Life Time Management of Rails Based on Structural Reliability Approach
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Date
2015-05
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Addis Ababa University
Abstract
Preventing broken-rail caused derailments is a high priority for the rail industry. The current
practice is to periodically inspect rails using non-destructive technologies. Determining the
effective inspection frequency is a critical decision in railway infrastructure management.
This thesis discusses some applications of the modelling work to rail defect management. In
particular, main applications are the determination of remedial actions and effective inspection
interval on the basis of the quantitative approach as well as the adaptation of rail inspection and
maintenance procedure.
The frequency of rail inspection tends to vary from one railroad to another, yet it is usually based
on either time or traffic tonnage. Railroad companies have evolved their rail inspection schedules
empirically based on long field experience. Rail defect management refers to the development and
implementation of strategies to control the risk of rail failure. The primary method to control the
risk is a rail inspection through nondestructive evaluation and is a replacement of rails based on
the remedial action plan.
To demonstrate the feasibility of the above applications first, a Linear Elastic Fracture Mechanics
(LEFM) analysis which can predict a crack size in a rail head, web and base is performed. Second,
First Order Reliability Method (FORM) of analysis evaluates the reliability of a rail, considering
some uncertainties of parameters. Third, an Event Tree (ET) analysis represents systematically all
possible events and actions regarding rail defect management. Finally, a Life- cycle cost (LCC)
estimation formulates the total expected cost during the service life are conducted.
Based on the analysis results, the mechanism for remedial action is developed based on critical
crack size at rail head, web and base as well as rail reliability value to help infrastructure manager’s
decision. Then, effective number of rail inspection frequency is determined as three times a year
to prevent the occurrence of rail failure by taking the required action at the right time, and extend
the rail life expectancy, reduce the rail maintenance work and its cost. Finally, appropriate rail
inspection and maintenance strategy model (flowchart) is adopted for Ethiopian railway industry.
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Keywords
Rail defects, Rail inspection., Rail deterioration, reliability Analysis, fracture Mechanics, reliability index, event tree Analysis, life cycle cost