Sistemas estruturais constituídos por perfis de aço são, em geral, dimensionados de uma forma \"indireta\", isto é, cada componente é analisado e verificado segundo suas capacidades teóricas individualmente, normalmente associando-se condições de extremidade e comprimentos teóricos para cada barra de modo a aproximar a sua capacidade portante sob a condição real. Contudo, importantes efeitos como a transmissão do empenamento entre as barras devido à torção e/ou distorção, as restrições localizadas impostas por sistemas de contraventamento ou componentes diversos, e também a compatibilidade de deslocamentos locais/globais entre barras conectadas não alinhadas entre si, são desconsiderados, uma vez que o estudo de tais efeitos envolve, normalmente, custosos trabalhos de modelagem através de elementos finitos de casca (e/ou sólidos), soluções numéricas complexas e demoradas, e/ou estudos experimentais caros e trabalhosos. Neste contexto, alguns recentes trabalhos apontam para um vasto campo de aplicações das inovadoras potencialidades da Teoria Generalizada de Vigas (GBT), permitindo, em particular, a análise de sistemas estruturais que consideram os diversos efeitos provocados por condições de apoio arbitrárias, diferentes posições do carregamento e efeitos decorrentes das ligações entre as barras. Contudo, apesar de tais recursos ampliarem as aplicações da GBT na análise de estabilidade de sistemas estruturais, apenas um conjunto limitado de problemas pode ser atendido, especialmente quanto às ligações entre as barras. Os recentes trabalhos envolvendo a aplicação da GBT para a análise de estabilidade de pórticos metálicos dedicaram-se ao estudo de alguns casos específicos de ligações rígidas, isto é, assumem a hipótese de transferência completa dos deslocamentos generalizados entre as barras. Assim, uma vez que a rigidez de tais ligações pode ser responsável por mudanças significativas no comportamento do sistema estrutural em questão, este trabalho procura fornecer uma solução capaz de considerar a semirrigidez das ligações metálicas associada aos parâmetros modais típicos da GBT. Além disso, dada a possibilidade de ampliar os tipos de ligações analisadas por meio da GBT, incluindo as configurações mais comumente utilizadas na prática, apresentam-se novos conjuntos de relações cinemáticas desenvolvidas para tal, assim como as referidas validações, que são realizadas por meio de análises utilizando o programa computacional ANSYS®. / Steel structural systems are usually associated with an \"indirect approach\", i.e., each component of the respective structure is analysed and verified according to its theoretical individual capacity. Normally, in order to approximate the real behaviour of the structural system, specific support conditions and effective length concepts are used to analyse each structural member separately. However, some important effects are disregarded in this procedure, like the warping transmission at frame joints (due to torsion and/or distortion), or those stemming from localized supports associated with bracing systems, as well as the local/global displacements compatibility of the cross-section walls at the joint region. Additionally, studies considering the above mentioned effects involves rather complicated and time-consuming numerical analyses using shell and/or solid finite elements, and/or expensive experimental investigation. On the other hand, some recent studies revealed a large field for application of the Generalized Beam Theory (GBT) in the context of the stability, first and second order analyses of structural systems, considering, particularly, the effects caused by arbitrary support conditions, different load positions, and the effects caused by connections between members. Nonetheless, all the recent works applying GBT for stability analysis of steel frames are focused on some specific cases of rigid connections, i.e., they assume the full transfer of the generalized displacements between the non-aligned members. Thus, given the well-known fact that the rigidity of connections may lead to considerable changes of the structural behaviour of steel structural systems, this work deals with the development of a solution to incorporate the semi-rigidity of the steel frame connections to the modal parameters of the GBT. Furthermore, given the possibility to expand the connection types analysed by means of GBT, including the most commonly used configurations adopted in practice, it is presented the related new kinematic relations developed, as well as the validation studies carried out in the software ANSYS®.

As typically designed, the beam-column-brace connections of buckling-restrained braced steel frames have undesirable failure modes that compromise the integrity and performance of the frames and are costly to repair. To decrease the time and resources needed to repair the frames following an earthquake, a new connection design was developed that attempts to confine yielding to replaceable frame components. The design incorporates a gap in the beam beyond the edge of the beam-gusset weld that acts as a hinge and reduces moment forces transferred to the connection; it is bridged by splice plates that are bolted to the beam top flanges. The splice plates and buckling-restrained braces are the only frame components that are expected to yield. To investigate the performance of the proposed connection design, a prototype bay was designed and two test specimens were fabricated and tested. Each specimen represented a corner of the prototype braced bay and consisted of a beam, column, gusset plate, brace core extension assembly, splice plates, and lateral bracing angles. Both standard design procedures and newly developed criteria were used to design the connection. In preparation for testing, a method was developed for estimating the hysteretic response of a buckling-restrained brace. By using this method to program an actuator, the specimens could be tested without using actual braces, resulting in a significant reduction in testing cost. Testing was conducted using two 600 kip actuators; the first followed a static loading protocol with a maximum design drift of 6.5%, and the second replicated the prototype BRB's response. The tests yielded promising results: both specimens withstood the maximum displacements and avoided yielding in the beams, columns, and gusset plates; yielding did occur in the splice plates and BRB core extension assembly, as anticipated. Possible limitations in the design may arise under the presence of increased shear loads, concrete floor slabs, or out-of-plane loading. Additional testing is recommended.

Muchas ciudades del Perú se encuentran ubicadas en el cinturón de fuego del Pacífico, en consecuencia, existe una mayor probabilidad de ocurrencias de sismos que generen cuantiosas pérdidas de vida y grandes perjuicios económicos. Debido a este problema, la ingeniería civil está en la obligación de investigar nuevos diseños sísmicos más precisos, los cuales originaron diversos métodos que usan a los desplazamientos de la estructura como parámetro principal, ya que a través de los desplazamientos se pueden obtener los momentos y cortantes de la estructura. A este método se le conoce como Diseño Basado en Desplazamientos. El autor que le dio los lineamientos teóricos más amplios y consistentes es Priestley, con su propuesta llamada Diseño Directo Basado en Desplazamientos. Por otro lado, en la realidad peruana, las edificaciones con sistema estructura del pórtico de acero son atípicos en comparación con las de sistema dual de concreto armado. En consecuencia, se desaprovecha las propiedades de este material y de este sistema estructural, el cual se sumerge más en el rango inelástico que el concreto. La tesis analizará los resultados obtenidos del análisis sísmico de una estructura de sistema dual y otra de pórticos de acero, ambas con una misma configuración arquitectónica, bajo las metodologías de Diseño Directo Basado en Desplazamientos y de Diseño Basado en Fuerzas. Esto generará la comparación entre los sistemas estructurales bajo las metodologías mencionadas. / Many cities in Peru are located in the Pacific ring of fire, consequently, there is a greater probability of earthquakes that generate large losses of life and great economic damage. Due to this problem, civil engineering is obliged to investigate new more accurate seismic designs, which originated several methods that use the displacements of the structure as the main parameter, since through the displacements the moments and shear of the structure can be obtained. This method is known as Displacement Based Design. The author who gave the broadest and most consistent theoretical guidelines is Priestley, with his proposal called Direct Displacement Based Design. On the other hand, in the Peruvian reality, steel frames buildings system are atypical compared to those of the dual wall-frame with reinforced concrete system. Consequently, the properties of this material and this structural system are wasted, which is more immersed in the inelastic range than concrete. The thesis will analyze the results obtained from the seismic analysis of a dual wall-frame building and another of steel frames, both with the same architectural configuration, under the Direct Displacement Based Design method and the Design Based Force method, which is the method used in most standards. The thesis will generate the comparison between the structural systems under the mentioned methodologies. / Tesis