Structural Performance of Weld Joints With Lack-Of-Fusion Defect At 35 Degrees Groove Face

Abstract eng:
The characteristics of a welding joint greatly influence seismic performance in steel structure buildings. Welding defects are well known to reduce the strength capacity and elongation of welding joint in steel structures. One of the welding defects is the lack-of-fusion occurring at a groove face in a welding joint. The lack-of-fusion defect might become the fracture origin when it is located near the welding joint surface. The influence of the lack-of-fusion at the groove face is experimentally investigated in this study. A series of cyclic bending loading tests was conducted on specimens with different defect sizes and shapes. How the defects influenced the fracture behavior was examined. The study object is the model with a defect along the groove face with a groove angle of 35°. The defect was artificially made in the specimen flange plate by electric spark machining. The defect position was the flange plate surface. The test parameters were the defect position (flange plate edge or center), size (length and depth), and face angle (35° or 0°). The specimens were made from 490 MPa class steel plate with a thickness of 25 mm. A hydraulic-type testing machine with 1000 kN capacity was used for this loading. The specimen was tied to jig-beams with high-tension bolts as a simple beam type. The bending moment was then loaded to the specimen through a loading beam following the two-point loading procedure. Applying the bending moment to the specimen was considered to increase stress on the defect located near the surface. The loading was controlled by displacement at the specimen center. The loadings were applied following the incremental amplitude procedures until fracture. The test temperature was set to 0°C. The summaries of the test result are as follows: a ductility crack occurred from the artificial defect, and the crack progressed with the cyclic loading, finally caused to the fracture; the relationships of the defect size between the maximum strength and the energy absorption capacity were obtained; and the allowable size of the edge defect was half the size of the center defect. The difference in the angles for the defects in the surface side is hardly observed.

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