Daniel N Maciel | Federal University of Rio Grande do Norte (original) (raw)
Papers by Daniel N Maciel
Research, Society and Development, Jan 16, 2022
Análise não linear de blocos de concreto armado sobre estacas como fundação de aerogerador onshor... more Análise não linear de blocos de concreto armado sobre estacas como fundação de aerogerador onshore considerando o atrito lateral entre as estacas e o solo Non-linear analysis of reinforced concrete pile caps as a foundation of onshore wind turbines considering the lateral friction between piles and the soil Análisis no lineal de bloques de hormigón armado en estacas como cimiento de aerogeneradores terrestre considerando la fricción lateral entre estacas y suelo
Page 1. ISSN 1809-5860 Cadernos de Engenharia de Estruturas, São Carlos, v. 8, n. 31, p. 63-75, 2... more Page 1. ISSN 1809-5860 Cadernos de Engenharia de Estruturas, São Carlos, v. 8, n. 31, p. 63-75, 2006 SEMI-ANALYTICAL BEM APPLIED TO EVALUATE DYNAMIC STRESS INTENSITY FACTORS OF FRACTURED BODIES Daniel Nelson Maciel1 & Humberto Breves Coda2 ...
Latin American Journal of Solids and Structures, 2022
The development of a numerical formulation is presented to describe viscoelastic behavior conside... more 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.
On precast concrete structures, the column foundation connections can occur through the socket fo... more On precast concrete structures, the column foundation connections can occur through the socket foundation, which can be embedded, partially embedded or external, with socket walls over the pile caps. This paper present an experimental study about reinforced concrete two pile caps with partially embedded socket submitted to central load, using 1:2 scaled models. In analyzed models, it was considered shear keys in the socket walls and column interface, as well as a smooth interface on this elements. The results are compared with monolithic pile caps connections. It is observed that the pile caps with shear keys on sockets has ultimate load greater than pile caps with monolithic connections, but the pile caps without shear keys has ultimate load up to 26% less than pile caps with monolithic connections. Resumo Em estruturas de concreto pré-moldado, a ligação pilar-fundação pode ocorrer por meio do cálice de fundação, que por sua vez pode estar embutido, parcialmente embutido ou externo, com o colarinho saliente em relação ao bloco de fundação. Apresenta-se nesse trabalho resultados de um estudo experimental de blocos de fundação sobre duas estacas com cálice parcialmente embutido submetido à ação centrada, utilizando modelos em escala reduzida 1:2. Nos modelos analisados, considerou-se a existência de chave de cisalhamento nas paredes do cálice e do pilar, e também a conformação de paredes lisas nos elementos. Os resultados são comparados com o de blocos de fundação que apresentam ligações monolíticas. Observa-se que os blocos com chave de cisalhamento apresentam força última superior à dos blocos com ligação monolítica, e que os blocos com interface lisa apresentam força última até 26% menor do que a dos blocos com ligação monolítica.
Revista IBRACON de Estruturas e Materiais, 2020
ABSTRACT: Wall-beam interaction (wall-beam system) is a phenomenon that requires further investig... more ABSTRACT: Wall-beam interaction (wall-beam system) is a phenomenon that requires further investigation in order to be consistently incorporated into structural building analysis. Researchers such as Wood, Rosenhaupt, Burhouse, Stafford Smith, Navaratnarajah, Davies, Riddington and Armed conducted tests on specimens to develop simplified analysis models, emphasizing the behavior of walls without openings under one span beams. The present study performed computational analysis using an specific equivalent frame model in order to study the behavior of the wall-beam system in more complex wall and beam arrangements. The examples considered the linear elastic behavior of materials and consisted of assessing stress distribution and displacements on support beams, in addition to stresses at the bottom of the walls, for panels in a real structural masonry building. Two- and three-dimensional analyses were used and the results showed the importance of three-dimensional analysis of wall inter...
International Journal of Structural Stability and Dynamics, 2018
This paper analyzes the dynamic response of space and plane trusses with geometrical and material... more This paper analyzes the dynamic response of space and plane trusses with geometrical and material nonlinear behaviors using different time integration algorithms, considering an alternative Finite Element Method (FEM) formulation called positional FEM. Each algorithm is distinguished from each other by its specific form of position, velocity, acceleration and equilibrium equation concerning the stability, consistency, accuracy and efficiency of solution. Particularly, the impact problems against rigid walls are analyzed considering Null-Penetration Condition. This formulation is based on the minimum potential energy theorem written according to the nodal positions, instead of the structural displacements. It has the advantage of simplicity when compared with the classical counterparts, since it does not necessarily reply on the corotational axes. Moreover, the performance of each temporal integration algorithm is evaluated by numerical simulations.
Research, Society and Development
Estruturas de concreto armado estão sujeitas à diversas formas de deterioração, sendo a principal... more Estruturas de concreto armado estão sujeitas à diversas formas de deterioração, sendo a principal delas a corrosão da armadura metálica que causam prejuízos sociais e econômicos, especialmente em regiões com alta agressividade ambiental. Diante disso, diversos países têm estudado a viabilidade de utilização de armaduras não metálicas, como as de polímeros reforçados com fibras (PRF). Nesse âmbito, o presente trabalho realizou um estudo teórico e numérico do comportamento de vigas de concreto armadas com barras de polímeros reforçados com fibras de vidro (PRFV), carbono (PRFC) e aramida (PRFA), em comparação com uma viga de concreto armada com barras de aço. Para um mesmo carregamento foi dimensionado a viga de concreto com barras de aço conforme a ABNT NBR 6118:2014, e as vigas de concreto armado com barras de PRF segundo o ACI 440.1R:2015. Em seguida, as mesmas foram simuladas numericamente no software ANSYS® para analisar as tensões, deformações e deslocamentos. Por fim, verificou...
Research, Society and Development
As escadas especiais conquistaram maior espaço em projetos estruturais nos últimos tempos. Os mod... more As escadas especiais conquistaram maior espaço em projetos estruturais nos últimos tempos. Os modelos estruturais de cálculo destas escadas devem retratar o comportamento na ruptura (ELU) e em serviço (ELS), podendo ser gerados através de modelos analíticos simplificados ou com o emprego de métodos numéricos. Nesta perspectiva, este artigo apresenta a análise de escadas retas autoportantes em concreto armado a partir da variação de espessura da laje e da obtenção dos esforços normais de flexão e das deformações. Para tanto, foram utilizados os métodos analíticos de Knijnik & Tavares (1977) e o apresentado por Araújo (2014), assim como o Método dos Elementos Finitos (MEF), com o auxílio do programa de análise estrutural SAP2000®. Foram avaliados modelos computacionais compostos por elementos de barra e de casca. A partir das simulações realizadas, observou-se uma aproximação satisfatória entre os modelos analíticos e os modelos numéricos com elementos de casca, enquanto os modelos fo...
Research, Society and Development
Nos últimos anos, houve um aumento na utilização de materiais hiperelásticos em estruturas, como ... more Nos últimos anos, houve um aumento na utilização de materiais hiperelásticos em estruturas, como por exemplo, polímeros vulcanizados ou naturais. Em virtude disso, torna-se relevante expandir o conhecimento quanto ao desempenho mecânico destes materiais por meio do desenvolvimento de modelos numéricos que simulem o seu comportamento e que sejam capazes de apresentar previsões mais realistas. Para materiais representados por modelos hiperelásticos, a consideração das não linearidades física e geométrica é mais adequada para representar o seu comportamento mecânico quando submetidos a grandes deformações. Desse modo, o presente trabalho objetiva a implementação de um código computacional, com o propósito de analisar e comparar o comportamento mecânico de treliças considerando a não linearidade física, descrita por modelos hiperelásticos, e a não linearidade geométrica utilizando a formulação posicional em elementos finitos. Foi utilizado o método do comprimento de arco de Riks-Wempne...
This paper investigates the structural behavior of pile caps designed in precast concrete. Firstl... more This paper investigates the structural behavior of pile caps designed in precast concrete. Firstly, it is performed an introduction to the subject, indicating the advantages and disadvantages of using this element as structural solution. Secondly, some aspects related to its application in Brazil and abroad are discussed as well and finally, considerations are presented regarding the research in this area, followed by numerical analysis of two pile caps studied by Chan & Poh [3], using finite element method by Diana V 9.2 software. A load versus displacement response of a specimen is presented as the cracking panorama and nodal stress in the pile and the column. Comparison of ultimate load between experimental and numerical simulation shows that numerical model is able to represent the structural behavior.
ABSTRACT This paper presents an impact formulation for 3D solids with the positional finite eleme... more ABSTRACT This paper presents an impact formulation for 3D solids with the positional finite element method. The positional formulation is an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements as usually found in literature. Herein, it is analyzed impact problems against rigid wall considering the Null-Penetration Condition. The Newmark time integration scheme has been implemented, considering the eventual inclusion of a physical damping in the positional formulation. Unidirectional and bidirectional impact examples are shown in order to prove the accuracy of the proposed formulation.
ario/Natal-RN/Brazil Abstract. This paper presents the positional nonlinear geometric formulation... more ario/Natal-RN/Brazil Abstract. This paper presents the positional nonlinear geometric formulation for plane truss prob- lems in static analysis. The positional formulation presents an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of dis- placements (widely found in literature). The strain determination is done directly from the proposed positional concept. The initial configuration is assumed as the basis of calculation, i.e., Hooke's law relates reference stress and engineering strain. Some simple numerical examples are shown proving the accuracy of the proposed formulation.
This paper investigates the structural behavior of pile caps designed in precast concrete. Firstl... more This paper investigates the structural behavior of pile caps designed in precast concrete. Firstly, it is performed an introduction to the subject, indicating the advantages and disadvantages of using this element as structural solution. Secondly, some aspects related to its application in Brazil and abroad are discussed as well and finally, considerations are presented regarding the research in this area, followed by numerical analysis of two pile caps studied by Chan & Poh [3], using finite element method by Diana V 9.2 software. A load versus displacement response of a specimen is presented as the cracking panorama and nodal stress in the pile and the column. Comparison of ultimate load between experimental and numerical simulation shows that numerical model is able to represent the structural behavior.
Latin American Journal of Solids and Structures
The thermal effects of problems involving deformable structures are essential to describe the beh... more 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.
ABSTRACT This paper presents the positional nonlinear geometric formulation for plane truss prob-... more ABSTRACT This paper presents the positional nonlinear geometric formulation for plane truss prob-lems in static analysis. The positional formulation presents an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of dis-placements (widely found in literature). The strain determination is done directly from the proposed positional concept. The initial configuration is assumed as the basis of calculation, i.e., Hooke's law relates reference stress and engineering strain. Some simple numerical examples are shown proving the accuracy of the proposed formulation.
ABSTRACT This paper presents three different time integration schemes for plane frames dynamic fo... more ABSTRACT This paper presents three different time integration schemes for plane frames dynamic formulation with the finite element method based on positions. The positional formulation is an alternative approach for nonlinear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements as usually found in literature. Apparently, the equilibrium equations of a nonlinear system can be solved by any numerical method of integration, but the computational costs and accuracy must be considered, according to the system that is going to be analyzed. Thus the aim of this paper is to compare three different implicit methods of temporal integration -Newmark, Wilson-θ and Houbolt Method -in order to analyze their performances in the solution of the dynamic analysis of a structural system presenting nonlinear geometric response.
ABSTRACT The arc-length method is a commonly used technique in nonlinear analysis for solu-tion o... more ABSTRACT The arc-length method is a commonly used technique in nonlinear analysis for solu-tion of equilibrium paths, bifurcation points and limit points related to phenomenons as snap-through and snap-back. This paper describes two variants of the arc-length method, namely: the Riks' method and the Crisfield's method. They are applied to analysis of trusses using the positional formulation of finite element method. The positional formulation presents an alter-native approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements (widely found in literature). Numerical applications for trusses already established in the literature and comparisons with other studies are provided to prove the accuracy of the positional formulation.
Research, Society and Development, Jan 16, 2022
Análise não linear de blocos de concreto armado sobre estacas como fundação de aerogerador onshor... more Análise não linear de blocos de concreto armado sobre estacas como fundação de aerogerador onshore considerando o atrito lateral entre as estacas e o solo Non-linear analysis of reinforced concrete pile caps as a foundation of onshore wind turbines considering the lateral friction between piles and the soil Análisis no lineal de bloques de hormigón armado en estacas como cimiento de aerogeneradores terrestre considerando la fricción lateral entre estacas y suelo
Page 1. ISSN 1809-5860 Cadernos de Engenharia de Estruturas, São Carlos, v. 8, n. 31, p. 63-75, 2... more Page 1. ISSN 1809-5860 Cadernos de Engenharia de Estruturas, São Carlos, v. 8, n. 31, p. 63-75, 2006 SEMI-ANALYTICAL BEM APPLIED TO EVALUATE DYNAMIC STRESS INTENSITY FACTORS OF FRACTURED BODIES Daniel Nelson Maciel1 & Humberto Breves Coda2 ...
Latin American Journal of Solids and Structures, 2022
The development of a numerical formulation is presented to describe viscoelastic behavior conside... more 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.
On precast concrete structures, the column foundation connections can occur through the socket fo... more On precast concrete structures, the column foundation connections can occur through the socket foundation, which can be embedded, partially embedded or external, with socket walls over the pile caps. This paper present an experimental study about reinforced concrete two pile caps with partially embedded socket submitted to central load, using 1:2 scaled models. In analyzed models, it was considered shear keys in the socket walls and column interface, as well as a smooth interface on this elements. The results are compared with monolithic pile caps connections. It is observed that the pile caps with shear keys on sockets has ultimate load greater than pile caps with monolithic connections, but the pile caps without shear keys has ultimate load up to 26% less than pile caps with monolithic connections. Resumo Em estruturas de concreto pré-moldado, a ligação pilar-fundação pode ocorrer por meio do cálice de fundação, que por sua vez pode estar embutido, parcialmente embutido ou externo, com o colarinho saliente em relação ao bloco de fundação. Apresenta-se nesse trabalho resultados de um estudo experimental de blocos de fundação sobre duas estacas com cálice parcialmente embutido submetido à ação centrada, utilizando modelos em escala reduzida 1:2. Nos modelos analisados, considerou-se a existência de chave de cisalhamento nas paredes do cálice e do pilar, e também a conformação de paredes lisas nos elementos. Os resultados são comparados com o de blocos de fundação que apresentam ligações monolíticas. Observa-se que os blocos com chave de cisalhamento apresentam força última superior à dos blocos com ligação monolítica, e que os blocos com interface lisa apresentam força última até 26% menor do que a dos blocos com ligação monolítica.
Revista IBRACON de Estruturas e Materiais, 2020
ABSTRACT: Wall-beam interaction (wall-beam system) is a phenomenon that requires further investig... more ABSTRACT: Wall-beam interaction (wall-beam system) is a phenomenon that requires further investigation in order to be consistently incorporated into structural building analysis. Researchers such as Wood, Rosenhaupt, Burhouse, Stafford Smith, Navaratnarajah, Davies, Riddington and Armed conducted tests on specimens to develop simplified analysis models, emphasizing the behavior of walls without openings under one span beams. The present study performed computational analysis using an specific equivalent frame model in order to study the behavior of the wall-beam system in more complex wall and beam arrangements. The examples considered the linear elastic behavior of materials and consisted of assessing stress distribution and displacements on support beams, in addition to stresses at the bottom of the walls, for panels in a real structural masonry building. Two- and three-dimensional analyses were used and the results showed the importance of three-dimensional analysis of wall inter...
International Journal of Structural Stability and Dynamics, 2018
This paper analyzes the dynamic response of space and plane trusses with geometrical and material... more This paper analyzes the dynamic response of space and plane trusses with geometrical and material nonlinear behaviors using different time integration algorithms, considering an alternative Finite Element Method (FEM) formulation called positional FEM. Each algorithm is distinguished from each other by its specific form of position, velocity, acceleration and equilibrium equation concerning the stability, consistency, accuracy and efficiency of solution. Particularly, the impact problems against rigid walls are analyzed considering Null-Penetration Condition. This formulation is based on the minimum potential energy theorem written according to the nodal positions, instead of the structural displacements. It has the advantage of simplicity when compared with the classical counterparts, since it does not necessarily reply on the corotational axes. Moreover, the performance of each temporal integration algorithm is evaluated by numerical simulations.
Research, Society and Development
Estruturas de concreto armado estão sujeitas à diversas formas de deterioração, sendo a principal... more Estruturas de concreto armado estão sujeitas à diversas formas de deterioração, sendo a principal delas a corrosão da armadura metálica que causam prejuízos sociais e econômicos, especialmente em regiões com alta agressividade ambiental. Diante disso, diversos países têm estudado a viabilidade de utilização de armaduras não metálicas, como as de polímeros reforçados com fibras (PRF). Nesse âmbito, o presente trabalho realizou um estudo teórico e numérico do comportamento de vigas de concreto armadas com barras de polímeros reforçados com fibras de vidro (PRFV), carbono (PRFC) e aramida (PRFA), em comparação com uma viga de concreto armada com barras de aço. Para um mesmo carregamento foi dimensionado a viga de concreto com barras de aço conforme a ABNT NBR 6118:2014, e as vigas de concreto armado com barras de PRF segundo o ACI 440.1R:2015. Em seguida, as mesmas foram simuladas numericamente no software ANSYS® para analisar as tensões, deformações e deslocamentos. Por fim, verificou...
Research, Society and Development
As escadas especiais conquistaram maior espaço em projetos estruturais nos últimos tempos. Os mod... more As escadas especiais conquistaram maior espaço em projetos estruturais nos últimos tempos. Os modelos estruturais de cálculo destas escadas devem retratar o comportamento na ruptura (ELU) e em serviço (ELS), podendo ser gerados através de modelos analíticos simplificados ou com o emprego de métodos numéricos. Nesta perspectiva, este artigo apresenta a análise de escadas retas autoportantes em concreto armado a partir da variação de espessura da laje e da obtenção dos esforços normais de flexão e das deformações. Para tanto, foram utilizados os métodos analíticos de Knijnik & Tavares (1977) e o apresentado por Araújo (2014), assim como o Método dos Elementos Finitos (MEF), com o auxílio do programa de análise estrutural SAP2000®. Foram avaliados modelos computacionais compostos por elementos de barra e de casca. A partir das simulações realizadas, observou-se uma aproximação satisfatória entre os modelos analíticos e os modelos numéricos com elementos de casca, enquanto os modelos fo...
Research, Society and Development
Nos últimos anos, houve um aumento na utilização de materiais hiperelásticos em estruturas, como ... more Nos últimos anos, houve um aumento na utilização de materiais hiperelásticos em estruturas, como por exemplo, polímeros vulcanizados ou naturais. Em virtude disso, torna-se relevante expandir o conhecimento quanto ao desempenho mecânico destes materiais por meio do desenvolvimento de modelos numéricos que simulem o seu comportamento e que sejam capazes de apresentar previsões mais realistas. Para materiais representados por modelos hiperelásticos, a consideração das não linearidades física e geométrica é mais adequada para representar o seu comportamento mecânico quando submetidos a grandes deformações. Desse modo, o presente trabalho objetiva a implementação de um código computacional, com o propósito de analisar e comparar o comportamento mecânico de treliças considerando a não linearidade física, descrita por modelos hiperelásticos, e a não linearidade geométrica utilizando a formulação posicional em elementos finitos. Foi utilizado o método do comprimento de arco de Riks-Wempne...
This paper investigates the structural behavior of pile caps designed in precast concrete. Firstl... more This paper investigates the structural behavior of pile caps designed in precast concrete. Firstly, it is performed an introduction to the subject, indicating the advantages and disadvantages of using this element as structural solution. Secondly, some aspects related to its application in Brazil and abroad are discussed as well and finally, considerations are presented regarding the research in this area, followed by numerical analysis of two pile caps studied by Chan & Poh [3], using finite element method by Diana V 9.2 software. A load versus displacement response of a specimen is presented as the cracking panorama and nodal stress in the pile and the column. Comparison of ultimate load between experimental and numerical simulation shows that numerical model is able to represent the structural behavior.
ABSTRACT This paper presents an impact formulation for 3D solids with the positional finite eleme... more ABSTRACT This paper presents an impact formulation for 3D solids with the positional finite element method. The positional formulation is an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements as usually found in literature. Herein, it is analyzed impact problems against rigid wall considering the Null-Penetration Condition. The Newmark time integration scheme has been implemented, considering the eventual inclusion of a physical damping in the positional formulation. Unidirectional and bidirectional impact examples are shown in order to prove the accuracy of the proposed formulation.
ario/Natal-RN/Brazil Abstract. This paper presents the positional nonlinear geometric formulation... more ario/Natal-RN/Brazil Abstract. This paper presents the positional nonlinear geometric formulation for plane truss prob- lems in static analysis. The positional formulation presents an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of dis- placements (widely found in literature). The strain determination is done directly from the proposed positional concept. The initial configuration is assumed as the basis of calculation, i.e., Hooke's law relates reference stress and engineering strain. Some simple numerical examples are shown proving the accuracy of the proposed formulation.
This paper investigates the structural behavior of pile caps designed in precast concrete. Firstl... more This paper investigates the structural behavior of pile caps designed in precast concrete. Firstly, it is performed an introduction to the subject, indicating the advantages and disadvantages of using this element as structural solution. Secondly, some aspects related to its application in Brazil and abroad are discussed as well and finally, considerations are presented regarding the research in this area, followed by numerical analysis of two pile caps studied by Chan & Poh [3], using finite element method by Diana V 9.2 software. A load versus displacement response of a specimen is presented as the cracking panorama and nodal stress in the pile and the column. Comparison of ultimate load between experimental and numerical simulation shows that numerical model is able to represent the structural behavior.
Latin American Journal of Solids and Structures
The thermal effects of problems involving deformable structures are essential to describe the beh... more 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.
ABSTRACT This paper presents the positional nonlinear geometric formulation for plane truss prob-... more ABSTRACT This paper presents the positional nonlinear geometric formulation for plane truss prob-lems in static analysis. The positional formulation presents an alternative approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of dis-placements (widely found in literature). The strain determination is done directly from the proposed positional concept. The initial configuration is assumed as the basis of calculation, i.e., Hooke's law relates reference stress and engineering strain. Some simple numerical examples are shown proving the accuracy of the proposed formulation.
ABSTRACT This paper presents three different time integration schemes for plane frames dynamic fo... more ABSTRACT This paper presents three different time integration schemes for plane frames dynamic formulation with the finite element method based on positions. The positional formulation is an alternative approach for nonlinear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements as usually found in literature. Apparently, the equilibrium equations of a nonlinear system can be solved by any numerical method of integration, but the computational costs and accuracy must be considered, according to the system that is going to be analyzed. Thus the aim of this paper is to compare three different implicit methods of temporal integration -Newmark, Wilson-θ and Houbolt Method -in order to analyze their performances in the solution of the dynamic analysis of a structural system presenting nonlinear geometric response.
ABSTRACT The arc-length method is a commonly used technique in nonlinear analysis for solu-tion o... more ABSTRACT The arc-length method is a commonly used technique in nonlinear analysis for solu-tion of equilibrium paths, bifurcation points and limit points related to phenomenons as snap-through and snap-back. This paper describes two variants of the arc-length method, namely: the Riks' method and the Crisfield's method. They are applied to analysis of trusses using the positional formulation of finite element method. The positional formulation presents an alter-native approach for non linear problems, since it considers nodal positions as variables of the nonlinear system instead of displacements (widely found in literature). Numerical applications for trusses already established in the literature and comparisons with other studies are provided to prove the accuracy of the positional formulation.