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A presente dissertação centra-se no estudo de fadiga de uma ponte ferroviária com tabuleiro misto vigado pertencente a uma via de transporte de mercadorias. O caso de estudo incide sobre a ponte ferroviária sobre o rio do Sonho, localizada na Estrada de Ferro de Carajás situada no nordeste do Brasil. Nesta linha circulam alguns dos maiores comboios de mercadoria do mundo com cerca de 3.7 km de extensão e com cargas por eixo superiores a 300 kN.
Numa primeira fase apresentam-se diversas metodologias de análise da fadiga em pontes ferroviárias metálicas. É também descrita a ferramenta computacional FADBridge, desenvolvida em ambiente MATLAB, e que possibilita o cálculo sistematizado e eficiente do dano de fadiga em detalhes construtivos de acordo com as indicações dos eurocódigos.
Em seguida são abordadas as metodologias numéricas utilizadas para a realização das análises dinâmicas do sistema ponte-comboio e os aspetos regulamentares a ter em consideração no dimensionamento de pontes ferroviárias.
O modelo numérico de elementos finitos da ponte foi realizado com recurso ao programa ANSYS. Com base neste modelo foram obtidos os parâmetros modais, nomeadamente as frequências naturais e os modos de vibração, tendo sido também analisada a importância do efeito compósito via-tabuleiro e a influência do comportamento não linear do balastro.
O estudo do comportamento dinâmico da ponte foi realizado por intermédio de uma metodologia de cargas móveis através da ferramenta computacional Train-Bridge Interaction (TBI). As análises dinâmicas foram efetuadas para a passagem dos comboios reais de mercadorias e de passageiros e para os comboios de fadiga regulamentares. Nestas análises foi estudada a influência dos modos de vibração globais e locais, das configurações de carga dos comboios e do aumento da velocidade de circulação, na resposta dinâmica da ponte. Por último, foi avaliado o comportamento à fadiga de diversos detalhes construtivos para os cenários de tráfego regulamentar e reais. Foi ainda analisada a influência do aumento da velocidade, da configuração de cargas dos comboios e da degradação da estrutura nos valores do dano por fadiga e da respetiva vida residual.
The main objective of this thesis focuses on the study of the phenomenon of fatigue in a composite twin girder railway bridge, located in a freight traffic railway line. This case of study is centered in the railway bridge that crosses Sonho river, located on Carajás railway line in the northeast Brazil. This line is crossed by some of the longest freight trains of the world, measuring about 3.7 km in length, and axle loads higher than 300 kN. Initially several methods for fatigue analysis in steel railway bridges are presented. A computational tool developed in MATLAB, called FADBridge, which enables the systematic and efficient calculation of fatigue damage in the construction details according to the indications of the Eurocodes, is also described. The numerical methodologies used to perform the dynamic analysis of train - bridge system and the code aspects to consider in the design of railway bridges are presented. The finite element numerical model of the bridge was constructed using ANSYS software. Based on this model the modal parameters, namely the natural frequencies and vibration modes were obtained. It was also analyzed the importance of the track-bridge composite effect and the influence of the nonlinear behavior of the ballast in the dynamic response of the bridge. The study of the dynamic behavior of the bridge was carried out using a moving loads methodology by means of a computational application called Train-Bridge Interaction (TBI). The dynamic analyses were performed for the passage of real freight and passenger trains, and also for the fatigue trains specified in the codes. In these analyses, the influence of the global and local vibration modes, load configurations of the trains and increase of the circulation speed, on the dynamic response of the bridge is studied. Finally, the fatigue behavior of several construction details considering the code and real traffic scenarios is evaluated. Furthermore, the influence of the speed increment, loads configuration and structure degradation, in the values of fatigue damage and corresponding residual life, is evaluated.
The main objective of this thesis focuses on the study of the phenomenon of fatigue in a composite twin girder railway bridge, located in a freight traffic railway line. This case of study is centered in the railway bridge that crosses Sonho river, located on Carajás railway line in the northeast Brazil. This line is crossed by some of the longest freight trains of the world, measuring about 3.7 km in length, and axle loads higher than 300 kN. Initially several methods for fatigue analysis in steel railway bridges are presented. A computational tool developed in MATLAB, called FADBridge, which enables the systematic and efficient calculation of fatigue damage in the construction details according to the indications of the Eurocodes, is also described. The numerical methodologies used to perform the dynamic analysis of train - bridge system and the code aspects to consider in the design of railway bridges are presented. The finite element numerical model of the bridge was constructed using ANSYS software. Based on this model the modal parameters, namely the natural frequencies and vibration modes were obtained. It was also analyzed the importance of the track-bridge composite effect and the influence of the nonlinear behavior of the ballast in the dynamic response of the bridge. The study of the dynamic behavior of the bridge was carried out using a moving loads methodology by means of a computational application called Train-Bridge Interaction (TBI). The dynamic analyses were performed for the passage of real freight and passenger trains, and also for the fatigue trains specified in the codes. In these analyses, the influence of the global and local vibration modes, load configurations of the trains and increase of the circulation speed, on the dynamic response of the bridge is studied. Finally, the fatigue behavior of several construction details considering the code and real traffic scenarios is evaluated. Furthermore, the influence of the speed increment, loads configuration and structure degradation, in the values of fatigue damage and corresponding residual life, is evaluated.
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Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto.