Friction stir welded body and frame member therefor

A structural body, comprising:

• a first frame member and a second frame member welded together;
• said first frame member and said second frame member are abutted and each of said first frame member and said second frame member has a first face plate, a second face plate disposed in parallel to said first face plate, and plural ribs for connecting said first face plate thereof and said second face plate thereof;
• said second face plate of said first frame member and said second face plate of said second frame member are welded together;
• both end portions of a connection member having been overlapped with a seat having a recessed form of an end portion of said first face plate of said first frame member and a seat having a recessed form of an end portion of said first face plate of said second frame member;
• said first face plate of said first frame member having had a raised portion and a groove in a side wall portion of said first face plate of said first frame member;
• said connection member having had a projection portion in one of the end portions of said connection member toward a side of said first face plate of said first frame member;
• said projection portion of said connection member having been inserted into said groove of said first face plate of said first frame member;
• the other of said end portions of said connection member having been mounted on said seat of said end portion of said first face plate of said second frame member;
• a friction stir welding having been carried out to said overlapped portion of a side of said first frame member to weld said first face plate of said first frame member and said connection member;
• and
• a friction stir welding having been carried out to said overlapped portion of a side of said second frame member to weld said first face plate of said second frame member and said connection member.