1. A company of SeaBase  The Flexible MOB Alternative VLFS Trondheim, Norway Oct. 29 2004 Erik Pettersen Moss Maritime

2. A company of Three semi-submersible Main Modules, connected by Two Flexible Bridges SeaBase The SeaBase concept consists of

3. A company of 1500 m runway length, with takeoff and landing capabilities for C-17 Globemaster

4. A company of AIRCRAFT: AIR OPERATIONS: ACCOMMODATION: EQUIP. STORAGE: FUEL STORAGE: (AIRCRAFTS & MIL. EQUIP.) TRANSIT SPEED: DESIGN LIFE: DESIGN GOALS C-17 SEASTATE 6 20,000 Troops 460,000 m 2 700,000 Barrels TRESHOLD VALUES C-17 SEASTATE 6 10,000 Troops 320,000 m 2 700,000 Barrels 12 Knots 40 Years DESIGN CRITERIA

5. A company of FLIGHT DECK LENGTH:1,528.5 m FLIGHT DECK WIDTH:171.0 m FLIGHT DECK HEIGHT:44.5 m (ABOVE WATER) DISPLACEMENT TRANSIT:1,444,000.0 tonnes OPERATION:2,721,000.0 tonnes MIAN DIMENSIONS

6. A company of MAIN MODULE FLEXIBLE BRIDGE DECK LENGTH:221.5 m 430.0 m DECK WIDTH: 171.0 m 171.0 m HEIGHT (TO FLIGHT DECK):86.5 m86.5 m UPPER HULL HEIGHT: 30.0 m 10.3 / 4.0 m DISPLACEMENT TRANSIT: 304,000 tonnes 266,000 tonnes OPERATION: 621,000 tonnes 429,000 tonnes DRAFT TRANSIT: 15.5 m 11.0 m OPERATION: 42.0 m 42.0 m

7. A company of  Three semi-submersible Main Modules, giving small wave induced motions  Two Flexible Bridges that comply with the motions of the Main Units with elastic structural deformations while inducing moderate stresses  The units are connected together by means of simple fixed type connectors to form a seamless flight deck SeaBase Highlights of the SeaBase concept

8. A company of State of the art analysis tools from the offshore industry  Linear Regime: SESAM program package (Det Norske Veritas): WADAM hydrodynamic (sink source, based on WAMIT) SESTRA linear dynamic solutions POSTFRAME and POSTRESP fatigue and statistical post-processing  Non-linear Regime: ASAS (WS Atkins) WAVE-NL: Morrison type calculations with non-linear drag ASAS-NL: Non-linear time domain dynamic calculations Analysis Tools

9. A company of Original Geometry (Spring 1998)

10. A company of  Improve motions during normal operation  Reduce dynamic amplifications by increasing the damping of the structure hydrodynamic damping structural damping Original model proved the objectives of the flexible concept, yet there was potential for improvements

11. A company of Heading: 0 deg Period: 16 sec Original geometry Base case Main module, Operation

12. A company of Original geometry Base case Heave Response Heave RAO (m/m ) Wave period ( ) Heave RAO ( m/m) Wave period ( ) Main module, Operation

13. A company of Pitch Response Original geometry Base case Pitch ROA (deg/m ) Wave period ( ) Pitch ROA (deg/m ) Wave period ( ) Main module, Operation

14. A company of Natural Frequency, Torsional Mode

15. A company of Natural Frequency, Parallel Pitching

16. A company of Natural Frequency, Pitching End Units

17. A company of  Adjust the flexibility to keep as many as possible of the eigenmodes out of the excitation area  Reduce dynamic amplification of the remaining eigenmodes by means of structural damping Main objective is to prevent normal periods in the wave excitation area, generally considered impossible for complex structures. The Flexible Bridge response is “tuned” by the following two methods: Dynamic Response

18. A company of Period (sec) Energy Density Eigenperiods Wave Spectra vs. Eigenmodes - Base Case

19. A company of Energy Density Eigenperiods Period (sec) Wave Spectra vs. Eigenmodes - Base Case with Reduced Stiffnes

20. A company of Flexible Bridge Base Case

21. A company of

22.  Linear or non-linear fluid viscous damper assumed  Maximum required damping force of about 2000 tons is same order of magnitude as existing applications  Overall size of unit will be about 1.5 m diameter, 2.0 m long  [1,0.1] Typically 0.4 - 0.5 Typical Damping Element

23. A company of SeaBase Energy (kW)

24. A company of SeaBase Energy (kW)

25. A company of Flexible Bridge Base Case - Seastate 6, all periods

26. A company of Flexible Bridge Base Case - Seastate 8++, all periods

27. A company of SN assumption: Cast joints BASE CASEMAX DAMAGE RATIOS SITE OPERATIONSURVIVAL Site 1 – North Atlantic5.1 – Damage3.37 - Damage Site 2 – Western Pacific0.79 – OK0.47 – OK Site 3 – Arabian Sea0.33 – OK0.18 - OK Site 4 –Sea of Japan0.18 – OK0.10 – OK Assumption: 35 percent of life in operation, 35 percent in survival (stand alone). Fatigue budget for each site is 1/8 in operation and 1/8 in survival. Numbers below give fatigue damage relative to this budget. Fatigue Damage

28. A company of Maximum stresses in Seastate 6 (Hs=6 m) are acceptable Maximum stresses in Seastate 8++ (Hs=14 m) are high, but within the capability of the structure with minor modifications Fatigue exposure at all actual sites except the North Atlantic site is small. Continuous operation in the North Atlantic for more than one year will require special measure with respect to inspection and repair Connector forces are of a magnitude that can be handled by means of simple fixed type connectors Conclusions from the structural calculations

29. A company of  SeaBase  SeaBase does not require disconnection when conditions exceed Seastate 6  SeaBase  SeaBase can stay connected at all actual sites and all times except when encountering tropical cyclones or North Atlantic winter storms  There is still room for structural optimizations that will improve the fatigue endurance in North Atlantic environment I.e.

30. A company of Connection between the units: shall be able to disconnect in severe weather conditions shall be able to re-connect in moderate weather conditions (dynamic problem) shall have sufficient Ultimate Limit Strength shall have acceptable fatigue properties. Advantage with SeaBase compared to some other MOB solutions: the connector can be fixed, without flexibility or damping when finally connected the flexibility and required damping can be distributed over a large volume in the flexible bridge.

31. A company of Re-connection sequence.