A Study on Connection Strength and Deformation Capacity of H-Shaped Steel Beams to Concrete Filled Circular Tubular Columns

H形截面梁与钢管混凝土柱的连接采用横隔梁进行加劲，但在浇筑混凝土时横隔梁上不可避免地会开孔，容易引起局部变形。因此，在抗震设计中需要对节点的变形进行预测。在研究的第一年，通过简单拉伸试件的试验研究了节点的强度和变形能力，每个试件由短柱、梁翼缘和横隔板组成。其中一个测试参数是连接类型，即，与圆形或椭圆形外部膜片的连接、与切穿膜片的连接以及非膜片连接。试验结果表明，节点破坏形式为柱筒壁冲切裂缝和横隔板延性断裂。由于大的塑性伸长发生在破坏之前，如果连接被横隔板加强，变形能力可能是足够的。试件承受恒定轴向荷载和重复梁端荷载作为地震荷载。与简单拉伸试件不同，柱筒墙的破坏形式仅为冲切裂缝。其原因可能是荷载的重复作用加速了管壁的应变集中。建立了节点的有限元模型。通过与试验结果的对比，验证了有限元模型的准确性。今后，通过对模型进行参数化分析，建立数值数据库，发展节点局部变形的预测方法。

Although diaphragms are used for stiffening the connections of H-shaped beam to concrete filled circular tubular (circular CFT) columns, a hole is inevitable in the diaphragms for concrete casting, and is likely to result the local deformations. Therefore, a prediction of the deformations will be required in the seismic-resistant design for the connections.At the first research year, the strength and the deformation capacity were investigated by testing simple tension specimens, each of which was composed of a stub column, beam flanges, and a diaphragm. One of the test parameters was the connection type, i.e. a connection with an external diaphragm of polygon-shape or circular-shape, a connection with a cut-through diaphragm, and a non-diaphragm connection. The test revealed that connection failure modes were the punching shear cracks in a column tubular wall and/or the ductile fracture of a diaphragm plate. Since the large plastic elongation occurs prior to the failure, the deformation capacity may be enough, if the connection is stiffened by diaphragm plates.At the final research year, cruci-form frame specimens were tested. The specimen was subjected to a constant axial load and repeated beam-end loads as seismic loads. Differing from the simple tension specimen, the punching shear crack of column tubular wall was only the mode of failure. The reason may be the load repeating, which accelerates the strain concentration on tubular walls. However, the deformation capacity may be enough.A finite element model of connection (FEM model) is developed. The accuracy of the FEM model was demonstrated by a comparison with the test results. In the future, by performing a parametric analysis of the model, the authors will construct a numerical database and develop a prediction method of the local deformations of connections.