An object of the present invention is to provide an improvement in the shape of an open type slot in which a longe is pierced through a web frame, a partition wall, and the like, thereby relieving stress at the edge portion of the hole, abolishing the stiffener that was conventionally required, To provide a loose piercing structure.;When the web consisting of the web 1 and the face plate 2 passes through the web frame and the partition wall 4, the web and the face plate are opened to the web frame, the partition wall 4, Type slot structure. The shape of the slot 5 from the vicinity of the level of the face plate 2 to the side of the web 1 on the closed side of the slot 5 is formed into a substantially elliptical shape having a long axis P inclined to intersect the web 1 And the lower end of the slot 5 has a certain depth of cut.
展开▼
