Identification of random force acting on a layered structure

Abstract

The structural health monitoring is a very important technology for realizing a sustainable society. Building structures are subjected to random vibrations from the surrounding environment such as wind, and it is necessary to identify the random external forces for structural health monitoring. In this study, we assumed the case where the random external force such as wind acts on the layered structure, and proposed the identification method of the random external force. The identification method is to identify the power and cross spectrums of the random external force from the measured power and cross spectrums of the response and the frequency response function of the structure previously identified. In the governing equations of this inverse problem, the fact that the power spectrum is a real number and the conjugate relationship of a certain variables are used to reduce the ill-posedness of the inverse problem by reducing the variables in advance. After constructing a concrete identification procedure for a three-layered structure, the validity was verified by numerical simulation. It was shown that the spectrums of the random external force acting on the structure could be identified with sufficient accuracy. Next, we conducted an experiment to verify applicability. A simple three-layered structure was constructed, and inertia type exciters were installed on all layers. Then, when the vibration exciters are operated, the actual external force acting on the structure was measured with a load cell, and the external force was identified by applying the proposed method using the measured response data. Furthermore, numerical simulations were carried out to reproduce the experiments, and it was shown that the proposed method could identify random external forces.