Long-term remote monitoring of a cable stayed bridge and seasonal fluctuation of modal parameters

摘要

In vibration based health monitoring,a little change of natural frequencies would be observed.However changes of modal parameters are also observed on intact civil structures by environmental effects.Hence it is worth to investigate the effects of environmental fluctuation as basic information of long term structural monitoring.The authors continue remote vibration monitoring of a cable stayed bridge in Hokkaido,Japan.9 accelerometers and 2 thermometers are installed in the bridge.More than 1,200 samples of ambient vibration have been collected in 2 years.The Natural Excitation Technique(NExT)and the Eigensystem Realization Algorithm(ERA)are applied to ambient vibration data for detecting little changes of modal parameters.Temperature in the pylon fluctuates between-10 to 30 degrees Celsius throughout a year.And the natural frequency of the most predominant mode changes 3% according to temperature fluctuation.The relationship between modal parameters and temperature fluctuation is investigated in this study.