Study On Acoustic Emission Characteristics Of Bonded Interface Between Steel And Concrete

The main purpose of the research on bond performance between steel and concrete is to reveal the overall working performance of steel-concrete structure.Although abundant achievements have been made in the study of the bonding interface between the two materials,it is mainly confined to the research methods of mechanical tests,and there is little research on the application of acoustic emission technology.Acoustic emission experiments are carried out to study the bonding interface between steel and concrete,which can be used to warn the damage of the bonding interface.The main work and conclusions are as follows:(1)Cubic pull-out specimens with different diameters and bond lengths of reinforcing bars are designed and manufactured.The specimens are made of ribbed reinforcing bars embedded in the center of concrete.Acoustic emission experiment was carried out on center pull-out specimens.The results show that there is no significant difference in acoustic emission signals produced by specimens with different diameters and bonding lengths of reinforcing bars,and the changing trend is basically the same.(2)According to the load-displacement curve,the whole damage process of pulled-out specimens is divided into five damage stages.The AE signals of different damage stages are processed and analyzed by means of parametric analysis and waveform analysis,and an index for judging the dynamic characteristics of a damage source in stages ?,? and ? is obtained.(3)The development of inner defects in pull-out speeimens during bond damage was analyzed by 3D time difference location method.Compared with practical results,reasonable analysis results were gained.Highly preeise source location was gotten with locating approach and detecting parameter value adopted.(4)The transmission analysis of AE signals from two typical bond interfaces in steel-concrete composite beams shows that the energy and amplitude of the signals attenuate to different degrees when they pass through the bond interface between steel plate and ordinary concrete.The attenuation of signal propagating at the interface between ordinary concrete and UHPC concrete is independent of the initial position of the signal source,but the attenuation degree of the amplitude is the smallest,which keeps a good consistency with the source signal.(5)Based on the mid-span loading experiment of steel-concrete composite beams,the distribution and variation of acoustic emission characteristic parameters during micro-slip between steel plate and concrete bond interface are investigated,which provides an important reference for the analysis of acoustic emission signal propagation of composite beams in actual structures.