Abstract: A flared connection structure of a pipe end portion is provided. The structure includes a bridge flare with a spool portion with a U-shape or V-shape section that bulges outwardly to define front and rear inclined faces. A ring member with a U-shape cross-section has a rear portion disposed in the pocket between the front and rear inclined faces of the spool portion. The ring member also has a front face disposed between the front inclined face of the spool portion and the pressure receiving seat face of a counterpart joint. A pattern of concentric circles formed by recesses and projections is provided on at least one of the faces of the front portion of the ring member or the pressure receiving seat face of the counterpart joint.