Análise comparativa do desempenho mecânico de tipologias de treliças planas de madeira para classes de resistência distintas via algoritmo de otimização

A madeira é uma escolha viável para sistemas construtivos, dadas as suas propriedades mecânicas adequadas para aplicações estruturais. Além disso, a madeira é uma fonte renovável, tornando-se ainda mais atraente para uso em diversas aplicações para fim estrutural. Visando compreender o desempenho mecânico de duas treliças planas em diferentes condições de carregamento, foi realizado um estudo comparativo do desempenho mecânico de duas tipologias de treliças - a tipologia Fan modificada e Howe - considerando vãos de 6, 9, 12 e 15 m. A fim de avaliar a influência do material adotado no processo construtivo das treliças, foram caracterizadas as espécies Cambará-rosa, Cupiúba, Angelim-pedra, Garapa e Jatobá, identificadas como espécies ID 01, ID 02, ID 03, ID 04 e ID 05, respectivamente. O estudo baseou-se na ABNT NBR 7190 (2022a) para dimensionamento da treliça, além de aplicar o método de análise matricial para determinação dos esforços internos, deslocamentos nodais e um algoritmo de otimização de inteligência de enxame para minimizar o peso da estrutura. A caracterização das espécies resultou nas classes de resistência D20, D30, D40, D60 e D60, para as espécies denominadas ID 01, ID 02, ID 03, ID 04 e ID 05, respectivamente. Os resultados do processo de otimização indicam que a tipologia Howe apresentou resultados menores para a função objetivo (peso da estrutura) em relação à treliça Fan modificada. Além disso, quando analisada a distribuição dos esforços normais na treliça, observou-se uma correlação com a resistência característica na compressão e na tração das espécies, onde as treliças com espécies de menor resistência mecânica são mais solicitadas, enquanto as treliças com espécies de maior resistência mecânica são menos exigidas. Nesse sentido, é possível notar que a tipologia de treliça Howe apresenta uma amplitude maior em relação à tipologia de treliça Fan Modificada, na maioria das condições adotadas para as restrições do ELU. Ao analisar as restrições associadas à flecha na condição imediata, observou-se que se obtiveram valores próximos a zero, que indica que restrição desta natureza limitaram o processo de otimização. Em síntese, a madeira mostrou-se uma opção sustentável e viável para construções de treliças, e que diferentes espécies de madeira possuem propriedades mecânicas distintas que devem ser consideradas no dimensionamento da estrutura. Os métodos de análise matricial e algoritmos de otimização de inteligência de enxame permitiram avaliar os esforços internos e deslocamentos nodais nas treliças, além de minimizar o peso da estrutura. Além disso, é importante considerar todas as restrições no dimensionamento de estruturas de madeira.Wood is a viable choice for building systems, given its mechanical properties suitable for structural applications. In addition, wood is a renewable source, making it even more attractive for use in various applications for structural purposes. Aiming to understand the mechanical performance of two plane trusses under different loading conditions, a comparative study of the mechanical performance of two truss typologies - the modified Fan and Howe typologies - considering spans of 6, 9, 12 and 15 m, was carried out. In order to evaluate the influence of the material adopted in the construction process of the trusses, the species Cambará-rosa, Cupiúba, Angelim-pedra, Garapa and Jatobá, identified as species ID 01, ID 02, ID 03, ID 04 and ID 05, respectively, were characterized. The study was based on ABNT NBR 7190 (2022a) for truss dimensioning, besides applying the matrix analysis method for determining internal forces, nodal displacements and a swarm intelligence optimization algorithm to minimize the structure weight. The species characterization resulted in strength classes D20, D30, D40, D60, and D60, for the species named ID 01, ID 02, ID 03, ID 04, and ID 05, respectively. The results of the optimization process indicate that the Howe typology presented lower results for the objective function (weight of structure) in relation to the modified Fan truss. Furthermore, when the distribution of normal forces in the truss was analyzed, a correlation was observed with the characteristic strength in compression and tensile of the species, where the trusses with species of lower mechanical strength are more requested, while the trusses with species of higher mechanical strength are less requested. In this sense, it is possible to note that the Howe truss typology presents a larger amplitude in relation to the Modified Fan truss typology, in most of the conditions adopted for the ULS constraints. When analyzing the constraints associated with a deflection in the immediate condition, it was observed that values close to zero were obtained, which indicates that constraints of this nature limited the optimization process. In summary, wood turned out to be a sustainable and viable option for truss constructions, and that different wood species have distinct mechanical properties that should be considered when designing the structure. The matrix analysis methods and swarm intelligence optimization algorithms allowed the evaluation of internal efforts and nodal displacements in the trusses, as well as minimizing the weight of the structure. In addition, it is important to consider all constraints when dimensioning timber structures.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Uma revisão sobre os aspectos de projeto de peças pré-fabricadas / A review of the design aspects of prefabricated parts

Dada a ampla aplicabilidade do concreto pré-moldado nos diversos ramos da engenharia civil, e em consonância com o ideal de eficiência da sociedade moderna - produzir melhores resultados empregando menos  material - o presente trabalho visa rever as fases do projeto de peças pré-fabricadas e suas peculiaridades  a partir do processo produtivo, no transporte, armazenamento e montagem, focando nas fases transitórias na qual será submetido, situações essas que não ocorrem no concreto moldado in loco. Para tanto, será apresentado de forma geral as situações transitórias aliadas as verificações de estado limite último e de serviço, mostrando e detalhando as condições de içamento para cada tipo de peça.  A partir do exposto, é possível concluir que o concreto pré-moldado é a solução para diversos problemas atuais e possui espaço no mercado, principalmente brasileiro, requerendo assim um estudo aprofundado por parte dos novos engenheiros

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Utilization of computational swarm intelligence for optimum design of prefabricated and strengthened headslabs

O presente trabalho tem como objetivo a aplicação de técnicas de otimização como uma etapa inicial para o dimensionamento de lajes alveolares pré-fabricadas e protendidas com auxílio do Algoritmo Colônia de Vagalumes (ACV), considerando o cálculo médio das perdas de protensão imediatas e progressivas. As variáveis de projeto para a otimização da laje alveolar pré-fabricada e protendida são o diâmetro dos alvéolos, a área da seção transversal do cabo e a altura da laje. São consideradas também as condições de Estado Limite de Serviço e Estado Limite Último para os quais a peça está submetida como esforços de flexão, esforço cortante, normal, limitações construtivas e condições de falha. São avaliadas 37 restrições de projeto, objetivando atender a normativa vigente e a segurança estrutural para o dimensionamento da peça, utilizando a técnica de otimização como um selecionador inicial das variáveis de projeto do problema estudado.The aim of this work is to apply optimization techniques as an initial step in the design of precast and prestressed hollow core slabs using the Firefly Algorithm (FA), considering the average calculation of immediate and progressive prestressing losses. The design variables for optimizing the precast and prestressed hollow core slab are the diameter of the wells, the cross-sectional area of the cable and the height of the slab. Also considered are the Serviceability Limit State and Ultimate Limit State conditions to which the part is subjected, such as bending stresses, shear stresses, normal stresses, construction limitations and failure conditions. Thirty-seven design constraints are evaluated, with the aim of complying with current regulations and structural safety for the design of the part, using the optimization technique as an initial selector of the design variables of the problem studied

Reliability analysis of reinforced concrete frames subjected to post-construction settlements

Abstract Most papers in the literature address reliability analysis of isolated elements, like beams and columns. However, symmetry and regularity are often exploited in the construction of regular RC frames, resulting in the same or similar designs for all columns of a floor or all beams of a building. This leads to significant differences in member reliability, due to different axial load to bending moment ratios, in different parts of the structure. Moreover, load effects increase, and symmetry is lost under individual support settlements. In this scenario, reliability analyses are performed, for an intact 4-floors and 3-spans RC frame; and considering different settlement conditions. Monte Carlo simulation is performed, considering uncertainties in dead and live loading, and steel and concrete strengths. The results show that a settlement of 10 mm, corresponding to an angular distortion of 1/500, reduced the average reliability of the frame by only 14%, just the same, it reduced the reliability index of several cross-sections of the beams to up to 2.40, value lower than that recommended in the Model Code 2010. It is concluded that the methodology used in this work presents an important tool for the analysis of events not foreseen in the design, supporting the decision making about the need for intervention in the structures

Influence of the Harvesting Region on Batch Homogeneity of Ipe Wood (Tabebuia sp.) Based on Its Physical and Mechanical Properties

This paper aims to evaluate the hypothesis regarding the homogeneity of wood batches, as provided in the Brazilian standard for wooden structures ABNT NBR 7190 through an experimental study simulating the condition of a sawmill where the control of the harvest region, location of the sample in the trunk, edaphoclimatic condition, relief, and vegetation are variables that cannot be controlled. An experimental study was performed on 15 properties (3 physical and 12 mechanical) of Ipe (Tabebuia sp.) wood. Batches from three harvesting regions (Mucajaí [RR-A], Bonfim [RR-B], and Cláudia [MT]) were used to verify the existence of significant differences between the properties of the three areas. The properties were obtained following the test methods established in ABNT NBR 7190-3, with 540 specimens being manufactured and characterized, prior to being submitted to a statistical analysis, where ANOVA was applied with the Anderson–Darling normality test, the homogeneity of variance of multiple comparisons, and the Tukey test. Statistical analysis indicated that the wood harvesting regions showed significant differences in six (40%) and non-significant differences in nine (60%) of the fifteen properties evaluated. Among the properties evaluated, the compressive strength parallel to the grain (fc0) showed significant differences. This property is used to classify the wood strength class according to the Brazilian standard ABNT NBR 7190-1. The batches from the harvesting regions RR-A, RR-B, and MT were classified using the strength classes D60, D50, and D50, respectively. These results directly impact the consideration of the homogeneity of the batches, considering that the sawmills receive samples from different regions. For future research, a numerical method can be applied to consider the influence of the wood harvesting area

Comparative Analysis of the Mechanical Performance of Timber Flat Truss Typologies for Different Strength Classes via Optimization Algorithm

This study aimed to compare the mechanical performance of two truss typologies, the modified Fan and Howe trusses, using five different wood species: Cambará-rosa, Cupiúba, Angelimpedra, Garapa, and Jatobá. The spans considered were 6, 9, 12, and 15 m, and the optimization algorithm used was a swarm intelligence algorithm to minimize the structure weight. The study found that wood is a sustainable and viable option for truss constructions, with different wood species having distinct mechanical properties that must be considered when designing the structure. The Howe truss typology presented lower results for the objective function in comparison with the modified Fan truss. The distribution of normal forces in the truss correlated with the characteristic strength in compression and tensile of the species. The Howe truss typology presented a larger amplitude in relation to the modified Fan truss typology in most of the conditions adopted for the Ultimate Limit State constraints. Constraints associated with deflection in the immediate condition were observed to limit the optimization process. The study used the matrix analysis method to evaluate internal efforts and nodal displacements in the trusses. In summary, this study demonstrates the importance of considering all constraints when dimensioning timber structures and the benefits of using different wood species for sustainable construction