COLUMN JOINT STRUCTURE OF UNDERMATCHING WELD TYPE AND ESTIMATION METHOD THEREOF

To provide a column joint structure of a soft welding type excellent in weld workability and deformability.SOLUTION: A column joint structure 10 of an undermatching weld type is provided with: an upper column member 12 and a lower column member 11 each of which has a cross section of a rectangular box shape and formed of high tensile steel; and a joint part 13 for welding an upper end part of the lower column member 11 and a lower end part of the upper column member 12 using a weld metal with lower strength than those of the column members 11, 12, wherein the high tensile steel has a yield strength Bσy of 630 MPa or more. The weld metal is set so as to meet an axial force ratio n and a determination formula prepared according to a load direction.SELECTED DRAWING: Figure 1 【課題】溶接施工性と変形性能に優れた軟質溶接式の柱継手構造を提供する。【解決手段】アンダーマッチ溶接型柱継手構造１０が、矩形箱状の断面を有し、高張力鋼で成形された上柱部材１２および下柱部材１１と、下柱部材１１の上端部と上柱部材１２の下端部とを柱部材１１，１２よりも低強度の溶接金属で溶接する接合部１３と、を備え、高張力鋼が、630MPa以上の降伏耐力Ｂσｙを有する。軸力比ｎおよび載荷方向に応じて準備された判定式を満たすように、溶接金属が設定される。【選択図】図１