Modal identification of boiler plant structures by seismic records(Identification based on a single-input/multi-output model).

Abstract

This paper deals with an experimental modal analysis method for large-scale structures such as boiler plants in thermal power stations. Practical and accurate modal identification has been carried out by the proposed method, which is composed of two stages : (1) processing transfer functions by autoregressive (AR) spectral analysis, and (2) a curve-fitting technique to extract modal parameters. Seismic records of base acceleration are utilized as input data, and a series of response acceleration records at various points of the structure are utilized as multi-output data. This method is examined using time-series data of seismic response simulation. Introduction of two techniques, namely, decimation of time data and FPE criterion to optimize the order of the AR model, have realized effective and accurate identification. 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 seismic modeling of large-scale structures.