Tracking deflection in the field using optical system: A case study

Y. Xu, F. Huseynov, J. M.W. Brownjohn, E. J. O’Brien, D. Hester

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)


Monitoring displacement of in operation bridges is practically challenging but potentially very useful for condition assessment and decision support. The primary difficulties are in finding fixed physical reference points and, for the majority short span bridges under normal operation, the mm-level magnitudes of displacement under normal operating conditions (e.g. standard truck loading). With rare possibility for physical connection between a reference and a bridge, non-contacting technologies such as GPS need to be used. Other options include total station and more exotic technologies of laser interferometer and radar have also been tried. There are drawbacks for each technology related to limited sample rate (for total station) and signal to noise ratio (for GPS) while radar and laser are expensive and require specialist users. With advances in computing power, optics-based systems are becoming popular, relying on a standard lens but with capability to track multiple positions with potential to recover deformation with high spatial resolution. This paper reports the experiences of the authors exploring the suitability of a commercially available optics-based system in terms of spatial and temporal resolution and sampling and in challenging field conditions required for long term monitoring. For example issues such as stability of camera mounting (e.g. in wind) and varying lighting conditions while not problematic in a laboratory govern performance in the field. The paper tracks a sequence of experiments moving from lab to field, ultimately moving up to a field test on a road bridge in Devon. In each case the capabilities and limitations of the system have been critically examined. The study has defined both limitations and capabilities, while defining best approaches for use and at the same time providing some useful performance data on the subject bridges.

Original languageEnglish
Title of host publicationSafety and Reliability – Theory and Applications - Proceedings of the 27th European Safety and Reliability Conference, ESREL 2017
EditorsMarko Cepin, Radim Briš
PublisherCRC Press/Balkema
Number of pages6
ISBN (Print)9781138629370
Publication statusPublished - 01 Jan 2017
Event27th European Safety and Reliability Conference, ESREL 2017 - Portorož, Slovenia
Duration: 18 Jun 201722 Jun 2017


Conference27th European Safety and Reliability Conference, ESREL 2017

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality

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