Abstract The development of a numerical formulation is presented to describe viscoelastic behavior considering shear effects. The nonlinear positional formulation of the Finite Element Method is used considering plane frame elements with Reissner kinematics. The description of the viscoelastic behavior is considered through the adoption of a stress-strain relation based on Boltzmann rheological model. The used kinematics allows to describe the decoupling between the rotations and the displacements in element cross-sections. This approach allows to evaluate the contribution of shear effects in viscoelastic behavior in an original way. Based on the developments and the results obtained, it is possible to observe that strains and displacements due to viscoelastic behavior are significantly superior to the results obtained considering Bernoulli-Euler kinematics hypothesis. It is possible to notice a better agreement between the obtained numerical results and the results in the literature. Results obtained from the developed formulation allow the assessment of the shear effects on the viscoelastic behavior of plane frames.

Abstract The present paper aims to test recent (Truly self-starting two sub-step method and three-parameter single-step implicit method) and classical (Generalized-α, HHT-α, and WBZ-α methods) time integration methods using the geometrically nonlinear Positional Finite Element Method (PFEM). The numerical formulation is based on the total Lagrangian approach and uses the Hessian matrix to obtain the response. The mixed hardening inelastic model applied to PFEM is also presented. Two examples validate the time integration algorithms and the inelastic model. In the first example, the mixed hardening inelastic model is compared with the the bilinear stress-strain model and the elastic-perfectly plastic hinge model, and aspects such as amplitude decay and period elongation are discussed. In the second example, the implemented algorithms are verified in a severe geometrically nonlinear example, considering the influence of numerical dissipation, time interval, and the number of elements in the response. Results show the relevance of numerical damping for numerical stabilization and the good performance of the Generalized-α algorithm.

Abstract Elastomeric bearing pads are responsible for transfering loads at the junction between beams and columns of bridges and viaducts, providing restrict freedom of movement in the superstructure. The elastomeric material of bearing pads is a synthetic rubber reinforced with carbon black particles and subjected to a process of vulcanization, also represented by hyperelastic material models based on strain energy density functions. The objective of the present paper is to use the finite element analysis software Abaqus® to select the most appropriate hyperelastic model, as well as its constants, applying them to a bearing pad installed in an existing viaduct, evaluating its behavior and the displacements resulting from the application of usual loads. A data fitting procedure is performed through the finite elements analysis software to obtain the Neo-Hooke, Arruda-Boyce and Yeoh model constants. The proposed methodology presents results that are coherent when compared to technical specification limits for available bearing pads products.

Resumo Escoliose idiopática do adolescente (EIA) atinge de 2% a 4% de jovens no Brasil. Repetidas exposições aos exames radiológicos, no acompanhamento desta deformidade, podem ser danosos à saúde. O objetivo deste estudo é apresentar um protocolo de fotogrametria, como método não ionizante para quantificação da escoliose, e relacioná-lo ao método radiológico de Cobb. Dezesseis indivíduos portadores de escoliose idiopática (21,4 ± 6,1 anos de idade e 19,8±0,2 de índice de massa corporal) foram submetidos à radiografia posteroanterior do tronco, de pé e, posteriormente, fotografia do tronco posterior, após receberem marcadores anatômicos nos processos espinhosos das vértebras C7 até L5. As imagens foram encaminhadas para análise independente de dois examinadores treinados na quantificação da escoliose para o tipo de imagem recebida. A média angular torácica de Cobb e de fotogrametria foram 36,14° e 36,43°, respectivamente. A diferença média entre os métodos foi de 4,1°. Não houve diferença estatisticamente significante (p-valor < 5%) entre eles. A fotogrametria, por ser não ionizante, ter baixo custo e ser portátil, poderá representar uma alternativa ao método radiológico. Novos estudos são necessários no aprimoramento das técnicas não ionizantes no rastreamento da EIA.

Abstract Adolescent idiopathic scoliosis (AIS) affects 2% to 4% of young people in Brazil. Repeated exposures to radiation used in the monitoring of the deformity can be harmful to the health. This study aimed to present a photogrammetry protocol as a non-ionizing method to quantify scoliosis and relate it to the Cobb radiological method. Sixteen individuals with idiopathic scoliosis (age: 21.4 ± 6.1 years, body mass index: 19.8 ± 0.2 kg/m2) underwent standing posteroanterior X-ray examination of the trunk. Additionally, markers were placed on the spinal processes of the C7 to L5 vertebrae, and posterior trunk photographs were taken. All images were sent for independent analysis by two examiners who were trained in the quantification of scoliosis. The average of the thoracic curvature evaluated through the photogrammetry and Cobb methods were 36.43° and 36.14°, respectively. With an average difference of 4.1°, the methods were not statistically different (p < 0.05). As a non-ionizing method that is low cost and portable, photogrammetry may represent a suitable alternative to the radiological method. Further studies are needed for the improvement of non-ionizing techniques in AIS screening.

Resumo Escoliose idiopática do adolescente (EIA) atinge de 2% a 4% de jovens no Brasil. Repetidas exposições aos exames radiológicos, no acompanhamento desta deformidade, podem ser danosos à saúde. O objetivo deste estudo é apresentar um protocolo de fotogrametria, como método não ionizante para quantificação da escoliose, e relacioná-lo ao método radiológico de Cobb. Dezesseis indivíduos portadores de escoliose idiopática (21,4 ± 6,1 anos de idade e 19,8±0,2 de índice de massa corporal) foram submetidos à radiografia posteroanterior do tronco, de pé e, posteriormente, fotografia do tronco posterior, após receberem marcadores anatômicos nos processos espinhosos das vértebras C7 até L5. As imagens foram encaminhadas para análise independente de dois examinadores treinados na quantificação da escoliose para o tipo de imagem recebida. A média angular torácica de Cobb e de fotogrametria foram 36,14° e 36,43°, respectivamente. A diferença média entre os métodos foi de 4,1°. Não houve diferença estatisticamente significante (p-valor < 5%) entre eles. A fotogrametria, por ser não ionizante, ter baixo custo e ser portátil, poderá representar uma alternativa ao método radiológico. Novos estudos são necessários no aprimoramento das técnicas não ionizantes no rastreamento da EIA.

Abstract Adolescent idiopathic scoliosis (AIS) affects 2% to 4% of young people in Brazil. Repeated exposures to radiation used in the monitoring of the deformity can be harmful to the health. This study aimed to present a photogrammetry protocol as a non-ionizing method to quantify scoliosis and relate it to the Cobb radiological method. Sixteen individuals with idiopathic scoliosis (age: 21.4 ± 6.1 years, body mass index: 19.8 ± 0.2 kg/m2) underwent standing posteroanterior X-ray examination of the trunk. Additionally, markers were placed on the spinal processes of the C7 to L5 vertebrae, and posterior trunk photographs were taken. All images were sent for independent analysis by two examiners who were trained in the quantification of scoliosis. The average of the thoracic curvature evaluated through the photogrammetry and Cobb methods were 36.43° and 36.14°, respectively. With an average difference of 4.1°, the methods were not statistically different (p < 0.05). As a non-ionizing method that is low cost and portable, photogrammetry may represent a suitable alternative to the radiological method. Further studies are needed for the improvement of non-ionizing techniques in AIS screening.

Abstract This paper presents the development of a formulation, based on Positional Finite Element Method, to describe the viscoelastic mechanical behavior of space trusses. The numerical method used was chosen due to its efficiency in the applications concerning nonlinear numerical analyses. The formulation describes the positional variation over time under constant stress state (creep). The objective is to provide a way to quantify the creep behavior for space truss structures and thus contribute to the encouragement of GFRP usage in such structural components. Time-dependent behavior of such materials is one the most important factors for their use in design of structures, demanding studies about the deformations expected within the operational life of the structural systems. To perform this study, the proposed methodology considers a standard solid rheological model to describe stress-strain time-dependent law. This model is implemented in the formulation for quantify the total strain energy. The effects of the model parameters in the mechanical response of the structure with accentuated geometric nonlinearity were presented. In this analysis, it was possible to identify the influence of the elastic and the viscous moduli on the creep response. Model calibration was performed using test data obtained from literature and a GFRP transmission line tower cross-arm was simulated to predict the evolution of displacements under real operational loads. From the results, it was possible to observe a fast evolution of displacements due to the creep effect in the first 7,500 h. This increase was close to 0.6% in relation to the displacement obtained in the elastic behavior. The presented methodology provided a simple and efficient way to quantify the creep phenomenon in viscoelastic GFRP composites truss structures, as can be seen in the developed analyses.

Resumo Introdução: A postura do indivíduo sentado, utilizada rotineiramente na execução de grande variedade de tarefas, constitui-se num potencial aumentado para o desenvolvimento da postura de projeção da cabeça, a qual pode ocasionar sérios comprometimentos à saúde de vários sistemas no corpo humano. Objetivo: Um estudo do equilíbrio estático foi realizado, relacionando a posição da cabeça com a curvatura da coluna lombar em três diferentes posturas do indivíduo sentado. Métodos: Foi realizado o cálculo do valor aproximado de força e momento fletor dos músculos extensores da cabeça na manutenção do equilíbrio estático em cada uma das seguintes posturas: (A) sem uso de encosto para as costas; (B) com uso de encosto de 100° de inclinação; (C) com uso de encosto de 100° associado a um suporte lombar cilíndrico em nível da vértebra L3. Resultados: Os ângulos tragus-C7 foram 43°, 50° e 52°; os ângulos de Frankfort foram 5°, 9° e 9°; as forças musculares extensoras da cabeça foram 53,0N, 59,7N e 43,5N e os momentos fletores foram 2,60N.m, 2,05N.m e 1,78N.m, nas posturas A, B e C, respectivamente. Conclusão: Os resultados revelaram que a postura sentada com encosto inclinado a 100° e calço lombar, onde houve a menor distância horizontal tragus-L3, apresentou menor esforço para a musculatura cervical extensora na manutenção do equilíbrio da cabeça. Este estudo demonstrou a necessidade da preservação do eixo lombar fisiológico, caracterizado pelo posicionamento da vértebra L3, para garantir o bom posicionamento da cabeça.

Abstract Introduction: The sitting position routinely used for a wide variety of tasks increases the potential of developing forward head posture, which can seriously compromise the health of different systems in the human body. Objective: A static equilibrium analysis was conducted, comparing the position of the head with the lumbar curve in three different sitting positions. Methods: The approximate force and flexion moment of the head extensor muscles in static equilibrium was calculated in each of the following positions: (A) without a backrest; (B) using a backrest with a 100° tilt angle; (C) using a 100° tilted backrest associated with a cylindrical lumbar support cushion at the level of the L3 vertebra. Results: The C7-tragus angles were 43°, 50° and 52°; Frankfort horizontal plane (FH) angles were 5°, 9° and 9°; force of the head extensor muscles was 53.0N, 59.7N and 43.5N and flexion moments were 2.60Nm, 2.05Nm and 1.78Nm, in positions A, B and C, respectively. Conclusion: The results revealed that the sitting position using a 100° tilted backrest and lumbar support with the smallest L3-tragus horizontal distance required less effort by the head and neck extensor muscles to retain the head in equilibrium. This study demonstrated the need to preserve the physiology of the lumbar spine, characterized by the position of the L3 vertebra, in order to ensure good head position.

Abstract Introduction: Biomedical studies involve complex anatomical structures, which require specific methodology to generate their geometric models. The middle segment of the thoracic spine (T5-T10) is the site of the highest incidence of vertebral deformity in adolescents. Traditionally, its geometries are derived from computed tomography or magnetic resonance imaging data. However, this approach may restrict certain studies. The study aimed to generate two 3D geometric model of the T5-T10 thoracic spine segment, obtained from graphical images, and to create mesh for finite element studies. Methods A 3D geometric model of T5-T10 was generated using two anatomical images of T6 vertebra (side and top). The geometric model was created in Autodesk® Maya® 3D 2013, and the mesh process in HiperMesh and MeshMixer (v11.0.544 Autodesk). Results The T5-T10 thoracic segment model is presented with its passive components, bones, intervertebral discs and flavum, intertransverse and supraspinous ligaments, in different views, as well as the volumetric mesh. Conclusion The 3D geometric model generated from graphical images is suitable for application in non-patient-specific finite element model studies or, with restrictions, in the use of computed tomography or magnetic resonance imaging. This model may be useful for biomechanical studies related to the middle thoracic spine, the most vulnerable site for vertebral deformations.

Abstract The thermal effects of problems involving deformable structures are essential to describe the behavior of materials in feasible terms. Verifying the transformation of mechanical energy into heat it is possible to predict the modifications of mechanical properties of materials due to its temperature changes. The current paper presents the numerical development of a finite element method suitable for nonlinear structures coupled with thermomechanical behavior; including impact problems. A simple and effective alternative formulation is presented, called FEM positional, to deal with the dynamic nonlinear systems. The developed numerical is based on the minimum potential energy written in terms of nodal positions instead of displacements. The effects of geometrical, material and thermal nonlinearities are considered. The thermodynamically consistent formulation is based on the laws of thermodynamics and the Helmholtz free-energy, used to describe the thermoelastic and the thermoplastic behaviors. The coupled thermomechanical model can result in secondary effects that cause redistributions of internal efforts, depending on the history of deformation and material properties. The numerical results of the proposed formulation are compared with examples found in the literature.

Objetivou-se no presente trabalho avaliar a eficiência energética na secagem de café (Coffea arabica L.) em secador de camada fixa, empregando-se diferentes combinações de tempo de revolvimento. O experimento foi realizado no mês de julho de 2004, no município de Jesuítas - Estado do Paraná. O secador, dotado de um sistema mecânico com pás, promovia o revolvimento rotatório do produto a diferentes intervalos de tempo. A temperatura do ar de secagem foi de 75 ± 5ºC. A ventilação e a secagem mantiveram-se contínuas no teste. Observou-se que a eficiência energética média foi de 12,3 MJ kg-1, não sendo verificadas diferenças significativas entre os tratamentos. Para o modelo de secador utilizado recomenda-se a utilização do sistema de revolvimento com intervalos de 3h e secagem contínua.

This study aimed to evaluate the energetic efficiency in coffee drying (Coffee arabica L.) with different combinations of revolving time in a fixed-bed coffee dryer. The experiment was conducted in July 2004 in Jesuítas - Paraná state/Brazil. The dryer featured a mechanic system with rotating blades to revolve of the product at different intervals. The drying air temperature was 75ºC ± 5ºC. The ventilation and drying was kept constant during the tests. It was observed that the average energy efficiency was 12.3 MJ kg-1 and there was no significant difference between the treatments. For the adopted dryer model, the revolving system is recommended with three-hour intervals and continuous drying.

Este trabalho teve como objetivo avaliar a redução da temperatura nas partes externas de um secador de camada fixa para café, mediante diferentes combinações de tempo de revolvimento, utilizando-se termômetro sem contato. O experimento foi desenvolvido no mês de junho de 2004 em uma propriedade localizada em Jesuítas, Estado do Paraná. Foi utilizado café (Coffea arabica L.), variedade IAC 81. O secador utilizado foi o modelo de camada fixa, com câmara de secagem metálica, de formato cilíndrico, com um sistema de revolvimento de grãos adaptado. Observou-se que houve, em média, uma redução térmica de 156,7ºC (79,1%) no sistema que vai da fornalha até a câmara de secagem. A combinação que proporcionou menor redução da temperatura foi a com ventilação contínua e revolvimento de 40 min. a cada 3h até o fim do processo. A combinação que proporcionou maior redução de temperatura foi a com revolvimento contínuo, com redução de 81,09% na temperatura superficial do produto.

This study aimed to evaluate the temperature reduction in the external parts of a fixed-bed coffee dryer, by means of different combinations of revolving times, using a noncontact thermometer. The experiment was developed in the month of June 2004 at a farm located in Jesuítas, Paraná State, Brazil. Coffee (Coffea arabica L.) variety IAPAR 59 was used. The dryer used was of the fixed-bed model, with metallic drying chamber, with cylindrical format, with an adapted grain revolving system. It was observed that there was a thermal reduction of 156.7ºC (79.1%) in the system going from the furnace to the drying chamber. The combination that provided smaller reduction of temperature was with continuous ventilation and 40 minutes revolving interval at every 3 hours until the end of the process. The combination that provided the greatest reduction in temperature was with continuous revolving, with a reduction of 81.09% in the surface temperature of the product.

O artigo apresenta uma metodologia analítica para analisar treliças com severo comportamento não linear geométrico. O objetivo principal do trabalho é encontrar soluções analíticas para treliças com diferentes esforços axiais nos elementos estruturais. A metodologia é baseada na cinemática estrutural, nas leis constitutivas elásticas e no equilíbrio de forças nodais. A formulação proposta pode ser aplicada em materiais hiperelásticos, como borracha e espumas com comportamento elástico. Uma treliça do tipo Von Mises com duas barras feitas de materiais diferentes é apresentada como exemplo de aplicação, com o objetivo de demonstrar a precisão e eficiência do método proposto.

This paper presents an analytical method for analyzing trusses with severe geometrically nonlinear behavior. The main objective is to find analytical solutions for trusses with different axial forces in the bars. The methodology is based on truss kinematics, elastic constitutive laws and equilibrium of nodal forces. The proposed formulation can be applied to hyper elastic materials, such as rubber and elastic foams. A Von Mises truss with two bars made by different materials is analyzed to show the accuracy of this methodology.

O objetivo do presente trabalho foi comparar a eficiência dos métodos de estimativa da evapotranspiração de referência em relação ao método de FAO Penman-Monteith. Os dados meteorológicos utilizados foram coletados na estação meteorológica da rede do Iapar, instalada em Palotina, Estado do Paraná. Os dados utilizados, nas estimativas de evapotranspiração de referência, corresponderam ao período de 1994 a 2003. A evapotranspiração de referência foi estimada pelos métodos de Thornthwaite, Camargo e HargreavesSamani, sendo seu desempenho comparado ao método de FAO Penman-Monteith. As médias diárias da evapotranspiração de referência variaram entre 2,58 e 3,62 mm dia-1 . Os resultados indicaram que, para a escala diária, os métodos avaliados apresentaram bom ajuste, quando comparados ao método de FAO Penman-Monteith, com coeficientes de correlação (r) variando entre 0,85 e 0,86. O coeficiente de exatidão ou de concordância (d) apresentou valores que variaram entre 0,82 e 0,85. Em relação ao método de FAO Penman-Monteith, os métodos de Hargreaves-Samani, Thornthwaite e Camargo apresentaram bom desempenho, quando avaliados pelo índice "c".

The aim of this study was to compare the efficiency of three estimate methods for reference evapotranspiration in comparison with the FAO Penman-Monteith equation. Meteorological data used in this study were collected from the IAPAR meteorological station, located in Palotina, Paraná State , Brazil. In order to estimate the reference evapotranspiration, data available from 1994 to 2003 were used. The performance of the Thornthwaite, Camargo and Hargreaves-Samani methods were compared to the FAO Penman-Monteith equation. The average of daily reference evapotranspiration ranged from 2.58 to 3.62 mm day-1. The results indicated that the evaluated methods showed good adjustment when compared to the FAO Penman-Monteith method, according to the daily scale. The correlation coefficient (r) ranged from 0.85 to 0.86. The coefficient of accuracy or agreement (d) presented values that ranged from 0.82 to 0.85. In comparison to the FAO Penman-Monteith method, the Hargreaves-Samani, Thornthwaite and Camargo methods demonstrated good performance, when evaluated by the index (c).