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

虽然横膈膜用于加强h形梁与圆管混凝土柱的连接，但在混凝土浇筑时，横膈膜上不可避免地存在孔洞，并可能导致局部变形。因此，在连接的抗震设计中需要对变形进行预测。在第一年的研究中，通过测试由短柱、梁法兰和膜片组成的简单拉伸试件来研究其强度和变形能力。其中一个测试参数是连接类型，即与多边形或圆形外部膜片的连接，与贯穿膜片的连接和非膜片连接。试验结果表明，连接破坏模式为柱管壁冲剪开裂和/或膜片延性断裂。由于大塑性伸长发生在破坏之前，变形能力可能是足够的，如果连接是加强膜片。在研究的最后一年，对十字形框架试件进行了测试。试件承受恒定的轴向荷载和重复的梁端荷载作为地震荷载。与简单的受拉试件不同，柱管壁的冲剪开裂只是其破坏模式。其原因可能是荷载的重复，加速了管壁应变的集中。然而，变形能力可能是足够的。建立了连接的有限元模型。通过与试验结果的比较，验证了有限元模型的准确性。在未来，通过对模型进行参数化分析，作者将建立一个数值数据库，并开发一种连接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.