Recent studies have demonstrated the existence of a relationship between a structures susceptibility to second-order effects and its natural period of vibration ([Formula: see text]) given that both these properties are fundamentally dependent on the structure stiffness and mass properties. The main advantage of the use of this characteristic is that [Formula: see text] can be obtained easily by the existing structural analysis software. In this study, different formulations are developed in order to propose an amplification factor ([Formula: see text]) to multiply first-order analysis results and satisfactorily obtain results of a second-order analysis. These formulations are based on D’Alembert’s principle, Rayleighs method, and the use of generalized coordinates to represent the dynamic displacement of flexible structures. It is observed that [Formula: see text] provides values closer to and in fact, more conservatively than, those obtained by the conventional simplified methods currently used by structural design engineers. Thus, the amplification factor [Formula: see text], which is based on the natural period of vibration, is proposed to be used as (i) an indicator of a structure susceptibility to second-order effects and (ii) an amplification factor to describe the second-order effects on reinforced concrete frames.

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Aos meus pais, José Carlos e Adelina, meus irmãos Fábio, Júnior e Érica, minhascunhadas Vanessa e Luciana, meu avô, João Siqueira, pessoa muito simples mas de sabedoria ímpar e, à minha noiva, Ana Paula e sua família, que sempre me deram apoio e amor durante esta fase.Aos meus grandes amigos da graduação, a galerinha mais ou menos, sem vocês a faculdade de engenharia não teria a menor graça.Ao meu orientador, Mounir Khalil El Debs, pela confiança, paciência, dedicação, amizade e os preciosos ensinamentos desde a iniciação científica.À professora Aline Barboza, pelo apoio e ajuda durante toda minha iniciação científica e pelo incentivo durante todo o mestrado.Aos funcionários do Laboratório pela ajuda e pelo profissionalismo na montagem e execução de todos os ensaios desta pesquisa.À todos os professores e funcionários do SET, que contribuíram para a conclusão deste trabalho.Aos amigos Paulino, Vinícius, Guilherme Said, Estevam, Guilherme David e Eric, com os quais tive a oportunidade de passar os momentos de lazer e descontração durante esses anos.À todos os membros da sala 03, Danilo, Kenneth, João, Antônio e Rafael e os amigos caçulas que fiz neste último ano de mestrado. Dosagem do compósito.............................................................................................. 59 3.3.2 Variáveis.................................................................................................................... 62 3.3.3 Caracterização do compósito.................................................................................. This research presents a study of a mortar modified to use as bearing pad between precast concrete elements. The mortar used in this research is achieved by the introduction of styrene-butadiene latex (SB) and polypropylene fibers into a cement mortar and sand, modifying their mechanical properties, as increase of the potential deformation by decrease of the composite modulus of elasticity, providing favorable characteristics to the use as bearing pad for precast concrete elements. Cylindrical samples of 50mm of diameter with height of 100mm were molded and tested to determination the compressive and the tensile strength and also the modulus of elasticity of the composite. Compression tests with cushions of 150mm x 150mm of base with thickness of 10mm were done to determinate the deformation capacity, rotation capacity and capacity of accommodation of imperfections and distribution of the stresses between precast elements. The results showed that the material has a capacity to deform in levels of tension from 10 to 20MPa maintaining his resilience.Values of rotations among 0,01 and 0,02rad were obtained, being these larger ones than the necessary values for most of the conventional cases of project. In the accommodation and distribution of the stresses, the presence of the bearing pad promoted an improvement of 25% in the strength of connections subject to uniform compressive stresses, with surface irregularities of 1,0mm.

The ultimate limit state of stability by equilibrium bifurcation, the limit states for stress and strain resulting from this condition were evaluated for an extremely slender real structure of reinforced concrete, with geometry varying along its length. The aspects related to nonlinearities of the material were considered through the recommendations on NBR 6118:2014, from the Brazilian Association of Technical Standards (ABNT). In the analytical solution, developed for stability analysis, all elements of the structural dynamics present in the system were taken into account, including the column self-weight. The critical buckling load was then dynamically defined to different instants of time. Reductions of 70% for the modulus of elasticity and 59% for the critical buckling force were found in analyses performed from zero and five thousand days. It was also possible to obtain the induced stresses on the homogenized cross-sections and those transferred to reinforcement steel bars. KeywordsLimit states, critical buckling load, analytical solution, NBR 6118:2014. Graphical AbstractEvaluation of limit state of stress and strain of free-fixed columns with variable geometry according to criteria from the Brazilian code for concrete structures Alexandre de Macêdo Wahrhaftig et al.

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Due to the paucity of studies regarding the seismic assessment of buildings in Brazil, this study aims to present and discuss a seismic reliability assessment of a reinforced concrete framed structure designed according to the Brazilian standard ABNT NBR 6118:2014 without the consideration of the seismic design requirements of ABNT NBR 15421:2006. Herein, fragility functions are generated through probabilistic seismic demand analysis, and integrated with hazard curves for Northeastern Brazil to generate regional failure probability maps for three limit-states: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). The results indicated that the building performance is adequate for IO; however, for LS and CP, an unacceptable performance is observed.