Bragg Grating and BOTDR Fiber Optic Principles Applied for Real-Time Structural Monitoring—The MONICO Project

Abstract

Structural engineering is a field of engineering dealing with the analysis and design of structures supporting or resisting various loads. Studies of structural engineering requirements, specifically for densely populated areas, have indicated the need for high safety standards particularly in structural monitoring having in mind latest shifts from construction costs to life cycle costs and lifetime performance including safety and use. Structural monitoring is now being supported by various emerging technologies especially in areas of high seismicity where structural monitoring can be regarded of particularly high importance. Optical sensing technologies have a lot to offer in the field of structural monitoring providing the basis for condition assessment before, during or after any event. Structural monitoring based on fiber-optic technologies provide real-time, wireless and remote deformation sensing capabilities making them ideal regarding safety of vulnerable tunnel crosssections or sections where very high standards of safety are required. Quick and reliable structural assessment can be enhanced with integrated software that collects and processes the data and assesses the structural reliability of the lining. Optical sensing technologies are most of the times supported by the above algorithms and are technologically progressing day by day. However it is quite important that the already existing and emerging deformation technologies are evaluated and optimised so that they alone, or in combination, can provide optimal performance in the structural sensing of structures and particularly tunnels. The MONICO EC Project has developed a prototype system consisting of an optimized fibre optics based deformation-sensing system for real-time measurement of deformations of reinforced concrete linings in tunnels and a Decision-Support-System (including user interface and decision suitable algorithms) that can drive proactive maintenance and earthquake risk management and can assess the structural reliability of the monitored lining under operating and seismic loads. Through this paper, the technologies, algorithms and supporting software components will be presented together with the results of the final large-scale tests of the MONICO project.