Application of random vibration technique in structural health monitoring

Abstract

Bridge health monitoring system are installed almost on long-span bridge during construction state and sevices state. Structural health monitoring (SHM) rapid assesment of a bridge’s health and is recognized as one of the best ways to increase the safety and optimize bridge operation and maintenance. Modal identification methodologies are performed to determine the dynamic characteristics of structures. In SHM, these dynamic parameters (including natural frequencies, mode shapes and damping properties) play an important role in the understanding of the dynamic behavior of structures. In term of bridge health monitoring, the excitation sources of structures have used several methods such as impact excitation, harmonic force excitation and difference mode of truck excitation, which are subsequent to free decay responses. These methods must be prevented or control vehicle flow. The other excitation is ambient such as wind, traffic which is more advantage and does not need to interrupt traffic flow. This study focuses on the using of Natural Excitation Technique combined with the Eigen Realization Algorithm (Next-ERA) for modal identification. This is an output-only system identification with first step to compute a covariant or cross spectra of output and then which is an input of ERA. The study includes providing a mathematic algorithm on Next-ERA method and then application to analyze dynamic responses of the bridge under ambient excitation.

Key words: Ambient vibration; Structural health monitoring, modal parameters.