Development Of Piezoceramic Concrete Structure Health Monitoring System Based On Virtual Instrument Technology

At present, China is in a period of large-scale infrastructure construction, and concrete structures have been widely used in various types of engineering structures construction. In their long service process, the inevitable occurrence of material aging and damage is always happening which reduces the reliability of the structure. Therefore, the security issues of structures have been widespread concern. Structural health monitoring (SHM) as a way to obtain the relevant information of the monitored structure to detect structural damages, and then to make safety warning, is one of the focus issues in the field of civil engineering in recent years. The SHM technology based on piezoelectric ceramic has advantages of its high sensitivity, fast response, and sensitivity for concrete crack damages, etc. It has been widely used in the study of the health monitoring of concrete structures. Through the efforts of scholars at home and abroad, the technology has achieved a fruitful achievements in recent years. However, there is still lack of corresponding supporting monitoring platform development, making this technology only being used in the theoretical simulation and laboratory experimental stage, not realizing in the large-scale engineering application. Based on the above background, the focus issues of this dissertation will be based on the virtual instrument (VI) technology to develop piezoelectric health monitoring system for the concrete structure health monitoring, and applied to engineering practice. The main work of this paper includes:(1) The strengths and weaknesses of the SHM technology which is based on piezoelectric ceramic in the concrete structure are summarized, and the main content of this dissertation for the existing problems is put forward.(2) An active monitoring module for real-time online monitoring of concrete cracks by using the piezoelectric wave method as the theoretical basis is developed, based on the U.S. NI CompactRIO embedded platform, NI9221, NI9263and graphical programming software LabVIEW. The developed module can realize the monitoring signal synchronization emission and acquisition, data real-time online processing, the crack damage identification and safety warning function. And through a test to detect crack damage of a reinforced concrete beam, the feasibility and stability of the developed system is verified.(3) The piezoelectric effect of piezoelectric ceramics is used to develop the force sensor with a high sensitivity, and a passive monitoring module for supporting the development is also researched. The module can achieve dynamic and real-time stress responses for the monitored concrete structure by using the passive monitoring technology based on acoustic emission. It has been used in the project of Guodian Tieling wind generator base for monitoring the concrete stress during a strong wind. (4) An acceleration monitoring module is developed based on the NI9234and piezoelectric acceleration sensor. The module can complete the function for the structure of the real-time online acceleration signal acquisition, filtering, spectrum analysis. Through the shaking able test of a three layer steel frame model, the efficiency of the developed module is verified.All developed modules are integrated by the Lab VIEW graphical programming software as the core of development platform, forming the portable structure health monitoring system based on a computer and NI CompactRIO embedded platform. The developed system can realize the real-time online monitoring for the concrete structure crack, dynamic pressure, acceleration and other physical quantities.