Modal Identification of Boiler Plant Structures by Seismic Records. Identification based on a Multi-Input/Output AR Model.

This paper deals with a practical experimental modal identification method for large-scale structures such as boiler plants in thermal power stations. The proposed method utilizes seismic records which include multi-directional base acceleration data, and multi-I/O identification is carried out. This method is composed of two stages : (1) processing frequency transfer functions by multi-variate autoregressive (AR) spectral analysis, and (2) curvefitting to extract modal parameters. This method is examined using time series data of seismic response simulation, and a comparative study is carried out between multi-input and single-input identification. It is shown that multi-I/O identification is essential for asymmetrical large structures such as boiler plants. This method has actually been applied to in-situ seismic observation data of a boiler plant in operation. As a result of these investigations, this kind of modal identification has proven to be an effective tool for dynamic modeling of large scale structures.