Este trabalho apresenta uma análise comparativa de diferentes sistemas estruturais para um edifício de 20 pavimentos. Cada um dos modelos foi dimensionado através dos princípios do método da análise direta, presente na ABNT NBR 8800:2008. O método da amplificação dos esforços solicitantes (MAES) foi usado para se obter de forma simplificada os esforços atuantes nos elementos do edifício considerando os efeitos locais e globais de segunda ordem. A incidência do vento foi simulada de duas formas diferentes. Na primeira, chamada de uniforme, o vento foi aplicado sem excentricidade, gerando apenas o efeito de tombamento nas estruturas. Na segunda hipótese, considerou-se uma excentricidade devida aos efeitos de vizinhança, prescrita pela ABNT NBR 6123:1988, responsável por ocasionar o tombamento e a torção dos edifícios. Todas as análises numéricas foram repetidas fazendo o uso de outro método simplificado de segunda ordem, conhecido como P-Delta. Por meio dos resultados obtidos, constatou-se que a possibilidade de se reduzir a sobrecarga para o dimensionamento de pilares proporciona uma economia de material, mas, por outro lado, tem como consequência o aumento do tempo de análise, pois exige a utilização de diferentes combinações de cálculo para o dimensionamento de vigas e pilares. A estratégia utilizada para simular os efeitos de vizinhança mostrou-se satisfatória, pois permitiu introduzir de maneira fácil e prática a torção ocasionada pela incidência excêntrica do vento. Observou-se também que esses efeitos ocasionaram o aumento dos momentos fletores e dos deslocamentos das estruturas analisadas. Em relação à avaliação dos efeitos de segunda ordem, comprovou-se que, para a classificação da deslocabilidade, a combinação de cálculo crítica é aquela que possui o maior carregamento gravitacional. Entretanto, para o dimensionamento dos elementos, foi constatado que outras hipóteses de cálculo, principalmente aquelas em que o vento é a ação variável principal, podem ser determinantes. Por fim, foi observado que os resultados obtidos pelo método P-Delta ficaram bastante semelhantes àqueles calculados pelo MAES, com desvios desprezíveis. O MAES, por sua vez, mostrou-se bastante trabalhoso, pois exige a modelagem de diferentes tipos de estruturas para a determinação dos esforços. / This work presents a comparative analysis of different structural systems for a 20-storey building. Each model has been designed using the principles of the direct analysis method (DAM), present in the ABNT NBR 8800:2008. The first-order amplification method (FOAM) was used to obtain, in a simplified manner, the forces acting on the building elements, including local and global second-order effects. The incidence of the wind was simulated in two different ways. In the first case, named uniform, the wind was applied without eccentricity, generating only structure overturning. In the second case, it was considered an eccentricity due to vicinity effects, prescribed by the ABNT NBR 6123:1988, responsible for causing twisting and building overturning. All numerical analysis were carried out a simplified second-order method known as P-Delta. From the results obtained it was found that the reduction of live loads in the design of columns provides material economy, but on the other hand, increases analysis time, since it requires different combinations for beams and columns. The strategy used to simulate the vicinity effects was satisfactory, because it allowed, in an easy and practical way, the consideration of the torsion produced by the wind eccentric impact. It was also observed that these effects increased the bending moments and the displacements of the structures. About the second-order effects, it was shown that, for sway or non-sway classification, the critical combination is one with greatest gravitational loading. However, for the design of the elements, it was observed that other loading conditions can be critical, especially those in which the wind is the main live load. Finally, the results obtained by the P-Delta method were very similar to those calculated by the first-order amplification method. The FOAM was, in turn, very laborious, because it requires the modeling of different types of structures for the determination of the forces.

The main objective of the thesis is evaluating and comparing Second-Order Elastic Analysis Methods defined in two different specifications, AISC 2005 and TS648 (1980). There are many theoretical approaches that can provide exact solution for the problem. However, approximate methods are still needed for design purposes. Simple formulations for code applications were developed, and they are valid as acceptable results can be obtained within admissible error limits. Within the content of the thesis, firstly background information related to second-order effects will be presented. The emphasis will be on the definition of geometric non-linearity, also called as P-&amp / #948 / and P-&amp / #916 / effects. In addition, the approximate methods defined in AISC 2005 (B1 &ndash / B2 Method), and TS648 (1980) will be discussed in detail. Then, example problems will be solved for the demonstration of theoretical formulations for members with and without end translation cases. Also, the results obtained from the structural analysis software, SAP2000, will be compared with the results acquired from the exact and the approximate methods. Finally, conclusions related to the study will be stated.

A recent development and innovation in elevator technologies have sprawled interest in how these technologies would affect the forms and shapes of future high-rise buildings. The elevator that uses linear motors instead of ropes and can thus travel horizontally and on inclines is of particular interest. Once the vertical cores are no longer needed for the elevators, new and radical building forms and shapes are anticipated. It is expected that the buildings will have bridges and/or the buildings themselves will structurally perform more like bridges than buildings, therefore this study addresses the following topic - structural design and performance of tube mega frame in arch-shaped high-rise buildings. Evidently, for a structure of an arched shape, the conventional structural system used in high-rise buildings does not address the structural challenges. On the other hand, The Tubed Mega Frame system developed by Tyréns is designed to support a structural system for high-rise building without the central core, in which the purpose is to transfer all the loads to the ground via the perimeter of the building, making the structure more stable by maximizing the lever arm for the structure. The system has not yet been realized nor tested in realistic circumstances. This thesis aims at evaluating the efficiency of the Tubed Mega Frame system in arched shaped tall buildings. Multiple shapes and type of arches are evaluated to find the best possible selection. Structural behavior of different arch structures is studied using analytical tools and also finite element method in software SAP2000. The most efficient arch shape is sought to distribute the self-weight of the structure. The analysis shows that it is possible to accurately determine efficient arch shape based on a specific load distribution. Furthermore, continuing with the arch shape found in previous steps, a 3D finite element model is built and analyzed for linear static, geometric non-linearity (P-Delta) and linear dynamic cases in the ETABS software. For the given scope, the results of the analysis show that the Tubed Mega Frame structural system is potentially feasible and has relatively high lateral stiffness in the plane of the arch, while the out-of-plane lateral stiffness is comparatively smaller. For the service limit state, the maximum story drift ratio is within the limitation of 1/400 for in-plane deformations, while for out-of-plane the comfort criteria limit is exceeded.

This thesis presents the results of basically two separate studies. The first study involved identifying structural and earthquake parameters that influenced seismic structural collapse. The parameter study involved nonlinear dynamic analyses using single-degree-of-freedom (SDOF) bilinear models. Four parameters were associated with the SDOF models — the lateral stiffness, the post-yield stiffness ratio, the yield strength, and the stability ratio (P-Delta effects). Then, three parameters were associated with the ground motions — the records themselves, the lateral ground motion scales, and the vertical ground motion scales. From the parameter study, it was found that the post-yield stiffness ratio augmented by P-Delta effects (rp) in conjunction with the ductility demand was the best predictor of collapse. These two quantities include all four structural parameters and the seismic displacement demands. It was also discovered in the parameter study that vertical accelerations did not significantly influence lateral displacements unless a given combination of model and earthquake parameters was altered such that the model was on the verge of collapsing. The second study involved Incremental Dynamic Analysis (IDA) using bilinear SDOF models representative of low rise buildings in both the Western United States (WUS) and the Central and Eastern United States (CEUS). Models were created that represented three, five, seven, and nine story buildings. Five sites from both the WUS and CEUS were used. Four different damage measures were used to assess the performance of the buildings. The IDA study was primarily interested in the response of the structures between the earthquake intensities that have a 10 percent probability of occurring in 50 years (10/50) and 2 percent probability of occurring in 50 years (2/50). The results showed that all structures could be in danger of severe damage and possible collapse, depending on which damage measure and which earthquake was used. It is important to note, though, that the aforementioned is based on a damage-based collapse rule. The damage-based rule results were highly variable. Using an intensity-based collapse rule, proved to be more consistent. Due to the nature of the bilinear models, only those structures with negative rp values ever collapsed using an intensity-based collapse rule. Most of the WUS models had positive rp values and many of the CEUS models had negative rp values. While many of the CEUS structures had negative rp values, which made them prone to collapse, most of the CEUS structures analyzed did not collapse at the 2/50 intensity. The reason was that the periods of the CEUS models were much longer than the approximate periods that were required to determine the strengths. Consequently, the strength capacity of most of the CEUS models was much greater than the seismic strength demands. While many of the CEUS models did have sudden collapses due to the large negative rp values, the collapses happened at intensities that were generally much higher than the 2/50 event. In the IDA, it was also shown that vertical accelerations can significantly affect the ductility demands of a model with a negative rp post-yield stiffness ratio as the earthquake intensity approaches the collapse intensity. Since IDA is concerned with establishing collapse limit states, it seems that the most accurate collapse assessments would include vertical accelerations. / Master of Science

En la presente investigación, se analiza la influencia de la irregularidad de la masa y del efecto PΔ sobre el comportamiento estructural de una edificación de 15 pisos. Se plantea el caso de una edificación regular 15 pisos, 4 casos de edificaciones con presencia de irregularidad de masa en un piso establecido y 4 casos de edificaciones irregulares con efecto PΔ. Primeramente, mediante el análisis dinámico lineal se determina la respuesta estructural en términos de derivas, fuerza cortante basal y momento. Posteriormente, se realiza el análisis estático no lineal (Push over) y se construye la curva de capacidad de la estructura. A partir de la curva de capacidad se obtienen los desplazamientos ultimo y de fluencia, y se estima la ductilidad global. Luego se procede a determinarse el desempeño sísmico para los diferentes niveles de sismo. Por último, se realiza un análisis comparativo de la respuesta estructural y el desempeño sísmico de los casos. Al analizar los momentos de las estructuras irregulares con efecto PΔ, se obtuvo una variación de hasta 5.60% con respecto a la edificación regular, de modo que se tiene mayor incremento de los momentos cuando en el análisis estructural de una estructura con irregularidad de la masa se considera el efecto PΔ. Se ha generado un incremento de la variación de la rigidez en el caso 1 cuando se considera el efecto PΔ, en la dirección x-x se obtuvo una variación de hasta 73.06 % y 77.76% en la dirección y-y. / In the present investigation, the influence of the irregularity of the mass and the PΔ effect on the structural behavior of a 15-story building is analyzed. The case of a regular 15-story building, 4 cases of buildings with the presence of mass irregularity in an established floor and 4 cases of irregular buildings with PΔ effect is presented. First, through linear dynamic analysis, the structural response is determined in terms of drifts, basal shear force and moment. Subsequently, the non-linear static analysis (Push over) is performed and the capacity curve of the structure is constructed. The ultimate and creep displacements are obtained from the capacity curve, and the overall ductility is estimated. Then, the seismic performance is determined for the different levels of earthquake. Finally, a comparative analysis of the structural response and the seismic performance of the cases is carried out. When analyzing the moments of the irregular structures with the PΔ effect, a variation of up to 5.60% was obtained with respect to the regular building, so that there is a greater increase in the moments when in the structural analysis of a structure with irregularity of the mass the PΔ effect is considered. An increase in the variation of the stiffness has been generated in case 1 when the PΔ effect is considered, in the x-x direction a variation of up to 73.06% and 77.76% in the y-y direction was obtained. / Trabajo de investigación