UNIVERSITYCOLLEGE LONDON DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING In association with

1. Recent Applications of CRISP 3DBy Amir RahimThe CRISP Consortium Ltd/South Bank University London15th CRISP User Group MeetingThursday 19th September 2002 UNIVERSITYCOLLEGE LONDON DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING In association with

2. Finite Element Analysis of Suction Caissons using CRISP 3D Work carried out for client Oil and Natural Gas Corporation of India. Joint venture between Thales Geosolutions (Belgium) SAGE Engineering, Inc (USA) and the CRISP Consortium Ltd for client ONGC/IEOT.

3. Analysis and Design of Suction Caissons for Floating Structures for a typical Indian offshore soil profile

4. Types of Suction Caissons for floating structures SUCTION CAISSON FOR CALM Catenary Anchor Line Mooring Seabed Anchor Pad eye

5. Types of Suction Caissons for floating structures SUCTION CAISSON FOR TLM Tout Leg Mooring Seabed Anchor 45 0 Pad eye

6. Types of Suction Caissons for floating structures SUCTION CAISSON FOR TLP Tension Leg Platform Load Seabed

7. Aims of Caisson Analyses • To obtain the limit collapse load due to immediate (undrained) static loading • To obtain horizontal contact stresses acting on the caisson sides. These are used for the design of the caisson

8. CALM Analysis • Load is applied at the side of the caisson wall in 55 equal load increments for a Catenary Anchor Mooring Line (CALM) as follows: • Failure criteria = Mohr-Coulomb • Two increment blocks • First load increment block – Pile self-weight as 9 equal nodal forces on the top cap of the caisson applied in 5 equal increments • Second load increment block – Total Resultant load of 18MN applied in 50 equal increments on full model • Load attachment point – 7.425 m below the top of the caisson on the side • Load angle – 15 degrees to Horizontal

11. Deformed mesh with load=7.2MN for CALM loading

12. Deviatoric stresses with load=7.2MN for CALM loading

17. TLM analysis • Load is applied at the side of the caisson wall in 55 equal load increments for a Taut Leg Anchor Mooring Line (TLM) as follows: • Failure criteria - Mohr-Coulomb • Two increment blocks • First load increment block – Pile self-weight as 9 equal nodal forces on the top cap of the caisson in 5 equal increments • Second load increment block – total Resultant load of 18000 kN in 50 equal increments on full model • Load attachment point – 7.425 m below the top of the caisson on the side • Load angle – 45 degrees to Horizontal

19. Deformed mesh with load=12.6MN for TLM loading

20. Deviatoric stresses with load=12.6MN for TLM loading

25. TLP Analysis • The load has been applied on top of the rigid cap of the caisson in 55 load increments for a Tension Leg Platform Tether (TLP) / Riser anchor as follows: • Failure criteria = Mohr-Coulomb • Two increment blocks • First load increment block – Pile self-weight as 9 equal nodal forces on the top cap of the caisson in 5 equal increments • Second load increment block – Total Resultant load of 18MN in 50 equal increments on top at the middle of the anchor • Load attachment point – Middle node of the top cap of the caisson • Load angle – 71.55 degrees to Horizontal

27. Deformed mesh with load=8.4MN for TLP loading

28. Deviatoric stresses with load=8.4MN for TLP loading

33. Design of Suction caissons for a Jacket platform for a typical Indian Offshore soil profile SUCTION CAISSON CONFIGURATION 11300 mm Seabed 10800 mm 10500 mm 30 mm THICK

34. Aims of Caisson Analyses • To obtain the limit collapse load due to immediate (undrained) static loading • To obtain horizontal contact stresses acting on the caisson sides. These are used for the design of the caisson

35. Failure criteria = Mohr Coulomb • 2 increment blocks • Total increments 55 • I st increment block – Pile self weight – 5 equal increments • 2 nd increment block –Moment and Resultant force in 50 Unequal increments • smaller load increments towards the end of the increment block • Iterative solution, tolerance - 0.005 • PRes = 20000 kN in 1H to 3V • M = 6000 kN-M

36. FE mesh for jacket platform caisson

38. Deformed mesh due to self weight only

39. Deformed mesh due to self weight(1.8MN), resultant load(10MN-1H to 3V) and moment (3MN.M)

40. Deviatoric stress due to self weight(1.8MN), resultant load(10MN-1H to 3V) and moment (3MN.M)