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The effects that thermally induced forces and deformations have on the performance and safety of steel columns subjected to fire are not well understood and are not clearly treated in building codes and standards. This thesis investigates the behavior of steel columns subjected to fire, with an emphasis on studying the significance of thermally induced forces and deformations. The approach used in this research is to conduct a series of analyses of steel columns using the finite element computer program ABAQUS. Columns are modeled in ABAQUS using beam elements that include nonlinear geometry, nonlinear temperature dependent material properties, and initial geometric imperfections. Using the ABAQUS model, a series of analyses are conducted on the behavior of columns under axial compression for temperatures varying from room temperature up to 2400° F. A series of individual columns are analyzed with and without restraint to thermal expansion. A column that is part of a truss is also analyzed to study a simple case of a flexible restraint to thermal expansion. Finally, the behavior of columns that are part of multi-story steel moment frames are investigated. All of the analyses conducted in this research indicate that forces generated by restraint to thermal expansion can have a very large impact on the performance of a steel column in fire. When evaluating the safety of a column in a fire, it is important to recognize that the total axial force in the column is the sum of the force generated by external gravity load on the frame and the force generated by restraint to thermal expansion. The force generated by restrained thermal expansion can be very large, and neglecting this force can lead to unsafe designs. / text

The design of several variants of the structure of the planetarium in Brno is the subject of the diploma thesis . The building has a ground plan size of 30x30 meters. The main supporting material is S235 steel. The bearing structure of the object consists of columns, joists and beams. The bearing structure of the dome consists of a spatial structure, which is formed as a half-globe above the diameter of 18 meters. 3 versions of this dome have been processed. The resulting design is Geodetic Dome. Part of the work is an assessment of the main structural elements and selected details. The Scia engineer 2016 version 16.1.3033 was used to calculate internal forces.

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Dentro do conjunto de aspectos relacionados à elaboração de projetos em estruturas de aço e mistas de aço e concreto, destaca-se como de grande importância e interesse, para fins de dimensionamento, a consideração de elementos estruturais submetidos a temperaturas elevadas. Nesse sentido, o presente trabalho tem como objetivo principal propor a construção de modelos numéricos tridimensionais de pilares de aço pertencentes a sistemas estruturais correntes da construção civil, para análise em situação de incêndio, com vistas a simular numericamente a evolução dos níveis de temperatura ao longo do tempo com posterior acoplamento termoestrutural. Considera-se uma análise paramétrica com vista a variar as restrições axiais totais e parciais da barra, no referente aos deslocamentos axiais, contemplando desde a situação de extremidade livre até a restrição completa em resposta à consideração de apoio do tipo fixo, por exemplo. Os resultados numéricos são comparados a ensaios experimentais de outros autores, bem como com outros trabalhos numéricos já publicados. São obtidas respostas de deslocamentos axiais e laterais do modelo termoestrutural para diversas disposições de paredes em relação ao perfil, bem como gráficos do acréscimo de força axial introduzido no sistema pela restrição axial. Os estudos aqui realizados poderão servir como base para novas pesquisas tanto no campo numérico quanto experimental, assim como para futuras revisões da ABNT NBR 14323:1999, buscando contemplar situações de interesse não abordadas neste documento normativo. Os resultados da pesquisa apontam que a consideração do campo térmico com a inclusão da alvenaria no modelo termoestrutural pode melhorar consideravelmente o desempenho do elemento estrutural em situação de incêndio. / Within the set of aspects related to the development of researches in steel and composite steel and concrete structures, stands out with great importance and interest, aiming to dimension, the consideration of structural elements subjected to high temperatures. In this way, the present work has as main objective to propose the construction of three-dimensional numerical models of steel columns that belong to current structural systems of civil construction, for examination in fire situation, aiming to simulate numerically the evolution of temperature levels throughout of time with later termoestrutural coupling. It will be considered a parametric analysis in order to vary the total and partial axial restraint in respect to the axial displacements, since the free end situation until the complete restriction in response to the consideration of support for the fixed type, for example. The numerical results are compared to experimental tests made by other authors, as well as with others numerical works already published. Answers are obtained from axial and lateral displacements of the thermo structural model to many displacement of wall related to the profile, also charts of adding axial force introduced into the system by the axial restraint. The results of the current research could serve as a basis for further research in both the numerical field or experimental, also for future revisions of ABNT NBR 14323:1999, aiming to see situations of interest not studied in the same normative document. The results of this work show that consideration of thermal field with the inclusion of masonry in the thermo structural model can, significantly, improve the performance of the structural element in a fire situation.

Dentro do conjunto de aspectos relacionados à elaboração de projetos em estruturas de aço e mistas de aço e concreto, destaca-se como de grande importância e interesse, para fins de dimensionamento, a consideração de elementos estruturais submetidos a temperaturas elevadas. Nesse sentido, o presente trabalho tem como objetivo principal propor a construção de modelos numéricos tridimensionais de pilares de aço pertencentes a sistemas estruturais correntes da construção civil, para análise em situação de incêndio, com vistas a simular numericamente a evolução dos níveis de temperatura ao longo do tempo com posterior acoplamento termoestrutural. Considera-se uma análise paramétrica com vista a variar as restrições axiais totais e parciais da barra, no referente aos deslocamentos axiais, contemplando desde a situação de extremidade livre até a restrição completa em resposta à consideração de apoio do tipo fixo, por exemplo. Os resultados numéricos são comparados a ensaios experimentais de outros autores, bem como com outros trabalhos numéricos já publicados. São obtidas respostas de deslocamentos axiais e laterais do modelo termoestrutural para diversas disposições de paredes em relação ao perfil, bem como gráficos do acréscimo de força axial introduzido no sistema pela restrição axial. Os estudos aqui realizados poderão servir como base para novas pesquisas tanto no campo numérico quanto experimental, assim como para futuras revisões da ABNT NBR 14323:1999, buscando contemplar situações de interesse não abordadas neste documento normativo. Os resultados da pesquisa apontam que a consideração do campo térmico com a inclusão da alvenaria no modelo termoestrutural pode melhorar consideravelmente o desempenho do elemento estrutural em situação de incêndio. / Within the set of aspects related to the development of researches in steel and composite steel and concrete structures, stands out with great importance and interest, aiming to dimension, the consideration of structural elements subjected to high temperatures. In this way, the present work has as main objective to propose the construction of three-dimensional numerical models of steel columns that belong to current structural systems of civil construction, for examination in fire situation, aiming to simulate numerically the evolution of temperature levels throughout of time with later termoestrutural coupling. It will be considered a parametric analysis in order to vary the total and partial axial restraint in respect to the axial displacements, since the free end situation until the complete restriction in response to the consideration of support for the fixed type, for example. The numerical results are compared to experimental tests made by other authors, as well as with others numerical works already published. Answers are obtained from axial and lateral displacements of the thermo structural model to many displacement of wall related to the profile, also charts of adding axial force introduced into the system by the axial restraint. The results of the current research could serve as a basis for further research in both the numerical field or experimental, also for future revisions of ABNT NBR 14323:1999, aiming to see situations of interest not studied in the same normative document. The results of this work show that consideration of thermal field with the inclusion of masonry in the thermo structural model can, significantly, improve the performance of the structural element in a fire situation.

Despite the crucial role they play in transferring loads from the superstructure to the foundation, steel column-to-footing connections have received little attention in research. Though shallow embedded connections are typically characterized as pinned, studies have shown that they exhibit significant rotational stiffness. The objective of this thesis is to quantify the rotational stiffness of such connections. A method named the continuum model is developed by which the rotational stiffness of embedded connections may be calculated. Outputs from this model are compared with experimental data on steel connections embedded in concrete. The continuum model is shown to be capable of reasonably predicting the rotational stiffness of such connections. Results from the model were consistent with those of previous experimental studies that showed that embedment lengths greater than twice the column depth fail to significantly increase stiffness. Plots of rotational stiffness vs. embedment length developed from the continuum model are provided such that rotational stiffness may be calculated for any wide flange shape at any embedment length. Simplified equations provide a simpler way for engineers to estimate the same information.

The response of wide flange steel columns subjected to constant axial loads and lateral blast loads was examined. The finite element program ABAQUS was used to model W8x40 sections with different slendernesses and boundary conditions. For the response calculations, a constant axial force was first applied to the column and the equilibrium state was determined. Next, a short duration, lateral blast load was applied and the response time history was calculated. Changes in displacement time histories and plastic hinge formations resulting from varying the axial load were examined. The cases studied include single-span and two-span columns. In addition to ideal boundary conditions, columns with linear elastic, rotational supports were also studied. Non-uniform blast loads were considered. Major axis, minor axis, and biaxial bending were investigated. The effects of strain rate and residual stresses were examined. The results for each column configuration are presented as a set of curves showing the critical blast impulse versus axial load. The critical blast impulse is defined as the impulse that either causes the column to collapse or to exceed the limiting deflection criterion. A major goal of this effort was to develop simplified design and analysis methods. To accomplish this, two single-degree-of-freedom approaches that include the effects of the axial load were derived. The first uses a bilinear resistance function that is similar to the one used for beam analysis. This approach provides a rough estimate of the critical impulse and is suitable only for preliminary design or quick vulnerability calculations. The second approach uses a nonlinear resistance function that accounts for the gradual yielding that occurs during the dynamic response. This approach can be easily implemented in a simple computer program or spreadsheet and provides close agreement with the results from the finite element method. / Ph. D.

The aim of this thesis is to create a design of a grandstand steel roof structure with ground plan dimensions of 15 x 116 m in Frýdek-Místek. The roof size must meet all the required dimensions, so that the comfort of sitting spectators is not disturbed. The transverse connection is FORMED by trusses, which are hinged on columns. The spacing between inner connections is 12 m and 10 m between outer connections. The columns are interlocked in the base. The rigidity is secured by a system of brace rods and truss purlins. The steel columns are composed of rolled profiles designed according to ČSN EN standards. The structure consists of steel S355, some parts are then made from S235 or S460 (ordinary steel).

The diploma thesis deals with the design of the administrative building from steel S420, S355 and concrete C25 / 30 with reinforcement made of steel B500B. The office building is a column-type with reinforced concrete ceiling. The building is equipped with a footbridge on the 10th floor. Two variants have been elaborated. Both of them were calculated in the program Scia Engineer. The winning variant is processed in detail.