Lag Superposition Method for Structural Analysis through Ambient Vibration

Vibration analyses for non-destructive evaluation of large-scale civil engineering structures often rely on ambient vibrations as excitation sources. In this case, the input force is typically not available for establishing the transfer functions for vibration analyses. Conventional technologies dealing with random vibration signals, such as correlation analysis and/or random decrement method, may yield less accurate results when the signal-to-noise ratio of the response measurement is not sufficiently high. In this paper, a method called lag-superposition is introduced that provides a better response spectrum and more accurate results with reasonable computation speed. Formulations of Single-Degree-of-Freedom (SDOF) and Multi-Degree-of-Freedom (MDOF) approaches are presented and verified by experimental tests and numerical examples. Comparisons with other methods are also made.