Research On The Anti Seismic Behavior Of Diaphragm-through Joints Of Box-column And Box-beam

Low-cycle reversed loading tests were performed on inner diaphragm joints of box column-box beam, including five joints with polyline enlarged juncture and opening holes at beam flanges(Hereinafter referred to as the improved joints) and one conventional joint．Studied the influenceof polyline enlarged juncture and opening holes at beam flanges on destruction mode, hystereticperformance, capacity, plastic rotation, stiffness degradation and energy dissipation behavior andother effects of seismic performance of these modified joints. The test results show that, for theconventional joint，butt weld at beam flange appears brittle fracture and the plastic rotation isabout0.010rad, the plastic rotation of joints with polyline enlarged juncture near butt weld andopeningholes at beam flanges increases by150%～250%compared withthatof conventionaljoint,and theloading capacityincreases by36.3%～62.9%.We proposed correction factor of fracture index CI considered with weld defect, based on thecomparation of numerical analysis results of ellipsoid yield model of structural steel andexperimental results. Finite element parametric study was conducted on improved joint, analyzedthe influence of beam-extended partition parameter L, diameter parameter of opening holes atbeam flanges beam flange D and other parameters on the force performance. The results show thatthe loading capacity increases when the parameter L increases and the parameter D decreases;Plastic rotation increases as the parameter L decreases and decreases when the parameter Dincreases; The envelope area of hysteresis curve of improved joint increases by107～250%compared with that of conventional joint, and the equivalent viscous damping factor increases by8～61%, indicate that energy dissipation behavior of improved joint is significantly better thanconventionaljoint.Considering the joint capacity and plastic rotation, propose suggestions about structuralparameter values of joints with polyline enlarged juncture and opening holes at beam flanges, theextended partition parameter L=390mm～450mm, diameter parameter of opening holes at beamflangesbeamflangeD=16mm～20mm.