| Abstract: | In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken-Nanbu earthquake (Japan), astonished engineers in the field of construction. The experience from recent earthquakes of USA and Japan shows that brittle fracture of welded steel structure always starts from high stress zone with welded crack1～5]. As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack-of-fusion at the root of flange weld. In this paper stress distribution of connection is computed with FEM, and stress concentration at the root of flange weld is also analyzed. Stress intensity factors (SIFs), KI, at the root of flange weld are computed in the method of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld. It is proved by the fact that brittle fracture is liable to start at the root of bottom flange weld on actual earthquake1,4]. Finally measures are brought forward to avoid fracture of weld structure against earthquake. |
