The conventional design of steel beams considers that any deformation of a member due to applied load must be a combination of the four rigid body modes (axial deformation, major axis bending, minor axis bending and twisting) i. e. the member retains its cross sectional shape without distortion. In a hot rolled member the warping stresses which arise due to violation of the assumption that plane sections remain plane can often be neglected. In thin walled sections, however, these warping stresses are typically of the same order of magnitude as the primary bending stresses induced in the member by the applied loading and therefore cannot be neglected. In addition, if plane sections do not remain plane, the cross section distorts when a load is applied. The first part of this Thesis presents a method of analysis for any open unbranched thin walled section which considers both rigid body movement and cross section distortion (including local buckling). The method is such that the four rigid body modes are automatically identified and separated from the remaining cross section distortion modes. The second part of this Thesis develops a finite difference method of analysis, in conjunction with the theory of part I, to consider the behaviour of a member subject to any arbitrary loading condition and end restraint. Both first order linear problems and second order elastic critical buckling problems are solved, including the interaction of local buckling, overall buckling and cross section distortion.

As vigas de rolamento são estruturas destinadas ao suporte de pontes rolantes, estas amplamente utilizadas para movimentação de cargas em galpões industriais. O presente trabalho apresenta um estudo sobre as vigas de rolamento de aço sem contenção lateral entre apoios, em geral projetadas com vão inferior a 7 metros, portanto destinadas ao suporte de pontes rolantes leves (capacidade nominal até 250 kN). A ausência de contenções laterais intermediárias aliada ao desalinhamento e à imprecisão na locação dos trilhos, bem como à presença de forças horizontais transversais ao eixo da viga (aceleração/frenagem do trole), impõem flexão lateral e torção, esforços que são equilibrados apenas pelas contenções nos apoios. A análise foi realizada utilizando o Método dos Elementos Finitos (MEF), considerando a análise não linear física e geométrica do problema, ou seja, um modelo mais próximo da viga real. Os resultados numéricos, quando comparados aos obtidos por meio da teoria de flexo-torção, mostraram uma inversão na distribuição esperada de tensões na mesa superior do perfil, ou seja, nos pontos onde deveria ocorrer aumento da tensão longitudinal de compressão, ocorreu redução. Esta inversão pode ou não ocorrer, dependendo da espessura da mesa superior, intensidade e posição da força vertical da roda da ponte. Além disso, os resultados determinados via MEF foram comparados com os obtidos via modelo tradicional de barra (momento de torção substituído por um binário de forças horizontais nas mesas). A comparação indicou divergência entre os resultados, podendo o dimensionamento pelo modelo de barra levar tanto a situações a favor da segurança como contra a segurança. / The runway girders are structures intended for support cranes, these broadly used to movement of loads in industrial buildings. This research presents a study about the runway girders without lateral bracing between support points, generally designed with span lower than 7 meters, therefore intended for support of light cranes (rated capacity until 250 kN). The absence of intermediate lateral bracing allied to misalignment and imprecision location of the rail, also the presence of the side thrust on the girder (acceleration/ braking of the trolley), causes lateral flexural and torsion, which are balanced only by the lateral containment on support points. The analysis was made using the Finite Element Method (FEM), which includes a nonlinear physical and geometric analysis of the structural problem, in other words, a model closest to the real girder. The numerical results, when compared to the results of the flexural-torsional theory, showed an inversion in the expected distribution of stress on the top flange of the shape, in other words, at the points where must occur increase of the longitudinal stress, reduction occurred. This inversion may or may not occur, depending on the thickness of the top flange, modulus and position of the load of the crane wheel. Besides, the numerical results were compared with the results of classical bar model for beams (torque is replaced by a couple of horizontal forces applied on the flanges). The comparison showed a divergence between the results, where the design by bar classical model can lead to situations of high safety or against safety.

This project involves a failure analysis of the internal structural collapse that occurred in World Trade Center 5 (WTC 5) due to fire exposure alone on September 11, 2001. It is hypothesized that the steel column-tree assembly failed during the heating phase of the fire. The results of this research have serious and far-reaching implications, for this method of construction is utilized in approximately 20,000 existing buildings and continues to be very popular. Catastrophic failure during the heating phase of a fire would endanger the lives of firefighters and building occupants undergoing extended egress times (e.g., high-rise buildings), or relying upon defend-in-place strategies (e.g., hospitals). Computer software was used to reconstruct the fire event and predict the structural performance of the assembly when exposed to the fire. Results from a finite element, thermal-stress model confirms this hypothesis, for it is concluded that the catastrophic, progressive structural collapse occurred approximately 2 hours into the fire exposure.

As vigas de rolamento são estruturas destinadas ao suporte de pontes rolantes, estas amplamente utilizadas para movimentação de cargas em galpões industriais. O presente trabalho apresenta um estudo sobre as vigas de rolamento de aço sem contenção lateral entre apoios, em geral projetadas com vão inferior a 7 metros, portanto destinadas ao suporte de pontes rolantes leves (capacidade nominal até 250 kN). A ausência de contenções laterais intermediárias aliada ao desalinhamento e à imprecisão na locação dos trilhos, bem como à presença de forças horizontais transversais ao eixo da viga (aceleração/frenagem do trole), impõem flexão lateral e torção, esforços que são equilibrados apenas pelas contenções nos apoios. A análise foi realizada utilizando o Método dos Elementos Finitos (MEF), considerando a análise não linear física e geométrica do problema, ou seja, um modelo mais próximo da viga real. Os resultados numéricos, quando comparados aos obtidos por meio da teoria de flexo-torção, mostraram uma inversão na distribuição esperada de tensões na mesa superior do perfil, ou seja, nos pontos onde deveria ocorrer aumento da tensão longitudinal de compressão, ocorreu redução. Esta inversão pode ou não ocorrer, dependendo da espessura da mesa superior, intensidade e posição da força vertical da roda da ponte. Além disso, os resultados determinados via MEF foram comparados com os obtidos via modelo tradicional de barra (momento de torção substituído por um binário de forças horizontais nas mesas). A comparação indicou divergência entre os resultados, podendo o dimensionamento pelo modelo de barra levar tanto a situações a favor da segurança como contra a segurança. / The runway girders are structures intended for support cranes, these broadly used to movement of loads in industrial buildings. This research presents a study about the runway girders without lateral bracing between support points, generally designed with span lower than 7 meters, therefore intended for support of light cranes (rated capacity until 250 kN). The absence of intermediate lateral bracing allied to misalignment and imprecision location of the rail, also the presence of the side thrust on the girder (acceleration/ braking of the trolley), causes lateral flexural and torsion, which are balanced only by the lateral containment on support points. The analysis was made using the Finite Element Method (FEM), which includes a nonlinear physical and geometric analysis of the structural problem, in other words, a model closest to the real girder. The numerical results, when compared to the results of the flexural-torsional theory, showed an inversion in the expected distribution of stress on the top flange of the shape, in other words, at the points where must occur increase of the longitudinal stress, reduction occurred. This inversion may or may not occur, depending on the thickness of the top flange, modulus and position of the load of the crane wheel. Besides, the numerical results were compared with the results of classical bar model for beams (torque is replaced by a couple of horizontal forces applied on the flanges). The comparison showed a divergence between the results, where the design by bar classical model can lead to situations of high safety or against safety.

The subject of the thesis is to design and consider steel superstructure of a composite steel-concrete road bridge. It is a continuous beam with seven spans of 36,0 + 57,0 + 75,0 + 90,0 + 75,0 + 57,0 + 36,0 = 426 meters. The superstructure consists of welded I-beams, which pass into closed box girder. The calculations take into account the construction phase.