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Distributed sensing of a masonry vault during nearby piling

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Acikgoz, S 
Giardina, G 
Aitken, J 
Soga, K 


Piles were constructed inside historic brick barrel vaults during the London Bridge Station Redevelopment. In order to ensure safe operation of the tracks above, movements of the vaults were monitored regularly by total stations. Concurrently, two distributed sensing technologies, fibre optic cables and laser scanners, were used to investigate the vault response to settlements. This paper discusses the monitoring data retrieved from these ‘point’ and ‘distributed’ sensing technologies and evaluates their use in structural assessment. The total station data are examined first. It is characterized by high precision and limited spatial coverage due to the use of optical targets. As a result, the total station data are useful for threshold detection but do not provide a detailed understanding of structural response or damage. In contrast, by utilizing distributed fibre optic sensors based on Brillouin optical domain reflectometry, the strain development in the structure during piling is quantified. The location and width of resulting crack openings are also determined, providing useful indicators for damage evaluation. The comparison of point clouds from laser scanners obtained at different stages of pile construction further expands the spatial coverage by detecting global movement of the structure on all visible surfaces. Using these data, the two hinge‐response mechanism of the vault is revealed. The rich distributed data enable the calibration of the 2D mechanism and the finite element models, elucidating the contribution of arch stiffness, arch and backfill interaction, potential lateral movements and inter‐ring sliding to the response.



distributed sensing, fibre optics, laser scanning, cloud comparison, masonry arch bridge, settlement

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Structural Control and Health Monitoring

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Engineering and Physical Sciences Research Council (EP/L010917/1)
Engineering and Physical Sciences Research Council (EP/N021614/1)
Engineering and Physical Sciences Research Council (EP/K000314/1)
Engineering and Physical Sciences Research Council (EP/I019308/1)
The work carried out was funded by EPSRC and Innovate UK, through the Cambridge Centre for Smart Infrastructure and Construction. The research materials supporting this publication can be accessed at The authors are grateful to Tim Embley of Costain and Jim Woodhams of Topcon for making this project possible. They’d like to thank Network Rail for allowing them to publish this data. Help from a number of individuals requires special mention; Vincent Auzel of Soldata, Dean Bain of Costain and Andy Evans of Topcon provided useful information that enabled this study. CSIC colleagues Peter Knott, Jason Shardelow and Emanuele Giglio assisted in site work and discussions with Matthew DeJong helped improve the manuscript.
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