Seismic Performance of Cold-Formed Square-Hollow-Section Steel Column To Through-Diaphragm Welding Connection Using a 25 Degrees Narrow Groove

Abstract eng:
The welding groove angle and is an important factor that affects the weld quality when welding steel members. Currently, a welding groove angle of 35° is normally used by Japanese fabricators. However, a 25° narrow-groove welding method can improve the production efficiency and reduce the environmental impact. From the previous research results, a welding with a 25° narrow groove is considered to be feasible. However, full-scale tests for this type of groove have not carried out and the performance of a connection welded using a 25° narrow groove has not been evaluated. In this study, we conducted a series of three-point bending tests on a cold-formed square-hollow-structural-section (SHSS) steel column to a throughdiaphragm welding connection by using a 25° narrow groove. Subsequently, we investigated the deformation capacity of the welded connection. The column of the test specimen was a steel rectangular pipe (HSS550x550x32: BCP325) formed by a cold-press forming process. The through-diaphragm of the specimen was made of a steel plate (PL36: SN490C). The length of the support span of the test specimen was 4 m, and the welding groove angle of the test specimen was 25°. A welding robot was used to weld the cold-formed SHSS column and the through-diaphragm. In addition, since the shape of the welded toe has a significant influence on the deformation capacity of the welded connection, the weld toe of one of the specimens was polished using a hand grinder to relieve the stress concentration at the weld toe. The results obtained in this study are as follows: (1) The deformation capacity of a cold-formed SHSS column to a through-diaphragm welding connection by using a 25° narrow groove is comparable to or higher than that obtained in the previous tests conducted using a 35° standard groove. (2) In all the test specimens, ductility crack initiation occurred at the weld toe, which did not progress to the heat-affected zone. The crack path was located at the corners of the column. The ductile crack grew, and finally, it induced a brittle fracture in the base material of the column. (3) Even when the welding defect existed in the first layer of the column corners, brittle fracture did not occur at the welding defects. (4) Relieving the stress concentration at the weld toe with grinder finishing delayed ductile crack initiation, thus improving the deformation capability of the welded connection of the cold-formed SHSS column.

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