Embedded Piezoelectric Acceleration Sensor And Its Monitoring In The Vibration Of Concrete Structure

In recent years,with the rapid and rapid development of social economy and the advancement of construction technology,a series of individual projects such as water conservancy dams,high-rise buildings,roads and bridges,or large-scale civil engineering structures with comprehensive use functions have been greatly promoted.Progress and development of human society.However,during their service,these large civil engineering structures neglected periodic damage detection or real-time,online health monitoring of these structures,resulting in some civil engineering structures being destroyed due to their own damage accumulation and resistance attenuation.Thereby triggering a sudden catastrophe.Therefore,real-time long-term online health monitoring / detection of civil engineering structures based on intelligent sensor systems and data collection and analysis systems is becoming more and more important for early warning before disasters strike.As a functional ceramic with positive and inverse piezoelectric effect,piezoelectric ceramic has fast response sensing characteristics and low excitation power driving characteristics.At the same time,it has good linearity,low energy consumption and cost,flexible combination and easy processing design.Many advantages have been widely researched and applied in the field of civil engineering.Piezoelectric acceleration sensors prepared based on the sensing characteristics of piezoelectric sensitive elements are an important direction in the field of civil engineering structure damage monitoring / detection.Based on the above background,this paper has prepared a kind of raw materials for PZT-5H piezoelectric ceramic,cement / polymer,galvanized steel sheet mass,etc.for the problems of poor coupling between the existing piezoelectric acceleration sensor metal package and concrete,poor waterproofness and durability The overall structural stability is suitable for embedded piezoelectric acceleration sensors embedded in the concrete structure without changing the local load-bearing characteristics of the concrete.The specific research work is as follows:(1)Based on the existing theory of the laboratory,the structure of the Embedded piezoelectric accelerometer is designed.At the same time,for the low-frequency vibration characteristics of the concrete structure,PZT-5H piezoelectric ceramic is used as the sensing element,and galvanized steel sheet is used as an additional An Embedded piezoelectric acceleration sensor was prepared by using a mass,cement / polymer mixture as a base and a packaging material.The influence of the thickness of piezoelectric ceramic and metal mass on the sensitivity and frequency response performance of the acceleration sensor assembly is discussed.The results show that as the thickness of the piezoelectric ceramic PZT-5H increases or as the thickness of the galvanized steel sheet mass increases,the sensitivity S of the sensor gradually increases,and the frequency response range tends to decrease.It shows that the acceleration sensor sensitivity S and the frequency response range are two mutually opposite performance parameters,and the performance parameters suitable for the low-frequency vibration test of concrete structures can be determined by coordinating the piezoelectric ceramic and the mass thickness.(2)The frequency independence,repeatability and hysteresis characteristics of the sensor were measured by means of test verification,and the modal parameters of the standard shaker system were tested based on the self-made implanted acceleration sensor.The test results show that the randomly selected multiple self-made Embedded accelerometers are loaded at different frequencies,the output amplitude is stable and does not fluctuate with the change of the loading frequency,indicating that it has a good frequency independence within the test range;The output response of the sensor is consistent under the positive and negative installation,and the linearity is high after fitting.Its good linear relationship indicates that the acceleration sensor has good hysteresis characteristics under different working conditions.Under the same conditions,the sensitivity of four sets of continuously measured sensors with acceleration changes basically unchanged,indicating that it has good frequency repeatability within the test range.(3)Designed and constructed a three-layer GFRP rebar frame model structure,conducted elastic modulus test and compressive strength test on fine stone concrete specimens,conducted tensile test on FRP bars,and vibrated the model structure Bench test,and the output data of the standard parts and self-made parts are plotted and analyzed.It is concluded that the output stability and accuracy of the self-made parts need to be improved,but the overall output trend and the amplification factor trend are basically consistent,proving that the self-made acceleration sensor It has value in practical application.At the same time,the damage degree of the structure can be roughly analyzed according to the sum of the amplification factor,the speed response amplitude and the natural vibration period,which has a certain reference value for the health monitoring of the FRP reinforced concrete frame structure.