O pilar misto parcialmente revestido é fruto da associação de um perfil metálico e concreto trabalhando em conjunto. Nestes pilares o perfil metálico, normalmente perfil I ou H, não é totalmente envolvido por concreto, sendo apenas a região entre as mesas preenchida. No Brasil, a utilização de pilares mistos parcialmente revestidos é ainda incipiente. Contudo a introdução do dimensionamento de elementos mistos na ABNT NBR 8800:2008 e as vantagens construtivas inerentes aos elementos mistos tem viabilizado a utilização destes elementos em obras pelo país afora, especialmente naquelas de grande porte. Neste contexto, o objetivo principal do trabalho é analisar o comportamento estrutural destes pilares e avaliar a possibilidade de substituição das armaduras tradicionais compostas por vergalhões por alternativas como telas de aço soldadas ou adição de fibras de aço ao concreto (taxa de 1,5% de fibras de 25 mm de comprimento). Para isto, foram feitos ensaios experimentais de cinco modelos físicos de pilares mistos parcialmente revestidos solicitados por compressão centrada e de um modelo solicitado por compressão excêntrica. Os resultados demonstraram-se promissores no que tange à substituição da armadura, mesmo para a situação com excentricidade na força aplicada. Em complemento, foi desenvolvida uma simulação numérica dos modelos físicos ensaiados utilizando o pacote computacional DIANA®, fundamentado no método dos elementos finitos, com o pré e pós-processador FX+. Apesar da hipótese simplificadora de aderência perfeita entre o aço e o concreto, o modelo numérico representou adequadamente o comportamento dos pilares mistos. / Partially encased composite columns are the result of the association of a steel profile and concrete filling working together. The most commonly used steel profiles have I or H cross sections not completely covered by concrete, with filling only in the region between flanges. In Brazil, the use of partially encased composite columns is still incipient. However, the introduction of design procedures for these columns in Brazilian Code ABNT - NBR 8800:2008 and also their inherent constructive advantages have enabled the use of these elements in buildings across the country, especially for large constructions. In this context, the main objective of this work is to analyze the structural behavior of these columns and evaluate the possibility of replacing the traditional reinforcement using steel rebar for alternatives such as welded steel meshes or steel fibers added to the concrete (rate of 1.5% and 25 mm long). To achieve these goals, experimental tests on five models of partially encased composite columns submitted to axial loading and one model subjected to eccentric loading were performed. The results proved to be promising in terms of replacing the traditional reinforcement, even for the situation with eccentricity of the applied force. In addition, a numerical modeling of the studied columns was developed, using finite element based software DIANA® with FX +. Despite simplifying assumptions of perfect bond between steel and concrete, the numerical model adequately represented the behavior of the columns.

Um pilar misto aço-concreto consiste basicamente de um elemento de aço, simples ou composto, predominantemente comprimido, que trabalhe em conjunto com o concreto simples ou armado. Há basicamente dois tipos de pilar misto: os revestidos e os preenchidos. Os revestidos são formados por um perfil de aço embutido em uma seção de concreto, garantindo a proteção ao fogo (havendo necessidade de armaduras). Os pilares preenchidos são tubos de aço, circulares ou retangulares, preenchidos com concreto, dispensando qualquer tipo de armadura e a necessidade do uso de formas; porém para proteger do fogo e da corrosão exige-se um tratamento \"extra\" do tubo de aço. A norma brasileira NBR 8800/86 - \"Projeto e execução de estruturas de aço de edifícios\" quanto as estruturas mistas se dedica apenas àquelas submetidas à flexão simples (vigas mistas), não abordando as estruturas basicamente comprimidas (pilares mistos). Já as normas LRFD-AISC/86 - \"Load and resistance factor design\", Eurocode 4, BS 5400 apresentam considerações específicas sobre o dimensionamento de barras axialmente comprimidas e flexo-comprimidas, tratando tanto dos elementos revestidos quanto dos preenchidos. Do ponto de vista estrutural, são analisadas e discutidas as prescrições das principais normas estrangeiras aplicáveis. Quanto aos aspectos construtivos, apresentam-se técnicas de execução e de acabamento, dando especial atenção a questão da resistência ao fogo. / A composite column may be defined as a member made of a structural steel section, basicaly under compression, working with simple or reinforced concrete. There are basically two kinds of steel-concrete composite columns: structural steel section encased in concrete which has fire protection and it is necessary to use reinforcement and tubes filled with concrete which it is not necessary to use reinforcement and formwork but it require an extra protection to fire. Steel Brazilian code NBR 8800/86 - \"Projeto e execução de estruturas de aço de edifícios\" give specifications only for steel-concrete member under bending (composite beams). This code neglegence composite members under compression (composite columns). LRFD-AISC/86 - \"Load and resistance factor design\", Eurocode 4, BS 5400 give specifications about steel-concrete composite columns under compression and bending combined to concrete encased composite columns and steel tubes filled with concret. Codes requirements, constructional aspects and fire behaviour of composite columns are presented and discussed.

Os pilares mistos são elementos estruturais compostos por um perfil metálico e concreto trabalhando em conjunto. Entre estes destaca-se o pilar parcialmente revestido que apresenta vantagens como a possibilidade de pré-fabricação, redução no uso de formas e eficiência estrutural, porém seu processo executivo envolve uma trabalhosa tarefa que é a ancoragem das armaduras ao perfil metálico. Neste contexto, o presente trabalho tem por objetivo estudar o comportamento estrutural de pilares mistos parcialmente revestidos submetidos a compressão simples e flexo-compressão e avaliar a possibilidade de substituição da armadura convencional por alternativas que possibilitem uma execução mais simples. Para isto foi desenvolvido um programa experimental envolvendo 23 exemplares de pilares mistos fabricados com o perfil W 150 x 22,5 e três configurações de armadura: armadura convencional, telas de aço soldadas entre as mesas do perfil e concreto com adição de fibras. Além disso, foram realizadas simulações numéricas e um estudo paramétrico utilizando o pacote computacional FX + DIANA a fim de extrapolar os resultados experimentais. Observou-se que o comportamento estrutural de pilares submetidos a forças excêntricas depende do eixo de flexão, de modo que a ruptura ocorre de modo mais gradual quando o pilar é submetido a flexão em torno do eixo de maior inércia. Além disso, respostas similares foram obtidas para as três configurações de armadura avaliadas, sendo o valor de força máxima obtido para os exemplares com concreto com fibras ligeiramente inferior aos demais. A substituição da armadura convencional por telas de aço ou concreto com fibras de aço não altera significativamente os valores de força máxima nem o comportamento pós-pico, mostrando a viabilidade da solução proposta. / Composite columns are structural elements made with steel profiles and concrete working together. Among these, there is the partially encased composite columns that presents advantages, such as, the possibility of pre-fabrication, reduction in the use of formwork and structural efficiency, but its fabrication process involves a laborious task that is the anchoring of the reinforcements to the steel profiles. In this context, the present work has the objective of studying the structural behavior of partially encased composite columns subjected to axial compression and eccentric compression and to evaluate the possibility of replacing conventional reinforcement with alternatives that allow a simpler execution. For this, an experimental program was developed involving 23 specimens of composite columns made with W 150 x 22.5 shape and three reinforcement configurations: welded steel mesh and fiber-added concrete. In addition, numerical simulations and a parametric study were performed using the FX + DIANA computational package in order to extrapolate the experimental results. The results show the structural behavior of columns subjected to eccentric forces depends on the axis of flexure, so that the rupture occurs more gradually when subjected to bending about the major inertia axis. In addition, similar responses were obtained for the three reinforcement configurations evaluated, and the peak load obtained for the specimens with fiber concrete was slightly lower than the others. Therefore, it can be observed that the replacement of conventional reinforcement by steel meshes or fiber concrete does not significantly alter the peak load or post-peak behavior, showing potential to be considered as a new alternative.

O presente estudo traz uma revisão bibliográfica dos sistemas estruturais, da estabilidade e análise estrutural de edifícios de múltiplos andares com estrutura de aço e, ainda, do emprego de elementos mistos aço e concreto nesses sistemas, com ênfase às vigas mistas. É aplicável a duas áreas, a saber: acadêmica e prática. Na área acadêmica, contribui com informações que permitem iniciar linhas de pesquisas para diversos assuntos. Na área prática, através de exemplos, contribui com a análise da viabilidade do processo construtivo e estrutural. E por meio de instruções mínimas, contribui para o desenvolvimento de projetos de estruturas metálicas. A referida pesquisa é embasada na ABNT NBR 8800:2008 e, quando indispensável, nas normas ANSI/AISC 360-10 e EN 1994-1-1:2004. / The concerned study brings a literature review of structural systems, stability and structural analysis of multistory buildings with steel structures and also the use of steel-concrete composite elements in those systems, with emphasis on composite beams. It applies to two subjects, namely: academic and practical. In academics, it contributes with informations that allows you to start several lines of research. In the practice, through examples, it contributes with the assessment of the viability of the construction and structural process. And using minimal instructions, it contributes to the development of steel structure projects. The related research is based on the ABNT NBR 8800:2008 and, when necessary, on ANSI/AISC 360-10 and EN 1994-1-1:2004.

As vigas mistas aço-concreto têm sido bastante utilizadas na engenharia civil, tanto no Brasil como no contexto mundial. O comportamento adequado deste elemento estrutural faz-se pela interação entre ambos os materiais, a qual é garantida por conectores de cisalhamento. O presente trabalho apresenta uma visão geral do comportamento das vigas mistas aço-concreto, e, principalmente o estudo do comportamento estrutural de conectores de cisalhamento. Para tanto, faz-se uma simulação numérica dos conectores tipo pino com cabeça (stud) e perfil “U” formado a frio, por meio de uma modelagem do ensaio experimental tipo “Push-out”, cujos resultados são confrontados com valores experimentais obtidos de ensaios realizados em laboratório. Para a simulação numérica utiliza-se um código de cálculo com base nos Método dos Elementos Finitos (MEF), cujas ferramentas disponibilizadas permitem análises dos modelos em regime de não-linearidade física e geométrica. Os modelos numéricos apresentam como variáveis de interesse o número de conectores na laje de concreto, a quantidade de armadura inserida no concreto, o diâmetro do conector tipo pino com cabeça (stud), a resistência do concreto, a espessura e posição de soldagem do conector tipo perfil “U” formado a frio. A variação desses parâmetros tem como finalidade a determinação da resistência última e da relação força-deslocamento dos conectores, bem como avaliar a concentração de tensão e deformação nas partes constituintes dos modelos / Composite steel-concrete beams have been used in civil engineering in Brazil as well other countries. A realistic determination of the behaviour of this structural element is estimated by considering the interaction between the two materials, which is safeguarded by providing shear connectors. The present research presents a general view of the behaviour of steel-concrete composite beams, and primarily the study of the behaviour of shear connectors. To meet this ends, a numerical analysis of stud bolt and cold formed U-channel under push-out test geometry was carried out and the results compared to experimental test results. The numerical analysis utilises a Finite Element Method (FEM) code that permits the analysis under non-linear material and geometric regimes. The main numerical variables in the study were the number of connectors used in the concrete plate, the quantity steel reinforcement, the diameter of stub bolt connector, concrete strength, the thickness and position of welding of the cold-formed U-channel. The main objective of varying these parameters was to determine the ultimate strength and the load-slip behaviour of the connectors as well as evaluate the stress and strain concentrations in certain parts that constitute the models

Ce travail de recherche est axé sur la compréhension du comportement en flexion, statique et instantané, des structures multimatériaux acier-béton collées du génie civil. La première étape consiste à mener une analyse expérimentale et numérique par éléments finis non linéaire sur la caractérisation de la connexion. L’essai Push-Out a été retenu : deux dallettes de béton C25/30 sont connectées à un profilé métallique. Nous faisons varier la géométrie des dallettes et du joint de colle. La ruine est cohésive dans le béton proche de l’interface par cisaillement. Un effet favorable du frottement entre dallette et presse peut se développer et induire le développement de contraintes de compression et augmenter la contrainte de cisaillement moyenne à l’interface. Les dimensions des éprouvettes et du joint de colle influent sur la charge de ruine. Ainsi, l’essai Push-Out est, dans l’état actuel de connaissances, difficile à utiliser pour la caractérisation de la connexion collée acier-béton en vue du dimensionnement de structures. La seconde partie est consacrée à l’analyse du comportement de poutres mixtes acier béton collées. Un essai sur poutre constituée de prédalles et d’une dalle de compression confirme que le collage est une alternative aux connexions traditionnelles. Nous développons aussi un modèle de calcul en variables généralisées et en variables locales en 3D non linéaire. La modélisation par éléments finis apporte plus de précisions, notamment sur l’état de contraintes à proximité de l’interface et à l’approche de la ruine. Les dimensions du joint de colle et la plastification du profilé influent sur la zone de rupture dans le béton. / This PhD thesis investigates the connection of steel-flexural members by bonding and focuseson static and instantaneous behavior. First, experimental and numerical analyses are performed. A push out test is used : two concrete blocks are connected to steel members. The influence of the concrete blocks and bonding joint geometry is examined. Cohesive shear failure appears in concrete near the interface. Failure can occur when the average shear strain is twice the tension limit of concrete, which can be explained by favorable slipping between the concrete block and the support. In this case, the bonding joint is not only solicited in shear but also in compression. Results depend on the length of bonding joint and concrete blocks geometry. So, push out test cannot be now used to characterize the bonding connection between steel and concrete in order to design structures. The second is about the analysis of the behavior of steel concrete composite beams. A precast beam with compressive concrete was tested. Results show that a bonding connection can be an alternativesolution regardless of the slab manufacturing. We develop two numerical models. The first one is based on multi-layer beam modeling and the second one is a nonlinear 3D finite element model. The stress distribution close to the interface and near failure is more accurate with the finite element model than with the generalized model. Bonding joint geometry and plastification of steel girder have an influence on the failure region in the concrete.

The diploma thesis deals with alternative design of bridge on highway D1 near Považská Bystrica. Bridge is designed as composite steel-concrete bridge with 6 spans in length 35,7m + 42m + 42m + 42m + 42m + 35,7m. Overall length of superstructure of the bridge is 241m. Construction material used in design is steel S355, concrete C35/45 and reinforcing steel bars are grade B500B. Calculation of superstructure of two variants was performed in preliminary design. First variant is twin-girder structure system and box-girder structure system is second variant. Selected twin-girder bridge was developed in more complex structural design report. Direct erection in place with temporary piers was selected as assembly method of steel structure. Slab concreting will be done by mobile formwork. The design and calculation of the bridge structure was carried out according to valid European design codes. The diploma thesis includes engineering report, structural design report of variants, structural design report of final variant, bill of quantities of assembly parts and drawing documentation.

yes / This paper presents the results of a numerical investigation on strategies for enhancing the fire behaviour of concrete-filled steel tubular (CFST) columns by using inner steel profiles such as circular hollow sections (CHS), HEB profiles or embedded steel core profiles. A three-dimensional finite element model is developed for that purpose, which is capable for representing the various types of sections studied and the nonlinear behaviour of the materials at elevated temperatures. High strength steel is considered in the numerical model, as a possible way to lengthen the fire endurance. The numerical model is validated against experimental results available in the literature for various types of steel-concrete composite sections using inner steel profiles, obtaining satisfactory results. Based on the developed numerical model, parametric studies are conducted for investigating the influence of the cross-sectional geometry and the steel grade of the inner profiles on the fire performance of these composite columns, for eventually providing some practical recommendations.

This thesis deals with the subject of lateral bracing between the bottom flanges of I-girder composite bridges. The focus is on the impact of adding lateral bracing on existing bridges, as well as on new bridges. Experience and knowledge from bridge projects around the world are investigated and implemented in the evaluation of the research subject. Many existing bridges are in need of being strengthened or replaced, due to the increased traffic volume and heavier traffic loads. Different approaches can be used to prolong the lifetime of existing bridges. The approach is different depending on the cause, but for increasing the lifetime regarding fatigue some of the most suitable options are described in this thesis. A proposed concept is presented, in this thesis, along with some research questions to be answered. The use of lateral bracings in composite bridges varies between different parts of the world. In one country it can be a requirement/common praxis for long span composite bridges with two I-girders, in other countries there are no requirements of using them. Some parts of these regulations and requirements can be traced back to the tradition in both manufacturing and construction of this type of bridges. This thesis investigates how lateral bracing is used around the world to distribute eccentric loads between primary longitudinal structural members, provide resistance to lateral loads, and to permit an existing two-girder structural system to be retrofitted to behave similarly to an often more expensive closed steel box girder. Furthermore, several case studies have been conducted to investigate the impact on the structural behavior of composite bridges where a lateral bracing is implemented in the structure. The results from these case studies are presented in the thesis and show the advantages of the quasi-box section for which the lateral bracing is closing the composite cross section. By making the I-girder composite cross section acting more like a box-section, the distribution of eccentric loads between the girders is improved. The impact on longitudinal stresses from traffic loads and the additional effects on internal sectional parts are also evaluated and discussed. Furthermore, proposals of the connection design for lateral bracings in existing bridges are suggested. Finally, conclusions from the results are stated.

No / This paper presents experimental results of temperature distribution in fire in four typical types of steel-concrete composite joint (web cleat, fin plate, flush endplate and flexible endplate) with different fire-protection schemes. The test specimens were unloaded and the steelwork of each joint assembly was exposed to a standard fire condition [ISO 834, 1975: Fire Resistance Tests, Elements of Building Construction, International Organization for Standardization, Geneva] in a furnace. In total, 14 tests were conducted, including 4 tests without any fire protection and 10 tests with different schemes of fire protection. The main objective of these tests was to investigate the effects of three practical fire-protection schemes as alternatives to full fire protection of the entire joint assembly. The three alternative methods of fire protection were: (1) protecting a segment, instead of the entire length, of the beams; (2) unprotected bolts and (3) protecting the columns only. The main results of these tests are: (1) if all the steel work (excluding the bolts) in the joint assembly was protected, whether or not protecting the bolts had very little effect on temperatures in the protected steelwork other than the bolts. The bolt temperatures were higher if they were not protected than if they were protected, but the unprotected bolt temperatures in a joint with fire protection to other steelwork were much lower than bolt temperatures in a totally unprotected joint; (2) as far as joint temperatures are concerned, protecting a segment of 400 mm of the beam was sufficient to achieve full protection and (3) if only the column was protected, only the joint components that were in the immediate vicinity of the column (such as welds) developed noticeably lower temperatures than if the joint assembly was unprotected, but due to heat conduction from the unprotected steel beams, these temperature values were much higher than if the joint assembly was protected. Furthermore, the column temperatures in the joint region were much higher than the protected column temperatures.