Strengthen and real-time monitoring of RC beam using “intelligent” CFRP with embedded FBG sensors

The reinforced concrete (RC) structures strengthened with carbon fiber reinforced polymers (CFRP) have been widely used since they have the prominent characteristics that the structures strengthened with traditional methods cannot compare with. FBG sensors have excellent performances of high sensitivity, interference resistance, corrosion resistance, micro-volume, lightweight and variable form, one-line multi-point monitoring, long distance monitoring etc. Due to the compatibility with CFRP sheets, they can be embedded into the CFRP-strengthened RC beams. In the paper the strain change of CFRP is calculated through monitoring the wavelength change of FBG sensors during load-bearing process of the tested RC beams. Then the theoretically calculated strain of tensile steel and compressive concrete is obtained according to the plane cross-sectional geometric relationship function. It is found that the theoretically calculated strains agree well with the experimental value monitored by FBG sensors. The wavelength signal of FBG sensors embedded in CFRP has a uniform linear relationship with the strain measured by strain gauge. The real-time theoretically calculated load agrees well with the applied load.