Eiichi Nishida

Simplified Aseismic Design Method of Boiler Structures Focused on Joint Element Characteristics

Efficient aseismic design method of boiler structures is studied focused on joint elements between boiler and its supporting structure, in which passive and semi-active dampers are equipped. Based on substructure synthesis approach, transformation method between dual-mass model/multi-mass model is proposed and the equations which relate the joint element parameters in both models are derived. Based on numerical examination, it was shown that results of dual-mass model parameter survey are reflected accurately to multi-mass model which is used in actual design.

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.

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

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.