Applications of distributed fiber Bragg grating sensors in civil engineering

Abstract

We report on civil engineering applications of wavelength multiplexed optical-fiber Bragg grating arrays produced directly on the draw tower for testing and surveying advanced structures and material like carbon fiber reinforced concrete elements and prestressing tendons. We equipped a 6mx0.9mx0.5 m concrete cantilever beam reinforced with carbon fiber lamellas with fiber Bragg grating sensors. Static and dynamic strain levels up to 1500 μm/m were measured with a Michelson interferometer used as Fourier spectrometer with resolutions of about 10 μm/m for all sensors. Comparative measurements with electrical resistance strain gauges were in good agreement with the fiber optic results. We used the fiber sensors in two different arrangements: some Bragg grating array elements measured the local strain while others were configured in an extensometric way to measure moderate strain over 0.1-1 m.