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Dynamic Soil-structure Interaction of Portal Frame Bridge Walls for High-speed Railways

Malm, Henrik LU (2016) In TVSM-5000 VSM820 20161
Structural Mechanics
Department of Construction Sciences
Abstract
In Sweden, high-speed railways is a subject for public debate. The first stage of a high-speed train network, Ostlänken between Stockholm and Linköping, is under investigation, and is planned to be trafficked in 2028. The high-speed railway is intended to hold traffic with speeds up to 320 km/h. At such speeds, the design requirements of the accelerations of the bridge superstructure become more stringent. Previous studies show that the interaction between the bridge and the backfill soil can reduce these accelerations.

In this thesis, dynamic soil-structure interaction (SSI) of portal frame bridge walls has been studied. The SSI was represented by complex impedance functions that were calculated and analyzed for different parameters... (More)
In Sweden, high-speed railways is a subject for public debate. The first stage of a high-speed train network, Ostlänken between Stockholm and Linköping, is under investigation, and is planned to be trafficked in 2028. The high-speed railway is intended to hold traffic with speeds up to 320 km/h. At such speeds, the design requirements of the accelerations of the bridge superstructure become more stringent. Previous studies show that the interaction between the bridge and the backfill soil can reduce these accelerations.

In this thesis, dynamic soil-structure interaction (SSI) of portal frame bridge walls has been studied. The SSI was represented by complex impedance functions that were calculated and analyzed for different parameters of a bridge-embankment interface.

The impedance, representing dynamic stiffness and damping, were in this thesis calculated in the frequency domain with finite element (FE) software, by performing steady state analyses on 3D solid bridge-embankment models. To discretize the infinite extent of an embankment, the standard viscous boundary method was used, implemented by inserting infinite continuum elements at the boundary in the FE-software ABAQUS. The method showed successful with mitigating waves at the boundary. A parameter study was conducted, where the influence of geometries and material properties were shown through a comparison of impedance functions. Both embankments on a fixed boundary, representing bedrock, and embankments on circular ground soil plates of various thickness and stiffness, were compared.

SSI showed to induce large amounts of dynamic stiffness and damping to a bridge structure. A stiffer embankment, as well as a stiffer ground soil, has shown large influence on the dynamic stiffness and is believed to reduce vibrations in a bridge deck. The study suggested that proper material modeling is important for both the soil and the concrete, to receive accuracy in the impedance functions. The work also indicates that a properly designed bridge wall geometry could be an important step towards developing the design of future high-speed railway bridges. (Less)
Abstract (Swedish)
I Sverige är höghastighetsjärnvägar ett debatterat ämne. Undersökningsarbeten har startat för det första steget i ett höghastighetsnät – Ostlänken mellan Järna och Linköping – som planeras vara trafikerad år 2028. Höghastighetsjärnvägen är avsedd att tillåta hastigheter på 320 km/h. Vid så höga hastigheter blir dimensioneringskraven för brobanans vibrationer strängare. Tidigare studier har visat att dessa vibrationer kan reduceras om man tillgodoräknar sig interaktionen mellan bron och jordbanken.

Det här examensarbetet behandlar dynamisk jord-struktur-interaktion (SSI, från Soil-structure Interaction) för ramben på plattrambroar. SSI representeras här av komplexa impedansfunktioner som har beräknats och analyserats för olika... (More)
I Sverige är höghastighetsjärnvägar ett debatterat ämne. Undersökningsarbeten har startat för det första steget i ett höghastighetsnät – Ostlänken mellan Järna och Linköping – som planeras vara trafikerad år 2028. Höghastighetsjärnvägen är avsedd att tillåta hastigheter på 320 km/h. Vid så höga hastigheter blir dimensioneringskraven för brobanans vibrationer strängare. Tidigare studier har visat att dessa vibrationer kan reduceras om man tillgodoräknar sig interaktionen mellan bron och jordbanken.

Det här examensarbetet behandlar dynamisk jord-struktur-interaktion (SSI, från Soil-structure Interaction) för ramben på plattrambroar. SSI representeras här av komplexa impedansfunktioner som har beräknats och analyserats för olika parametrar i ett gränssnitt mellan jord och bro.

I examensarbetet beräknades impedanser, som representerar dynamisk styvhet och dämpning, i frekvensdomänen genom steady-state analyser på tredimensionella FE-modeller som utgjordes av ett ramben och en intilliggande jordbank. För att avgränsa den oändliga utsträckningen av en jordbank, användes den så kallade standard viscous boundary-metoden, vilken implementeras i FE-mjukvaran ABAQUS genom 3D-element som simulerar oändlig utsträckning. Metoden visade sig effektivt kunna dämpa ut vågrörelser som nådde jordbankens bortre gräns. En parameterstudie utfördes, där betydelsen av geometrier och materialegenskaper kunde påvisas genom att jämföra impedansfunktioner. I parameterstudien jämfördes både modeller med jordbank på berggrund och jordbank på cirkulära jordskivor av olika djup och styvhet med varandra.

Studien visade att SSI kan bidra mycket till dynamisk styvhet och dämpning för en vidhängande struktur. Styvare jordbank, såväl som styvare mark, visade sig i stor utsträckning påverka den dynamiska styvheten, och tros kunna reducera vibrationerna i den intilliggande brobanan. Studien antyder att noggrant valda materialegenskaper i både jorden och betongen är viktigt för noggrannheten i uppskattning av impedansen. Studien visade även tendenser till att vidare utredning av utformningen av rambenen är ett viktigt steg för att utforma framtidens höghastighetsjärnvägsbroar. (Less)
Popular Abstract (Swedish)
Höghastighetståg har länge varit omdebatterat i Sverige, men ser nu ut att bli en realitet. För att kunna genomföra höghastighetsprojektet måste tekniken utvecklas och befintliga metoder för dimensionering av järnvägsbroar förbättras. Därför utarbetas en metod som ska ge en mer realistisk beskrivning av de vibrationer som uppkommer när ett tåg passerar en bro i hög hastighet.
Please use this url to cite or link to this publication:
author
Malm, Henrik LU
supervisor
organization
course
VSM820 20161
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
SSI, Soil-structure interaction, Structural dynamics, High-speed railway bridges, Impedance, Receptance, Finite element method, Portal frame bridge
publication/series
TVSM-5000
report number
TVSM-5219
ISSN
0281-6679
language
English
id
8895600
alternative location
http://www.byggmek.lth.se/english/publications/tvsm-5000-masters-dissertations/
date added to LUP
2016-12-19 10:33:57
date last changed
2016-12-19 10:33:57
@misc{8895600,
  abstract     = {In Sweden, high-speed railways is a subject for public debate. The first stage of a high-speed train network, Ostlänken between Stockholm and Linköping, is under investigation, and is planned to be trafficked in 2028. The high-speed railway is intended to hold traffic with speeds up to 320 km/h. At such speeds, the design requirements of the accelerations of the bridge superstructure become more stringent. Previous studies show that the interaction between the bridge and the backfill soil can reduce these accelerations. 

In this thesis, dynamic soil-structure interaction (SSI) of portal frame bridge walls has been studied. The SSI was represented by complex impedance functions that were calculated and analyzed for different parameters of a bridge-embankment interface. 

The impedance, representing dynamic stiffness and damping, were in this thesis calculated in the frequency domain with finite element (FE) software, by performing steady state analyses on 3D solid bridge-embankment models. To discretize the infinite extent of an embankment, the standard viscous boundary method was used, implemented by inserting infinite continuum elements at the boundary in the FE-software ABAQUS. The method showed successful with mitigating waves at the boundary. A parameter study was conducted, where the influence of geometries and material properties were shown through a comparison of impedance functions. Both embankments on a fixed boundary, representing bedrock, and embankments on circular ground soil plates of various thickness and stiffness, were compared.

SSI showed to induce large amounts of dynamic stiffness and damping to a bridge structure. A stiffer embankment, as well as a stiffer ground soil, has shown large influence on the dynamic stiffness and is believed to reduce vibrations in a bridge deck. The study suggested that proper material modeling is important for both the soil and the concrete, to receive accuracy in the impedance functions. The work also indicates that a properly designed bridge wall geometry could be an important step towards developing the design of future high-speed railway bridges.},
  author       = {Malm, Henrik},
  issn         = {0281-6679},
  keyword      = {SSI,Soil-structure interaction,Structural dynamics,High-speed railway bridges,Impedance,Receptance,Finite element method,Portal frame bridge},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM-5000},
  title        = {Dynamic Soil-structure Interaction of Portal Frame Bridge Walls for High-speed Railways},
  year         = {2016},
}