| During the period of its service,the building structure has been affected by the natural environment and human factors and accumulated damage.The existence of damage will seriously affect the performance and safety of the structure,so damage identification is of great significance to the safe operation of building structures.Hilbert-Huang transform has been widely used in structural damage identification due to its advantage in time-frequency analysis of nonlinear signals.However,as the core step of Hilbert-Huang transform,empirical mode decomposition（EMD）has some problems,such as end effect and mode mixing.In this paper,the end effect of EMD was analyzed,and a novel method for restraining the end effect was proposed based on the adaptive waveform matching extending.The ensemble empirical mode decomposition method（EEMD）based on the adaptive waveform matching extending was applied to the processing and analysis of structural response under earthquake,then a damage identification method based on the instantaneous frequency of the characteristic intrinsic mode function（IMF）and the relative deviation of first-order IMF energy was proposed,and the effectiveness of the proposed method was verified by numerical model and actual structure.The main research contents of this paper are as follows:（1）The problems in empirical mode decomposition was analyzed.Aiming at the mode mixing problem,the mechanism of mode mixing caused by the interaction of dense modes and intermittent signal was analyzed through simulation signals,then the basic principle of ensemble empirical mode decomposition to restrain mode mixing was described;aiming at the problem of end effect,the effects of the boundary conditions of cubic spline interpolation and the absence of extreme points at the ends on the decomposition results was studied,and the evaluation indexes of the end effects was summarized.（2）A method for restraining the end effect based on the adaptive waveform matching extension was proposed.In this method,the locally matched wave set was intercepted by the improved wave cutting method,and then the local optimal waveform was searched by the waveform matching index based on the amplitude matching degree and slope matching degree,finally,the global optimization of the local optimal waveform was carried out through the evaluation index of the end effect,so as to realize the matching extension of the optimal waveform at the end of the signal.（3）The EEMD method based on the adaptive waveform matching extension was applied to the seismic response analysis of structures,and a damage identification method based on the instantaneous frequency of the characteristic IMF and the relative deviation of first-order IMF energy was proposed.The effectiveness of the damage identification method was verified by the damage identification of a 3-DOF numerical structure model under various damage conditions under earthquake.（4）The damage identification method proposed in this paper was used to analyze the structural response of an actual building under two earthquakes,and the damage identification results was compared with the actual damage status of the structure.The comparison results show that the damage identification method can effectively identify the damage of structures under earthquake,and the damage identification results are consistent with the actual damage status. |
