Study On Data Acquisition And Damage Identification For Structural Health Monitoring

With the development of inspection/monitoring technology and more attention paid on buildings, structural health monitoring has become an important part of civil engineering safety and hazard mitigation. The testing system based on virtual instrument (VI) which is used in structural monitoring has been more and more popular for its friendly interface, low cost, simple operation and many other advantages. Meanwhile, because of limitations of existing inspection methods, more safe, efficient and economic approaches should be proposed to improve security of structure such as submarine pipeline.The data acquisition (DAQ) and damage identification for structural monitoring based on VI and computers is studied in the dissertation. An all-purpose system of data acquisition is developed by using of VI. The contents of the dissertation are summarized as follows:Firstly the importance, meaning and content of structure inspection are explained, and the monitoring status of great projects, including submarine pipeline, is analyzed. Relevant information on VI has been studied also. Because of importance of projects and shortcomings of existing inspection methods, a structure health monitoring approach based on VI is presented. Finally the target and jobs of paper are brought forward.Secondly, with the help of VI technology, overall design of structural health monitoring system is proposed which is divided into three parts according to function and requirement of monitoring. The three parts contain sensor subsystem, DAQ and preprocessing subsystem, damage identification and safety evaluation subsystem, which together realize the DAQ functions, such as data acquisition, measurement and damage identification. Then software and hardware of the system is introduced briefly, including PXI DAQ card and LabVIEW software platform of NI, used as a development tool of DAQ system. Programming of system and realization of user interface is also presented.Thirdly, an algorithm of structural damage identification based on wavelet packet decomposition and signal average power, which is suited to the cases of the ambient vibration responses, is proposed in the chapter 4. The theoretical formulation is derived from the stochastic vibration, and the damage features are extracted with the formwork of the statistical patter recognition. The correctness and the effectiveness of the proposed algorithm are studied by using of the data generated from Benchmark Model. Finally, the system is applied on the DAQ of the model test of super-high structure and its safety evaluation. Automatic data acquisition, process and display of structural vibration response are basically realized, and kinds of damage before structure failure could be efficiently identified in this system. All results show that the function and reliability of the system presented in this paper have met the design requirement and have satisfied engineering practice.