Statistical Estimation of Changes in the Dominant Frequencies of Structures in Long Noisy Series of Monitoring Data

Figure 7

Spectra of the vertical response acceleration of the Kanellopoulos bridge during five annual surveys. Results were obtained after spectral analysis of the accelerometer recordings from different vibration events using the Normperiod code. Results from different events are marked with different colors. A dramatic shift of the dominating frequency peaks from 2.6 to 1 Hz can be identified between 2007 and 2009, followed by a gradual drop from 2009 to 2013. This shift is real and led to the abandonment of the bridge.