Full-scale study on the mechanism of flexural damage evolution of in-service prestressed concrete box girdersOA

Prestressed concrete box girders are widely used in bridge engineering.Effective monitoring to accurately detect,localize,and evaluate damage development in inservice box girders is essential to ensure their operational safety.In this study,a four-point bending test based on acoustic emission(AE)technology was conducted on a full-scale in-service box girder with 20 years of service.The correlation between damage evolution and AE parameters was investigated,laying the foundation for the application of AE technology in bridge monitoring.The results show that the cracking load of the box girder after 20 years of service is lower than the theoretical design value.Changes in the cumulative AE ring counts can characterize different failure stages of the box girder.AE signals were grouped by amplitude and peak frequency for analysis,and the effectiveness of different AE signals in tracking damage development was examined.The Gaussian mixture model(GMM)clustering algorithm was used to perform the clustering analysis of rise time/peak amplitude(RA)and ring-down counts/duration(AF).This method can effectively distinguish microcrack types and identify failure modes in different damage stages.In conclusion,AE monitoring can characterize the structural damage state and improve the safety and reliability of box girders.