Truss Spar Platform Motions for Combined Wave, Current and Wind Forces

Truss spar platform is the second development
concept that replaces the cylindrical lower section of a
classic spar with an open truss structure that includes
heave plates. In this paper, the dynamic responses of the
Marlin truss spar in regular waves, current and wind are
presented. A MATLAB code named TRSPAR was
developed for the dynamic analysis of the structure. The
structure was modeled as a rigid body with three degrees
of freedom. The hyperbolic extrapolation and the
extended Morison equation for an inclined cylinder were
used for simulating the sea state and for determining the
dynamic force vector. Time domain integration using
�ewmark Beta method was employed. The simulated
results show insignificant effect of current and wind on
the responses. However, these forces cause significant
increase in the surge mean offset.
Keywords- truss spar; dynamic analysis; time domain;
hydrodynamic responses; rigid body