A harmonic vibration, output only and time-frequency representation based method for damage detection in Concrete piers of complex bridges

Due to damage, vibrations of bridge piers compared with undamaged state would be changed. A new signal-based algorithm is proposed to extract feature and detect damage in complex bridges. According to the proposed algorithm, it is necessary to vibrate the bridge before and after damage by exciting force and record responses at the middle and top of the piers. For this purpose, sine and cosine transient forces were applied to the analytical model of Ghotour Bridge and the signals of pier responses were recorded. Using reduced interference distribution, the response signals were processed and time-frequency plans were calculated. Modified matrix subtraction method was proposed to detect damage. Based on the results, damage was identified and located with good accuracy. The proposed algorithm is an output-only method and in practice there is no need to create an analytical model of an existing complex bridge for damage detection.