Design Of Anti-interference PZT Active Sensor Monitoring System And Analysis Of Concrete Health Monitoring Based On HHT Spectrum

Concrete structure is one of the most widely used structural forms.With the continuous development of China's social economy,various large-scale engineering structures are emerging,and civil engineering structure health monitoring technology has gradually become a research hotspot in academia.In recent decades,the successful application of smart material in the engineering field has provided an effective way for real structural health monitoring.Piezoelectric materials have the excellent characteristics of integrating sensing and driving,and have fast response speed.So they are suitable for the field of structural health monitoring.In addition,the wave propagation method has the advantages of real-time dynamics and little impact on the structure.Concrete health monitoring based on the piezoelectric smart aggregate has achieved rich research results,but there are still some shortcomings: poor anti-interference ability of the monitoring system,lack of research on the attenuation of ultrasound waves in concrete,and monitoring methods are insensitive to defects.Based on the above background,this paper studies the related technologies of using piezoelectric materials to monitor the health of concrete structures.The specific work includes the following aspects:(1)A concrete health monitoring system based on PZT active sensing technology with better antiinterference capability was built.In view of the shortcomings of smart aggregates that are subject to large electromagnetic interference,a metal shielding shell was added to the piezoelectric smart aggregates,and the noise obtained by the improved sensor was effectively reduced through experimental comparison tests.Considering the signal-to-noise ratio of the ultrasonic signal for longdistance transmission,charge amplifiers was applied and a concrete health monitoring system was established.Through the test,the signal-to-noise ratio of the signal amplifier was greatly improved after the application of the charge amplifier.For the inaccurate positioning of the embedded sensor and the problem of insecure installation,a precast concrete test was proposed.Compared with other sensor fixing methods,the sensor fixing method of the block is accurately positioned,which can effectively avoid interference during the concrete pouring process.(2)The relationship between stress wave attenuation and frequency and distance based on embedded piezoelectric sensors was researched.The experiment of measuring the sound attenuation by the narrow-band pulse transmission method of concrete was designed.The relationship between attenuation and distance was researched,and the attenuation coefficient and the attenuation rate coefficient curve with distance were obtained,and the influence of the sound field diffusion attenuation was discussed.The relationship between the attenuation and frequency was studied,and the attenuation coefficient and the attenuation rate coefficient curve with frequency were obtained.(3)Concrete health monitoring methods based on HHT spectrum were researched.A method for describing the water seepage condition of concrete using HHT spectrum and energy index was proposed,and a method for characterizing the water seepage condition using instantaneous phase difference and water seepage index was proposed.The mechanism of concrete health monitoring using energy index and instantaneous phase index is explained based on finite element simulation The concrete seepage monitoring test was designed,and the HHT method can effectively monitor the concrete seepage changes,and the differences in the identification methods of different material parameters are discussed.