The Effect of Track Irregularity on the Underframe Car Body Structure in Light Rail Vehicles

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dc.contributor.advisorAraya Abera
dc.contributor.authorYalemtsehay Alebachew
dc.date.accessioned2026-06-20T15:27:46Z
dc.date.available2026-06-20T15:27:46Z
dc.date.issued2026-03
dc.description.abstractThis study investigates the effect of track irregularities on the dynamic behaviour and fatigue life of light rail vehicle underframes. This was done by a combination of multibody dynamics simulation (MBDS) and finite element analysis (FEA). A 3D underframe geometry model was developed in SOLIDWORKS and integrated as a flexible body to a multibody system dynamic model in SIMPACK to simulate load time histories for various speed conditions. Stresses were analysed using FEA with a quasi-static stress method, and fatigue life was evaluated in ANSYS nCode Design Life. Results show that motor car underframes experience higher vertical and lateral accelerations than trailer car underframes, with effects intensifying at higher speeds. FEM analysis indicates that track irregularities have a significant effect at higher vehicle speeds, thus reducing underframe fatigue life. At 70 km/h, fatigue life reduces to 1.36e⁵ cycles for motor cars and 7.76e⁵ cycles for trailer car underframes, both lower than standard design life. The fatigue life results were validated using the Smith-Watson-Topper (SWT) fatigue life approach and found to be in good agreement. This study provides key findings for improving underframe durability and maintenance practices in urban transit systemsThis study investigates the effect of track irregularities on the dynamic behaviour and fatigue life of light rail vehicle underframes. This was done by a combination of multibody dynamics simulation (MBDS) and finite element analysis (FEA). A 3D underframe geometry model was developed in SOLIDWORKS and integrated as a flexible body to a multibody system dynamic model in SIMPACK to simulate load time histories for various speed conditions. Stresses were analysed using FEA with a quasi-static stress method, and fatigue life was evaluated in ANSYS nCode Design Life. Results show that motor car underframes experience higher vertical and lateral accelerations than trailer car underframes, with effects intensifying at higher speeds. FEM analysis indicates that track irregularities have a significant effect at higher vehicle speeds, thus reducing underframe fatigue life. At 70 km/h, fatigue life reduces to 1.36e⁵ cycles for motor cars and 7.76e⁵ cycles for trailer car underframes, both lower than standard design life. The fatigue life results were validated using the Smith-Watson-Topper (SWT) fatigue life approach and found to be in good agreement. This study provides key findings for improving underframe durability and maintenance practices in urban transit systems
dc.identifier.urihttps://etd.aau.edu.et/handle/123456789/8242
dc.language.isoen
dc.publisherAddis Ababa University
dc.subjectTrack Irregularity
dc.subjectUnderframe Structure
dc.subjectLight Rail Vehicles
dc.subjectFatigue Life
dc.subjectMultibody Dynamics
dc.subjectFinite Element Analysis
dc.subjectSWT Approach
dc.titleThe Effect of Track Irregularity on the Underframe Car Body Structure in Light Rail Vehicles
dc.typeThesis

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