Simple abnormality diagnosis of layered structures using an additional vibratory system

This study introduces a primary diagnosis method for multi-layered structures, leveraging response measurements from an additional vibratory system (AVS) installed on each floor. The goal of the proposed method is to identify the location and severity of abnormalities. Drawing from research in the architectural field, a reduction in the stiffness (spring constant) of building walls and columns is treated as an abnormality. The concept behind the proposed method is as follows. An AVS with known characteristics is attached to each floor. When a structure is subjected to base excitation due to slight ground vibration or road traffic, the frequency response function (FRF) of the response of the AVS to the base excitation is measured. Then, the method is used to perform a diagnosis starting from the bottom layer. At this time, abnormalities are diagnosed based on the mass of the multi-layer structure to be diagnosed and the characteristics of the AVS. A key feature of the proposed method is that the diagnosis is not affected by the damping magnitude of the target structure. The method was explained using a three-layered structure as an example, and its validity and applicability were verified through numerical simulations and experiments. Numerical simulations using noise-free FRFs demonstrated that the spring constant was identified with high accuracy under all four abnormal conditions with different levels of abnormality. Experimental validation using FRFs containing actual measurement noise also confirmed that the spring constant was identified well.