An Overview of Operational Modal Analysis: Major Development and Issues

An overview of the major development of operational modal identification is presented. It includes four time domain approaches, i.e. NExT-type, ARMAV model-based, stochastic realization-based, stochastic subspace-based methods, and two frequency domain approaches, i.e. FDD-type and output-only LSCF-type methods. The internal relation with traditional modal identification using input/output measurements for EMA, as well as with classical and modern system identification are revealed. The major issues in OMA are also summarized, which cover full or partial references, multiple sensor setups, nonstationary excitation, data-driven vs covariance-driven SSI, structural mode sorting, bias or unbiased modal parameter estimation, as well as mode shape scaling.