Dynamic Test signal Analysis and Modal Parameters Identification of High-pier Long-span Rail Bridge Based on HHT

Dynamic loading test is exerted on a railway continuous beam bridge with a main span of 100m and a pier of 99m high, and dynamic responses are tested under natural excitation. Chebyshev digital filter is used to signal for low-pass filter according to the frequency distribution in FFT spectrum. A series of IMFs are obtained from the Hilbert-Huang Transform of a measured lateral displacement response, which shows: EMD is a self-adaptive signal analysis method that can effectively process non-stationary signal; IMFs can clearly show local features of complicated signal. Modal parameters of the bridge are identified based on HHT and Random Decrement Technique (RDT), the comparison of the identified results obtained from FFT, HHT-RDT and Finite Element Method is made, which show that HHT-RDT is an effective method to identify modal parameters of large bridge structures.