Monitoring Of Concrete Shrinkage And Creep Based On Electro-mechanical Impedance Technique

The shrinkage and creep of concrete are the important factors that affect the stability and durability of concrete structure,so it is of great practical engineering significance to monitor it.However,the conventional monitoring techniques have many limitations such as expensive equipment,complicated operation,and limited the size of the specimen.Piezoelectric ceramic(PZT)sensors have the advantages of easy processing,low cost and high sensing accuracy,so they are widely used in structural health monitoring.In view of the shortcomings of conventional monitoring techniques,this paper carried out the research on the monitoring of concrete shrinkage and creep based on electro-mechanical impedance technique.The main contents are as follows:(1)Based on the concrete shrinkage experiment and piezoelectric monitoring,the feasibility of the electro-mechanical impedance technique to monitor concrete shrinkage is explored.The PZT sensor and vibrating wire strain gauge are embedded in the specimen at the same position.The relationship between concrete shrinkage and piezoelectric signal is established to establish a new shrinkage prediction model,and finally,the validity of the model is verified.(2)Based on the concrete creep experiment and piezoelectric monitoring,the feasibility of the electro-mechanical impedance technique to monitor concrete creep is explored.The specimens are subjected to compressive creep experiment after 28 days of curing.The shrinkage strain is compensated by the results of shrinkage experiment,and the creep prediction model based on electro-mechanical impedance technique is established.Finally,the validity of the model is verified.(3)Finally,the numerical study of concrete shrinkage,creep and piezoelectric is carried out by the ANSYS finite element software,then the finite element simulation of concrete shrinkage and creep monitoring based on electro-mechanical impedance technique is carried out,so as to verify the feasibility of the electro-mechanical impedance technique in the monitoring of concrete shrinkage and creep from the numerical perspective.The research results of this paper show that the prediction model based on electro-mechanical impedance technique and new shrinkage and creep prediction model can effectively monitor the shrinkage and creep of concrete,in which the bilinear shrinkage prediction model based on Euclidean distance improves the stability of the bilinear model while keeping its high precision,and the nonlinear creep prediction model based on Euclidean distance has higher accuracy and stability than that of nonlinear model.Finally,the finite element simulation results show that the concrete shrinkage has a linear relationship with the resonant frequency of piezoelectric signal,and the creep has a logarithmic nonlinear relationship with the resonant frequency of piezoelectric signal,which mean that the concrete shrinkage and creep can be monitored by electro-mechanical impedance technique.