Application of distributed optical fiber sensors for the health monitoring of two real structures in Barcelona

Abstract

The versatility and easy installation of Distributed Optical Fiber Sensors (DOFS) compared with traditional monitoring systems is an important characteristic to consider when facing the Structural Health Monitoring (SHM) of real world structures. The DOFS used in this study provide continuous (in space) strain data along the optical fiber with high spatial resolution. The main issues and results of two different existing structures monitored with DOFS, are described in this paper. The main SHM results of the rehabilitation of an historical building used as hospital and the enlargement of a prestressed concrete bridge are presented. The results are obtained using a novel DOFS based on an Optical Backscattered Reflectometry (OBR) technique. The application of the optical fiber monitoring system to two different materials (masonry and concrete) provides also important insights on the great possibilities of this technique when monitoring existing structures. In fact, the influence in strain transfer between the DOFS and the bonding surface is one of the principal effects that should be considered in the application of the OBR technique to real structures. Also, and because structural surfaces generally present considerable roughness, the procedure to attach the optical fiber to the two monitored structures is described.

Distributed optical fibre sensors in concrete structures: Performance of bonding adhesives and influence of spatial resolution

“…Furthermore, in the authors' personal experience, a combined use of epoxy adhesive with polyimide fibre when bonded to the concrete surface had offered promising results in different experiments …”

“…Raman scattering is highly dependent of temperature variations, which has led to some applications in civil engineering SHM but has been more typically used in other fields …”

“…2 Raman scattering is highly dependent of temperature variations, which has led to some applications in civil engineering SHM but has been more typically used in other fields. 5 Brillouin scattering-based DOFS on the other hand have been the most studied and used DOFS systems in civil engineering SHM applications due to their large-scale capability, which can go up to the kilometre range. This technique was initially introduced with the use of optical time domain reflectometry (OTDR), which has an inherent low spatial resolution (of around 1 m), which is not ideal for crack detection applications.…”

“…Previous work has displayed the promising capabilities of this technology on the monitoring of civil engineering infrastructures …”

“…Previous work has displayed the promising capabilities of this technology on the monitoring of civil engineering infrastructures. [3][4][5][6][7][8] Nevertheless, as mentioned before, this is still a relatively new approach of this technology in the application on civil engineering infrastructures, which still presents substantial uncertainties regarding its use. Therefore, a continuous and deeper research of this topic is of vital importance for an eventually more systematically and regular use in SHM applications.…”