The bridge is constructed of one inner tube (2) and an outer tube (1) surrounding the inner tube (2). The inner and outer tube (1, 2) are joined to each other by connecting pipes (3 - 13) welded to the outer surface of the inner tube (2) and to the inner surface of the outer tube (1) so that the inner tube (2) and the outer tube (1) are connected to each other through said connecting pipes (3 - 13) whereby a rigid composite structure is formed. The tubes and pipes are preferably laser welded to each other, preferably by a continuous seam.