Bundled tensioning member having a long length for use in prestressing a concrete structure with subsequent composite action, said tensioning member formed of a plurality of individual tensioning elements such as at least one of steel rods, steel wired or steel wire strands, means forming an axially elongated tensioning duct located in the concrete structure, said tensioning duct extending generally upwardly and having a first end at the lower end thereof and a second end at the upper end thereof, said tensioning duct having an axial region extending from the first end thereof, said tensioning duct being accessible only at the second end, means for supporting said tensioning member adjacent the second end thereof, said means comprising an anchor disk, wherein the improvement comprises that said tensioning elements are joined together in a compact contacting unitary arrangement in the axial region at the first end of said tensioning duct, means secured on said tensioning members for affording additional anchoring with a hardenable material to be injected into the tensioning duct for providing a composite action and forming an anchored length in the axial region at the first end in said tensioning duct wherein the anchored length extends for the axial region of the duct from the first end thereof.