Structural monitoring using optical fibre technology: Fid-Bau Portal

Structural monitoring using optical fibre technology

Metje, N. / Chapman, D.N. / Rogers, C.D.F. / Kukureka, S.N. / Miao, P. / Henderson, P.J.

In recent years there has been increasing interest in methods that give structures the ability to monitor their structural health throughout their life so that deterioration and remediation can be more efficiently managed. Increasingly, fibre optic technology is being viewed as a potential method to monitor the condition of structures with the information transmitted through telephone lines or satellite links to a central monitoring station. This paper describes a new retro-fitted optical fibre system under development for monitoring tunnel displacements, yet with potential for general structural monitoring. The system is based on embedding multiple optical fibre sensors with Fibre Bragg Gratings (FBGs) in a continuous fibreglass rod. As part of the background research into the sensor design, tests have been performed on the optical fibres to show the effects that handling of the fibres and writing of the FBGs have on the breaking stress and the time to failure in a two-point bend test. The effects of stripping the optical fibre are potentially significant, while the effects of H2-loading and UV radiation may safely be ignored. Initial laboratory tests using the new measuring system indicate an encouraging degree of sensitivity, with displacements of the order of 2 mm recorded by longitudinal rods attached to a crane girder. The need for bench testing with accurate control over the movement of the rod's fixings is highlighted and the proposed tests are described.