Acoustic Emission Monitoring And Health Diagnosis For Damage Of Hybrid FRP-Steel Tube Confined Concrete

Composite structure is one of the most important structure types in civil engineering. The types of composite structure are getting more and more, and the structures that use composite structure are usually important, once the damage occurs, the economic and social loss will be extremely serious. Up to now, the study on the new structure type mostly focus on the mechanical properties, while the research for damage mechanism is still lack of enough studies. The thsis mainly study on the damage development and damage pattern recognition of hybrid CFRP-steel tube confined concrete based on acoustic emission.Firstly, the damage development for the component of hybrid CFRP-steel tube confined concrete was studied. The experiment that CFRP-steel composite plates under uniaxial tension and cyclic tension and monitored by AE technique was conducted. The damage development of CFRP-steel composite plates under uniaxial tension was evaluated based on sentry function, and the damage development of CFRP-steel composite plates under cyclic tension was evaluated based on index of damage and modified index of damage. Both of the methods can evaluate and forecast the damage of CFRP-steel composite plates.Secondly, the experiment of hybrid CFRP-steel tube confined concrete columns under axial load was conducted and the damage development was analyzed based on the acoustic emission signal. The stress condition, variation of the concrete cracks, the degree of damage and the development of damage cracks for the hybrid CFRP-steel tube confined concrete columns was analyzed by AE accumulated energy, RA and AF value analysis, AE signal intensity analysis and b-value analysis separately. Analysis results showed that the effective parameter of acoustic emission could evident represent the evolutionary process of damage and failure mode for hybrid CFRP-steel tube confined concrete.Finally, damage pattern recognition was conducted based on AE data of hybrid CFRP-steel tube confined concrete columns under axial load. The AE signals was divided into several clusters by fuzzy C means, and the damage pattern was recognized preliminarily, and the acoustic emission signals for different damages were discussed based on the cluster results Then some characteristic signal was analyzed through wavelet analysis, and the damage pattern was recognized further.