Damage Determination Of Pre-stressed Reinforced Concrete Beam Based On The Acoustic Emission Detection Technology

The damage evolution process of reinforced concrete members is a hot research topic in the field of concrete materials engineering.The concrete members subjected to the destructive process is the internal micro crack initiation, fracture propagation and along with destruction process of concrete component will produce acoustic emission phenomenon.It has been studied that the characteristic parameters of acoustic emission signal associated with the failure process of reinforced concrete members are closely related to the damage evolution process.Choosing characteristic parameters of acoustic emission is the core of the research.As a unique concept of earthquake engineering, b-value has been regarded as a special parameter of acoustic emission characteristics in recent years.Capture and predict the macroscopic crack of reinforced concrete beam is an important link in the study of damage evolution process of concrete members.Due to its unique physical meaning, b-value has a secondary benefit for this work and its objective reflection of the relationship between the proportion of the event and the component of the macro cracks appearance.In view of the interference caused by the uncertainty of the a-value,this paper proposes a method of using constant a-value to replace the change of a-value and by using single parameter fitting method to calculate the b-value.By using this method, the change law of b-value at each stage of loading is more singularity at the crack point, according to the minimum b-value of the acoustic emission the stage of the crack in the beam is accurately captured,which improves the recognition accuracy of this kind of method and lays a certain foundation for the later computer intelligent judgment.After the corresponding relationship between the number of AE events and the b-value is established, the b-value can be incorporated into the calculation formula of the damage variable based on the damage growth rate theory which provides a new way to judge the damage degree of concrete damage evolution.The fitting formula is introduced to reduce the fluctuation of the number of acoustic emission events and the results is obtained.At the same time, the corresponding relationship between acoustic emission cumulative energy and stress level is established and the calculation formula of another damage variable is established by using acoustic emission cumulative energy as damage factor. The damage variable by these two methods of calculating are corresponding studied along with the real-time map of the testspecimen.Finally the two calculation methods were compared and we can find out the former one has higher accuracy compared with the damage degree determination method based on cumulative energy.The conclusion provide a means of prejudgment for the failure of the specimen and help to further analyze and study the acoustic signal correspondence between damage mechanisms provide warning for practical engineering damage.