ABSTRACT
Modal properties including natural frequencies, damping ratios and mode shapes are important characteristics for civil engineering structures. These characteristics are the fundamentals of structural response analysis under traffic, wind and earthquake induced loads. In addition to analysis, these characteristics have also been used for a variety of other purposes such as finite element model updating, vibration mitigation and control, condition assessment, and health monitoring of structures. Modal properties normally are obtained indirectly through processing some measured responses from the structure. The most frequently used response for such a purpose is the acceleration time history which can be easily and accurately measured by accelerometers. Accelerometers although provide accurate and sensitive acceleration measurements, they are nevertheless discrete sensors that measure acceleration along one direction at the installed locations only. While the discrete measurement does not affect the extraction of natural frequencies and damping ratios, it unavoidably limits the determination of mode shapes which are spatially continuous.
