Abstract: A marine structure, for example an offshore production plantform comprises a floating base section, which can be flooded, having caissons thereon and a topsides mounted on the caissons. The caissons comprise at least two telescopic sections,the uppermost section carrying the topsides and the lowermost being mounted on the base. The structure can be installed by supporting hte topsides for example, using the derrick of a jack-up rig, and then partially flooding the base section until the jack-up rig is supporting the topsides. On lowering the hook, more of the topsides weight is applied to the base and the structure sinks to the sea-bed where it is secured by grouting. The upper supported section is then lifted to the desired height and the telescopic sections locked. Piling and drill casings, strings etc. may be lowered through the topsides into the hollow regions within the legs.

Abstract: A guyed stack has a system of horizontal rings and vertical struts surrounding it to which the guy wires are attached. The rings and struts allow free expansion and contraction of the stack. The vertical struts support the vertical components of the guy tensions. The stack supports wind induced bending moments and shear forces. Friction between the stack surface and the horizontal rings under wind induced motion acts as a damping mechanism to suppress the motion and reduce the risk of dynamic instability.