Programa de Pós-Graduação em Engenharia Civil
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Master Thesis Análise não linear de blocos de concreto armado sobre estacas como fundação de aerogerador onshore considerando o atrito lateral entre as estacas e o solo(Universidade Federal do Rio Grande do Norte, 2021-11-29) Dantas, Diego Lima; Barros, Rodrigo; Nascimento Neto, Joel Araújo do; 83991301415; http://lattes.cnpq.br/2747505817148030; http://lattes.cnpq.br/6314974214441091; http://lattes.cnpq.br/7843363742294141; Silva Filho, José Neres da; http://lattes.cnpq.br/0915972389480304; Delalibera, Rodrigo GustavoIn the search for alternative sources to meet the growing demand for energy, wind production has been highlighted due to the great potential for its use in Brazil. Given the magnitude of the foundations of wind turbines, understanding their behavior as a structure is essential for designing optimized solutions that reduce costs and facilitate the implementation of this technology on a large scale. From this perspective, this research seeks to deepen the studies on the structural behavior of foundations for onshore wind turbines, represented by reinforced concrete pile caps. Computational models were developed using the Finite Element Method (FEM) with the aid of the Ansys Workbench R20 software, considering the contribution of the lateral friction of the pile shaft in the conduction of loads to the ground, using non-linear numerical modeling. The reinforcements of a wind tower foundation were designed and two different mesh organizations were proposed: circular (CR) and orthogonal (OR). It was observed that the reinforced caps, although classified as flexible foundations due to their geometry, presented a behavior similar to that of rigid caps, with a tendency to linearize the pile reactions and vertical displacements. The results showed that the distribution of reinforcement in orthogonal mesh provided smaller vertical displacements for the blocks, a fact that was attributed to the greater stiffness of the foundation provided by this way of arranging the bars. In the different types of soils considered, the vertical displacements of the OR models were, on average, 10.74% lower than those of the CR models. On the other hand, the consumption of steel, in kilograms, was considerably lower in the CR models. The amount of steel used in the reinforcement of the CR models was 30.97% smaller than that of the OR models.Master Thesis Análise estática e sísmica de fundação de aerogerador em radier estaqueado(Universidade Federal do Rio Grande do Norte, 2021-05-24) Leal, Felipe Carlos de Araújo; Freitas Neto, Osvaldo de; ; http://lattes.cnpq.br/6335708403185496; ; http://lattes.cnpq.br/9239721936319389; Santos Júnior, Olavo Francisco dos; ; Gusmão, Alexandre Duarte; ; http://lattes.cnpq.br/4312371877753383; Cavalcante, Erinaldo Hilário; ; http://lattes.cnpq.br/0174408449858772The present dissertation proposes to evaluate the static and seismic behavior of piled rafts foundations for a wind turbine located in the city of Macau, on the northern coast of the state of Rio Grande do Norte. Static and seismic analysis were performed using the Finite Element Method, using the ABAQUS software. Initially, in the static analysis, it was observed that in a piled raft with 24 piles (originally predicted number of piles in the foundation design) the raft resisted 63% of the vertical load applied on system, which demonstrates the importance of considering the raft-soil contact in this case. It was concluded, in the static analysis, that a piled raft with 8 piles (RE8) was sufficient to fulfill the necessary safety and displacement criteria. In this case, the raft started to support 85% of the vertical load applied on foundation and the criterion that limited the reduction of more piles was the rotational stiffness, which is related to the differential settlement of the foundation. For seismic analysis, an artificial accelerogram compatible with the seismic conditions observed in Brazil was generated. It was observed that the action of the earthquake at the base of the model caused variations in the loads and vertical displacements of the foundations, as well as in their rotational and translational stiffness, throughout the duration of the event. The RE8, a proposal optimized for a situation of only static loading, experienced an increase in settlement of up to 34% during the seismic loads, as well as decreases of the same order of magnitude in its rotational and translational stiffness. This made the foundation unsuitable for the case, as it did not meet the displacement criteria imposed by the wind turbine manufacturer, as well as the possibility of structural failure due to pile traction. Finally, it was noticed that a piled raft with 20 piles (RE20) fulfilled all the design criteria during static and seismic loads and, therefore, proved to be a suitable foundation proposal for the case. It was concluded that, although the seismic loads are of low magnitude, consistent with the Brazilian territory, it is capable of causing important effects in structures sensitive to displacements and rotations, such as wind turbine foundations.Master Thesis Estudo dos efeitos localizados de segunda ordem em paredes de contraventamento de edifícios de alvenaria estrutural(Universidade Federal do Rio Grande do Norte, 2020-10-23) Dantas, Kaio Geovanne de Medeiros; Nascimento Neto, Joel Araújo do; ; http://lattes.cnpq.br/2747505817148030; ; http://lattes.cnpq.br/1805731189416583; Maciel, Daniel Nelson; ; http://lattes.cnpq.br/4343155598427033; Parsekian, Guilherme Aris; ; http://lattes.cnpq.br/7798651726059215The present study consists of the evaluation of local second order effects on unreinforced shear walls in structural masonry through a numerical approach using the Finite Element Method. For this purpose, an adaptation was made to the equivalent frame model to simulate the out-ofplane response of selected shear walls on storeys of a building. The validation of the new model was performed by comparing its results with those obtained from an experimental model for slender walls in which a flexion out-of-plane of the walls was mobilized. The shear walls were modeled in three configurations: completely modeled shear walls under loads applied in full extension; isolated columns; and completely modeled shear walls under the application of loads separately in each column. The analysis considered the magnitudes of the displacements of the walls, the mobilization of the columns, as well as the second order moments caused by the model’s geometric nonlinearity. Finally, verifications in the design of walls and isolated columns were carried out using the methodologies prescribed in the Brazilian standards NBR 15961-1:2011, NBR 16868-1:2020, and in the Eurocode 6 - PD 6697:2019, with subsequent comparison with the results obtained from numerical modeling. The analysis of the results showed the influence of the lateral support, provide by the transversal walls, on the shear walls’ stiffness, and highlighted the importance of considering the local second order effects in shear walls’ design, whose the required values of compressive strength increased substantially when considering these effects. In addition, it was possible to observe the efficiency of the model developed in the proposed approach, since it presented similar results to those resulting from the prescriptions of NBR 16868-1.