Fracture research on Welded Beam-Column Connection under Cyclic Loading

试验研究了梁柱焊接节点的延性裂纹萌生、裂纹稳定扩展、最终爆炸破坏的断裂过程。试验试件为周边柱与梁组成的T型节点。柱为矩形空心截面(-250x250x9)，梁为H型截面(BH-300x150x6x12)。试验参数为：1)焊接孔的存在与否；2)控制位移幅值-1.0_p~2.5_p。焊接梁柱节点在循环荷载作用下的断裂试验结果如下：1.试件的断裂是梁翼缘的大范围破坏，其扩展方式来自(1)非扇形的横隔板与梁翼缘之间的坡口焊缝，(2)当位移幅值大于1.5_p时，扇贝底部。当裂纹长度扩展到翼缘宽度的20%~40%时，梁的强度下降到梁的全塑性弯矩的80%。在裂纹扩展速率关系dN/da=C(J)^m中，非扇形裂纹扩展速率为m=1.15~1.44，扇形裂纹扩展速率关系为m=1.34~1.61。非扇形结构的疲劳寿命约为扇形结构的两倍，说明在灾害性地震作用下，非扇形结构是可行的结构细节。

The fracture process composed of ductile crack initiation followed by stable crack growth and finally explosive failure in the welded beam-to-column connections we investigated experimentally.Tested specimens were T-type connections consisted of the perimeter column and beam. The column was a rectangular hollow section (□-250x250x9), and the beam was H-section (BH-300x150x6x12). The test parameters were 1) welded access hole-in or out of existence of scallop 2) controlled displacement amplitude-1.0△_p to 2.5△_p.The results of fracture test of welded beam-column connections under cyclic loading were as follows ;1. Fracture of specimens were the fell wide failure of beam flange by the crack propagation from (1) the groove weld between the diaphragm and the beam flange in non-scallop type, (2) the bottom of scallop when the displacement-amplitude was over 1.5△_p, in scallop type.2. The beam strength fell to 80% of full-plastic-moment of beam when the crack length grew up to 20% to 40% of flange width.3. In the crack propagation rate relation dN/da = C(△J)^m, test results were m = 1.15 to 1.44 for non-scallop type, and m = 1.34 to 1.61 for scallop type.4. The fatigue life of the non-scallop type were about two times of one of scallop type, so it made clear that non the scallop type was available structural detail under the disastrous earthquake motion.