Experimental Study On The Damage Detection Of A Prestressed Concrete-steel Structuremodel Based On PZT

With the increasingly serious environmental and energy problems,wind energy,as a kind of clean and renewable resources,has attracted more and more attention.In recent years,large-scale wind turbine towers have been constructed to make good use of wind energy both home and abroad.With the constant increase of individual installed capacity,the shortcomings of traditional concrete tower and pure steel tower gradually highlight.As a new type of wind turbine tower,prestressed concrete-steel hybrid wind turbine tower combines the concrete tower section and steel tower section,which have the advantages of both two kinds of materials respectively.How ever,the protential concrete cracks may shorten the service life and cause reliability problems during the service.The structural health monitoring of the hybrid wind turbine tower is significant.Since the traditional monitoring method is difficult to evaluate the health status of the hybrid wind turbine towereffectively,a wave propagation analysis method based on the advantages of piezo-ceramic(PZT)material is proposed in this paperto monitorthe prestressed concrete-steel hybrid wind turbine tower.The following studies are carried out.(1)After introducingthe selection of piezoelectric ceramic materials and the fabrication methods of piezoelectric ceramic sensors in detail,the development and application background of piezoelectric stress wave analysis theory for structure health monitoringare summarized and the selection of excitation signal and the analysis of monitoring signal are explained.(2)In this paper,the damage monitoring experiment ona prestressed concrete-steel hybrid wind tower scale model is carried out.The damage condition of the specimen subjected to cyclic loadingsis monitored.Both the PZT patchactuators and sensors aresurface mounted on the specimen.The stress wave signal measurement are analyzed to monitor the crack initiation and propagation progress in the specimen.(3)Both sinusoidalharmonic signal and sinusoidal sweep frequency signal are selected to excite the PZT actuator.A normalized damage index based on the amplitude of the sinusoidalharmonic signal and a normalized damage index based on the wavelet packet energy are defined.The defined damage indices can be used to detect the location of cracks and the defined damage indices have obvious variation due to the development of the cracks.The proposed approach is efficient to monitor the cracks initaiton and development in concrete.