Effects of Shear Behavior of Column-to-Beam Joint Panels on Beam Frexural Behavior

抗弯钢框架在遭受强烈地震作用时，梁柱节点节点的板区会产生较高的剪应力。板区剪切变形会在梁翼缘连接处产生二次应力，并可能导致梁端的脆性断裂。通过加载试验研究了板区剪切变形对梁受弯性能的影响。此外，为了检验节点处的应变分布，利用有限元程序进行了数值弹塑性分析。剪裁结果表明：1.节点区的剪切变形在梁翼缘连接处产生了二次应力，增加了梁翼缘的应变集中。如果梁翼缘材料的断裂韧性较高，则梁翼缘不会发生早期脆性断裂。因此，板区的剪切屈服可以减轻梁中必须容纳的塑性变形量。结果表明，随着板梁强度比的降低，框架的变形能力增大。对于断裂韧性较低的梁翼缘，即使板梁强度比为0.85，也会出现梁翼缘的脆性断裂。在这些试验中，断裂模式(延性或脆性)取决于试验温度，而不是板梁强度比。因此，虽然板的屈服先于梁的屈服，但应避免使用断裂韧性较低的梁翼缘，或改进连接细节，以防止剪切裂缝的发生。

When moment resisting steel frames are subjected to severe earthquake, high shear stress occurs in the panel zones of column-to-beam connections. The shear deformation of panel zones may induce secondary stress into the beam flange at the connection, and may cause the brittle fractures at the beam end In this study, loading tests were carried out to investigate the effects of the shear deformation of panel zones on the beam flexural behavior. Further, for the purpose of examining the strain distribution at the connection, numerical elasto-plastic analyses were carried out by using the finite element program. The Mowing conclusions can be made :1. The shear deformation of panel zones induces secondary stress into the beam flange at the connection, and increases the strain concentration at the beam flange.2. If the fracture toughness of the beam flange material is high, the brittle fracture of the beam flange cannot occur in early stage. So, the shear yielding of the panel zone can relieve the amount of plastic deformation that must be accommodated in the beam. As the result, the deformation capacity of frames increases as the panel to beam strength ratio decreases.3. In the case of the beam flange with low fracture toughness, the brittle fracture of the beam flange occurred, even if the panel to beam strength ratio was 0.85. In these tests, the fracture mode (ductile or brittle) depends on the test temperature rather than the panel to beam strength ratio. Therefore, although the panel yielding precedes the beam yielding, it is necessary to avoid the use of the beam flange with low fracture toughness, or to improve the connection detail in order to keep out the occurrence of shear cracks.