E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
E04B1/38—Connections for building structures in general
E04B1/58—Connections for building structures in general of bar-shaped building elements
E04B1/5825—Connections for building structures in general of bar-shaped building elements with a closed cross-section
E04B1/5837—Connections for building structures in general of bar-shaped building elements with a closed cross-section of substantially circular form
E04B1/5843—Connections for building structures in general of bar-shaped building elements with a closed cross-section of substantially circular form with ends provided with protuberances