Acoustic Emission Multi-parameter Analysis And Damage Identification Of Reinforced Concrete Beam Damage Process

The damage and failure process of reinforced concrete structures is very complex,making it difficult to analyze their damage status.Acoustic emission technique can effectively monitor the damage process of reinforced concrete structures by directly obtaining damage signals inside the material to determine the state of material damage.This article conducts four points bending graded loading experiments on reinforced concrete beams,using acoustic emission technique to monitor the entire loading and failure process,the damage state of reinforced concrete beams during the entire process of destruction was analyzed using multiple acoustic emission parameters,and the results obtained are as follows:(1)By combining the basic parameters of acoustic emission signals with the precursor characteristics of microseismic warning signals,multiple comprehensive parameters of acoustic emission were obtained,namely the normalized energy level m of acoustic emission,the b-value of acoustic emission,the total area of acoustic emission faults A(t),the activity index A(b)of acoustic emission,and the complexity AC value of acoustic emission algorithm.It was found that during the time period when the specimen damage worsened,they all showed obvious abnormal changes,and compared to the basic parameters of acoustic emission,this comprehensive parameter variation has obvious characteristics,laying the foundation for further multi-parameter analysis in the future.(2)A damage model for the loading process of reinforced concrete beams was established using acoustic emission ringing counting.The changes in the damage displacement curve correspond to the elastic stage without cracks,crack’s germination and expansion stage,and final oblique splitting failure stage in the process of reinforced concrete beams.This can be used to divide the loading failure stages of reinforced concrete structures.(3)By using principal component analysis to process the basic parameters and comprehensive parameters of acoustic emission,it was found that using comprehensive parameters of acoustic emission has a better processing effect.The calculation formulas for the three main components Z1,Z2,and Z3 were obtained.Z1,Z2,and Z3 can contain most of the information on damage and are independent of each other.Their changes over time can be used to evaluate the damage process of reinforced concrete beams,and the abnormal changes in their numerical values can be used as signal features for material damage aggravation.(4)The RA-AF correlation analysis method was used to classify the acoustic emission events during the failure process of reinforced concrete specimens into tensile failure events and shear failure events.K-means clustering method,K-medoids clustering method,GMM clustering method,and FCM clustering method were used to classify them and compare their classification effects.It was found that GMM clustering method performs better than other clustering methods.Through the variation trend of tensile shear ratio,it was found that 60%of the ultimate bearing capacity of the specimen can be used as the basis for dividing the stable and unstable stages of the failure process.