DIRECT SHEAR TEST OF BEAM-COLUMN JOINTS OF PRESTRESSED PREFABRICATED MONOLITHIC CONCRETE FRAME

In order to study the shear bearing mechanism of the beam-column interface of the pre-stressed prefabricated monolithic concrete frame, the provisions of the friction coefficient in the domestic and foreign codes were summarized and analyzed. Through the study of five groups of 19 direct shear specimens of beam-column joints, the effects of joint area, pre-stressed, eccentricity of pre-stressed screw position and grouting material on friction performance were analyzed, and the shear bearing capacity and equivalent friction system of specimens under pure shear state were obtained. The test results showed that the shear bearing capacity of beam-column joints was discrete when there was no prestressing force, which was mainly related to the construction quality of post-poured joints; the shear area of the specimen and the eccentricity of the prestressing screw position had little effect on the shear capacity; the relationship between shear capacity and prestressing force was basically linear, increasing prestressing force could effectively improve the shear bearing capacity of joints; equivalent friction coefficient of shear joint could be effectively improved by using steel fiber mortar in grouting joint; the equivalent friction coefficient decreased with the increase of prestressing stress; for joints without rough treatment, using the friction coefficient in Technical Specification for Integral Prefabricated Prestressed Concrete Slab-Column Structure(CECS 52:2010) or Technical Specification for Concrete Structures with Precast Components(SJG 18-2009) would result in insufficient shear bearing capacity or insufficient safety reserve. The friction coefficient in the formula of shear bearing capacity should be determined according to the magnitude of prestressing force.