Advanced monitoring of fiber plastic reinforced structures

Abstract

Advanced composites offer some advantages over traditional procedures for repairing concrete structures due to their optimal corrosion properties, low weight and decreasing costs. Thin cured laminates may be externally bonded or dry fabrics can be wet applied and in situ cured over the concrete structure, conforming to its surface irregularities. Fiber optic strain sensors, specially Bragg graings, show some advantages when compared to conventional strain gauges: absolute measurements, spectrally encoded output, no EMI, no drift (long-term stability), low size, multiplexing capabillity and their avility to be embedded into laminates without degradation. The combination of both techiques is easy and offers important advantages. The longterm mechanical behaviour of the repair may be checked and information on evironmental degradation could be obtained. In this way, a repaired ?smart? structure is obtained comparable to a new one. On the short term, information on the stress transfer from the concrete to the laminate is obtained, and the validity of models is verified. Tests on a concrete beam repaired with CFRP (Carbon Fiber Reinforced Plastic) and instrumented with Bragg gratings are reported, showing the possibility of the intelligent repair.