Abstract: A vessel such as a nuclear reactor containment vessel is provided with a bottom extension in the form of a cylindrical skirt in which are formed peripheral openings in uniformly spaced relation. A horizontal cross-pin extends through each orifice, projects on each side of the cylindrical skirt and is provided with means for translational locking with respect to the orifice. The threaded upper portion of an anchor-bolt is mounted at each end of the cross-pin while the lower ends of the two bolts are anchored in the foundation raft. The device produces a substantial reduction of stresses in the anchorage zone.