Hybrid numerical-analytical approach for predicting the vertical levelling loss of track geometry in a heavy-haul railway

Oliveira de Melo, Andre Luis ORCID: 0000-0002-1186-6403 (2023). Hybrid numerical-analytical approach for predicting the vertical levelling loss of track geometry in a heavy-haul railway. University of Birmingham. Ph.D.

Preview

Oliveira2023PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (7MB) | Preview

Abstract

Post-construction track geometry deterioration is one of the major problems for railway track maintenance. Increasing train velocities, frequencies of railway transport, and axle loads can accelerate rapidly this deterioration due to repeated traffic loadings. Technically, this trend requires higher standards not only for each individual track component but also for the track geometry. An important contribution to the track geometrical deterioration is the ballast settlement, which impacts on the track geometry, specifically on one of the most important track geometrical parameters: the vertical levelling (VL). Any weakness in the railway track support sub-system will affect negatively the railway track vertical profile. It means inferior ride comfort quality and excessive dynamic forces for railway track and vehicles components, resulting inevitably in a less attractive and safe railway. Track geometrical vertical levelling loss (VLL) is defined as a parameter of how much the rail losses its vertical position in the track physical space. The track conditions (smooth, unsupported-sleeper, and uneven tracks) plays a significant role in accelerating the VLL.
With an emphasis on the combined degradation of railway track geometric elements and components, an innovative hybrid numerical-analytical approach is proposed for predicting the VLL. In contrast to previous studies, this research unprecedentedly considers the effect of unsupported sleepers (US) and the influence of initial track irregularities (ITI) on VLL under cyclic loadings, elastic-plastic behaviour, and different operational dynamic conditions. The nonlinear numerical models are simulated using an explicit finite element (FE) package, and their results are validated by experimental data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, which innovatively extends the effect of track condition on VLL in a long-term behaviour. Additionally, a power function factor innovatively extends the response of US on VLL over a long term. New findings reveal that this innovative numerical-analytical approach can very well predict the VLL long-term performance considering not only the number of cycles or MGT but also different dynamic conditions to support the development of a specification to proceed the investigation of track geometrical degradation. This approach can also support more complex analysis of track geometry elements with a minimal need of carrying out expensive field experiments. Moreover, the proposed methodology can accurately predict both the effect of US and the influence of initial track irregularities on the track geometrical VLL considering different railway operational conditions (and configurations). Finally, this hybrid numerical-analytical approach can be applied to enhance the development of new practical maintenance and construction guidelines to support the maintenance activities in a heavy-haul ballasted railway track for a minimum effect on VLL extending the railway track service life.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):