Bridge monitoring through ambient vibration measurement

Bridge monitoring through vibration analyses often have to use ambient vibration as excitation sources for the input force is not available and therefore the transfer functions cannot be obtained. The signals from bridge responses are often random. Conventionally used technologies that deal with random vibration signals, such as correlation analysis and/or random decrement method, may be less accurate when the signal-to-noise ratio is too low. In this paper, a new approach called the lag superposition method is presented, which may provide better response spectrum and more accurate results with reasonable computation speed. Formulas for SDOF and MDOF systems using this method are suggested. Experimental tests and numerical examples are presented to verify the method.