Operational Modal Analysis on Structures with Rotating Parts

Operational Modal Analysis was originally invented for vibration analysis on civil engineering structures exposed to ambient excitation being purely stochastic and broadband in nature. When performing Operational Modal Analysis on civil or mechanical engineering structures with dominating rotating parts, the original algorithms are often inadequate in providing accurate results due to deterministic excitation. This paper describes recently developed algorithms allowing Operational Modal Analysis to be performed on structures, where a significant part of the vibration is originating from the rotating parts. This includes Fast Kurtosis Checking, Enhanced Kurtosis Checking and the Curve-fitting Frequency Domain Decomposition technique. In addition, practical measurement considerations concerning dynamic range and time recording length are discussed. The applicability of the algorithms is assessed for cases within civil and mechanical engineering.