Dynamic analysis of high-speed railway bridges in Finland
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Journal Title
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2024-01-22
Department
Major/Subject
Mcode
Degree programme
Master's Programme in Building Technology (CIV)
Language
en
Pages
80+19
Series
Abstract
The development of high-speed trains is increasing and has created a new attention to the study of vibration and resonance effects in railway bridges along the new Espoo-Salo railway line. The thesis aims to do research of the dynamic behavior of railway bridges under high-speed trains implementing Eurocode and NCCI design principles. The primary objective of this study is to obtain the resonance speed of bridge using a finite element method and compare it to the resonance speed derived from the Eurocode formula. The comparison would draw a connection between the methodologies and help to omit the detailed dynamic analysis of the bridges. Likewise, it also aims to investigate the dynamic behavior of the bridges by exploring the dynamic characteristics of the structure, such as eigen frequencies, eigen mode, resonance, etc. by thorough examination of different bridge models, load cases, train speed, time step and so on. The investigation employs the method of moving load and considers various bridge parameters, such as mass, stiffness and damping to evaluate their influence on the dynamic response. The response of the modelling assumptions, such as effective width, torsional stiffness, and uncracked slab stiffness, is also investigated. The results suggest that, for all high-speed trains, the bridge is resonating, and both the speed and damping ratio play a significant role in the amplitude of the dynamic response. Similarly, the mass and stiffness of the bridge, along with the axle load of the train, have significant influence on both the dynamic response and the resonance speed of the bridge. Eurocode formula accurately approximates the resonance speed by using the eigenfrequency of the bridge and can be used to estimate the resonance speed in earlier design phase, but it does not provide explanation for the complete response of the dynamic structure. It has also been shown that the static load train results in higher bending moment values than the dynamic values of high-speed trains. However, the negative dynamic moment at the midspans is found to be higher than the static moment. For bridges with long cantilever beams, the acceleration is high from early speed and resonates extremely in high speeds. Similarly, the simplified modelling approach with effective width, reduced torsional stiffness and uncracked slab stiffness is an efficient way of modelling with governing values of results. The single section modelling technique can be used to calculate bending eigenfrequency and eigenmodes of the bridge, but not for dynamic analysis.Description
Supervisor
Niiranen, JarkkoThesis advisor
Helin, RistomattiKeywords
high-speed trains, dynamic analysis, railway bridge, finite element method, dynamic interaction, resonance speed