Application of the ERA Method in Vibration Testing of Frame-Structured Material Feeding Bridges Under Ambient Excitation

Ambient excitation modal analysis falls under operational modal analysis (OMA), requiring only knowledge of the output signals from the investigated structure during the analytical process. The Eigensystem Realization Algorithm (ERA) is a time-domain analysis method for conducting modal analysis of structures under ambient excitation. This paper elaborates on the fundamental principles and computational methodology of ERA. Through field data acquisition of acceleration response from a frame-structured material feeding bridge in a biomass power plant subjected to random equipment-induced vibrations, wavelet denoising is employed to extract the free vibration response signals of the structure, effectively separating structural dynamics from noise contamination, ultimately facilitating modal parameter extraction for the feeding bridge through the ERA. The Modal Amplitude Coherence (MAC) was introduced to eliminate spurious modes and discriminate authentic structural modal parameters. Subsequent cross-verification with finite element analysis (FEA) results demonstrates that the ERA algorithm achieves superior precision in identifying dynamic parameters of frame structures under ambient excitation.