Jacket frame floating structures comprise one or more elongate vertical support columns formed of an open cross-braced jacket formwork of tubular members interconnected together and at least one cylindrical buoyancy capsule disposed in the open framework near an upper end and at least one cylindrical second buoyancy capsule near a lower end in vertically spaced relation. The buoyancy capsule(s) may be a single, or a plurality of upper and lower capsules bundled in circumferentially spaced relation with a central opening therethrough. Alternatively, a keel tank may replace the lower capsule. The buoyancy of the upper buoyancy capsule(s) is adjustably tuned to provide a buoyant force and a sufficient water plane area and moment of inertia required for stability of the floating structure, and the water mass and weight of the lower buoyancy capsule(s) or keel tank(s) is adjustably tuned to raise or lower the center of gravity of the entire mass of the floating structure with respect to its center of buoyancy according to ballast and variable or fixed loads including deck payloads to stabilize the structure. Alternatively, a keel tank may replace the lower capsule. The buoyancy of the upper buoyancy capsule(s) is adjustably tuned to provide a buoyant force and a sufficient water plane area and moment of inertia required for stability of the floating structure, and the water mass and weight of the lower buoyancy capsule(s) or keel tanks(s) is adjustably tuned to raise or lower the center of gravity of the entire mass of the floating structure with respect to its center of buoyancy according to ballast and variable or fixed loads including deck payloads, to stabilize the structure, and to compensate for different operational, environmental, survival and installation stages of the structure. The length of the upper buoyancy capsule(s) is sufficient so as to be partially submerged and allow oscillation of the trough and crest of waves within its top and bottom ends.