Study On Seismic Behavior And Design Method Of Widen Beam-end Flange Weak Axis Connection With Box-shaped Pannel Zone Of I-section Column

Since the Northridge earthquake and the Kobe earthquake in Japan,the research and development of beam-to-column connection with high ductility has become a significant research topic.Joint with widened beam-end flange is a novel connection which can increase the bending capacity at beam-end by widening the flange and can make a weakened section area at the end of the flank artificially.Meanwhile,the plastic hinge can be formed at a certain distance from the surface of the column,and then the purpose of making the plastic hinge away from the connection is reached.At present,domestic and foreign scholars have done lots of work on connection with widen beam-end flange for strong axis of I-section column,but reaserch on weak axis of I-section column is relatively less.In this paper,a full-scale test of widen beam-end flange weak axis connection with box-shaped pannel zone of I-section column under cyclic loading was carried out.The seismic performance of the specimen,such as the failure mechanism,hysteretic behavior,mechanical property,ductility and the energy dissipation,were studied in detail.A series of finite element models with variable parameters were established by ABAQUS,and the nonlinear analysis was performed,in order to find out the critical parameters that influence the seismic behavior of the connection with widen beam-end flange and determine the reasonable value of these parameters.Based on the experimental study and finite element analysis results,a design method for this type of joints is proposed and verified.The main results are summarized as follows:1.The loading-test results show that: the widen beam-end flange connection can achieve an ideal failure mode to form a plastic hinge away from the pannel zone.The shear deformation occurred in joint region while loading process,however,the stress and strain data were almost in elastic condition,which means that the box strengthen-joint region have the feature of ‘strong joint region'.Due to the quality of welding,brittle fracture occurred at the butt welding of the column skin plate and beam flange,which makes the displacement ductility coefficient less than 3.The hysteresis curve of the joint shows relatively full fusiform and kind of pinch phenomenon.The capability of energy dissipation and stiffness degradation of joints are both affected by weld cracking,but the joint still have good seismic performance.2.The results of finite element simulation analysis show that: When the widen beam-end flange connection is applied,the proportion of the right angle side of the widened side plate should be controlled between 1:2 and 1:3.5,the plastic hinge can be fully developed,which can ensure that the joint has higher bearing capacity and ductility;The axial compression ratio of the joint with widened beam-end flange should be limited to 0.6 or less,otherwise column local buckling instability will occur;The failure pattern of the joint depends mainly on the bending capacity of the beam,the linear stiffness ratio of beam to column should be limited within 1.5;The form of widened beam-end flange has an obvious influence on the seismic performance of the joint,triangle and trapezoid side plates can better meet the design requirements and show good seismic performance and practicality.3.This paper put forward a design method which is proved to be reasonable and reliable for the widen beam-end flange weak axis connection with box-shaped pannel zone of I-section column.