Strengthening and monitoring concrete structures using glass fiber composites and FBG sensor

The research works related to the use of fibre reinforced plastics (FRP) in civil concrete engineering application have been found increasingly only in recent years. Most of the studies were concentrated on the use of bonding FRP onto the plain rectangular beams and columnar concrete specimens under three point bending and uni-axial compression tests, respectively. The results gave a compromising solution for both strengthening and retrofitting of plain concrete samples. Unfortunately, the defection of the reinforced sample cannot be measured visibly due to the coverage of the bonding patch. To increase the efficient and precision in monitoring of the strengthened structure, Fibre-optic Bragg Grating (FBG) sensor is being introduced in embedding it into the structure to measure the internal strain under applied load. This paper presents the experimental results of cylindrical concrete specimens with and without strengthening by wrapping glass fibre composites under uni-axial compression loading. FBG sensors were pre-embedded into concrete specimens and at the interface between the reinforced laminate and concrete surface. The test results show a considerable increase in the ultimate compressive strength and confine the lateral expansion of the strengthened specimens. The strains extracted from the embedded FBG sensor compare well with that measured by the surface bonded electrical strain gauges.