Abstract: To facilitate the construction of a very high structural member for use in a body of water such as at an offshore location with the structural member extending from the floor of the body of water to above its surface, tensioning members are inserted into relatively narrow tensioning ducts accessible only from the top of the structural member. The tensioning members, such as steel rods, steel wires, or steel wire strands, are provided with members for effecting a positive locking engagement in a hardenable material forming an anchored length of the tension member at the lower end of the tensioning ducts. Initially, the tension members are lowered into the lower ends of the ducts and then are grouted in the ducts by a hardenable material. After the hardenable material has set over an anchored length, the tension members are tensioned within the ducts. Next, the tensioned length of the tension members in the ducts is grouted with a hardenable material to provide a composite action with the structural member.