Damage Identification of Bridge Structures Under Moving Loads Based on Fractional Fourier Transform

Timely and accurate damage identification can provide necessary guidance for bridge operation and maintenance. As the moving load is the main live load during service period, this paper proposes a damage identification method for bridges subjected to moving load based on fractional Fourier transform (FRFT). First, bridge response induced by moving load in time domain is rotated into fractional Fourier domain by using FRFT. Filtering and decomposing are conducted on the transformed moving load induced response by adjusting the angle parameter of FRFT and inverse FRFT to obtain the first intrinsic mode function. Then the relative FRFT entropy (RFE) index is defined based on the first intrinsic mode function for damage localization. The functional relationship between RFE and damage severity is established for damage quantification. Numerical and experimental examples of a simply supported beam with positive damage and negative damage under the excitation of moving load are carried out to investigate the performance of the proposed method. The results reveal that the proposed method can effectively and rapidly localize and quantify damages of the bridge subjected to moving load with a single sensor.