Objectives  In order to improve the hydrodynamic performance of the second generation deepsea Spar platform, the design and optimization of truss structure is tudied in this paper.

  Methods  The equation of motion of the heave plate was investigated based on the three-dimensional potential flow theory, and the Morrison formula was used to calculate the hydrodynamic force of the truss structure. Then, combined with engineering experience, a preliminary scheme of the truss structure(including the heave plate) was proposed. Then, the numerical calculation of the heave plate and truss structure of the Spar platform was carried out, and the time-domain and frequency-domain analysis of the truss structure under different parameters was carried out to explore the the influence of the number, thickness and space of heave plate, the cross section area of the trusses and the number of inclined trusses on the hydrodynamic performance of the Spar platform, so as to further optimize the design scheme.

  Results  The results show that, the motion of various degrees of freedom of the Spar platform should be considered comprehensively with respect to the determination of the number of heave plates. The thinner the thickness of heave plates, the better the hydrodynamic performance of the platform. The spacing between heave plates should find the most efficient value to improve the heave and pitch performance of the platform. The cross-sectional area of trusses has a greater impact on the motion response of the platform, while the number of inclined trusses has a relatively small impact.

  Conclusions  The study in this paper can provide a certain reference to the design of deepsea drilling platform.