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

当抗弯矩钢框架受到强烈地震作用时，柱-梁连接的面板区域出现高剪应力。板区剪切变形可能在连接处对梁翼缘产生二次应力，并可能导致梁端脆性断裂。本研究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，为了检查连接处的应变分布，使用有限元程序进行了数值弹塑性分析。可得出以下结论：面板区域的剪切变形在连接处对梁翼缘产生二次应力，增加了梁翼缘处的应变集中。如果梁翼缘材料的断裂韧性较高，则梁翼缘早期不会发生脆性断裂。因此，面板区的剪切屈服可以缓解梁内必须容纳的塑性变形量。结果表明，随着板梁强度比的减小，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，梁翼缘也会发生脆性断裂。在这些试验中，断裂模式（延性或脆性）取决于试验温度，而不是面板与梁的强度比。因此，虽然面板屈服先于梁屈服，但为了防止剪切裂缝的发生，有必要避免使用断裂韧性较低的梁翼缘，或改进连接细节。

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.