Study On Stress Measurement And Damage Detection Of Concrete Structural Specimen Based On The Piezoelectric Lead Zirconate Titanate

With the rapid development of economy, science and technology, structures become larger and more complex in the recent years. However, due to aging misuse, changing environments, and lacking appropriate maintenance, the initiation and accumulation of damage as well as functional degradation are inevitably existed in a vast account of civil infrastructures. Failure of these infrastructures often leads to high social consequence. Consequently, it is critical to evaluate their current reliability, performance, and condition for the prevention of potential catastrophic events.Due to the excellent properties of the materials, such as fast response, wide frequency response, linearity, easy to cut and inexpensive molding process, as well as the unique sensing and actuation characteristic advantages, piezoelectric ceramic (Lead Zirconate Titanate, PZT) materials is becoming a widely used smart material and much attention has been devoted to develop this material for structural health monitoring (SHM) in practical civil engineering. In this thesis, based on PZT smart material, a stress measurement technology and a damage detection approach were proposed while the structure was under dynamic and quasi-static loadings.The main contents of the thesis are shown as follows:1. Introduced the motivation and background of the SHM briefly, reviewed the variously vibration-based system identification and damage detection methodologies, introduced smart materials and dynamic system in detail, and gave emphasis to the description of the researches on the PZT-based SHM techniques.2. Introduced the basic characteristics of piezoelectric materials and the corresponding constitutive theory, described the producing techniques of the PZT-based transducer, the measuring principle, the circuit, as well as the equipments which were employed to measure the signal. All of the discussions made a good preparation for the fabrication of stress sensor and the calibration test.3. Developed a kind of PZT-based transducer which can be used for health monitoring of concrete structures, presented the producing techniques in detail, designed a small dropping hammer impact test, calibrated the sensitivity of the proposed transducer, moreover, tried to utilize the jack for calibrating the sensitivity of the transducer under quasi-static loadings. The experiment results indicate the feasibility of the home-made piezoelectric stress sensors used for dynamic stress and the quasi-static stress measurement.4. Introduced the wavelet packet analysis method and the associated basic principles, carried out test on the structure components, e.g. the reinforced concrete columns and shear wall, analyzed the signal obtained from the test by using wavelet packet method, proposed a PZT-based SHM approach for concrete structures, validated the efficiency of the proposed approach by using the test data.