Evaluation of the inelastic behavior of steel columns and frames subjected to minor‐axis bending

Este trabalho tem como objetivo avaliar o comportamento inelástico de sistemas estruturais metálicos submetidos à flexão em torno do eixo de menor inércia. Consideram‐se seções transversais compactas do tipo I. Nessas seções, a flexão em torno do eixo mais fraco apresenta benefícios importantes como a capacidade de desenvolver toda resistência plástica sem ocorrência de flambagem lateral por torção. Adota‐se uma formulação de elementos finitos reticulados planos, na qual o processo de plastificação do aço é acompanhado através do método da rótula plástica refinado. Nesse método, os efeitos decorrentes do escoamento do material são capturados através de um parâmetro que reduz a rigidez do membro estrutural em função do desenvolvimento de regiões plásticas. Emprega‐se ainda nesse método o módulo tangente para considerar a degradação da rigidez em função das forças internas. Efeitos de segunda ordem, tensões residuais e imperfeições geométricas também são considerados nas análises. Como critério para definir o estado limite último de resistência da seção transversal adotam‐se superfícies de plastificação que descrevem a interação entre esforço normal e momento fletor. Para solução das equações não lineares de equilíbrio estrutural usa‐se o método de Newton‐Raphson acoplado a estratégias de continuação. Colunas isoladas e pórticos planos são analisados e os resultados obtidos são comparados aos encontrados por outros pesquisadores. Essas comparações permitem concluir que as técnicas usadas neste trabalho são eficazes e necessárias para uma melhor previsão do comportamento das estruturas com membros submetidos à flexão em torno do eixo de menor inércia.This work presents an evaluation of the inelastic behavior of steel structures subjected to minor‐axis bending. Profiles type I and compact cross‐sections are considered. In these sections, the bent about weak axis presents important benefits, such as the ability to develop all of their plastic resistance without the occurrence of lateral torsional buckling. A nonlinear beam‐column element formulation is adopted, in which the steel yielding process is accounted by the refined plastic‐hinge method. In this method the effects of material yielding are captured by a parameter that reduces the structural member stiffness with the development of cross‐section plastic regions. The tangent modulus approach is used to consider the stiffness degradation caused by the increase in internal forces. Second–order effects, residual stresses and geometric imperfections are also considered in analysis. To define the cross‐section strength ultimate limit state, the study adopts strength surfaces that describe the interaction between internal forces — axial force and bending moment. The nonlinear equations at the structural system level are solved using the Newton‐Raphson iterative strategy coupled with path‐following methods. Isolated steel columns and portal frames are analyzed, and the results obtained are compared to those of other investigators. The comparison shows that the numerical methodology presented in this work is effective and can be used for predicting the behavior of steel structures with members under minor‐axis bending.Peer Reviewe

Determination of structural composite elements strength through the use of the refined plastic‐hinge method

O presente trabalho tem como finalidade implementar e avaliar uma estratégia generalizada baseada no método da compatibilidade de deformações (MCD) para a obtenção das curvas de resistência e de início de plastificação de estruturas mistas de aço e concreto. Devido à anisotropia do concreto, a definição da resistência de seções transversais que possuem tal material em sua composição não é tão simples como nas estruturas metálicas. Recorre‐se ao método da rótula plástica refinado (MRPR) para realizar, via método dos elementos finitos (MEF), análises avançadas, ou seja, considerando conjuntamente os efeitos não lineares geométricos e físicos. Desse modo, a perda gradual da rigidez no MRPR é determinada através da combinação de esforço normal e momento fletor na seção transversal. Para a solução das equações não lineares global e local (a nível da seção transversal) utiliza‐se o método iterativo de Newton‐Rahpson acoplado a estratégias para passar por pontos críticos. Apresentam‐se análises numéricas avançadas de sistemas estruturais mistos de aço e concreto através da formulação implementada. Os resultados obtidos são comparados com respostas numéricas e experimentais presentes na literatura.This work presents the computational implementation and evaluation of a generalized strategy based on Strain Compatibility Method to obtain the initial and full yield curves of steel‐concrete composite structures. Due to anisotropy of concrete the evaluation of the full yield capacity of cross sections that have this material in its compostion is not so simple as for steel structures. Use is made of the Refined Plastic Hinge Method (RPHM) to perform, via Finite Element Method (FEM), the advanced analysis considering simultaneously second order and inelasticity effects. Thus, the gradual decrease of the stiffness in RPHM is determined by a section combination of axial force and bending moment. The Newton‐Raphson method with path‐following strategies is adopted for solving the nonlinear global and local (in cross section level) equations. Advanced numerical analysis of composite steel‐concrete structural systems are performed through the presented numerical formulation and the results obtained here are compared with experimental and numerical data given in the literature.Peer Reviewe

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications 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, 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

Evaluation of the inelastic behavior of steel columns and frames subjected to minor‐axis bending

This work presents an evaluation of the inelastic behavior of steel structures subjected to minor‐axis bending. Profiles type I and compact cross‐sections are considered. In these sections, the bent about weak axis presents important benefits, such as the ability to develop all of their plastic resistance without the occurrence of lateral torsional buckling. A nonlinear beam‐column element formulation is adopted, in which the steel yielding process is accounted by the refined plastic‐hinge method. In this method the effects of material yielding are captured by a parameter that reduces the structural member stiffness with the development of cross‐section plastic regions. The tangent modulus approach is used to consider the stiffness degradation caused by the increase in internal forces. Second–order effects, residual stresses and geometric imperfections are also considered in analysis. To define the cross‐section strength ultimate limit state, the study adopts strength surfaces that describe the interaction between internal forces — axial force and bending moment. The nonlinear equations at the structural system level are solved using the Newton‐Raphson iterative strategy coupled with path‐following methods. Isolated steel columns and portal frames are analyzed, and the results obtained are compared to those of other investigators. The comparison shows that the numerical methodology presented in this work is effective and can be used for predicting the behavior of steel structures with members under minor‐axis bending

Determination of structural composite elements strength through the use of the refined plastic‐hinge method

This work presents the computational implementation and evaluation of a generalized strategy based on Strain Compatibility Method to obtain the initial and full yield curves of steel‐concrete composite structures. Due to anisotropy of concrete the evaluation of the full yield capacity of cross sections that have this material in its compostion is not so simple as for steel structures. Use is made of the Refined Plastic Hinge Method (RPHM) to perform, via Finite Element Method (FEM), the advanced analysis considering simultaneously second order and inelasticity effects. Thus, the gradual decrease of the stiffness in RPHM is determined by a section combination of axial force and bending moment. The Newton‐Raphson method with path‐following strategies is adopted for solving the nonlinear global and local (in cross section level) equations. Advanced numerical analysis of composite steel‐concrete structural systems are performed through the presented numerical formulation and the results obtained here are compared with experimental and numerical data given in the literature

Numerical analysis of nonlinear behavior of steel-concrete composite structures

Abstract This paper presents the development of an effective numerical formulation for the analysis of steel-concrete composite structures considering geometric and materials nonlinear effects. Thus, a methodology based on Refined Plastic Hinge Method (RPHM) was developed and the stiffness parameters were obtained by homogenization of cross-section. The evaluation of structural elements strength is done through the Strain Compatibility Method (SCM). The Newton-Raphson Method with path-following strategies is adopted to solve nonlinear global and local (in cross-section level) equations. The results are compared with experimental and numerical database presents in literature and a good accuracy is observed in composite cross sections, composite columns, and composite portal frames

Determinação da capacidade resistente de elementos estruturais mistos através do método da rótula plástica refinado

ResumoO presente trabalho tem como finalidade implementar e avaliar uma estratégia generalizada baseada no método da compatibilidade de deformações (MCD) para a obtenção das curvas de resistência e de início de plastificação de estruturas mistas de aço e concreto. Devido à anisotropia do concreto, a definição da resistência de seções transversais que possuem tal material em sua composição não é tão simples como nas estruturas metálicas. Recorre‐se ao método da rótula plástica refinado (MRPR) para realizar, via método dos elementos finitos (MEF), análises avançadas, ou seja, considerando conjuntamente os efeitos não lineares geométricos e físicos. Desse modo, a perda gradual da rigidez no MRPR é determinada através da combinação de esforço normal e momento fletor na seção transversal. Para a solução das equações não lineares global e local (a nível da seção transversal) utiliza‐se o método iterativo de Newton‐Rahpson acoplado a estratégias para passar por pontos críticos. Apresentam‐se análises numéricas avançadas de sistemas estruturais mistos de aço e concreto através da formulação implementada. Os resultados obtidos são comparados com respostas numéricas e experimentais presentes na literatura.AbstractThis work presents the computational implementation and evaluation of a generalized strategy based on Strain Compatibility Method to obtain the initial and full yield curves of steel‐concrete composite structures. Due to anisotropy of concrete the evaluation of the full yield capacity of cross sections that have this material in its compostion is not so simple as for steel structures. Use is made of the Refined Plastic Hinge Method (RPHM) to perform, via Finite Element Method (FEM), the advanced analysis considering simultaneously second order and inelasticity effects. Thus, the gradual decrease of the stiffness in RPHM is determined by a section combination of axial force and bending moment. The Newton‐Raphson method with path‐following strategies is adopted for solving the nonlinear global and local (in cross section level) equations. Advanced numerical analysis of composite steel‐concrete structural systems are performed through the presented numerical formulation and the results obtained here are compared with experimental and numerical data given in the literature

Estudo radiográfico do posicionamento da falange distal e suas possíveis correlações com obesidade em equinos de patrulhamento da Polícia Militar do Estado de Minas Gerais

Com o objetivo de se verificarem possíveis correlações entre a falange distal, o estojo córneo e a obesidade, 55 equinos de patrulhamento provenientes do Regimento de Cavalaria Alferes Tiradentes do Estado de Minas Gerais - RCAT tiveram seus dígitos torácicos radiografados. Posteriormente, os animais foram classificados quanto ao acúmulo de tecido adiposo regional por métodos subjetivos (escore corporal e escore de pescoço) e objetivos (índice de massa corporal, circunferência do pescoço e determinação de espessura do tecido adiposo por meio de ultrassonografia na inserção da cauda e do abdômen). Na população estudada, o índice de massa corporal evidenciou que 52,6% dos equinos se encontravam acima do peso. A circunferência do pescoço a 50% de seu comprimento dorsal e a medida ultrassonográfica na inserção da cauda se mostraram os melhores métodos objetivos para quantificar o acúmulo de tecido adiposo. Foram identificadas particularidades radiográficas características da população estudada que diferem de parâmetros internacionais. Observaram-se correlações significantes entre sinais de obesidade e medidas radiográficas indicadoras de laminite, sugerindo associação entre essas duas condições na população estudada

Effect of aerobic training on EEG alpha asymmetry and depressive symptoms in the elderly: a 1-year follow-up study

The effect of physical exercise on the treatment of depressive elderly adults has not been investigated thus far in terms of changes in cortical hemispheric activity. The objective of the present study was to identify changes in depressive symptoms, quality of life, and cortical asymmetry produced by aerobic activity. Elderly subjects with a diagnosis of major depressive disorder (DSM-IV) were included. Twenty patients (70% females, 71 ± 3 years) were divided into an exercise group (pharmacological treatment plus aerobic training) and a control group (undergoing pharmacological treatment) in a quasi-experimental design. Pharmacological treatment was maintained stable throughout the study (antidepressants and anxiolytics). Subjects were evaluated by depression scales (Beck Depression Inventory, Hamilton Depression Rating Scale, Montgomery-Asberg Depression Rating Scale) and the Short Form Health Survey-36, and electroencephalographic measurements (frontal and parietal alpha asymmetry) before and after 1 year of treatment. After 1 year, the control group showed a decrease in cortical activity on the right hemisphere (increase of alpha power), which was not observed in the exercise group. The exercise group showed a significant decrease of depressive symptoms, which was not observed in the control group. This result was also accompanied by improved treatment response and remission rate after 1 year of aerobic exercise associated with treatment. This study provides support for the effect of aerobic training on alpha activity and on depressive symptoms in elderly patients. Exercise facilitates the treatment of depressive elderly adults, leading to clinical and physical improvement and protecting against a decrease in cortical activity