandes vãos são cada vez mais comuns, principalmente quando se utiliza aço em edificações, gerando então amplos espaços de serviço em uma direção, mas obstáculos na outra pela continuidade das vigas. A utilização de aberturas na alma das vigas para passagem de tubulações de ar-condicionado, incêndio, etc., evita um acréscimo na altura. Em consequência há uma grande diminuição da capacidade resistente nestes elementos estruturais que dependem diretamente da forma, do tamanho e da posição destas aberturas. A presente dissertação descreve alguns métodos construtivos de aberturas em almas de vigas de aço, cálculos de dimensionamentos e normas relacionadas. Alguns estudos numéricos com aplicações do método dos elementos finitos foram realizados investigando: angulação de aberturas hexagonais, vigas com três aberturas nos terços médios, vigas casteladas (tipo Litzka, com quantidades diferentes de aberturas), vigas expandidas em altura e uma viga Litzka Expandida. Para tal, utilizou-se de seis perfis de uso prático e comparando-os entre estas alternativas descritas. A viga Litzka Expandida se destacou em resistência quando comparada com outros métodos de fabricação, como também pelo menor peso linear, praticidade na fabricação e posicionamento das aberturas. / [en] More slender structures are used in order to reduce costs, floors depht and floor to ceiling clear heights. Steel construction and composite construction for buildings often employs long spans for beams and girders, offering service room between beams in one direction only. The use of web openings for passage of service ducts avoids increasing the depth of construction. Beams with web openings have reductions on flexural and shear resistances depending on the geometry, size and position of such openings on the beam. This dissertation presents some construction methods of beam web openings, analysis and design recommendations, related standards and codes. Some numerical studies by the finite elements method were carried out and results are presented for: type of openings, number and spacing of openings, castelled beams (Litzka type and nonuniform distribution of openings) and expanded in depth beams. For this purpose, six commonly used profiles were used for testing the described web openings solutions. Some comparison results are presented. The Litzka type of web expanded beam presented the best performance in terms of strength, easy of fabrication and reduction of material costs.