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Dynamic Design of Bridges on High-Speed Railway Lines

Nilsson, Felicia LU and Dahl, Filippa LU (2019) In TVSM-5000 VSMM01 20191
Department of Construction Sciences
Structural Mechanics
Abstract
In recent years, high-speed railway has been on the upswing in the public debate, as Swedish authorities have affirmed the plans of a high-speed corridor connecting Stockholm, Gothenburg and Malm¨o. The track speed limit is not fully determined, but will be in the range of 250-320 km/h. At these higher speed levels, it is harder to ensure traffic safety and passenger comfort, and dynamic analyses of the included bridges are required. Substantial research has already been published on the subject of high-speed railway dynamics; yet, there are still areas that need further investigation to understand the behaviour of bridges that undergo this type of loading.

In this thesis, parametric studies were performed on a three-spanned slab bridge... (More)
In recent years, high-speed railway has been on the upswing in the public debate, as Swedish authorities have affirmed the plans of a high-speed corridor connecting Stockholm, Gothenburg and Malm¨o. The track speed limit is not fully determined, but will be in the range of 250-320 km/h. At these higher speed levels, it is harder to ensure traffic safety and passenger comfort, and dynamic analyses of the included bridges are required. Substantial research has already been published on the subject of high-speed railway dynamics; yet, there are still areas that need further investigation to understand the behaviour of bridges that undergo this type of loading.

In this thesis, parametric studies were performed on a three-spanned slab bridge and on a portal frame bridge. The main objective was to investigate how the response of the bridges changed when the train speed, the span length and the cross-section height werevaried. The analyses were executed in BRIGADE/Plus and the response was primarily evaluated in terms of vertical accelerations of the bridge deck. However, verifications of vertical deflection, torsion, rotation at bearings, and section forces, were also covered in the study. Previous research has shown that the representation of the boundary between the foundation and the surrounding soil is a critical part of the modelling. In the major part of this study, the conventional method using fixed boundary condition was adopted in all DOFs except for those representing the rotation around the in-plane axes, where linear elastic rotational springs were inserted. A slightly more realistic approach with an
increased Young’s modulus of the soil and an additional spring in the vertical DOF, was also evaluated. In addition, a minor literature study of more comprehensive works on the topic of Soil-Structure Interaction (SSI), was conducted.

The results suggest that none of the bridges in the study meet the dynamic design requirements for a track speed interval of 250-350 km/h. Furthermore, an increase in crosssectional height seems to be an efficient way of reducing the maximum accelerations, whereas an enlargement of the span length may drastically increase the response. A 10 % increase in span length can increase the acceleration by a factor 2 for the slab bridge, and by a factor 3 for the portal frame bridge. It has also been shown that using fixed boundary conditions at the soil-structure interface can yield non-conservative results. For the frame bridges of different span lengths, the accelerations were significantly larger for the case with vertical springs; however, no such trend was able to be identified for the slab bridges. In contrast to the existing body of research, the acceleration was not the
decisive parameter in all aspects of this study. The section forces, and particularly the choice of dynamic enhancement factor, were critical for the shorter bridges in the track speed interval 125-250 km/h. (Less)
Popular Abstract (Swedish)
Sedan myndigheterna fastställt planerna på en höghastighetskorridor som ska knyta samman Stockholm, Göteborg och Malmö, har intresset f¨or höghastighetståg ökat hos såväl allmänhet som forskare. Hastighetsbegränsningen på banan är ännu inte satt, men den kommer vara inom intervallet 250-320 km/h. Eftersom det är svårare att garantera trafiksäkerhet och passagerarkomfort vid dessa högre hastigheter, krävs dynamiska analyser av de ingående broarna. Även om det redan har genomförts avsevärd forskning på ämnet dynamik på järnvägsbroar för höghastighetståg, finns det flera områden som behöver utredas vidare för att förstå broarnas beteende.

I det här examensarbetet utfördes parameterstudier på en plattbro som spänner över tre fack och en... (More)
Sedan myndigheterna fastställt planerna på en höghastighetskorridor som ska knyta samman Stockholm, Göteborg och Malmö, har intresset f¨or höghastighetståg ökat hos såväl allmänhet som forskare. Hastighetsbegränsningen på banan är ännu inte satt, men den kommer vara inom intervallet 250-320 km/h. Eftersom det är svårare att garantera trafiksäkerhet och passagerarkomfort vid dessa högre hastigheter, krävs dynamiska analyser av de ingående broarna. Även om det redan har genomförts avsevärd forskning på ämnet dynamik på järnvägsbroar för höghastighetståg, finns det flera områden som behöver utredas vidare för att förstå broarnas beteende.

I det här examensarbetet utfördes parameterstudier på en plattbro som spänner över tre fack och en plattrambro. Huvudsyftet var att utreda hur broarnas respons förändras när tåghastigheten, spännvidden och tvärsnittshöjden varieras. Analyserna genomfördes i BRIGADE/Plus och responsen utvärderades primärt i form av brodäckets vertikala acceleration. Verifiering av vertikal deformation, vridning, rotation kring lagerpunkter och snittkrafter inkluderades också i studien. Tidigare forskning har visat att modelleringen av gränsen mellan brofundamentet och omkringliggande jord är en kritisk del i dimensioneringsprocessen. I den större delen av arbetet användes den konventionella metoden med fixa upplagsvillkor i alla frihetsgrader förutom de som motsvarar rotation kring axlarna i planet, där linjärelastiska fjädrar applicerades. Ett något mer realistiskt angreppssätt med en ökad elasticitetsmodul för jorden och en ytterligare fjäder i den vertikala frihetsgraden utvärderades också. Dessutom utfördes en mindre litteraturstudie av
mer omfattande arbeten om Jord-Struktur Interaktion (SSI).

Resultaten tyder på att ingen av broarna i studien uppfyller dimensioneringskraven för ett banhastighetsintervall p˚a 250-350 km/h. Vidare verkar en ökning av tvärsnittshöjden vara ett effektivt sätt att minska den maximala accelerationen, medan en förstoring av spännvidden drastiskt kan öka responsen. Accelerationen kan öka med en faktor 2 för plattbron och en faktor 3 för rambron, när spännvidden ökas med 10 %. Arbetet har också visat att användandet av fixa upplagsvillkor vid gränsen mellan jord och bro kan ge icke-konservativa resultat. För plattrambroar med olika spännvidder var accelerationerna avsevärt större för fallet med vertikala fjädrar. Dock kunde någon sådan trend inte identifieras för plattbroarna. I motsats till befintlig forskning var accelerationen inte den storhet som styrde alla aspekter av den dynamiska dimensioneringen. Snittkrafterna, och i synnerhet valet av dynamisk förstoringsfaktor, var kritiska för de kortare broarna i banhastighetsintervallet 125-250 km/h. (Less)
Please use this url to cite or link to this publication:
author
Nilsson, Felicia LU and Dahl, Filippa LU
supervisor
organization
alternative title
Dynamisk analys av järnvägsbroar i betong – inverkan av geometriska parametrar
course
VSMM01 20191
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
High-speed railway bridges, bridge-train resonance, structural dynamics, modal dynamics, time stepping, soil-structure interaction, finite element method, BRIGADE/Plus
publication/series
TVSM-5000
report number
TVSM-5236
ISSN
0281-6679
language
English
id
8992339
alternative location
http://www.byggmek.lth.se/english/publications/tvsm-5000-present-2014/
date added to LUP
2019-08-22 09:48:38
date last changed
2019-08-22 09:48:38
@misc{8992339,
  abstract     = {In recent years, high-speed railway has been on the upswing in the public debate, as Swedish authorities have affirmed the plans of a high-speed corridor connecting Stockholm, Gothenburg and Malm¨o. The track speed limit is not fully determined, but will be in the range of 250-320 km/h. At these higher speed levels, it is harder to ensure traffic safety and passenger comfort, and dynamic analyses of the included bridges are required. Substantial research has already been published on the subject of high-speed railway dynamics; yet, there are still areas that need further investigation to understand the behaviour of bridges that undergo this type of loading.

In this thesis, parametric studies were performed on a three-spanned slab bridge and on a portal frame bridge. The main objective was to investigate how the response of the bridges changed when the train speed, the span length and the cross-section height werevaried. The analyses were executed in BRIGADE/Plus and the response was primarily evaluated in terms of vertical accelerations of the bridge deck. However, verifications of vertical deflection, torsion, rotation at bearings, and section forces, were also covered in the study. Previous research has shown that the representation of the boundary between the foundation and the surrounding soil is a critical part of the modelling. In the major part of this study, the conventional method using fixed boundary condition was adopted in all DOFs except for those representing the rotation around the in-plane axes, where linear elastic rotational springs were inserted. A slightly more realistic approach with an
increased Young’s modulus of the soil and an additional spring in the vertical DOF, was also evaluated. In addition, a minor literature study of more comprehensive works on the topic of Soil-Structure Interaction (SSI), was conducted.

The results suggest that none of the bridges in the study meet the dynamic design requirements for a track speed interval of 250-350 km/h. Furthermore, an increase in crosssectional height seems to be an efficient way of reducing the maximum accelerations, whereas an enlargement of the span length may drastically increase the response. A 10 % increase in span length can increase the acceleration by a factor 2 for the slab bridge, and by a factor 3 for the portal frame bridge. It has also been shown that using fixed boundary conditions at the soil-structure interface can yield non-conservative results. For the frame bridges of different span lengths, the accelerations were significantly larger for the case with vertical springs; however, no such trend was able to be identified for the slab bridges. In contrast to the existing body of research, the acceleration was not the
decisive parameter in all aspects of this study. The section forces, and particularly the choice of dynamic enhancement factor, were critical for the shorter bridges in the track speed interval 125-250 km/h.},
  author       = {Nilsson, Felicia and Dahl, Filippa},
  issn         = {0281-6679},
  keyword      = {High-speed railway bridges,bridge-train resonance,structural dynamics,modal dynamics,time stepping,soil-structure interaction,finite element method,BRIGADE/Plus},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM-5000},
  title        = {Dynamic Design of Bridges on High-Speed Railway Lines},
  year         = {2019},
}