Impact resonance method for damage detection in carbon-fibre-reinforced polymer-strengthened reinforced concrete beams subjected to fatigue and thermal cycling

Much of North America's civil infrastructure is rapidly aging and, in some cases, exceeding its design life and load. To combat this, the exploration of simple and effective methods for rehabilitation and structural health monitoring has been receiving much attention in industry and academia. This paper reports on the use of the impact resonance method (IRM) for evaluating the structural health of thermal-cycled reinforced concrete (RC) beams with and without externally strengthened carbon-fibre-reinforced polymer (CFRP) pultruded plates. In the experimental program, 1.2 m long specimens were subjected to 55 thermal cycles ranging from +23 to -18 degrees C. Fatigue loading consisting of up to two million cycles at high and low stress levels was performed. At pre-determined load cycle intervals, the loading was stopped and the IRM was performed on the specimens. Parameters including the appearance of the fast Fourier transform (FFT) spectrum of the specimens' vibration, modal fundamental frequencies, and dynamic properties were used to assess damage in the specimen. Conclusions were made regarding the use of the IRM in monitoring the health of strengthened and unstrengthened RC beams subjected to thermal and fatigue cycles.