Research On Concrete Damage Of Bending Members By Acoustic Emission

Of all the bridges,90 percent is concrete bridge.Many concrete bridges have some damage.Damage of concrete bridges is an important factor affecting the performance of bridges.The damage of existing concrete bridge is an important factor affecting the performance of bridge.Acoustic emission technique is an effective method to detect concrete damage.The intensive research on the relationship between AE signal and the internal damage of concrete is not enough.In this paper,the acoustic emission signal and the concrete damage are studied.The specific work is as follows:(1)The concrete specimens subjected to three-point load were tested.Concrete strain and acoustic emission during the whole process were monitored.The relationship between acoustic parameters and damage was analyzed.At the initial loading stage,the original defects such as microcracks at the interface between the cement mortar and the aggregatel produced low-amplitude,low-energy impact signals.With load increasing,new cracks developed,and acoustic emission signals activity enhanced.High amplitude signals and multiple bursts of energy release happened during loading process.(2)Based on the wavelet theory,the wavelet denoising parameters for concrete specimens were analyzed.When the db4 wavelet was used for the two-layer wavelet decomposition,the soft threshold function was used under the Heursure threshold criterion,the effect was good.By comparing the signal waveforms before and after the denoising,it can be seen that the processing signal retained most of the main features of the original signal,removed some noise signals.So that the collected signal can represent the acoustic emission source signal feature.(3)Based on the wavelet denoising of the collected signals,the time delay of the two acoustic sensors was calculated by using the cross-correlation analysis method.The acoustic emission source can be located by the measured time and velocity.The accuracy of acoustic emission damage positioning can be improved.