Abstract: Tubular structural elements and assemblies comprising an outer tube and a concentric inner tube connected to each outer by ribs and having very high stability. Lengthwise recessed groove spaces are provided between the ribs, covered on the outside by removable strips or sectors of the outer tube and designed to receive flat structural elements. One or more of the groove spaces, which are sealed off by the strips or sectors of the outer tube, can be exposed by removal of the covering strips or sectors so that flat structural elements such as walls or facade panels, glass panes, or the like can be inserted where desired. The tubular structural element is sealable at the ends by end caps or sealing elements, or is connectable by axial or branched coupling parts with other tubular sections connectable at various angles, to erect halls, room partitions, pavilions, or the like.