Analysis Of Shear Performance And Damage Evaluation Of Double Interface Connections Between Prefabricated Concrete Components

The assembled shear wall structure has been vigorously promoted due to its advantages of good integrity,large lateral stiffness and flexible space arrangement.The mechanical properties of the connections between prefabricated components are important factors to ensure the integrity of the prefabricated structure,which directly affects the safety of the overall structure.The concrete at the end of the member is designed to be rough and connected to the steel bar through the grouting sleeve.There is a grouting layer between the connecting members,forming a concrete-grouting material-concrete double interface connection.At present,a lot of research has been carried out on the shear performance of the new and old concrete interface,but there is a lack of in-depth analysis of the double interface connection of prefabricated components.In this paper,the shear performance of double interface connection of prefabricated components is studied by direct shear test.The failure mechanism and shear performance of double interface connection are analyzed.Combined with acoustic emission detection technology,the internal damage of interface shear is evaluated.(1)According to the stress condition of prefabricated components and the structural characteristics of the connection interface,six groups of direct shear specimens with concretegrouting material-concrete double interface connection and a group of contrast cast-in-place specimens were designed.The effects of longitudinal reinforcement ratio,interface roughness,grouting layer thickness and lack of grouting material on the characteristics of double interface failure mode,crack morphology,steel strain and load-displacement curve of prefabricated components were studied.The shear strength,shear stiffness,displacement ductility and residual load of the double interface were analyzed.(2)The failure of the double-interface direct shear test of the prefabricated component connection begins at the grouting layer.The failure mode of the flat joint interface is the cracking of the connection interface,and the tooth key joint interface shows obvious diagonal bar failure characteristics.Increasing the roughness of the connection interface and the reinforcement ratio of the longitudinal bars significantly improves the shear strength.The increase of grouting layer thickness can also improve the interface shear strength,but the interface ductility decreases.When the grouting material is missing,the shear bearing capacity is adversely affected,the interface shear strength decreases,the ductility decreases,and the residual load decreases.Based on the interface load-displacement curve and FEMA model,a constitutive model for shear resistance of double interface connection between concrete and grouting material is proposed.According to the interface friction coefficient and internal friction angle obtained from the compression-shear test,an improved shear bearing capacity formula based on the shear-friction theory is proposed.The calculated values are in good agreement with the experimental values.The calculation formula of interface shear bearing capacity in domestic and foreign codes is evaluated,and the adaptability of double interface shear performance of prefabricated component connection is poor.(3)The parameters such as energy,amplitude and ringing count of the acoustic emission signal are analyzed.The results show that the parameters are approximately normal distribution during the interface loading process.At the moment of interface failure,the acoustic emission ringing count and energy change suddenly,and the activity of each parameter of the whole cast specimen is higher than that of the double interface connection specimen.The average frequency AF-RA scatter diagram is obtained by the correlation analysis method.The AF value is less than 0.5,and the rapid decrease of b value is related to the interface failure.The specimen mainly undergoes shear failure.For the internal damage location of concrete,the failure of the specimen mainly occurs in the grouting joint and the prefabricated part of the grouting sleeve.