Study On Static Damage Of Concrete Structures Based On Acoustic Emission Theory

Acoustic emission(AE)detection is a kind of nondestructive testing teehnology whieh can monitor the internal motion of the structure in real time and dynamically.It is a passive receiver of the acoustic errussion signal generated by the internal motion of the structure.It has been widely used in structural damage location and damage assessment.In this paper,acoustic emission test of concrete structure is carried out based on acoustic emission theory and its detection technology.The main contents and achievements of this paper are as follows:(1)The damage process of prestxessed concrete box girder under bending and shear loading is simulated by using the,”squaring,concrete specimen,and acoustic enission technique is mainly used to monitor the movement law of the main shear plane of the concrete specimen.According to the change rule of acoustic emission characteristic parameters,the damage and failure of concrete can be divided into three stages:initial compaction stage,steady development stage(elastic-plastic stage),main rupture generation stage and specimen failure stago.The change of event counting rate,accumulative energy and amplitude of acoustic emission signal is obviously different at different stages.(2)According to the accumulative energy and the cumulative ringing count,the damage evolution of concrete structure under load can be analyzed quantitatively.Moreover,the cumulative energy can not only quantitatively analyze the damage of concrete structure,but also characterize the characteristics of acoustic emission source to a certain extent.(3)The cumulative acoustic emission event number curve changes with the stress level in approximately three stages,and each stage corresponds to different damage state of the structire.It is verified that the damage evolution curve calculated by the third order polynomial function is in good agreement with the measured data,and it can well reflect the variation law of cumulative acoustic emission curve.(4)The cracking mode of concrete specimen is studied by using RA value and average frequency,combined with k-means algorithm model.With the increasing of load,shear crack becomes the main source of damage.At the end of failure,shear cracks lead to instability failure of concrete structures.Therefore,the damage crack is divided into tensile crack and shear crack.