The Seismic Design Method Of Bolt-welded Hybrid Weakened Connections Of Box-beam To Box-column

Since the earthquakes of Northridge and Kobe,the community of engineer conducted a lot of experimental research and theoretical analysis about the steel frame beam-column joints.Then the joints were strengthened or weakened to improve the seismic performance of the joints.RBS（Reduced Beam Section）and tapered weakened nodes are both new-type Northridge nodes,which can make the plastic hinge out of the beam.On the basis of early studies,the PKPM design software was used to calculate the seismic performance and design specifications of the high-rise square steel tube concrete frame-core tube project which use H-shaped beams.The floor displacement,floor displacement angle,stiffness ratio,stiffness ratio,shearing weight ratio,economic indicators and other aspects were compared and analyzed with the alternative structure using box beams,and the high-rise was analyzed from the aspects of mechanical properties and economics when the structure adopts box beams to replace the advantages of traditional H beams.The results show that the box beam has an unparalleled superiority in seismic performance,and it also has a good effect in economy.In order to study the seismic design method about the new-type Northridge nodes connection of the box beam,PKPM software was used to construct the BASE model as a basic test piece for variable parameter analysis of RBS and cone weakening.After verifying the correctness of the ABAQUS finite element model and analysis method in this paper,the RBS and cone weakening of the BASE model were simulated with variable parameters;a total of 7 series with 55 finite element models were established to study variable parameters and analyze the impact of weakened parameters.The main conclusions and advise are as follows:（1）Each weakening parameter has different degrees of influence on the bearing capacity,energy dissipation performance and ductility of the new box-shaped RBS weakened connection and tapered weakened connection nodes;（2）Design suggestions for the RBS weakened connection of the new box beam is as follows:the value of the beam end weakening parameter a is（0.50-0.70）b_f,and the weakening parameter b is recommended to be（0.65-0.95）h_b,the recommended value range of c is（0.20-0.25）b_f,where b_frepresents the width of the beam’s flange and h_brepresents the height of the beam.（3）Suggestions for the design of the new box-shaped tapered weakening connection is as follows:the recommended value range of the beam end weakening parameter L₁is（0.10-0.30）b_f,and the recommended value range of the weakening parameter L₂ is（0-0.15）b_f,the recommended value range of the beam end weakening parameter L₃ is（0.45-0.90）h_b,the recommended value range of the beam end weakening parameter L₄ is（0.17-0.25）b_f,where b_frepresents the flange width of the beam and h_brepresents the beam The height of the section.