Study On Seismic Performance Of The Selfcentering Joint Composite Frame Structure Of PEC Columns Fabricated With Thin-walled Steel Plate Composite Section-steel Beams BRS Plate

Partially encased concrete(PEC)columns with thin-walled steel plates welded composite section had an H-shaped section welded with three thin steel plates and lateral ribbings welded at a certain spacing on both sides of the flange to prevent local buckling of the outer steel frame,and the concrete with corresponding strength was pouring from the reversed holes on the end plate to both sides of the web.Such steel plate-concrete composite section kept the concrete forced in three directions as much as possible,significantly increasing the contribution of the concrete to the bearing capacity of the structural components.As a result,the lateral resisting stiffness and the seismic ductility of the structural components were improved,and construction inconvenience of beam-column joint of stiff concrete and concrete filled steel tube.Self-centering structure was created by setting pre-tensioning rod and the auxiliary energy dissipation(ED)devices resonably on the main force-receiving components,such as columns,beams and walls,to realize selfcentering function after structure earthquake,reduce residual deformation and reduce postearthquake repair cost.Compared with the general structure,the main force-receiving components of the self-centering structure were not damaged excessively,and the energy dissipation devices were connected to the main structure by bolts,which is easy to replace and repair.In our work,to systematically investigate the seismic performance of the selfcentering joint composite frame structure of the bottom two-story single-span PEC columns fabricated with thin-walled steel plate composite section-steel beams BRS plate,a test specimen of two-layer substructure with 1:2 scale at the bottom of the composite frame was designed and fabricated combining our lab condition,based on the achievement of our research group in PEC column-steel beam self-centering joint connection and the intermediate layer frame,and low cycle reversed load was applied on the specimen.Firstly,the failure mode and hysteresis characteristic curve of the specimen were obtained,and the lateral resisting stiffness,energy dissipation capacity and deformation mode of the specimen were analyzed based on the experimental results.Secondly,the ABAQUS finite element model was established for this framework,and the simulation results were compared with the experiment results.Finally,four different parameter models,arrangement of the piercing bolts,the vertical force effect,the long round hole size and connection form of the column bottom,were designed.The four models were simulated separately to investigate the influence of each parameter on the seismic performance of the specimen,such as the bearing capacity,connection performance,energy dissipation capacity,deformation mode,joint force transmission mechanism and residual deformation.The research result shows that by setting BRS energy-dissipation plate and pretensioning rod,the structure possessed the self-centering ability and satisfied the requirement of energy dissipation when hit by an earthquake.The specimen with the single-sided arrangement of the piercing bolt had higher self-centering ability but lower energy dissipation than the bilaterally arranged specimen.Applying a certain vertical force was found to have little effect on the self-centering function of the specimen.Lengthening the the long bolt hole of the BRS plate can delay the bearing force of the specimen,and improve the self-centering function.The early energy dissipation of column foot fixing specimen was mainly due to the yield of the BRS plate and the beam end in the joint zone,and the later energy dissipation depended on the crush of the concrete at the foot of the column and the yield of the steel skeleton.When reaching1/30 limitation of the lateral displacement of the large earthquake,the relative residual side shift angle of the specimen was less than 0.012 rad,and the corresponding finite element model was less than 0.008 rad.When the interlayer lateral shift angle reached 5.0%,the overall relative residual side shift angles of finite element models were less than 0.016 rad,with good seismic performance and self-centering effect.