The spar platform concept develops quickly in the oil and gas exploitations in offshore areas, especially in deep and ultra-deep water. From the first generation of classic spar, the spar concept has developed into the second generation of truss spar and the third generation of cell spar, and many new spar concepts are being put forward by the ocean structure design companies and research institutes. The purpose of those designs mainly focuses on the reduction of fabrication difficulties and cost, while satisfying the requirement of exploitation at meantime. This paper presents a numerical study on the hydrodynamic behavior of a cell-truss spar platform. Features of truss spar and cell spar were both taken into account in the new spar concept, aiming to take advantage of the heave plate damping feature of the truss spar to obtain satisfactory heave motion performance, while reduce manufacture and installation difficulties with cell concept. The whole spar concept with risers and mooring system were modeled by means of numerical simulation, and fully time-domain coupled analysis was conducted to investigate hydrodynamics of the spar platform both in operating and survival conditions.
