Ductile plastic hinge zones in beams of reinforced concrete frames are known to incur extensive damage and elongate. This ‘beam elongation’ can inflict serious damage to adjacent floor diaphragms, raising concerns of life safety. In light of this, the slotted reinforced concrete beam was investigated as a promising non-tearing floor substitute for conventional design. It consists of a conventional reinforced concrete beam, modified with a narrow vertical slot adjacent to the column face, running approximately three-quarters of the beam depth. Seismic rotations occur about the remaining concrete “top-hinge”, such that deformations are concentrated in the bottom bars of the beam, away from the floor slab, and beam elongation is minimised. The inclusion of the slot raised several design issues which needed to be addressed. These were the shear transfer across the top-hinge, buckling of bottom longitudinal reinforcement, low cycle fatigue, bond anchorage of reinforcement in interior joints, interior joint design, detailing with floor units and beam torsion resulting from eccentric floor gravity loads. These issues were conceptually investigated in this project. It was found that most issues could be resolved by providing additional reinforcement and/or specifying alternative detailing. As part of the experimental investigation, quasi-static cyclic tests were performed on in-plane beam-column joint subassemblies. Specimens tested included exterior and interior joint subassemblies with slotted-beams and a conventional exterior joint as a benchmark. This was followed by a test on a slotted-beam interior joint subassembly with precast floor units and imposed gravity load. Experimental tests revealed significant reductions in damage to both the beam and floor when compared to conventional beams. Issues of bar buckling, bond-slip and altered joint behaviour were also highlighted, but were resolved in the final test. A simple analytical procedure to predict the moment-rotation response of slotted-beams was developed and verified with experimental results. This was used to perform sensitivity studies to determine appropriate limits for the concrete top-hinge depth, top-to-bottom reinforcement ratio and depth of diagonal shear reinforcement. For the numerical investigation, a multi-spring model was developed to represent the flexural response of slotted-beams. This was verified with experimental tests and implemented into a five-storey, three-bay frame for earthquake time history analyses. To provide a benchmark, a conventional frame was also setup using the plastic hinge element developed by Peng (2009). Time history analyses showed that the slotted-beam frame response was very similar to the response of a conventional frame. Due to greater hysteretic damping, there was a slight reduction in the average interstorey drift and lateral displacement envelopes. The slotted-beam frame also exhibited 40% smaller residual drifts than the conventional frame. The research carried out in this thesis showed slotted reinforced concrete beams to be an effective non-tearing floor solution, which could provide a simple and practical substitute for conventional reinforced concrete design.

Improvement of Rotation Capacity of Composite Beam-to-HSS Column Connections Using External Horizontal Stiffeners Mahdi Afshar Arjmand This thesis focuses on the analysis of out-of-plane deformation (OOP) in column flange located in the panel zone of composite beam-to-column steel connection, as a critical aspect of steel structural engineering. This type of connection is an integral component of steel structures, and understanding their behavior is essential for ensuring safety and performance. The investigation involves examining the causes, factors influencing, and potential mitigation strategies for out-of-plane deformation of HSS flange column in these connections. Beam-to-column connections play a vital role in transferring loads and maintaining structural stability. Out-of-plane deformation, where the flange displaces from its primary plane, can compromise the connection's performance. This study aims to shed light on the mechanisms causing out-of-plane deformation and explore techniques to minimize its effects. Out-of-plane deformation of column flange connections can result from various factors, including eccentric loading, bending moments, torsion, and material properties. Understanding these causes is crucial for accurate analysis and design. Analytical methods and numerical simulations, such as finite element analysis (FEA), are employed to predict and quantify out-of-plane deformation. Models are created to represent real-world connections, enabling the exploration of their behavior under different loads and conditions. The study investigates strategies to mitigate out-of-plane deformation, such as adding horizontal stiffeners, or vertical stiffeners. These approaches aim to enhance the column flange’s resistance to out-of-plane displacements and improve overall structural performance. Real-world case studies of steel beam to-column connections are analyzed to demonstrate the effects of out-of-plane deformation and the efficacy of mitigation strategies. The results highlight the importance of accurate analysis and design to ensure connection integrity. Based on the findings, the study proposes design guidelines for flange-column connections to minimize out-of-plane deformation. These guidelines provide engineers with insights into optimizing connection design and ensuring stability under varying loads. The unique characteristic of beam-to-HSS column connections is the out-of-plane deformation of the HSS column flange at the beam web-to-column flange interface which can reduce contribution of the connection web to the overall resistance of the connection. To explore effect of the column flange OOP deformation, performance of three connection types, namely composite beam-to-HSS column connection, composite beam-to-HSS column connection with slab-column gap, and bare beam-to-HSS column connections are evaluated using pre-validated 3D finite element (FE) simulations. FE models can simulate low-cycle fatigue and post-rupture behavior of the connection. Comprehensive global and local responses are presented and discussed. It is found that column compactness, i.e., column’s width-to-thickness ratio, has considerable effect on maximum moment capacity, rotation capacity, post rupture residual capacity and energy dissipation capability of the connection. On the other hand, external horizontal stiffeners can significantly increase the rotation capacity of the connection. External horizontal stiffeners in steel beam-to-column connections are crucial for boosting structural efficiency and load-bearing capacity. Carefully designed, accurately placed, and securely attached, they ensure a reliable and safe system capable of withstanding diverse loads and environmental conditions, contributing to the long-term safety and stability of the entire steel structure.

Este trabalho abordou o estudo de ligação viga de aço e pilar misto preenchido com concreto a partir da aplicação de modelos numérico para representar o comportamento de duas tipologias de ligação: uma ligação parafusada com aderência entre os parafusos passantes e o núcleo de concreto e uma ligação soldada, validadas com base em resultados experimentais existentes. Os resultados obtidos nessa etapa foram considerados satisfatórios, dentro da proposta de modelagem, apesar das simplificações adotadas. Após a validação do modelo numérico foi desenvolvido um estudo paramétrico dos modelos de ligação para entender a influência de alguns parâmetros no comportamento global da estrutura, que foram: resistência à compressão do concreto e espessura do perfil tubular e perfil da viga, com posterior discussão da relação momento-rotação das duas tipologias de ligação estudadas. A mudança do perfil da viga foi o parâmetro que mais influenciou no comportamento global da ligação parafusada; enquanto que, para a ligação soldada, as variações de todos os parâmetros influenciaram no comportamento da ligação, com destaque para a variação do perfil da viga. / This research studied connections typology between steel beams to column filled with concrete from the application of numerical models that reproduce the behavior of two connections: bolted beam-column connection and welded beam-column connection, which were calibrated using existing experimental results. At this stage, the results were considered satisfactory, within the proposed model, despite the adopted simplifications. After the calibration, a parametric study was developed with the aim of verifying the influence of some parameters on the overall behavior of the structure, such as the concrete compression strength, the thickness of the tube wall and the beam properties, with discussions of bending moment-rotation of the studied connections. The beam properties were the parameters that most influenced on the overall behavior of the bolted beam-column connection, while, for the welded connection, all parameters influenced on the overall behavior of the connection, specially the beam properties.

Este trabalho abordou o estudo de ligação viga de aço e pilar misto preenchido com concreto a partir da aplicação de modelos numérico para representar o comportamento de duas tipologias de ligação: uma ligação parafusada com aderência entre os parafusos passantes e o núcleo de concreto e uma ligação soldada, validadas com base em resultados experimentais existentes. Os resultados obtidos nessa etapa foram considerados satisfatórios, dentro da proposta de modelagem, apesar das simplificações adotadas. Após a validação do modelo numérico foi desenvolvido um estudo paramétrico dos modelos de ligação para entender a influência de alguns parâmetros no comportamento global da estrutura, que foram: resistência à compressão do concreto e espessura do perfil tubular e perfil da viga, com posterior discussão da relação momento-rotação das duas tipologias de ligação estudadas. A mudança do perfil da viga foi o parâmetro que mais influenciou no comportamento global da ligação parafusada; enquanto que, para a ligação soldada, as variações de todos os parâmetros influenciaram no comportamento da ligação, com destaque para a variação do perfil da viga. / This research studied connections typology between steel beams to column filled with concrete from the application of numerical models that reproduce the behavior of two connections: bolted beam-column connection and welded beam-column connection, which were calibrated using existing experimental results. At this stage, the results were considered satisfactory, within the proposed model, despite the adopted simplifications. After the calibration, a parametric study was developed with the aim of verifying the influence of some parameters on the overall behavior of the structure, such as the concrete compression strength, the thickness of the tube wall and the beam properties, with discussions of bending moment-rotation of the studied connections. The beam properties were the parameters that most influenced on the overall behavior of the bolted beam-column connection, while, for the welded connection, all parameters influenced on the overall behavior of the connection, specially the beam properties.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Pre-cast sections have the advantages of structural efficiency, better quality control and less construction time, which enable them to be widely used in building structures. The connections of pre-cast buildings play a vital role for the stability and strength of structures. Nowadays, more attention is drawn to the aesthetical appearance of building structures, especially by architects. The Hidden Corbel Connection (HCC) was then developed to make the building structures stable and aesthetically pleasing. A modified HCC was designed and investigated in this study. Amongst all the mechanisms in the connection zone, the mechanism of the end anchorage length of tension reinforcement plays a key role in the economy of the connection and is hence further investigated. In order to investigate whether the end anchorage length of tension reinforcement can be reduced for a simply supported beam, a 2D non-linear finite element model is used to analyze the stress distribution inside the connection zone. Based on the stress distribution in the connection zone, the tensile force was calculated at the face of the support, which directly correlates to the required end anchorage length of tension reinforcement. The confinement in the connection zone increases the bond stress, which in turn reduces the required anchorage length of tension reinforcement. Therefore, a 3D model is used to analyze the region inside the modified HCC to find the position of the best confinement. By comparing the finite element (FE) results with Eurocode 2 (2004), and SABS 0100-1 (2000), it is demonstrated that the FE results require the shortest anchorage length, while the longest anchorage length is specified in SABS 0100-1 (2000). Based on the comparison between the FE results and the design codes, a laboratory experiment was then performed to determine if the end anchorage length of tension reinforcement can be reduced. Four beams with different support conditions and with different end anchorage length of tension reinforcement were tested. The results of the laboratory experiment indicate that the end anchorage length for simply supported beams can be shortened from the specification of SABS 0100-1 (2000).

O presente trabalho trata do estudo do comportamento de chumbadores grauteados inseridos em concreto com fibras de aço em ligações viga-pilar de estruturas de concreto pré-moldado. Este estudo é importante para se entender e poder quantificar a influência da rigidez deste componente no comportamento de ligações semirrígidas de estruturas de concreto pré-moldado. O objetivo do trabalho é estudar o mecanismo do chumbador no concreto com fibras de aço em ensaios específicos e avaliar também o comportamento de uma ligação viga-pilar de concreto pré-moldado utilizando estas fibras no consolo e no dente da viga. Nesta pesquisa foi realizado um programa experimental no Laboratório de Estruturas da EESC, uma análise numérica com o emprego do software DIANA® e uma comparação com formulações analíticas existentes para o cálculo da força última destes componentes. Foram ensaiados nove modelos experimentais para avaliar especificamente o mecanismo resistente do chumbador, variando-se os diâmetros das barras, sua inclinação e a porcentagem de fibras de aço no concreto. Além destes modelos, foi realizado ensaio de uma ligação viga-pilar de concreto pré-moldado para avaliar a rigidez da ligação com chumbador inserido em concreto com fibras de aço. Nos ensaios experimentais dos chumbadores observou-se que modelos com concreto com fibras de aço apresentam rigidez até 25% maior se comparado ao modelo com concreto convencional. Verificou-se que o graute utilizado para solidarizar os chumbadores exerce significativa influência na capacidade última do modelo, podendo diminuir em cerca de 30% a capacidade de carga. A ligação viga-pilar de concreto pré-moldado utilizando concreto com fibras de aço no consolo e no dente da viga se comportou de maneira satisfatória, não apresentando fissuração na interface dos diferentes concretos. Na comparação dos modelos ensaiados com as formulações teóricas extraídas de trabalhos de referência verificou-se que, para os modelos específicos de chumbador, a formulação existente é representativa. Para a ligação viga-pilar, alguns ajustes na formulação analítica se fizeram necessários para considerações de efeitos de grupo e de borda observados e decorrentes da utilização de dois chumbadores na ligação proposta neste trabalho. / This research deals with the study of the behavior of grouted dowels embedded in concrete with steel fibers. This study is important to understand and quantify the stiffness transmitted by this component in a semi-rigid connection of precast concrete structures. The objective is to study the mechanism of the dowel in the concrete with steel fibers and evaluate the mechanical behavior of a precast beam-column connection using this type of concrete on the corbels and in the dapped-end beam. In this research, an experimental program in the EESC Structures Laboratory was carried out, as well as a numerical analysis with the use of DIANA® software and a comparison with existing formulations to calculate these components. Nine models were experimentally tested to specifically evaluate the dowel resistant mechanism by varying the diameters of the bars, the declination and the percentage of steel fibers in concrete. Furthermore, an experimental test was performed in order to evaluate the behavior of the connector. The results indicate that for the dowels with concrete and steel fibers, the ultimate capacity of the connection occurs by failure of the connector (excessive deformation of the bars), while in conventional concrete this capability is associated with the rupture of the concrete and that the concrete with steel fibers decreases by 25% the deformability of the models. The grout has a significant impact on the ultimate capacity of the model, which may increase in less than 30%. In the analysis of the beam-column connection, it is possible to observe that the proposed connection exceeds by more than 20% the ultimate capacity compared to traditional beam-column connections. In comparing the theoretical models tested with the formulations shown by previous studies, it was found that for specific models dowels, the existing formulation is representative. For the beam-column connection, adjustment was performed in the previous formulation considerations group and edge effects that occur due to the use of two dowels on the tested connection.

No presente trabalho, utiliza-se concreto com fibras de aço, traspasse de armaduras e chaves de cisalhamento para desenvolver uma ligação viga-pilar capaz de resistir a ações cíclicas e dinâmicas e que possa ser empregada na pré-moldagem de estruturas de casas de força de usinas hidrelétricas. Para atingir este objetivo, inicialmente foram realizados ensaios de caracterização dos materiais, cujos resultados mostraram aumentos de 34% na resistência à tração na flexão, 16% na resistência à compressão e 33% na tenacidade, comprovando os efeitos benéficos das fibras de aço nas propriedades mecânicas do concreto. Em seguida, foram realizados ensaios de tração em tirantes, cujos resultados sugeriram que um comprimento de 15Ø é suficiente para que a emenda desenvolva as tensões de aderência de modo adequado; e ensaios de cisalhamento, cujos resultados mostraram que a ligação viga-pilar resiste a tensões de cisalhamento direto de até 0,77 MPa. Na sequencia, foram realizados ensaios cíclicos em dois modelos cruciformes para caracterização da ligação (um monolítico e outro de concreto pré-moldado, o qual empregava concreto com 1% de fibras na região da ligação), sendo o carregamento aplicado em cinco níveis de força, cada um com dez ciclos de carregamento e descarregamento. Os resultados desses ensaios mostraram que a ligação do modelo em concreto pré-moldado apresentou 85% da resistência do modelo monolítico e ruptura governada por flexão. Por fim, os ensaios dinâmicos foram realizados nos modelos cruciformes em três diferentes situações (íntegros, fraturados e após ruptura da ligação) para estimar o coeficiente de amortecimento, o qual sofreu uma redução de 31% após o ensaio cíclico. Simulações computacionais foram realizadas para complementar a investigação realizada neste trabalho. Elas mostraram representação aceitável da rigidez, mas não da resistência do modelo. / In the present work, steel fiber reinforced concrete, splicing bars and shear keys are used in order to develop a beam-column connection able to support cyclic and dynamic loadings and which can be used in precasting power houses structures of power plants. To achieve this goal, tests were carried out to characterize the materials, which showed increases of 34% in flexural tensile strength, 16% in compressive strength and 33% in toughness factor, confirming the beneficial effects of steel fibers in mechanical properties of the concrete. Then, tensile tests were carried out on rods, whose results suggested that a length of 15Ø can assure appropriate development of bond stresses through the splice; and shear tests, whose results showed that the beam-column connection resists to shear stresses of up to 0,77 MPa on shear key. After, cyclic tests were performed in two cruciform models in order to characterize the beam-column connection (one monolithic and the other precast concrete, which employed 1% steel fiber reinforced concrete in connection region, being the loading applied in five loading levels, each one in 10 cycles of loading and unloading. Results of these tests showed that precast beam-column connection presented 85% of the strength presented by the monolithic model and bending failure. Finally, dynamic tests were performed in cruciform models in three different situations (uncracked, cracked and after failure) for estimating the damping ratio, which was reduced by 31% after cycles. Computer simulations were performed to complement the research developed in this work. They showed acceptable representation of stiffness, but the strength of the model.

A pesquisa em questão é direcionada ao estudo de uma ligação provisória entre o pilar e a viga pré-moldada para que possa servir de suporte durante a execução da ligação de estrutura, que consiste na utilização de barras de aço salientes do pilar e da viga, traspassando entre si, finalizada por concreto com adição de fibras. O uso de consolo metálico formado por perfil tipo \"U\" e dente metálico constituído de um perfil de seção retangular vazado foi o método proposto para a ligação provisória, na qual a montagem da viga no pilar se dá pelo encaixe dos elementos. O modelo adotado como dente metálico é denominado \"Cazaly Hanger\". Para avaliar o comportamento da ligação estudada foram analisados os modelos analíticos referentes aos elementos da ligação e, posteriormente, foi montado um pórtico estrutural com a ligação provisória em estudo, para analisar o seu comportamento sob um carregamento estático e monotônico. Inicialmente foi aplicada uma força referente a 71,75% da capacidade da ligação, no meio do vão da viga e excêntrico ao seu eixo para analisar a torção na ligação, simulando uma possível força acidental que venha a ocorrer durante a montagem dos elementos. Na segunda etapa foi aplicada uma força a 1/2,94 do vão da viga a fim de determinar a capacidade do dente metálico e, na terceira e última etapa, o carregamento foi aplicado a 1/7,14 do vão da viga, na extremidade oposta a força aplicada na etapa 2, para determinar a capacidade de suporte do consolo metálico. Os resultados dos ensaios mostraram que a capacidade resistida pelo dente metálico foi 33% maior que o determinado no modelo analítico e, o estado limite último do consolo metálico constituído por perfil \"U\" foi caracterizado pela deformação excessiva da alma, na região superior do consolo. Pode-se concluir que o modelo de cálculo usado no trabalho foi coerente com os resultados encontrados para o dente metálico, mas, para os consolos metálicos, os valores teóricos não foram compatíveis com os resultados encontrados no modelo prático. / The research is directed to the study of a beam-column temporary connections to provide support during the execution of structure connection, which consist on using steel bars protruding from the column and beam finalized by addition of concrete with fibers. The use of steel \"U\" shaped corbel in the column and a steel hangers rectangular hollow core section in the beam was proposed for temporary connection method, in which the erecting the beam in the columns occurs by the nest of the elements. To evaluate the behavior of the studied connections it was analyzed the analytical models of connections and, after were building a structural portico with the connection to analyze their behavior under static and monotonic loading. Initially it was applied a load corresponding to 71,75% of the connection capacity, mid-span of the beam and its eccentric to check the torsion moment on the connection, simulating a possible live load that may occur during assembly of the elements. In the second stage was applied a load of 1/2,94 span beam to determine the capacity of steel hanger rectangular hollow core section and the third and last step the load was applied at 1/7,14 span of the beam, the end opposite the load applied in step 2, to determine the ability of the steel \"U\" shaped corbel. The results showed that the steel hanger inserted capacity was 33% higher than determined in the analytical model and the ultimate limit state of the steel \"U\" shaped corbel was characterized by excessive deformation of vertical plate, in the upper region of corbel. Can conclude that the calculation model used in the study was consistent with the results found for the steel hangers rectangular hollow core section, but for the steel \"U\" shaped corbel, the theoretical values were not consistent with the results found in practical model.

Este trabalho tem como objetivo analisar a influência da laje de concreto armado em uma ligação viga-pilar misto mediante um estudo experimental e uma modelagem numérica. A ligação considerada é constituída por uma viga de aço unida a um pilar misto preenchido através de barras rosqueadas que trabalham como parafusos passantes. Esse tipo de ligação já foi investigado em trabalhos anteriores, mediante análise experimental em modelos que não incluíam a laje, resultando em uma indesejável ruptura dos parafusos. A análise da ligação completa, com a presença da laje de concreto tornando a ligação uma ligação mista, além de ser mais realista, melhora as características de resistência e rigidez do modelo, além de tornar mais dúctil o seu comportamento. Para isso foram analisados três modelos experimentais que se diferenciam pela ausência ou tipo de conector de cisalhamento presente na região interna do pilar misto. Os resultados obtidos mostraram que a ruptura da ligação passou a ser determinada pela laje, associada ao escoamento da armadura longitudinal sem que a ligação viga-pilar fosse comprometida. Para a análise numérica foi utilizado o pacote computacional DIANA®, baseado no método dos elementos finitos. Os modelos numéricos foram desenvolvidos e calibrados pelos resultados experimentais, produzindo resultados bastante satisfatórios. Finalmente foi realizada uma análise numérica paramétrica variando a armadura longitudinal da laje e a resistência do concreto com o objetivo de se entender melhor a influência desses parâmetros no comportamento da ligação investigada. / The main objective of this work was to analyze the contribution of the concrete slab for the behavior of a steel beam-concrete filled composite column connection through an experimental program and also a numerical modeling. The considered connection was constituted of steel beams connected to a concrete filled tubular column of rectangular cross section by means of passing bars. This type of connection was studied before through an experimental analysis of connections that did not include the slab, resulting in failure of the passing bars. In the present study, the presence of the slab is considered, turning the connection a composite one. The studied model is more representative of the real structure, and also improves the resistance and the stiffness of the connection, turning the behavior more ductile. Three specimens were tested, where the studied variable was the type of shear connector, angles or stud-bolts, and one specimen without connectors as a reference. The obtained results showed that the failure was determined by the slab, associated to the yielding of the longitudinal reinforcement, without affecting the beam column connection. The finite element based software DIANA® was used to the numerical analysis. The numerical models were developed and calibrated by the experimental results, producing a good agreement. Finally, a parametric analysis was done, varying the slab longitudinal reinforcement and the concrete strength in order to better understand the influence of these parameters in the behavior of the studied connection.

Neste trabalho estudou-se o comportamento dos chumbadores grauteados, usados em ligações viga-pilar parcialmente resistentes a momento fletor. O foco da pesquisa foi a análise teórica e experimental do mecanismo resistente do chumbador inclinado. O programa experimental englobou 15 modelos, sendo que as variáveis analisados foram: a) diâmetros dos chumbadores, de 16 mm, 20 mm e 25 mm; b) inclinações dos chumbadores, de 0º (chumbador normal à interface), 45º e 60º; c) resistência à compressão do concreto adjacente ao chumbador, sendo usado concreto das classes C35 e C50; d) aplicação de força de compressão normal à interface. Os resultados experimentais indicaram aumentos significativos tanto na capacidade última quanto na rigidez a cisalhamento do chumbador. Foram realizadas simulações numéricas, onde foi verificada a sensibilidade dos resultados aos parâmetros inerentes à interface concreto - almofada de apoio, sendo desenvolvidas expressões para estimar tais parâmetros. Com base na análise experimental e em análises numéricas, foram propostos modelos analíticos que conseguiram representar de forma satisfatória a influência da inclinação e demais parâmetros analisados no mecanismo resistente do chumbador. / This research deals with the behavior of grouted dowels, used in partial moment resistant beam-to-column connections. The focus of the research was the theoretical and experimental analysis of dowels resistant mechanism. The experimental program include 15 models, and its variables analyzed were: a) the dowel diameter of 16 mm, 20 mm and 25 mm; b) the dowel inclination of 0° (dowels perpendicular to the interface), 45° and 60°; c) compressive strength of concrete adjacent to the dowels of classes C35 and C50, d) application of compression load, normal to the interface. Experimental results indicated significant increases in ultimate capacity and the shear stiffness of the dowels. Numerical simulations were carried out which identified the sensitivity of results to the parameters of the interface concrete bearing pad, and developed expressions to estimate such parameters are given. Based on experimental and numerical analysis analytical models have been proposed that could adequately represent the influence of inclination and other parameters in the mechanism resistant dowels.