Health monitoring of reinforced concrete structures with hysteretic dampers subjected to dynamical loads by means of the acoustic emission energy

A test specimen representing a scaled reinforced concrete frame structure with hysteretic dampers was subjected to sequential seismic simulations of incremental peak acceleration on a 3 x 3 m(2) shaking table. From this specimen, two beam-column connections-one exterior and one interior-were continuously monitored with wideband low-frequency acoustic emission sensors properly attached on the structure. Complementing other Non-Destructive Testing (NDT) methods, acoustic emission has proven to be a reliable technology for structural health monitoring within a predictive maintenance program. In particular, it was found that the accumulated energy of acoustic emission signals-properly filtered by means of the root mean squared and the spectral partial power of the waveforms in order to avoid the influence of secondary sources-correlated well with the plastic strain energy released by the specimen. Moreover, the use of the rise angle and average frequency of the filtered acoustic emission signals allowed for successful discernment between tensile and shear cracks in the concrete. The acoustic emission energy associated with shear cracks was found to be substantially lesser than that corresponding to tensile crack. This observation is consistent with the fact that the beams and column of the tested reinforced concrete frame were designed under modern codes aimed at preventing the brittle shear failure of members.