Investigation on strengthening and strain sensing techniques for concrete structures using FRP composites and FBG sensors

This paper reports tile results of an experimental investigation on the mec hanical properties of the laboratory size rectangular concrete beams with t he notch formation on the tension surface strengthened by using fil,rr: rei nforced plastic composites. Fibre-optic Bragg grating (FBG) sensors have be en embedded at the interface between the concrete surface and external bond ed composites to measure the strain variations when the strengthened struct ures were subjected to three-point bending load. Multiplexing strain-sensin g technique has been used for measuring the strains in different locations of the beam by using one single optical fibre. External bonded strain gauge s were also attached on the surfaces of composites to measure the surface s train and the results were compared with that obtained from the embedded FB G sensors. The observation in the experiments showed that the flexural load capacity of the strengthened concrete beams was increased significantly af ter strengthening by laying-up the composite laminate for both plain and no tched concrete structures. Debond and concrete failure occurred at the: pla te end region when the thick composite laminate was used. The embedded FBG sensors could provide the indication to the operator when the structure ser viced in strange conditions. The strains measured at the interfaces from th e sensors were higher than that from the surface bonded strain gauges ill g eneral.