A study on seismic performance of semi-rigid connection in steel frame

以组合梁的钢构件与矩形截面柱的钢翼缘直接焊接而不设横隔板的连接方式为例，进行了组合梁-矩形截面柱半刚性组合节点的试验研究。其连接强度按半导体的强度比分为以下三类：刚性连接到组合梁构件，即（i）梁翼缘的屈服是在连接之前预期的，（ii）梁翼缘的屈服是在连接之后预期的，以及（iii）连接的失效是在梁翼缘的屈服之前预期的。无论失效模式的不同，子组件的滞回特性都是稳定的主轴型，直到漂移角为1/25。对3个2跨2层组合梁-矩形钢管混凝土柱无支撑钢框架进行了试验研究，其梁柱无隔板连接均为上述3种类型。得到的各框架的载荷-位移角关系均为稳定的纺锤型，无论破坏模式如何，均具有良好的变形能力。采用转动弹簧模型分析了连接的半刚性特性对框架结构性能的影响，并利用三维弹塑性有限元法可以精确分析这种连接的jM-jrheta关系，连接的jM-jrheta关系的公式化是可能的，通过有限元分析累积案例研究的结果。

The connection type, which the steel element of the composite beam is welded directly to the steel flange of the rectangular hollow section (RHS) column without any diaphragms, was selected for an example of the semi-rigid composite joint.The composite beam-and-RHS column subassemblage specimens, whose connection strength are of the following three categories classified by the strength ratio of the semi-rigid connection to the composite beam member, that is (i) the yielding of the beam flange is expected in advance of the connection, (ii) the yielding of the beam flange is expected after the connection, and (iii) the failure of the connection is expected in advance of the yielding of the beam flange, were carried out. The hysteretic characteristic of the subassemblages is stable spindle type until the drift angle of 1/25 regardless of the difference of failure mode. And the relationship between the moment (jM) and local rotational angle of the connection (jrheta) is obtained for each connection.Three 2 bay-2 story unbraced steel frames consisted of the composite beams and RHS columns, whose beam-to-column connections without diaphragms are of the above three categories, were tested. The obtained load-drift angle relationship of each frame is stable spindle type with satisfactory deformation capacity regardless of the difference of failure mode. The effect of the semi-rigid behavior of the connection on the structural behaviors of the frames is analyzed by using the rotational spring model for the connection.In addition, as jM-jrheta relationships of this type connections can be analyzed precisely by the three dimensional elasto-plastic finite element method, the formulation of the jM-jrheta relationship of the connections is possible by accumulating the results of the case studies by the finite element analysis.