Research On Monitoring Damage Range Of Concrete Based On Spherical Piezoelectric Intelligent Aggregate

In recent years,with the construction and development of civil hydraulic engineering,the scale of the project continues to expand,the safety of the project has been paid more and more attention.Especially in hydraulic engineering DAMS and other hydraulic structures,earthquake and other loads will seriously threaten the safety of hydraulic structures.If the dam in the upstream and middle reaches is damaged due to the load,it will cause incalculable losses to the people and property downstream,causing irreversible consequences.Therefore,the evaluation and damage monitoring of dam concrete under strong earthquake is an important research topic in the field of disaster prevention and reduction and hydraulic structure.Piezoelectric ceramic material has the characteristics of fast response speed,easy shape processing,wide frequency response range,and has positive and inverse piezoelectric effects.It can be used as intelligent monitoring equipment for real-time monitoring of the health status of structures,so it has considerable application potential in the field of structural health monitoring of civil hydraulic engineering.The damage monitoring of mass concrete structure is carried out by using piezoelectric intelligent aggregate based material,and the relationship between the monitoring data index and the volume ratio of concrete damage is established,so as to achieve the purpose of rapid and quantitative evaluation of concrete damage degree.Firstly,the sensitive range of piezoelectric intelligent aggregate to concrete damage is determined.Spherical piezoelectric smart is built up by using finite element software the finite element model of concrete aggregate and different range,using the method of impedance of piezoelectric smart aggregate is calculated under the different concrete area admittance,impedance curve,analyses the different monitoring signal range,the sensitivity of the damage degree of concrete,and the concrete block on the failure process under uniaxial compression test and numerical simulation analysis,The sensitive area of piezoelectric smart aggregate to concrete damage was verified by comparative analysis.The research results will provide a basis for rapid and quantitative evaluation of damage degree of concrete structures by using piezoelectric intelligent aggregate.The main research contents of this paper include:1.Finite element modeling was carried out for the spherical piezoelectric intelligent aggregate sensor based on piezoresistive reactance method proposed by the project,and concrete and its damage in different size regions were simulated.In the case of concrete damage,the variation curves of impedance,conductance,suscendence,resistance and reactance with frequency were obtained.The results show that,in the frequency range of120 k Hz-160 k Hz,Conductance is more sensitive to concrete damage.2.The sensitivity of different monitoring data to concrete damage was studied.The root mean square deviation(RMSD),mean absolute percentage deviation(MAPD)and cross relation number(CC)of the monitoring signals were calculated by using impedance method.The sensitivity of each index to concrete damage in different ranges and the applicability of concrete damage monitoring were analyzed.The results show that the root mean square deviation(RMSD)is the most convincing index for concrete damage evaluation.3.The damage process of concrete block under uniaxial compression is analyzed and studied by means of test and numerical simulation.Three 150mm×150mm×150mm standard concrete cube test blocks were made by embedding the spherical piezoelectric smart aggregate in concrete.The compression failure test was carried out on a uniaxial tester.The impedance data of the piezoelectric smart aggregate were collected in real time,and the variation law of monitoring indexes with loading displacement was studied.In the numerical simulation,the finite element model of concrete cube embedded with piezoelectric intelligent aggregate sensor was established,and the damage process of concrete under uniaxial compression was simulated.The damage degree of concrete was evaluated by using the electrical conductivity eigenvalue and damage volume ratio(DVR)of the spherical piezoelectric intelligent aggregate sensor.The numerical simulation model was verified by comparing the root mean square deviation(RMSD)index of the conductance signal with the experimental results.On this basis,the relationship curve between DVR and RMSD was fitted,and the relationship between DVR and RMSD in different ranges was analyzed.The results show that the RMSD index of the spherical piezoelectric intelligent aggregate sensor has a linear relationship with the DVR of concrete.According to the relationship between RMSD and DVR,the damage degree of concrete can be quantitatively evaluated by using RMSD damage evaluation index,so as to further determine the scope of concrete damage monitored by the spherical piezoelectric intelligent aggregate sensor.