Track-Bridge Interaction – Sensitivity Studies on the bridge across Bryngeån and TBI Analysis on the bridge across Sege å
(2025) In 0349-4969 VBKM01 20251Division of Structural Engineering
- Abstract
- As Sweden expands and modernizes its railway network, the design of durable and cost-
efficient railway bridges becomes increasingly important. A central technical challenge in this
context is track-bridge interaction (TBI), the mechanical interplay between the rail and bridge
structure. This interaction affects how forces from traffic loads, temperature variations and
braking are transferred within the system. It plays a decisive role in determining rail stresses,
substructure loads and whether rail expansion joints are needed. A deeper understanding of
TBI is critical for ensuring structural performance, material efficiency and long-term
functionality, particularly as design standards evolve.
This thesis investigates... (More) - As Sweden expands and modernizes its railway network, the design of durable and cost-
efficient railway bridges becomes increasingly important. A central technical challenge in this
context is track-bridge interaction (TBI), the mechanical interplay between the rail and bridge
structure. This interaction affects how forces from traffic loads, temperature variations and
braking are transferred within the system. It plays a decisive role in determining rail stresses,
substructure loads and whether rail expansion joints are needed. A deeper understanding of
TBI is critical for ensuring structural performance, material efficiency and long-term
functionality, particularly as design standards evolve.
This thesis investigates track-bridge interaction (TBI) in railway systems. The study focuses
on how bridge geometry, boundary conditions and updated design standards influence
additional stresses in the rail and the distribution of forces between the rail and the bridge
components. Using finite element modeling, two case studies were examined: the existing
Bryngeå bridge and the planned Sege å bridge. For Bryngeån, a detailed sensitivity analyses
were conducted by systematically varying parameters such as support stiffness, embankment
length and spring behavior between rail and deck. For Sege å, a TBI analysis was performed
without further parameter studies.
The sensitivity analysis showed that the vertical linear stiffness model for the rail-to-deck
connection can be used without significant loss of accuracy compared to more complex
bilinear alternatives. They also revealed that reducing the horizontal stiffness of the supports
decreases both rail stresses and reaction forces, which could lead to more material-efficient
bridge designs. Additionally, embankment lengths of 300 meters were sufficient to capture
the additional stresses in the system. The analysis of Sege å further showed that nearly half of
the total longitudinal forces are carried by the rail and transferred into the embankments. This
demonstrates a load-sharing behavior that may justify the use of simplified Eurocode
methods, even for bridges exceeding 40 meters in span. Based on the calculated rail stresses,
the bridge across Sege å is expected to meet the requirements for additional axial forces
according to both the current, SS-EN 1991-2:2003, and upcoming, prEN 1991-2:2021,
Eurocode. Consequently, the bridge should be able to be constructed without a rail expansion
joint.
A collaborative workshop with industry and academic experts provided additional insights on
the practical application of Eurocode and the potential for model simplifications. Overall, this
thesis contributes to the understanding of how design assumptions and evolving standards
affect TBI assessments and offers recommendations for more efficient, yet reliable, railway
bridge design. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9196000
- author
- Magnusson, Moa LU and Nilsson, Rakel LU
- supervisor
- organization
- alternative title
- Räls-Bro interaktion – Känslighetsanalys av bron över Bryngeån och TBI analys av bron över Sege å
- course
- VBKM01 20251
- year
- 2025
- type
- H3 - Professional qualifications (4 Years - )
- subject
- keywords
- Track-Bridge Interaction, TBI Analysis, railway bridges, stresses, horizontal reaction forces, sensitivity analysis, Eurocode, Brigade+, finite element modeling
- publication/series
- 0349-4969
- report number
- 25/5309
- other publication id
- LUTVDG/TVBK/25/5309
- language
- English
- additional info
- Examinator: Jonas Niklewski
- id
- 9196000
- date added to LUP
- 2025-06-24 11:47:26
- date last changed
- 2025-06-24 11:47:26
@misc{9196000,
abstract = {{As Sweden expands and modernizes its railway network, the design of durable and cost-
efficient railway bridges becomes increasingly important. A central technical challenge in this
context is track-bridge interaction (TBI), the mechanical interplay between the rail and bridge
structure. This interaction affects how forces from traffic loads, temperature variations and
braking are transferred within the system. It plays a decisive role in determining rail stresses,
substructure loads and whether rail expansion joints are needed. A deeper understanding of
TBI is critical for ensuring structural performance, material efficiency and long-term
functionality, particularly as design standards evolve.
This thesis investigates track-bridge interaction (TBI) in railway systems. The study focuses
on how bridge geometry, boundary conditions and updated design standards influence
additional stresses in the rail and the distribution of forces between the rail and the bridge
components. Using finite element modeling, two case studies were examined: the existing
Bryngeå bridge and the planned Sege å bridge. For Bryngeån, a detailed sensitivity analyses
were conducted by systematically varying parameters such as support stiffness, embankment
length and spring behavior between rail and deck. For Sege å, a TBI analysis was performed
without further parameter studies.
The sensitivity analysis showed that the vertical linear stiffness model for the rail-to-deck
connection can be used without significant loss of accuracy compared to more complex
bilinear alternatives. They also revealed that reducing the horizontal stiffness of the supports
decreases both rail stresses and reaction forces, which could lead to more material-efficient
bridge designs. Additionally, embankment lengths of 300 meters were sufficient to capture
the additional stresses in the system. The analysis of Sege å further showed that nearly half of
the total longitudinal forces are carried by the rail and transferred into the embankments. This
demonstrates a load-sharing behavior that may justify the use of simplified Eurocode
methods, even for bridges exceeding 40 meters in span. Based on the calculated rail stresses,
the bridge across Sege å is expected to meet the requirements for additional axial forces
according to both the current, SS-EN 1991-2:2003, and upcoming, prEN 1991-2:2021,
Eurocode. Consequently, the bridge should be able to be constructed without a rail expansion
joint.
A collaborative workshop with industry and academic experts provided additional insights on
the practical application of Eurocode and the potential for model simplifications. Overall, this
thesis contributes to the understanding of how design assumptions and evolving standards
affect TBI assessments and offers recommendations for more efficient, yet reliable, railway
bridge design.}},
author = {{Magnusson, Moa and Nilsson, Rakel}},
language = {{eng}},
note = {{Student Paper}},
series = {{0349-4969}},
title = {{Track-Bridge Interaction – Sensitivity Studies on the bridge across Bryngeån and TBI Analysis on the bridge across Sege å}},
year = {{2025}},
}