Hi TW,
Based on the drawing I made below, piece to be attached to a structure looks similar to it. Its purpose is to ensure a full weld is done between the base and the piece. With that, if removal is required, is easier using an acetylene or disc grinder. But sometimes if the area is a fire hazard, disc grinder is used since hot beads are more easier to contain than acytelene.
Actually, the pieces shown above are considered 'small' compared to the same type use in oil rig structure.
Angel