Given the large amount of construction and demolition waste (CDW) generated in the construction industry, as well as the constant need to extract natural aggregates (NA) from deposits on the planet (which are becoming scarcer every day), it is clear that it is necessary to invest in efficiently sustainable alternatives. One alternative that is often overlooked is the use of mixed recycled aggregates (MRA), since most Brazilian and international studies are limited to applications in non-structural concrete or mortars. However, since most of the CDW produced is classified as MRA, studies are needed to analyze its properties for structural purposes, especially the durability aspect. Thus, the general objective of the work is to evaluate the durability of concrete produced with coarse mixed recycled aggregate (MRA_c) when exposed to chloride ions. Concretes were produced with three different dosages, using the method proposed by ABCP, varying the percentage of replacement of the coarse natural aggregate (NA_c) by MRA_c (20% and 50%) and adopting, in all mixtures, the replacement of 20% of the CP V – ARI cement by the mineral addition metakaolin (MK). In the fresh state, the performance was evaluated through the slump test and the specific mass test. The analysis of the properties in the hardened state was carried out through the compressive strength tests, as well as physical indexes of the concretes, such as water absorption, void index and specific mass. To analyze the durability, the chloride content was determined in test specimens cured in the laboratory, as well as in samples exposed to the action of the environment, positioned at different distances in relation to the sea (199 m and 881 m). Regarding the use of MRA_c, the compressive strength results tended to decrease compared to conventional concretes, although this reduction was smaller in concretes using 20% MRA_c and greater in those using 50% MRA_c. The use of MK improved the compressive strength results in these concretes, allowing them to have values closer to conventional concrete. Regarding the property of water absorption by capillarity, concretes using MRA_c absorbed more water compared to conventional concrete, which was already expected due to the high porosity of these materials. The use of MK improved this property in all concretes, due to the high content of fines in this supplementary material. Regarding the influence of the type of curing in the concretes, it was found that the averages of the compressive strength results are statistically equal and the sample averages of the results of water absorption by capillarity are equal, demonstrating that the type of curing did not influence the results in the hardened state of the concretes. Regarding the chloride penetration results, all concretes analyzed (conventional, 20% and 50% MRA_c) presented values within the normative limit and the use of MK did not significantly influence the results; this was also observed in relation to the “distance from the coast” factor, whose average results were statistically equal, showing that this factor did not influence the results. Regarding the isolated effect of chloride penetration on the compressive strength of concretes, statistically, the average results were equal.

The objective of this work is to conduct a transient analysis of heat transfer in vertical oil wells, proposing a mathematical model to predict transient temperature fields in these structures. Traditionally, the most widely used strategy for modeling thermal phenomena in wells is the pseudo-steady-state approach, which assumes steady state heat transfer in the wellbore. However, this simplification may lead to significant errors, particularly under dynamic conditions or during the initial stages of operation. In such scenarios, accounting for transient heat transfer can improve prediction accuracy. To address this, this study develops a mathematical model for transient heat transfer in vertical wells, incorporating frequently neglected mechanisms such as radiation in annuli and convection at the well surface. The methodology comprises four main steps: a) a literature review on thermal modeling in oil wells; b) development of a mathematical model to predict temperature profiles in oil wells, based on mass, momentum, and energy conservation equations; c) proposal of a numerical strategy to solve the aforementioned mathematical model; and d) application of the model to determine temperature distributions in oil wells, comparing results with field data and existing literature models, as well as conducting parametric studies. Results demonstrated that the model aligns well with sensor data from an onshore well and other literature models, with errors typically below 5%. Parametric studies further highlighted that radiation significantly impacts annuli filled with gases, while surface convection is critical for predicting well cooling during shut-in operations. The model exhibited higher accuracy in dynamic scenarios, such as well start-ups and shut-ins, outperforming the pseudo-steady-state approach. This study advances the understanding of transient thermal e!ects in oil wells, emphasizing the influence of mechanisms like annular radiation and surface convection. Its application may enhance the analysis of oil well integrity under dynamic operational conditions.

Fibers are known to improve the performance of concrete in post-cracking behavior,
particularly in terms of mechanical properties such as tensile strength, flexural capacity, and
toughness. The stress transfer bridging effect of the steel fibers and the confinement caused by
them alter the moment redistribution in the frames. In this context, this study aims to
contribute to the design of steel fiber-reinforced concrete (SFRC) frames based on numerical
analysis by applying the ABNT NBR 16935 (2021). The constitutive relationship of SFRC is
made by means of the plastic damage model Concrete Damaged Plasticity (CDP), when a
nonlinear behavior of the composite is adopted. To validate the applicability of the model, a
numerical validation was performed, reproducing in ABAQUS the beams and frames tested
experimentally. Initially, the numerical validation was carried out by simulating the SFRC
beams tested experimentally by Conforti et al. (2018) and Buttignol et al. (2017). Next, the
reinforced concrete frames tested experimentally by Cranston (1965) and Li et al. (2022) were
simulated. Subsequently, the same frames were analyzed with the addition of steel fibers.
Finally, reinforced concrete and SFRC columns subjected to centric and eccentric
compression were analyzed numerically. In general, the numerical results indicate a good
correlation with the experimental results, thus validating the methodology proposed in this
work. In the SFRC frames, the steel fibers increased the stiffness of the beam-column joint,
leading to a change in the moment redistribution. The SFRC frame nodes began to resist a
higher bending moment, and with a smaller rotation, compared to the reinforced concrete
frame. The addition of steel fibers also allowed for the reduction of longitudinal
reinforcement in the beam and improved the performance of the column, especially regarding
tensile forces. However, the addition of fibers did not increase the load capacity and ductility
of the columns. Regarding the shear behavior of the beams, for the two volumes of fibers
studied, the possibility of partially or totally replacing the transverse reinforcement was
confirmed. The importance of using a minimum amount of flexural reinforcement in SFRC
beams was also highlighted, even though the ABNT NBR 16935 (2021) allows the total
replacement of conventional reinforcement.

The Rate of Penetration (ROP) is a parameter of great interest in real-time drilling optimization. A
higher ROP reduces drilling time and can lead to significant cost reductions in well construction.
Predictive models for ROP are applied to predict ROP based on measured data while drilling,
enabling the determination of optimal operational parameters such as RPM, WOB, and fluid
flow when combined with optimization techniques. Obtaining more accurate ROP models is a
challenging task due to the large number of factors interacting nonlinearly. This study involves the
examination of different ROP models, including traditional ones, like Bourgoyne & Young and
Specific Mechanical Energy, and their adaptations, compared with machine learning models such
as Artificial Neural Networks (ANN) and Random Forests (RF). Public data from 7 wells were
structured into a dataset with relevant information for evaluating the performance of different
models in estimating ROP, including operational parameters, drill-bit data, lithology, geophysical
logging data, pore pressure gradient, and unconfined compressive strength. In comparative
analyses, error metrics such as Mean Absolute Error (MAE) and Root Mean Square Error
(RMSE) are compared among the different models for each of the 7 wells. Statistical significance
analysis is performed with the Bourgoyne & Young model to understand more significant effects
on ROP. The interpretability of traditional models, along with hyperparameter tuning, is adopted
to employ machine learning models with more meaningful inputs and greater predictive capacity.
Next, two strategies found in the literature for using predictive models for ROP in real-time
optimization are compared: models trained with offset well data or with the well’s own data,
simulating a gradual data acquisition process (continuous learning). The results indicate better
performance of machine learning models compared to traditional models. The RF model shows
overall better performance in comparative analyses, with smaller errors and lower computational
cost. The relevance of torque and the inclusion of formation data (Delta-T compressional) in
machine learning models is identified. Also, continuous learning strategy can achieve lower
errors, although both strategies are capable of generating appropriate predictions.

The Northeast is the third largest region in Brazil in terms of construction and demolition waste generation, according to ABRELPE (2021). With increasing urbanization, there is a growing trend in waste generation, which has led the United Nations to highlight solid waste as one of the main current problems. Therefore, finding an appropriate destination for this waste strengthens environmental sustainability and the development of sustainable cities. In this context, a sustainable opportunity arises for the destination of C&D waste, such as the production of new construction materials, for example, recycled blocks. This research evaluates the technical feasibility of using mixed recycled demolition aggregates in the production of blocks, seeking to reinsert them into the construction chain and generate new sustainable materials. To this end, the study was carried out using waste provided by the company Braskem. The recycled aggregates were collected, processed, underwent an impurity removal process and characterization procedures. After these steps, a unifactorial experimental design was adopted, with granulometry as a factor, using the following aggregate combinations: 100% natural, recycled fine and natural coarse and natural fine and recycled coarse, in order to determine the influence of these combinations on the axial compressive strength of the blocks. For the dosage study, the optimum composition was defined, by means of the granular skeleton, in addition to the compressive rheometry technique being performed to determine the optimum moisture content. In the block production stage, a new dosage study was carried out, with the objective of determining the optimum moisture content for the blocks. The results indicated that the blocks produced with recycled sand and natural crushed stone were the only ones that presented characteristic strength for structural blocks. In addition, statistical tests proved, at a significance level of 5%, that blocks with recycled sand and natural crushed stone presented significant differences in their average strength when compared to the other sets of blocks (natural and combination with natural sand and recycled crushed stone).

Topology optimization stands out as an important technique for analysis and design of projects, seeking to maximize structural performance through efficient material distribution, considering boundary conditions and problem constraints. However, manufacturing these structures through traditional methods are not always feasible, due to the complex and unconventional configuration of the geometry. Thus, additive manufacturing (AM) emerges as an innovative solution, allowing the production of objects layer by layer, without the need for molds. However, projection angles greater than 45º in the geometry may require support material to avoid failures and deformations during printing, increasing material costs and manufacturing time. Therefore, this study aims to evaluate the use of topological optimization in conjunction with the support structure filter for additive manufacturing, highlighting the potential benefits in terms of material and production time savings. In this sense, the AMfilter, developed by Langelaar (2016), is used together with the 88-line educational code developed by Andreassen et al. (2010), whose performance is verified through simulations of printing the optimized models. The AMfilter seeks to eliminate the need for support structure based on geometric restriction, removing protruding surfaces that exceed the maximum allowed angle, making the geometry directly printable without support structures. The results indicate some limitations of the AMfilter, such as mesh dependence and gradual increase in intermediate density in the printing direction. In addition, the solutions resulting from topological optimization together with the AMfilter did not completely eliminate the support structures. Despite the modifications of the topologies in relation to the reference model, these were not sufficient to achieve the expected result. However, a reduction in the estimated time for support printing and consequently in material consumption is observed compared to the reference model. This reduction was less significant in simulations with a 45º angle for support generation, but in simulations with higher angles of 53º and 60º, it reached an average reduction of 25.06% and 37.02%, respectively, among the examples discussed

This work presents a novel structural health monitoring (SHM) framework for damage identification in linear steel structural elements (compressed bars and beams), in the context of dynamical systems. The framework integrates a hybrid physics-based and data-driven model (that can result in a generalizable, accurate, interpretable and computationally efficient model) and supervised machine learning methods, to construct a digital twin. The governing equations of motion of the healthy structure, discovered by hybrid modeling, are used to simulate the response of the system with damage at different locations and intensities. From these simulations a dataset is constructed to train the machine learning classifiers, considering the beam scenarios with damage and undamaged. The constructed digital twin relates the inputs of the physical twin to specific damage scenarios to quickly warn if there is damage, where it is located and what is its severity, supporting engineering decisions. The DT framework was evaluated in different application configurations, demonstrating the potential for significant contribution to the establishment of SHM systems. Support Vector Machine was the best performing classifier, with an precision of 93.97% for the cantilever bar and 80.33% for the fixed-end bar. The damage to the cantilever and fixed-end bars, considering axial vibration, was identified and robust for certain noise levels. However, it was observed that damage identification was more difficult in hyperstatic structures. The identification of damage in beams, considering transverse vibration, proved promising, with an accuracy of 84.31% for the Support Vector Machine classifier using the displacement feature and 99.98% for the Quadratic Discriminant Analysis classifier using the displacement and acceleration features. 

The casing system is essential to guarantee integrity on oil wells. To ensure a correct casing design, equations and methodologies are suggested by international standards for resistances and loads that should be verified if the casing system designed is adequate to the well throughout its life. One example of such standard is API/TR 5C3, which on its 2008 revision added suggestions for equations and methodologies to use reliability techniques on casing design, going even as far as supplying statistic characterization of various casing tubulars using a database made of different manufacturers from along a few decades. Even so, the use of these reliability techniques and tools are still restricted to specific analyses and are not used as a routine by casing designers. With that in mind, this work aims to study various load cases on a number of casings generally used on oil wells, comparing the results obtained using the standard techniques (Safety Factors - SF) and reliability (Failure Probability - FP). The loads will be equal to the casing resistance considering the Serviceability Limit State (SLS), which is still the most used by casing designers, and would lead to a failure limit (SF = 1.0), with the objective of making a comparison between the results of the techniques. At the end of this work, it is expected to have a better understanding of how much of a risk an FP number actually means, making it easier to add the reliability analysis on regular casing design.

This work proposes a methodology for estimating the residual strength of tubes damaged by wear and/or corrosion in oil wells, involving geometric inspection of the elements and their numerical modeling in a probabilistic approach. The objective is to provide a robust assessment of the structural integrity of tubular components in a high-complexity and high-risk environment, such as the Brazilian pre-salt region. Casing and production/injection columns are importante safety barrier elements, playing crucial structural roles and isolating the well and formation to prevent unexpected fluid flow.Wear and corrosion in these tubular components occur during diferente operations throughout their lifecycle, and they are conservatively considered in the design phase to avoid integrity loss situations. However, there is a lot of uncertainty in these predictions. Modern inspection equipment available in the market, such as ultrasonic and electromagnetic logging tools, have allowed for the assessment of the actual state of in-service tubes. Tube radius, thickness, and mass loss are the parameters measured along the well columns. Proper interpretation of this data allows for the identification of tube damage and quantification of the corresponding severities. A methodology is proposed for characterizing the cross-sectional geometry of tubes based on inspection data, in the presence of measurement uncertainties. Bidimensional nonlinear Finite Element Method models are used to estimate the residual colapse strength of the tubes. Additionally, a probabilistic analysis of the residual geometry of damaged tubes is presented, considering random variables related to damage configuration parameters such as maximum depth and position. The results obtained lead to the conclusion that the initial geometric configuration of the damaged tube can result in significant variations in residual strengths for different damage parameters, including depth, radius, position, and distribution. It is worth noting that the analytical models found in the literature only partially consider these factors, not in their entirety. A case study is developed using real ultrasound inspection data to demonstrate the application of the proposed methodology, comparing the results with reference values.

Directional drilling techniques are applicable in fields, such as petroleum, buildings and the mineral extraction industry. Compared to vertical drilling, directional drilling is much more complex. The curvature of the well axis passing through the stratified rock mass causes the conditions around its cross section to be strongly anisotropic. Not infrequently, the same rock material in each layer exhibits anisotropic properties. Proper determination of the stress, strain, and displacement states around the borehole is critical in the design of directional boreholes. Numerical analysis tools that take into account the rock mass structure and rock mechanical properties along the well path are used for this purpose. This paper aims to numerically evaluate the structural stability of rock masses around a directional well using the Finite Element Method. The calculations are conducted with linear elastic and viscoelastic constitutive models, used in the rock strata models. Based on the results, the influence of rock behavior on the stability of the directional well is discussed.

Many structures are under the risk of impact with natural hazards such as mudslides,
avalanches, and submarine landslides. In the oil and gas industry, as example, the assessment
of the positioning of pipelines must consider the risk of impact with submarine landslides, as
an impact with such phenomena could cause leakage that would lead to severe economic
and socioenvironmental losses. Therefore, a study of the impact of natural hazards upon
structures is necessary. That study must begin from the resistance parameters associated
with the impact events, among which impact pressure stands out. That parameter is difficult
to measure in practice, however, as experimental studies with centrifuges are hard to carry
out, and field measuring is, in most cases, impracticable. Besides, the utilization of analytical
solutions is overly restrictive in the presence of physical and geometric nonlinearities. Thus,
numerical simulations come as a viable alternative, as they expand from basic physics
principles and are not limited by the same apparatus and space restrictions as the laboratory
and field measurements. The expanding processing capabilities of modern computers is
another argument in their favor. Among numerical methods, the material point method
(MPM) stands out, as it has the capacity to simulate large deformation and displacement,
which are common in impact events. To utilize the MPM, an investigation of the numerical
procedure for the computation of the impact pressure is performed, as that procedure is not
shared in the literature, although used by many authors. Limitations of possible solutions
for this problem are explored in this manuscript, as well as suggestions of alternative ways
of computing the impact pressure parameter. The analyses are performed in the context of
classic problems, such as the study of cone penetration (T-bar), and the impact of submarine
landslides upon subsea infrastructure via synthetic models.

More and more, inspiration is sought from nature to solve complex problems in modern society. Whether observing the morphological characteristics of animals and plants or even the behavior of living beings in the environment they live. The naturalist Charles Darwin studied this behavior in depth and proposed a theory that explains how life became what it is today, the Theory of Natural Selection. This theory helped solve problems in the biological sciences, social sciences, and engineering. The theory of natural selection of the directional type inspires the topological optimization method proposed in this study. The Progressive Directional Selection method seeks to optimize a structure by selecting the parts that contribute the most to support the mechanical loads and eliminating the parts that contribute the least in different stages of removal. Numerical applications of PDS (Progressive Directional Selection) were performed in two-dimensional truss structures, starting from a ground structure type structure. The initial design domain is formed by a grid of points interconnected by two-dimensional truss elements. The matrix analysis of plane trusses and the direct stiffness method are employed to analyze the plane truss in the linear elastic regime. The selected optimal topologies are structurally stable, efficient, and similar to those obtained by other topological optimization techniques found in the literature. The results demonstrate that this method can be employed in the optimized design of two-dimensional trusses through the topological optimization of ground structure type structure.

The concrete in its macro scale can be considered a heterogeneous material, even being tested as such, however, when reducing its scale, it has phases inherent to each level. Modeling concrete has always been a great challenge, due to all the complexity of this cementitious material, despite that proposals constantly arise, such as homogenization by micromechanics. The mean-fields micromechanics has in its basic foundation the homogenization of two-phase composites, composed of inclusions immersed in an infinite matrix. In fact, on a macroscopic scale, concrete can be understood as being composed simply by inclusions (gravel) immersed
in a matrix (paste), being often modeled in this macro configuration. However, it is known that there are more phases that need to be evaluated to obtain a result closer to laboratory tests, as an example can be cited in the interfacial transition zone. In addition to modeling, it can be said that the construction industry seeks to maximize the properties of concrete, being an initial idea to seek the packaging of particulate systems (inclusions) minimizing the dispersed phase (matrix). In view of this open field, the present work proposes to study the coupling of optimization models of particulate systems to composite homogenization models, aiming at maximizing the mechanical properties of concrete using multiscale modeling. As a subsidy to this problem, an object-oriented framework is built to carry out the aforementioned modeling. The results obtained with the coupling between the techniques confirm the maximization of the mechanical properties when optimizing the particulate systems.

Ground-supported cylindrical concrete tanks are largely used with many purposes, such as storing of liquids (water and wastewater, for example) and grains, or even used in projects that have bolder architectural appeal. These structures are often composed of thin walls and are commonly explored worldwide due to their versatility and structural performance. Despite many computational techniques developed on the study of reservoirs, these structures draw attention to the high number of recovery and structural reinforcement interventions that are still commonly done. In some cases, restauration processes are expensive and must be performed still early in structure’s lifespan. Not considering indirect loads is a common reason to a lower structural performance, since these neglected actions at design level may cause internal stresses-strains that have the potential to turn the structural performance impracticable. In reinforced concrete tanks, some indirect actions must be considered in order to obtain accurate structural performance, such as concrete shrinkage and thermal gradient effects, in the case of hot liquid storing. Therefore, this work aims to study the mechanical behavior of reinforced concrete reservoirs subjected to indirect actions caused by shrinkage and thermal gradient effects through classical analytical theories of axisymmetric structures. The results show that indirect loads generate stresses of great magnitudes in shell elements subjected to elastic analysis. Furthermore, variables such as humidity may increase strains caused by shrinkage, implying in loads that overcome concrete’s traction resistance, which favors the formation of cracks. The examined examples also show that stresses generated by thermal gradient effects are even higher than the other actions, leading to impractical structural performance when they are not considered in the design phase of the structure.

Man's search for change linked progress to new ways of building and ways of conceiving structures, their materials, and methods. Faced with so many changes, concrete no longer presents itself as a simple mixture defined by the composition of aggregates, cement, and water, being today susceptible to the incorporation of new ones and the replacement of these basic materials by fibers, residues, and additives of various types. The incorporation of steel fibers, which resulted in the use of Steel Fiber Reinforced Concrete (SFRC) has shown great benefits to the conventional material in the world scenario, acting mainly in the post-cracking stage and mobilizing a portion of tensile strength triggered by the need of durability guarantee. In this context, the optimization of the use of short steel fibers in an element under bending, through a layered fiber grading, resulting in a functionally graded element (FGM), demonstrates its relevance. Fibers concentrated in higher percentages are located in the strip most stressed to traction and on the opposite compressed surface a null amount of these reinforcements is used. In this work, the elements have a cross-section graduated in 3 layers, for which the phase of determining the percentages of each fiber layer is highlighted, using the pre-existing results of SFRC beams in the three-point bending test (EN – 14651/2017) measured in previous works and comparing the height and area of cracks found in tests that correlate digital images and with displacement transducer measurements. It was possible to evaluate the influence of concrete casting through induction techniques and surface analysis. The results provide an effective overview of the preferential orientation of the fibers found in this configuration, 68° in relation to the oriented axis of the load application direction and 49° in relation to the plane perpendicular to the load application, confirmation of the initially desired proportion and expressive gains in post-peak crack containment, about 34.15%, when compared to beams in traditional molding, consequently, more effectively influencing the post-cracking resistance, bending and economy of steel fibers in the less tensioned regions of beams and plates molded in SFRC, like beams and slabs under bending.

The finite-volume theory is an equilibrium-based approach and has been successfully employed in solid mechanics analysis due to the equilibrium equations' local satisfaction and the imposition of continuity conditions in a surface-averaged sense through the subvolume interfaces. Previous investigations include stress and displacement fields convergence and computational cost, showing the approach's efficiency, especially in heterogeneous materials and structures. However, those investigations did not include an energy analysis, which is especially important in compliance minimization problems. As the finite element method, energy-based approaches impose energy balance, which guarantees a monotonic energy convergence. The first idea of this contribution is to address a numerical investigation about the main mechanical energy aspects involving the generalized finite-volume theory for continuum elastic structures in quasi-static analyzes. The obtained results are verified with analytical and finite element-based analyzes, showing a monotonic energy convergence for the three versions of the finite-volume theory and the energy balance's satisfaction for the higher-order versions when a sufficiently refined mesh is employed. Topology optimization is a well-suited method to establish the best material distribution inside an analysis domain. It is common to observe some numerical instabilities in its gradient-based version, such as the checkerboard pattern, mesh dependence, and local minima. This research demonstrates the generalized finite-volume theory's checkerboard-free property by performing topology optimization algorithms without filtering techniques. The formation of checkerboard regions is associated with the finite element method's displacement field assumptions, where the equilibrium and continuity conditions are satisfied through the element nodes. On the other hand, the generalized finite-volume theory satisfies the continuity conditions between common faces of adjacent subvolumes, which is more likely from the continuum mechanics point of view. The topology optimization algorithms based on the generalized finite-volume theory are performed using a mesh independent filter that regularizes the subvolume sensitivities, providing optimum topologies that avoid the mesh dependence and length scale issues. The solid isotropic material with penalization (SIMP) approach is employed to avoid discrete optimization problems. The proposed optimization problem has shown to be efficient, avoiding numerical instabilities, such as checkerboard pattern, mesh dependence, and length scale issues.

Apresenta-se neste trabalho o emprego de formulações do método dos elementos de contorno (MEC) em problemas de fratura e também na análise mecano-probabilística de sólidos fraturados. O MEC é um método adequado para resolução desses tipos de problemas, uma vez que a ausência de malha de domínio resulta em uma modelagem mais eficiente de regiões com alta concentração de tensões. Além disso, a redução de dimensionalidade da malha diminui fortemente os dados de entrada e também o trabalho de remeshing no processo de propagação de fissuras. Com relação a formulação não linear do MEC, será utilizada uma alternativa a formulação clássica dual, com a introdução de um campo de tensões iniciais para representação da zona coesiva e formulado a partir do conceito de dipolos. Esta formulação é particularmente interessante por conseguir representar matematicamente a presença da Zona de Processos Inelásticos (ZPI) em apenas três equações algébricas (equações relacionadas à correção de tensões) por ponto fonte situado no caminho da fissura. Em contraste, a formulação dual requer quatro equações algébricas (deslocamentos e forças) por ponto fonte. Quanto aos efeitos pertinentes ao sistema não linear, serão utilizados dois algoritmos distintos de resolução iterativa, Operador Constante (OC) e Operador Tangente (OT). No acoplamento com modelos da confiabilidade, apenas o OT será utilizado por apresentar respostas satisfatórias em um número menor de iterações. Com relação à análise probabilística, duas abordagens são consideradas, a primeira refere-se ao acoplamento direto entre o modelo numérico e um método de transformação (HLRF/FORM), já a segunda consiste no acoplamento mais simples com o emprego do Método de Monte Carlo. Os parâmetros de fraturamento são tratados como aleatórios e o Método de Confiabilidade de Primeira Ordem (FORM) é empregado para avaliação de fatores de importância bem como probabilidade de falha. Por fim, a técnica de Amostragem inteligente por Hipercubo Latino é também empregada, por apresentar melhores taxas de convergência. Exemplos são apresentados para validar o uso da formulação de dipolos na análise de propagação de fissuras, à luz da confiabilidade estrutural.

Os concretos reforçados com fibras (CRF) apresentam uma menor propagação de fissuras e, consequentemente, promovem para o compósito um acréscimo de tenacidade e resistência residual. Apesar disso, o aumento dessa capacidade só acontece se o concreto for dosado e aplicado de maneira adequada e, para isso, existem códigos de referência que estabelecem aspectos de controle tecnológico e de dimensionamento para o uso do CRF. No entanto, nesses documentos, ao que refere-se a um dos aspectos de dimensionamento, a parcela de força resultante resistente das fibras é descrita para algumas aplicações específicas, onde faz-se a consideração de que a carga máxima corresponde a carga de fissuração, o que pode não se aplicar para concretos que possuam uma orientação preferencial das fibras. Diante disso, sabendo da significativa mudança que a orientação das fibras pode proporcionar, e a fim de determinar a força resultante resistente das fibras na parte tracionada de um concreto fibroso fluido, apresenta-se um estudo relacionado a proposição de um modelo de cálculo de CRF fundamentado nessa definição. O estabelecimento desse modelo foi obtido com base na teoria de flexão em vigas, a partir do ensaio de flexão a três pontos normatizado pela EN 14651 (2007), onde foram utilizadas uma amostra de concreto reforçado com fibras de aço (CRFA) e outra amostragem produzida com fibras poliméricas (CRFP). De acordo com o estudo realizado, verificou-se que o valor de carga máxima não correspondeu ao valor de carga de fissuração para nenhuma viga em análise e, de modo geral, percebeu-se que as cargas são estatisticamente diferentes entre si. Com base nessa diferença, definiu-se analiticamente o posicionamento da linha neutra da estrutura e determinou-se, a partir de equações de equilíbrio, um modelo de cálculo referente à força resultante resistente das fibras na parte tracionada do concreto. A partir disso, os valores obtidos por meio do modelo proposto foram comparados com os resultados determinados em conformidade com o FIB Model Code 2010 (2013) e de acordo com o ACI 544.8R (2016), onde verificou-se que os resultados apresentaram variações. A fim de investigar essas dispersões, fez-se uma análise dos parâmetros de sensibilidade das equações e conclui-se que o modelo de cálculo proposto não apresenta nenhum parâmetro de influência no contexto analisado, o que evidenciou que a equação analítica desenvolvida neste trabalho pode ser preliminarmente validada para o dimensionamento de elementos estruturais de CRF.

O objetivo deste trabalho é automatizar o processo de análise, dimensionamento e detalhamento do sistema estrutural de uma parede de concreto moldada in loco. A automatização é realizada com base em um ambiente computacional, elaborado a partir do desenvolvimento e customização de módulos computacionais. O sistema estrutural de parede de concreto pode ser projetado através de diferentes metodologias, entretanto, a solução utilizando métodos numéricos proporciona uma série de pontos positivos que colaboram para uma melhor compreensão dos fenômenos com um bom balanceamento entre tempo, custo e qualidade. Nesse contexto, o presente trabalho apresenta o desenvolvimento de um estudo voltado as principais premissas do projeto estrutural de parede de concreto moldada in loco, com o intuito de promover a criação de um ambiente computacional integrado. O ambiente é elaborado a partir da customização da interface do software comercial ABAQUS/CAE®, integrando módulos computacionais já existentes que realizam a modelagem e a análise estrutural via Método dos Elementos Finitos com outros módulos que incorporam algoritmos utilizados nas fases de dimensionamento e detalhamento das paredes, com base nas premissas da NBR 16055 (2012). Utilizou-se como estudo de caso um projeto de uma edificação de parede de concreto do programa “Minha Casa Minha Vida”. A ideia é que o estudo realizado neste trabalho se torne útil ao meio técnico-científico por desenvolver um ambiente computacional que permite a realização automatizada de um projeto estrutural de uma parede de concreto moldada in loco.

In the drilling stage of oil and gas wells, the drilstring can come into contact with the casing
strings, generating lateral forces that, associated to the rotation of the drillstring, cause the
removal of material from the inner wall of the tubulars. High casing wear values induce a
reduction in mechanical strength of casing string and may compromise the well integrity. This
work deals to the implementation and comparative analysis between methodologies for casing
wear evaluation, comprising models for trajectory planning, lateral forces calculation and wear
volume estimate. Torque and drag models are employed to quantify the lateral forces, using the
soft-string and stiff-string approaches. The latter differs from the soft-string model by taking
into account effects related to the drillstring stiffness, besides inserting the contact angle into the
formulation. The stiff-string model depends on directional parameters as torsion and curvature,
for which a model based on cubic splines is applied. The spline-based model is then compared
with the minimum curvature method, widely employed by industry. The results show that the
model based on splines provides smooth curvature and non-zero torsion. The influence of spacing
between the survey stations on the accuracy of the trajectory models is also analyzed. Finally,
a complete case study is developed, allowing to conclude that the use of stiff-string model can
reduce the predicted wear on the casing string, due to its distribution as a function of the contact
angle.

Casing systems for oil and gas wells consist of tubular elements installed along the depth,
providing stability and tightness, and must meet the strict premises of structural integrity,
especially in the case of offshore scenarios. Given this, some events may expose the casing to
high differentials. pressure, leading the tubular to failure under external pressure, called collapse.
Imperfections associated with casing tubular manufacturing processes, such as eccentricity,
ovality of the cross section, and the residual stress of the steel, can have a significant influence
on the failure mechanism by collapse. In addition to these, there is the presence of wear in
wells performed, caused predominantly by the contact of the drilling column with the inner wall
of the casing. In many cases, these imperfections can lead to a considerable reduction in the
collapse strength, especially in thin-walled tubes, whose failure mechanism is associated with
geometric instability caused by high transverse slenderness. Robust section tubes tend to fail
under stress levels near to the yield limit or material tensile strength limit. This work presents a
numerical analysis of the collapse strength of imperfect and internally worn tubulars, admitting
the deformation plane state, in a physically and geometrically nonlinear regime. The finite
element method is used in the analysis and verification of the collapse pressure of the tubes, as
used by ABAQUS® software. The mechanical behavior of steel is described by the constitutive
elastoplastic model with nonlinear hardening provided by the ASME BPVC (2015). Evaluation
of finite element models is performed based on the responses obtained by the formulations and
experimental results proposed by Clinedinst et al. (1939), Klever e Tamano (2006), and Moreira
Junior (2012), for perfect tubes or with manufacturing and wear imperfections. The consideration
of internal wear is made by removing material from the section in groove wear zones or by data
obtained from profiling, based on real measurements of the internal wall of the casing. Parametric
studies are presented to assess the influence of slenderness, wear, and imperfection parameters
on the collapse strength. From the results obtained, it appears that the presence of manufacturing
imperfections, depending on their levels, promotes considerable reduction of collapse strength,
the most pronounced of which being ovality. Regarding the worn specimens, it is noted the
influence of parameters such as wear depth, diameter of the tool joint that produces the groove,
and their angular positions. In the case of profiled tubulars, it is verified that in addition to the
depth of wear, its extension along the inner wall can imply a considerable decrease in collapse
pressure.