Experimental Study Of Steel Frame Cover-plate Reinforced Joints Under Cyclic Loading

Cover-plate reinforced connection studied in this paper is a typical flange-reinforced connection.By welding cover-plate,section modulus has been improved,and plastic hinge be formed some distance from the end of beam,and achieve the goal of improving ductility of connection and avoiding brittle failure of connection.4 1/2 scale cover-plate reinforced moment resisting specimens are fabricated which are CPC-1, CPC-2, CPC-3, CPC-4 respectively and the shape of cover-plate is rectangular. By changing the length of cover-plate(for specimen FPC-1,FPC-2) and changing the thinkness of cover-plate(for specimen FPC-3,FPC-4),hysteretic behavior of connection is studied to get the proper value of dimension of cover-plate.The specimens were designed with our country's code and referenced the USA FEMA350,FEMA351 design method and construction requirements. Q235 steel and E43 welding rod were used.The phenomenon of experiments for 4 cover-plate reinforced connection under cyclic loading shows:the plastic is formed 1/4 beam depth from the end of cover-plate under loading which protect the welding of connection and avoid brittle failure of connection.The results of experiments shows:compared with 3 other specimens,the bearing capacity of CPC-2 is the biggest which is 164KN;for cover-plate reinforced connection,the plastic rotation varied from 3.63%rad to 3.91%rad,total rotation varied from 5.01%rad to 5.24%rad,ductility varied from 3.11 to 3.31, equivalent viscous damping factor varied from 0.427 to 0.476,which satistied the lowest standard of seismic behavior :dictility factor is bigger than 3.0 and plastic rotation and total rotation are bigger than 3%rad and 5%rad respectively.By comparing with the data of experiments,results are found:with the increase of dimension of cover-plate,the bearing capacity increases while the platic rotation, total rotation,ductility factor and equivalent viscous damping factor decreases.Thickness of cover-plate should be less than 1.2 thickness of beam flange and the length of cover-plate should vary between 0.5 and 0.85 beam depth.