Bridge vibration logarithmic decrement estimation at the presence of amplitude beat

Logarithmic decrement is one of the key dynamic parameters characterizing bridge status. It is usually estimated from vibration records applying digital signal processing. Among the processing procedures band-pass filtering is commonly used to extract spectral components of interest. We analyze the case when two very close spectral components are present in the acceleration records. We show that construction of the filter is non-trivial in such a situation and failing to choose optimal filter’s parameters leads to significant logarithmic decrement estimation errors. Therefore we propose a method that does not require band-pass filtering but utilizes knowledge of amplitude beat presence. Simulation of the method indicated errors by an order less than using filtering.