Abstract: A liquefied natural gas container including a loadbearing structure and an impermeable and thermally insulated tank designed to contain liquefied natural gas. Each tank wall having in succession, in a direction of a thickness, proceeding from an inside of the tank to an outside, a primary impermeable barrier, a primary thermally insulating barrier, a secondary impermeable barrier, and a secondary thermally insulating barrier. The secondary impermeable barrier of a vertical wall includes a first impermeable sheet at the top of the wall and a connecting device which impermeably connects the first impermeable sheet to the loadbearing structure. The connecting device includes a first metal plate parallel to the first impermeable sheet, and a second impermeable sheet which is on the one hand bonded to the first impermeable sheet, and on the other hand connected to the first metal plate.

Abstract: A fluidtight tank including a bearing structure, a fluidtight barrier, the fluidtight barrier having a polygonal, cylindrical shape and including a vertical wall and a bottom wall, in which the said vertical wall of the fluidtight barrier has a plurality of vertical panels the bearing structure surrounding the vertical wall, and in which the bottom wall includes a plurality of rectangular components arranged in sectors that are the image of one another but rotated, the edges of the rectangular components of one of the sectors being respectively parallel and perpendicular to one of the vertical panels, wherein the number of the vertical panels is twice the number of the sectors.

Abstract: A mechanically welded structure comprising a first flat and thin metallic structural element extending in a plane and delimited by a straight edge on one side, and a second metallic structural element welded to the straight edge of the first structural element, or welded to an intermediate element connected to the straight edge and inserted between the first and second structural elements, the second structural element exerting, at least one point of the straight edge, a force resolving into at least one component extending in said plane perpendicularly to the straight edge, wherein the first structural element has a stress-relieving slit extending parallel to the straight edge and situated facing the point at which said force is exerted.

Abstract: A watertight, thermally insulating tank built into a bearing structure and including a primary watertight barrier contacting material within the tank and including strakes having edges turned upwardly towards an interior of the tank. A secondary watertight barrier is positioned between the primary watertight barrier and the bearing structure. The tank includes primary and secondary insulating barriers. The insulating barriers are alternately arranged with the watertight barriers. A weld support is mechanically held on the primary insulating barrier and forms an expansion joint. The strakes are butt-welded to two faces of the weld support. The secondary watertight barrier and the insulating barriers each include prefabricated panels fixed to the bearing structure. A zone at a junction between two adjacent panels is filled in at least to ensure continuity of the secondary watertight barrier. Each prefabricated panel is formed of a first rigid plate including a layer of thermal insulant.