One of the significant difficulties in representing the behavior of reinforced concrete structures in mathematical models is the post-cracking non-linearity. And so, reinforced concrete slabs are no exception to the rule. Still, the usual analysis models for this structural element are verified in the elastic regime when the concrete tensile strength is considered. This model is acceptable for the service limit states but not the ultimate limit state. These aspects associated with the great difference in the behavior of concrete when subjected to tension or compression make it necessary to study a nonlinear mathematical model that can represent a reinforced concrete slab subjected to bending, from the beginning of loading until its failure, as accurately as possible. With this, the ANSYS software, from its version 18, made available in its library the Drucker-Prager-Rankine model arranged with two distinct rupture surfaces. A Drucker-Prager criterion for the concrete subjected to compression and a Rankine criterion for concrete in tension. In addition, the software is based on the finite element method, giving the possibility of precise and nonlinear analysis through load and deformation increments, taking into account both elastic and plastic deformations after concrete cracking. Thus, this work aims to present the modeling of reinforced concrete slabs through the Drucker-Prager-Rankine surface, validating the model by comparing it with several experimental tests. The model results were coherent and acceptable, presenting a good approximation of the results of the tests.

Different reasons can make certain structures need reinforcement to achieve specific levels of safety and performance. The occurrence of events of significant magnitudes, such as earthquakes, are examples of this. Retrofitting vulnerable structures becomes a practice to mitigate the destructive effects of earthquakes, and the RC Jacketing becomes an alternative. The present work studies this type of reinforcement, proposing and applying an assessment methodology under vulnerable construction built in a high seismic risk zone. The diagnostic of the current situation was determined, and the structural suitability was evaluated using RC Jacketing. With the computational software S-Model, created in this research, the effectiveness of the proposed reinforcement was verified, based on the results of the analysis carried out with commercial software. The preload was considered, and the strength of the reinforced column section was verified against all load combinations. The S-Model program was able to verify the non-simultaneous occurrence of the amplification of moments with the most critical loading. Both conditions demand more significant stresses on the element, and therefore the calculation of the steel areas of the column may be underestimated if they are not considered.

Ao longo dos anos, estamos vivenciando uma revolução na área da informática, onde o aumento da capacidade de armazenamento de dados e o desenvolvimento de sistemas computacionais são exemplos bons dessa evolução. Porém, o custo elevado de softwares desenvolvidos para o dimensionamento de estruturas de concreto armado, acarreta no distanciamento deles com os estudantes do curso de engenharia civil e a falta de vivência com os mesmos. Desta forma, o presente trabalho tem como objetivo automatizar e sistematizar através de uma rotina computacional, o dimensionamento de lajes maciças em concreto armado, em formato retangular, submetidas a um carregamento uniformemente distribuídos, podendo estarem apoiadas em bordos apoiados, engastados ou livres, de acordo com o proposto pela norma NBR 6118:2014. Para isto, se utilizou a linguagem de programação Visual Basic, desenvolvida para compilar aplicações orientadas a objeto, possibilitando a utilização do software em ambiente Windows através de uma interface gráfica muito prática e acessível. A partir dos dados de entrada introduzidos pelo usuário, o programa executa o dimensionamento de lajes usuais em edifícios de concreto armado com as características descritas.

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NBR 6118 (2014) is the Brazilian standard that guides the design of reinforced concrete structures and adopts semi-probabilistic methods as a reference. These establish safety criteria that confront internal forces resulting from actions, increased by majoring coefficients, with the characteristic strengths of steel and concrete materials also reduced by minoring coefficients so that the former is equal to or less than the latter (Sd≤Rd ). However, unlike the Brazilian standard, the international standards determine the calibration of these coefficients through probabilistic methods. This calibration is a factor of paramount importance concerning the measurement of the risk of the structure. It is known that the material's properties present a certain level of dispersion. Depending on the workmanship quality, there are also uncertainties regarding the geometry of the structural parts. Furthermore, the actions in the structure show considerable variation throughout its useful life. In this context, one of the objectives of this work was to determine the reliability of reinforced concrete slabs designed according to NBR 6118 (2014), with loads determined by the recently updated standard NBR 6120 (2019), through a probabilistic analysis using a Finite Element numerical model and through a non-linear analysis. For this, the proposed study addresses the determination of resistance, represented by a theoretical distribution adjusted from simulations generated by the Monte Carlo Method using the ANSYS software. The reliability indices were obtained using the FORM method. As a result, it was possible to verify that most slabs are above the reliability indices indicated as acceptable by the American standard ACI 318 (2014). In addition, the significant influence of the variable loading on the results was confirmed due to its great variability.