Finite Element Analysis Of Hysteretic Behavior On Expanded Flange Of Box Strengthen-Joint Region Connection In Fringe Frame For Weak Axis Of I-Section Column

In the northridge earhtquake and kobe earthquake,the traditional steel frame beam-column joints produced a large number of brittle crack. The results showed that weld crack has restricted the plasticity development of beam-column joints,and cannot effectively dissipate the earthquake energy. In order to improve the influence of steel frame beam-column joints of I-shaped column under severe earthquakes, Japan proposed beam-end-expanded flange connection joints.In this paper, the standard joints and beam-end-expanded flange joints carried out a large number of finite element analysis for the new weak axis,and the main contents as followed:1、Through beam-end-expanded flange joints and the standard joints comparative analysis,it concluded that: Bearing capacity, ductility factor and plastic rotation capacity of beam-end-expanded flange joints was better than standard joints, and the beam-end-expanded flange connection joints can obviously reduce the stress level of beam-column welds by expanding the beam flange,making the stress of the design plastic hinge section to full develop, achieving the goal of offshoring forced plastic hinge.2、《Code for seismic design of buildings》prescribed that: the right-angle side ratio of beam end expanding portion was 1:2 ~ 1:3. In this paper, a series of finite element model was established in and outside the scope of the right-angle side ratio,it showed that:when the short edge size of triangle sides within a certain range, with the increase of long side size, plastic hinge moved outward gradually. But only when the right-angle side ratio within the scope of 1:2 ~ 1:3, plastic hinge appeared in the end of the expanding part. Visible, the relevant provision in《Code for seismic design of buildings》applyed to the joints in this paper.3、Skin panel was an important part of the new joint in this paper, the influence of the changes of skin panel height and thickness on the joint force performance is slightly different. Along with the change of height, the basic performance of the joint was not affected, but the change of the thickness of the skin pedal had a greater influence on the joint performance. For beam-end-expanded flange joints in this paper, when the skin panel thickness reduced to 14 mm, skin panel itself undergone significant plastic deformation, and no longer meet the "strong nodes, weak component" seismic requirements.4、 Considering the influence of axial compression ratio,anti-slip coefficient of friction surface, beam-column linear stiffness ratio,steel properties and a series of parameters on the performence of the joint,this paper established the corresponding finite element model and analyzed the impact of parameters on the properties of the joint,and presented a certain valuable suggestion.