Technology and Application of Structural Health Condition Assessment for Sutong Bridge (2): Damage Alarming of Main Girder

In order to establish an environmental-condition-normalized damage alarming method for main girder of Sutong Bridge,the seasonal correlation analysis of wavelet packet energy spectrum(WPES) and temperature of Sutong Cable-stayed Bridge is performed by means of the 240-day health monitoring data.The analysis results reveal that the measured WPES has remarkable seasonal correlation with the environmental temperature.The seasonal change of environmental temperature accounts for the variation of the damage alarming parameter Ip of the dominant frequency bands with an averaged variance of 200%.The statistical modeling technique using a 6th-order polynomial is adopted to formulate the correlation between the WPES and temperature,on the basis of which the abnormal changes of measured damage alarming parameter Ip are detected using the mean value control chart.It is found that the proposed method can effectively eliminate temperature complications from the time series of WPES and exhibit good capability for detecting the damage-induced 10% variances of the damage alarming parameter Ip.And the proposed WPES-based method is proved to be suitable for online real-time condition monitoring for main girder of Sutong Bridge.