This paper provides an overview of the Truss Spar structural design with emphasis on the design and analysis of the truss structure, based on firsthand design experiences. The structural design criteria and main loading conditions are outlined. Discussions are focused on the methodologies and procedures using random wind and wave time domain analyses. In particular, the paper covers the truss in-place strength analysis, truss wet tow transportation analysis, upending analysis, and truss fatigue analysis. Structural analyses of the truss critical connections and the heave plates are also discussed. Technical issues related to structural and hydrodynamic modeling, time domain motion and environmental load simulation, structural load mapping, as well as computer software requirements are addressed. Analysis results are presented to illustrate the various loading conditions and the structural behavior for a generic Truss Spar design.
The Spar platform has become one of the most attractive development concepts as the offshore industry moves towards deep and ultra-deep water frontiers for new oil & gas discovery and production. It can be designed for drilling/work-over, production and storage of oil, and is well suited for water depths from 500 to 3000 meters, and above. Since the first Spar platform was installed in 1996, the Spar technology has evolved from the first generation Classic Spar design to the second generation Truss Spar design. The first Truss Spar will be installed in the fall of 2001 in the Gulf of Mexico. The second and the third Truss Spars will be installed in later part of 2001 and the spring of 2002, respectively. It is expected that more Truss Spars will be built in the future as the Truss Spar gains greater recognition by the offshore industry.
