Experiments on Toughness Deterioration of Brittle Region at Welded Joints of Steel Beam to Column

1995年兵库地震中，钢梁与柱的焊接接头出现了频繁的断裂。尤其是焊缝附近的母材出现了较多的断裂。我们推测，这种断裂是由于远离焊接熔合区的脆性区域的韧性恶化造成的。用常规钢和新开发的钢结构用钢进行了脆性区强度和韧性的两种试验。带焊接接头的板的拉伸试验1)梁翼缘接头焊接到横隔板2)柱节点焊接到横隔板2。在试验中，除钢种外，还采用了层间温度、焊接线能量和根部间隙作为参数进行梁的弯曲试验。试验结果表明：1.在焊接板材拉伸试验中，未出现由于焊接区附近脆性区韧性劣化而导致母材断裂的现象。在层间温度为440*、焊接热输入为29KJ/cm的条件下，1个试件的梁翼缘在焊接区附近的脆性区域出现了梁翼缘断裂。但其他试件的脆性区域没有梁翼缘断裂。

Fractures at welded joints of steel beam to column were frequently observed in 1995 Hyogo Earthquake. Especially, many fractures occurred in the base metal near along the welding line. We presumed that such fractures derived from the toughness deterioration of the brittle region which was apart from a welding fusion zone. The following two kinds of experiments on the strength and the toughness of the brittle region were performed using conventional steels and a newly developed steel for the steel structure.1. Tension tests of plates with a welded joint1) Beam flange joint welded to diaphragm2) Column joint welded to diaphragm2. Bending tests of beams with beam joint welded to columnInterpass temperature, weld heat input and root gap were adopted as the parameters in addition to the steel grades in the experiments.The following results were obtained from the experiments :1. No fractures of the base metals due to the toughness deterioration of the brittle region near the welded zone were produced in the welded plate tension tests.2. One specimen with the beam flange welded to the diaphragm at an interpass temperature of 440* and weld heat input of 29 Kj/cm exhibited the beam flange fracture of the brittle region near the welded zone. But the other specimens had no beam flange fractures of their brittle regions.