Structural Identification Using Response Measurements under Base Excitation

Abstract

In vibration-based structural identification, experimentally obtained modal parameters from measured structural responses are often used, along with some information about the structural model, for identifying the physical parameters, i.e. mass and stiffness matrices of the structural system. In this study, we consider this problem of physical parameter identification for building structures subjected to base excitation, and attempt to address the issues of (a) unknown scaling of experimental mode shapes, (b) incomplete instrumentation, and (c) incomplete information of the physical parameters of the structural system prior to identification. A mode shape normalization and expansion approach, which incorporates the information available from the structural topology of the physical system in terms of its modal parameters, is discussed. Using this proposed approach, along with the modal orthogonality relations, the mass and stiffness matrices of the system can be estimated. The performance of the algorithm is finally evaluated through numerical simulations of base acceleration induced vibrations of a 4-story shear-type frame, as well as using experimental data collected from a 4-story frame subjected to base excitation on a shake table facility. The use of the modal-and-physical parameter identification method for the purpose of structural damage detection is also investigated using the experimental data, with the damage being represented by a reduction in the cross-sectional area of two columns of the “healthy” frame.