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O EFEITO DA VELOCIDADE DOS COMBOIOS NO DESEMPENHO DE ZONAS DE TRANSIÇÃO: UM ESTUDO NUMÉRICO
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As transições ferroviárias têm sido alvo de diversos estudos experimentais e numéricos nos anos mais recentes, visto que se verificou que nestes locais é usual desenvolverem-se de-feitos de geometria na via-férrea que resultam na redução da segurança e conforto dos passageiros e que obrigam, por isso, a trabalhos acrescidos de manutenção e correção. Apesar dos variados trabalhos relativos a esta temática, ainda existe uma insuficiência de estudos que tenham em conta o efeito da velocidade de circulação no desenvolvimento de defeitos nas transições ferroviárias. Para este propósito, é usada uma implementação numérica tridimensional que considera explicitamente a interação dinâmica roda-carril. Esta implementação permite o cálculo do desenvolvimento da deformação plástica das camadas granulares de apoio à via-férrea, com especial atenção à camada de balastro e, com isso, da evolução da geometria da via em termos de nivelamento longitudinal. Com a metodologia de cálculo seguida, é tida em conta a recíproca interdependência entre a variação dos efeitos dinâmicos associado às eleva-das velocidades de circulação e a correspondente deformação plástica gradual das camadas granulares de apoio. As simulações numéricas focadas numa ponte ferroviária de pequeno vão e diferentes veículos ferroviários a diversas velocidades revelaram que o aumento da velocidade e o aumento do peso do veículo podem resultar num aumento das deformações plásticas permanentes a nível da camada de balastro nas zonas de aproximação à estrutura, em especial a zona a jusante da ponte ferroviária. Também foi possível comprovar que a aplicação de palmilhas mais flexíveis sob o carril na zona da ponte pode contribuir para a melhoria do comportamento da via-férrea numa perspetiva a longo prazo.
Railway transitions have been the target of several experimental and numerical studies in recent years, as it has been found that at these locations it is usual to develop geometry defects in the railway track that result in reduced safety and comfort for passengers and, there-fore, require increased maintenance and correction work. Despite the various works on this subject, there is still a lack of studies that consider the effect of traffic speed on the development of defects in railway transitions. For this purpose, a three-dimensional numerical implemen-tation that explicitly considers the dynamic wheel-rail interaction is used. This implementa-tion allows the calculation of the development of the plastic deformation of the granular layers supporting the railway track, with special attention to the ballast layer, and thus of the evolu-tion of the track geometry in terms of longitudinal levelling. With the calculation methodology used, the reciprocal interdependence between the variation of dynamic effects associated with high traffic speeds and the corresponding gradual plastic deformation of the supporting gran-ular layers is taken into account. Numerical simulations focused on a short span railway bridge and different railway vehicles at different speeds revealed that the increase in speed and the increase in vehicle weight can result in an increase in the permanent plastic defor-mations at the ballast layer level in the areas approaching the structure, especially in the exit area of the railway bridge. It was also possible to prove that the application of more flexible rail pads in the bridge area can contribute to the improvement of the railway track behaviour in a long-term perspective.
Railway transitions have been the target of several experimental and numerical studies in recent years, as it has been found that at these locations it is usual to develop geometry defects in the railway track that result in reduced safety and comfort for passengers and, there-fore, require increased maintenance and correction work. Despite the various works on this subject, there is still a lack of studies that consider the effect of traffic speed on the development of defects in railway transitions. For this purpose, a three-dimensional numerical implemen-tation that explicitly considers the dynamic wheel-rail interaction is used. This implementa-tion allows the calculation of the development of the plastic deformation of the granular layers supporting the railway track, with special attention to the ballast layer, and thus of the evolu-tion of the track geometry in terms of longitudinal levelling. With the calculation methodology used, the reciprocal interdependence between the variation of dynamic effects associated with high traffic speeds and the corresponding gradual plastic deformation of the supporting gran-ular layers is taken into account. Numerical simulations focused on a short span railway bridge and different railway vehicles at different speeds revealed that the increase in speed and the increase in vehicle weight can result in an increase in the permanent plastic defor-mations at the ballast layer level in the areas approaching the structure, especially in the exit area of the railway bridge. It was also possible to prove that the application of more flexible rail pads in the bridge area can contribute to the improvement of the railway track behaviour in a long-term perspective.
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Palavras-chave
Transições ferroviárias Zonas de transição Ponte ferroviária Defeitos de geometria Velocidade Ferramenta numérica