Dissertations / Theses on the topic 'Semi-rigid connector'

In the analyses of steel framed structures it is customary to assume the beam to column connections as either fully rigid which means that all moments are transferred from beam to column with negligible rotation or ideally pinned that resists negligible moment. This assumption is reasonable for some types of connections. However when considering steel connections such as bolted-bolted double web angle connections it can be seen that the behavior of these connections is in between the two extreme cases. Thus a third connection type, namely semi rigid or partially restrained connection, is introduced. However this type of connection exhibits such a nonlinear behavior that modeling this behavior necessities a substantial effort. Moreover to perform a performance based analyses the true behavior of these connections should be incorporated as part of the modeling effort. Several researches dealing with these two topics have been undertaken in literature. Despite these efforts, modeling of the moment rotation behavior of these connections still requires improvement especially under cyclic loading conditions. In addition to this, performing an analysis with existing elements incorporating semi-rigid connections as a spring attached to beam ends is not practical because of the fact that displacement based formulation increases meshing significantly which requires substantial computational power. In this study a hysteretic (quadra-linear) moment rotation model considering pinching, damage and possibility of residual moment capacity is developed. The behavior is calibrated via experimental data available in the literature. Furthermore a force based macro element considering spread inelastic behavior along the element is presented. With this element several connections located anywhere along the beam could be incorporated in the analysis with less degree of freedom with respect to displacement based elements. Moreover the macro element model can be used in conjunction with corotational formulation for the capture of nonlinear geometric effects.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Ligações semi-rígidas em estruturas de aço tem apresentado uso crescente na construção metálica, pois é uma opção que permite um melhor aproveitamento da capacidade da estrutura. Neste trabalho apresentam-se as características e a classificação das ligações semi-rígidas bem como a evolução da modelagem numérica e analítica do comportamento destas ligações. Apresenta-se uma metodologia com base no método dos elementos finitos para avaliar numericamente a relação momento-rotação de conexões viga-coluna em estruturas de aço. Parte essencial desta metodologia é a modelagem da ligação e de seus diversos componentes. Um modelo completo em termos da geometria, capaz de representar a interação entre os diversos componentes da conexão é proposto. Esta modelagem inclui a discretização de todos os componentes da conexão: placa e ou cantoneiras, porcas, coluna e viga, sendo a extensão da viga e da coluna a ser considerada no modelo escolhida por calibração do mesmo. O contato entre os componentes da ligação é considerado por meio de algoritmo específico de contato com base na formulação de um problema linear complementar. Considera-se contato sem atrito entre corpos deformáveis. A fim de representar com mais fidelidade as características tridimensionais do problema, adota-se uma modelagem também tridimensional com base em elementos finitos híbridos hexaédricos de oito nós, permitindo o emprego de uma discretização relativamente grosseira. Fenômenos como a presença de grandes deformações, plastificação dos componentes e a pré-tensão dos parafusos são incluídos no modelo. Os modelos apresentados são empregados para o estudo do comportamento de ligações tipo placa de extremidade estendida e tipo cantoneira de alma simples. Para validação dos modelos são comparados os resultados numéricos com dados experimentais. Analisa-se também a participação da flexibilidade dos diversos componentes da conexão, tais como: parafuso, placa de extremidade, mesa da coluna, na resposta da conexão.
Semi-rigid connections are now-a-days widely employed by steel structures. Such connections take better advantage of the overall structure capabilities. In this work the properties and classification of semi-rigid connections is discussed. Additionally numerical and analytical models for prediction of connection behavior are presented. A finite element based methodology for the numerical evaluation of moment-rotation relations and load carrying capacity of semi-rigid connections is proposed. An important feature of this model is a complete a three dimensional geometrical description of the many components of the connection, such as plates, column, beam, bolts and nuts and the interaction between them. The extension of beam and column to be modeled is determined by numerical calibration. Frictionless contact between the connection components is considered by a specific contact algorithm which ensures non- penetration and permits separation of the individual parts. In this work a solution strategy for the contact problem based on the establishment of a linear complementary problem is adopted. The three dimensional modeling is carried out by a mesh of hybrid hexahedral eight node elements, which allow the use of relatively coarse meshes. Effects such as the presence of large deformations, yielding of components and pre- stressing of bolts are present in the model. The proposed model is applied to the analysis of the behavior of extended end-plate connections and web cleat connections. The numerical results are compared to experimental data for model validation. One of the objectives of this analysis is the evaluation of the participation of each component on the overall flexibility of the connection.
El uso de ligaduras semirígidas en extructuras de acero ha experimentado un crescimiento importante en la construcción metálica. Esta opción permite un mejor aprovechamiento de la capacidad de la extructura. En este trabajo se presentan las características de las ligaduras semirígidas, su clasificación; y la evolución de los modelos numéricos y analíticos del comportamiento de estas ligaduras. Se discute una metodología con base en el método de los elementos finitos para evaluar numéricamente la relación momento-rotación de conexiones viga-columna en extructuras de acero. La parte esencial de esta metodología es el modelo de la ligadura y sus diversos componentes. Se propone un modelo completo en términos de geometría, capaz de representar la interacción entre los diversos componentes de la conexión. Este modelo incluye la discretización de todos los componentes de la conexión, siendo que la extensión de la viga y de la coluna a ser considerada en el modelo, deberá ser elegida por calibración del mismo. Para considerar el contacto entre los componentes de la ligadura se utiliza el algoritmo específico de contacto con base en la formulación de un problema lineal complementar. A fin de representar con más fidelidad las características tridimensionales del problema, se adoptó un modelo tridimensional con base en elementos finitos híbridos hexaédricos de ocho nodos, permitiendo el empleo de una discretización relativamente grosera. Se incluyen en el modelo fenómenos como la presencia de grandes deformaciones, plastificación de los componentes y la pretensión de los tornillos. Los modelos presentados se emplean en el estudio del comportamiento de ligaduras tipo placa de extremidad extendida y tipo esquinero de alma simple. Para evaluar los modelos se comparan los resultados numéricos con datos experimentales. También se incluye un análisis de la participación en la respuesta de la conexión, de la flexibilidad de los diversos componentes de la conexión, tales como: tornillo, placa de extremidad, mesa de la columna.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Nos projetos de engenharia é comum desconsiderar-se o comportamento semirrígido das ligações, ou seja, as ligações são assumidas com as condições ideais de rigidez. A primeira condição ideal é aquela na qual há transferência total de momento fletor, assumindo-se que não existe rotação relativa entre os elementos ligados, estas ligações são as chamadas rígidas. Na segunda opção, a transferência de momento fletor é desconsiderada e a ligação é definida como rotulada ou simples. Entretanto, sabe-se que a maioria das ligações comporta-se como semirrígida e o problema é que ao se fazer essas simplificações em projeto, dois aspectos podem ser comprometidos: segurança estrutural e custo do projeto. Neste trabalho, uma ligação semirrígida mista é proposta e estudada com o objetivo de obter-se as suas características principais e necessárias para utilizá-la em projeto: curva momento-rotação, rigidez de serviço e momento fletor resistente. Com a ligação mista proposta, busca-se uma nova maneira de transferência de forças na região de momento negativo em uma viga semicontínua. Adotou-se para a transferência dos esforços, entre a laje de concreto e a viga de aço, conectores de cisalhamento do tipo Perfobond Rib. Este conector foi inicialmente utilizado em pontes e depois alguns estudos o viabilizaram para o uso em edificações. Para atingir os objetivos do trabalho, foram realizados dois ensaios em escala real das ligações propostas. Os testes experimentais foram feitos em modelos cruciformes invertidos e realizados no laboratório de estruturas e materiais da PUC-Rio. Os resultados experimentais foram comparados com dois modelos analíticos: o método proposto por Leon et al. em 1996 e o método presente no Anexo R da NBR 8800:2008.
In engineering design it is common to disregard the semi-rigid behavior of connections, i.e., connections are assumed to have the ideal conditions of rigidity. The first ideal condition is the one in which there is full transfer of bending moment, assuming that there is no relative rotation between the connected elements, this connection is defined rigid. In the second option, the transfer of bending moment is disregarded and the connection is defined simple. However, it is known that most connections have a semi-rigid behavior and the problem is that when making these simplifications in design, two aspects can be compromised: structural safety and project cost. In this work, a composite semi-rigid connection is studied in order to obtain its main and necessary features to use it in design: moment-rotation curve, service rigidity and bending moment capacity. With the proposed composite connection, a new way to transfer forces in the negative moment region on a semicontinous beam. Shear connectors like the Perfobond Rib were adopted for the transfer of efforts between the concrete slab and the steel beam. This connector was first used on bridges and since then some studies have made possible its use in buildings, showing its advantages over the more usual connectors. To achieve this work s objectives, two real scale tests of the proposed connections were conducted. Experimental tests were done in inverted cruciform models and carried out in the laboratory of structures and materials at PUC-Rio. Information on these tests was obtained, such as displacements, strains, and cracking of the slab. The experimental results were compared to two analytical models: the method proposed by Leon et al. in 1996 and the present method in Annex R of NBR 8800: 2008.

In practice, steel frames are analyzed and designed by assuming all beam to column connections as either rigid or simple. In real life, there are no such idealizations as rigid or simple and all connections would actually belong to a group of connections named as semi rigid connections. Various difficulties exist in modeling an accurate non-linear behavior of a steel structure, where one of these challenges is the modeling of semi-rigid behavior of connections. A detailed finite element model would take into account the complex interaction between all surfaces due to contact, friction and bolt pretension besides the material and geometrical nonlinearity effects. All these nonlinearity effects could be simply lumped as a moment-rotation type model at the connection region. Such a methodology is followed in this thesis and the main aim is to study the lumped nonlinear behavior of steel semi-rigid connections on the overall structural responses of steel Special Moment Frames. In this thesis three, nine and fifteen story steel Special Moment Frames are analyzed and designed as rigid frames first, and then the frames are reanalyzed considering non-linear effects due to semi-rigid connections. Changes in the ductility and overstrength reduction factors obtained from pushover curves are compared between the rigid and semi rigid modeling alternatives.

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.

As ligações com chumbador e almofada, sem continuidade estrutural, são comumente empregadas em obras de concreto pré-moldado como galpões, edifícios de poucos pavimentos e no topo de pilares. Na análise estrutural, este tipo de ligação é caracterizado como articulado. Este trabalho teve como objetivo fazer um estudo com este tipo de ligação levando em conta que a transferência de momento fletor ocorrerá em função da rigidez proporcionada por uma almofada de compósito de argamassa e por chumbadores de aço. A idéia é considerar o benefício da redução das solicitações nos elementos de concreto pré-moldado, particularmente, na base dos pilares. A análise experimental foi feita com modelos em escala reduzida 1:2. Foram ensaiados quatro modelos da ligação que são: a) Modelo 1 - chumbadores de aço CA-25 e almofada de compósito de argamassa; b) Modelo 2 - chumbadores de aço CA-25 e almofada de policloropreno; c) Modelo 3 - chumbadores de aço CA-50 e almofada de compósito de argamassa e; d) Modelo 4 - chumbadores de aço CA-50 e pilar com largura igual a 50% maior que os casos anteriores e almofada de argamassa. Foi feita ainda a análise numérica tridimensional dos modelos da ligação utilizando o software Ansys e análises de pórtico plano para avaliar a distribuição de solicitações ao longo de estruturas representativas. Foi desenvolvido um modelo de projeto para prever o comportamento da ligação. Com as simulações de pórtico plano, onde foram consideradas as semirigidezes das ligações, obteve-se uma redução de até 48% do momento fletor na base dos pilares para um edifício de quatro pavimentos, cujas ligações viga-pilares apresentavam um consolo de 40 cm, e de 21,8% para um edifício de um pavimento do tipo galpão, cujas ligações continham quatro chumbadores, considerando apenas a carga de frenagem. A análise de deslocamentos nos pórticos planos também aponta o benefício da consideração da semirigidez nas ligações. Uma redução de deslocamento horizontal do topo do pórtico do tipo galpão de até 32,8% para o modelo com ligações com quatro chumbadores e somente força horizontal, e de até 71,9% para o edifício de quatro pavimentos considerando as ligações semirígidas com consolos de 40 cm.
Connections with bolts and pad, without structural continuity, are commonly used in construction of precast concrete as one-storey building, building with a few storeys and on top of columns. In structural analysis, this type of connection is characterized as pinned, that is, without restriction of the rotation on the connection. This work aims to make a study of this type of connection taking into account that the transfer of bending moment will occur due to the stiffness provided by a pad of mortar composite and the steel bolts. The idea is to consider the benefit of reducing the demands on the elements of precast concrete, particularly at the base of the columns. The experimental analysis was done with models scale 1:2. Four models of connection were tested: a) Model 1 - steel bolts CA-25 and pad of mortar composite, b) Model 2 - steel bolts CA-25 and chloroprene rubber pad, c) Model 3 - bolts of CA-50 steel and pad of mortar composite, and d) Model 4 - steel bolts CA-50 and column with a width of 50% larger that the others and mortar pad. It was still a three-dimensional numerical analysis of the lead models using Ansys software and frame plan analysis to evaluate the stress distribution along the representative structures. A model design to predict the behavior of the connection was developed. Based on the numerical simulations on precast concrete frames, semi-rigidity of connections was take in to account, it was obtained a reduction of up to 48% of the bending moment at the base of the columns of a four-storey building, which beam-to-column connections had a corbel 40 cm, and 21,8% for a one-storey building, which connections contained four bolts, considering only the horizontal load. The analysis of displacements in the plane frame also shows the benefit of considering the semi-rigidity connections. Reduction in horizontal displacement of the top of the one-storey building to 32,8% for the model with four bolts in the connections with only horizontal force, and 71,9% for the four-storey buildings with semi-rigid connections considering the corbels of 40 cm.

Neste trabalho estudou-se o comportamento de uma ligação viga-pilar de estrutura pré-moldada parcialmente resistente a momento fletor quando submetida a momentos negativos e positivos. A ligação estudada é composta por dois chumbadores inclinados presos à viga através de chapa metálica, porcas e arruelas e uma capa de concreto com armadura longitudinal passando por dentro do pilar. No programa experimental foram elaborados dois modelos submetidos a carregamentos alternados, em ciclos e de curta duração. Em seguida foi desenvolvido um modelo analítico para cálculo dos momentos resistentes e feita uma simulação numérica para avaliar a influência da semi-rigidez da ligação em estruturas típicas de concreto pré-moldado. Os resultados experimentais indicaram que a ligação apresenta uma boa capacidade de transmissão a momento fletor negativo e a momento fletor positivo com um comportamento bastante dúctil. Sem a necessidade de grandes alterações de custos e de execução, a ligação proposta promoveu uma redução significativa dos momentos na base dos pilares (aproximadamente 50%) quando comparada à ligação articulada. Quando comparada à ligação similar, porém com os chumbadores retilíneos, há um aumento superior a 2,5 vezes no momento de plastificação e de 3 vezes na rigidez no sentido do momento fletor positivo
In this research the behavior of a partial moment resistant beam-to-column connection in precast concrete subjected to negative and positive moments was studied. This connection has two inclined dowels fixed to the beam with steel plate, washer and nut and a concrete cap with longitudinal reinforced bars passing trough the column. In the experimental program two prototypes was made and subjected to an alternative cyclic e short duration load. Afterwards it was develop an analytical model and a numerical simulation to analyze the influence of the semi-rigid connection in a typical precast structure. The experimental results shown that the connection has a good capacity of transmitte the bending moments and has a ductile behave. Without any significative difference of cost and manufacture, the connection studied promoted a reduction on the column base bending moment (approximately 50%) when compared to pinned connection. When compared to similar structures but with a vertical dowel, the connection presents strength over 2.5 times and over 3 times the stiffens for positive bending moments

Estruturas em concreto pré-moldado vêm sendo utilizadas com freqüência em sistemas reticulados do tipo multi-piso, destinados às mais variadas atividades como: estabelecimentos comerciais, estacionamentos, escolas, hospitais e etc. A utilização de ligações viga-pilar do tipo semi-rígida constitui uma alternativa interessante para o enrijecimento e para a garantia da estabilidade global deste tipo de estrutura. Atualmente, a rigidez e a resistência destas ligações têm sido determinadas por ensaios de modelos em escala real. Estes ensaios, além de apresentarem um custo elevado, têm aplicação restrita à ligação examinada o que torna esta metodologia limitada e não adequada à prática de elaboração de projeto. Apresenta-se, neste trabalho, um modelo mecânico para determinação numérica da relação força-deslocamento de uma ligação viga-pilar semi-rígida a partir da contribuição da rigidez individual de cada componente de transferência de força utilizado na vinculação. A formulação do equilíbrio do modelo é implementada em planilha eletrônica constituindo-se numa ferramenta de cálculo para o projetista, permitindo o estudo, de forma rápida e amigável, da influência do posicionamento e da rigidez individual de cada componente de transferência de força na rigidez e na resistência da ligação. Este modelo mecânico foi utilizado para o cálculo da rigidez à rotação para momento fletor positivo de uma ligação viga-pilar ensaiada em laboratório. Os valores para a rigidez da ligação obtidos em ensaio e pelo modelo mecânico ficaram muito próximos. Da formulação do equilíbrio do modelo mecânico pode-se extrair ainda uma matriz de rigidez que é utilizada na representação da ligação semi-rígida no modelo de barra da estrutura. Um programa computacional foi desenvolvido para a análise de pórticos planos com ligação viga-pilar semi-rígida considerando ainda as não linearidades físicas e geométricas do modelo de cálculo. O programa foi validado pela comparação de resultados de exemplos também processados no programa ANSYS. A não-linearidade geométrica é considerada pelo método modal, não incremental-iterativo, e que obtém a parcela não-linear da resposta estrutural pela combinação dos seus modos de flambagem. A não-linearidade física do concreto é considerada pelo método da rigidez secante no qual a rigidez de cada barra da estrutura é reduzida na análise conforme suas armaduras e o nível de sua solicitação. Para o cálculo da rigidez secante dos pilares desenvolveu-se um programa que permite a consideração de armaduras ativas e passivas na seção. A análise de alguns exemplos revelou que a protensão dos pilares é também uma alternativa interessante para o enrijecimento da estrutura. Além de exemplos práticos, outros temas pertinentes ao projeto deste tipo de estrutura como: estabilidade na fase construtiva, esforços finais após a montagem, efeitos dependentes do tempo, assimetria de rigidez e plastificação das ligações, são também abordados no trabalho.
Precast concrete multi-storey structures have been more frequently used to construct commercial buildings, parking, schools and hospitals. The use of semi-rigid beam-tocolumn connections is a good strategy to guarantee the global stability of this type of structure. Actually the rigidity and the strength of this type of connection are obtained in an experimental program using full scale prototypes. This procedure is not only expensive but limited and not adequate for design since the results are only valid for the examined connection. This research presents a mechanical model used to determine numerically the force-displacement relationship of a beam-to-column semirigid connection. The procedure uses the contribution of any individual force transfer component active in the connection. The equilibrium equation of the model is implemented in an electronic-worksheet where the designer can rapidly and friendly study the influence of the position and the individual rigidity of each force transfer component in the global rigidity and strength of the connection. For validation, this procedure was used to calculate the flexural rigidity for positive bending moment of a beam-to-column semi-rigid connection that was tested in laboratory. The numerical values of the connection rigidity obtained by test and by the mechanical model are very close. The matrix used in the formulation of the mechanical model equilibrium can also be used to represent the semi-rigid connection in the finite element model of the structure. A computational program was developed for plane frame analysis including semi-rigid beam-to-column connections and both physical and geometric nonlinearities. The program was tested by comparing the results of some examples that are also analysed in the ANSYS program. The geometric nonlinearity is considered by a modal method where the nonlinear response of the structure is obtained by a combination of its buckling modes. The physical nonlinearity of the concrete is considered by the secant rigidity method. In this method the rigidities of all concrete bars in the structure are reduced by coefficients that depend of the reinforcement in the cross section and the level of the efforts. A special computational program was developed to calculate the secant rigidity for a concrete cross section with reinforcing bar and prestressing steel. The analysis of some examples shows that the use of prestressing steel in collums is also an interesting alternative to sttifen the structure. Beyond of some practical examples, others themes related to the design of this type of structure like: stability in the erection process, efforts in the end of the erection process, time-dependent effects, non symmetrical and plastic behavior of the connections, are also treated in this work.

Diploma thesis deals with the design and assessment of the load bearing structure of a multi-storey building, proposed by the combination of two materials, steel and glued laminated timber. The building has a V-shape, the angle between legs is 120 °. Floor plan dimensions of one arm of the building are approximately 40x20m, building height is 24.3 meters. The building is designed with a flat green roof. The load bearing structure is solved as a heavy frame, lower three floors are made of steel and serves as the business premises, top four floors are residential, and their structure is designed of the glued laminated timber. Bracing of the whole structure is solved by a system of crossed steel rods.

In this paper, using the general purpose software ABAQUS, a three dimensional (3-D) finite element model was built to simulate semi-rigid composite connection with precast hollowcore slabs. 3D continuum elements are used for all parts of the composite connections and the contact conditions between all the components are explicitly modelled. The model also incorporates nonlinear material characteristics and non-linear geometric behaviour. A simplified method to simulate the bolted end plate connection is introduced and validated. The proposed simulation method of the longitudinal shear transmission can accurately simulate the plastic state of the longitudinal rebars after cracking. Different materials are chosen by the authors to simulate the concrete slab, and the elastic¿plastic material property is adopted which can accurately simulate the moment¿rotation response of the connections. Numerical results are presented and compared with the experimental data and good agreement is obtained.

This paper describes the 3-dimensional finite element modelling of composite connection with steel beams and precast hollow core slab. A finite element model to simulate the structural behaviour of the composite beam was described and was used to study the behaviour of a wide range of composite connections to gain a better understanding of the structural behaviour especially the moment¿rotation characteristic of the connections. Parametric studies were carried out to investigate the structural behaviour with variations in: size of the beam, thickness of the endplate, thickness of column web, depth of precast hollow cored slab and stud spacing. Through the parametric study, the structural behaviour of the composite connection has been discussed in detail, and recommendations for the design purpose has been made.

Semi-rigid composite connections with precast hollowcore slabs are a newly developed technique with few applications in current construction practice. The research on the structural behaviour of this new type of connection is limited, with no existing method available to predict its important characteristics such as moment and rotation capacities. In this paper, based on the parametric studies of the three-dimensional finite element model and full-scale tests, analytical methods to calculate the moment and rotation capacity of this type of composite joint are proposed. A comparison between the proposed calculation method and the full-scale test results was made, and good agreement was obtained.

The purpose of this study is to develop an approach that considers fire as a load in the design of structures. Recent studies of the full-scale fire tests in Cardington, UK and the World Trade Centre collapse have shown that the behaviour of steel structures in fire when assembled into a frame differs from that measured or predicted by fire testing of individual structural elements, revealing the importance of accounting for realistic fire loads in the design of structures and the potential inadequacy of fire testing individual elements as employed by current building codes. Yet, there has been limited basic research and development to allow consideration of fire as a load in the analysis and design of structures. In response to this much needed work, this thesis develops an approach to include fire as a load in the analysis of a 2-bay by 2-storey structure when a semi-rigid connection is exposed to thermal loads typical of those that might be encountered during a real fire. The structural fire analysis is principally based on incorporating moment-rotation-temperature data for the connection, as found in archival literature, into a structural analysis software package developed at the University of Waterloo. The software employs a modified Displacement Method for analyzing structures, which involves the computation of stiffness reduction factors that represent the deterioration of strength of the structural elements as they are subjected to various loads. By modifying the moment-rotation-temperature data for a semi-rigid connection into a form recognized by the software, a fire load is simulated by incrementally elevating the temperature of the affected steel connection. In this way, a fragility analysis of the entire structure under fire load is conducted. A series of example calculations are presented for cases in which the semi-rigid connection is exposed to increasing temperatures of 20°C, 200°C, 400°C and 600°C. The analysis showed that as the connection is heated, it is weakened, and the steel structure undergoes a redistribution of moments from the heated connection to other non-heated elements within the framework, which is essentially a form of fire-resistance of the assembled structure that unassembled members in isolation do not have. The study also demonstrated that the experimental moment-rotation-temperature data reported in archival literature can be incorporated into the structural analysis, and that additional force-deformation data obtained from further experimental work or through finite-element analyses would allow the study to be extended to analyze the effects of fire loading on other structural elements of an assembled framework. To demonstrate the link between the predicted structural response at different temperatures and the development of a compartment fire, a fire modelling analysis is also performed.