Fibre Optic Sensing of Ageing Railway Infrastructure enhanced with Statistical Shape Analysis

Haris Alexakis*, F. Din-Houn Lau, Matthew DeJong

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Developing early-warning sensor-based maintenance systems for ageing railway infrastructure, such as masonry arch bridges, can be a challenging task due to the difficulty of identifying degradation/damage as the source of small, gradual changes in sensor data, as opposed to other environmental and loading effects. This paper offers a new method of applying statistical modelling and machine learning to enhance the interpretation of fibre optic sensing data, and, therefore, improve deterioration monitoring of railway infrastructure. Dynamic strain and temperature monitoring data between 2016 and 2019 from a fibre Bragg grating (FBG) network installed in a Victorian railway viaduct are first presented. The statistical shape analysis adopted in this study is modified to track changes in the shape of FBG signals directly linked to train speed and dynamic strain amplitudes. The method is complemented by a support vector machine, which is trained to identify different classes of trains. After distinguishing train types, dynamic strain was found to be clearly correlated to temperature, verifying previous findings. No correlation with train speed was observed. The integrated system is then able to compensate for changes in the structural performance due to variations in train loading and ambient temperature, and identify changes in dynamic deformation caused by degradation, in an order comparable to the signal noise (± 2 micro-strain). As a result, the new procedure is shown to be capable of detecting small magnitudes of local degradation well before this degradation manifests itself in typical global measures of response.
Original languageEnglish
Pages (from-to)49–67
Number of pages19
JournalJournal of Civil Structural Health Monitoring
Early online date29 Sept 2020
Publication statusPublished - Feb 2021

Bibliographical note

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Funding: This work is being funded by the Lloyd’s Register Foundation, EPSRC and Innovate UK through the Data-Centric Engineering programme of the Alan Turing Institute and through the Cambridge Centre for Smart Infrastructure and Construction. Funding for the sensing system development and deployment was also provided by the EPSRC (Grant Ref. EP/N021614/1) and by Innovate UK (Grant Ref. 920035).


  • Asset management
  • Bridges
  • Fibre optics
  • Masonry structures
  • Shape analysis


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