Recent Applications of CRISP 3DRecent Applications of CRISP 3DBy Amir RahimBy Amir Rahim

The CRISP Consortium Ltd/South Bank University LondonThe CRISP Consortium Ltd/South Bank University London

15th CRISP User Group Meeting15th CRISP User Group MeetingThursday 19Thursday 19thth September 2002 September 2002

UNIVERSITYCOLLEGE LONDONDEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING

In association with

Finite Element Analysis of Suction Finite Element Analysis of Suction Caissons using CRISP 3DCaissons using CRISP 3D

Work carried out for client Oil and Natural Gas Corporation of India.Work carried out for client Oil and Natural Gas Corporation of India.

Joint venture between Thales Geosolutions (Belgium) SAGE Joint venture between Thales Geosolutions (Belgium) SAGE Engineering, Inc (USA) and the CRISP Consortium Ltd for client Engineering, Inc (USA) and the CRISP Consortium Ltd for client ONGC/IEOT.ONGC/IEOT.

Analysis and Design of Suction Analysis and Design of Suction Caissons for Floating Structures for a Caissons for Floating Structures for a

typical Indian offshore soil profiletypical Indian offshore soil profile

SUCTION CAISSON FOR CALMCatenary Anchor Line Mooring

Anchor

Pad eye

Seabed

Types of Suction Caissons for floating Types of Suction Caissons for floating structuresstructures

Types of Suction Caissons for Types of Suction Caissons for floating structuresfloating structures

SUCTION CAISSON FOR TLMTout Leg Mooring

Anchor 450

Pad eye

Seabed

Types of Suction Caissons for Types of Suction Caissons for floating structuresfloating structures

SUCTION CAISSON FOR TLPTension Leg Platform

Load

Seabed

Aims of Caisson AnalysesAims of Caisson Analyses

To obtain the limit collapse load due to immediate (undrained) static To obtain the limit collapse load due to immediate (undrained) static loadingloading

To obtain horizontal contact stresses acting on the caisson sides. These To obtain horizontal contact stresses acting on the caisson sides. These are used for the design of the caissonare used for the design of the caisson

CALM AnalysisCALM Analysis Load is applied at the side of the caisson wall in 55 equal Load is applied at the side of the caisson wall in 55 equal

load increments for a Catenary Anchor Mooring Line load increments for a Catenary Anchor Mooring Line (CALM) as follows:(CALM) as follows:

Failure criteria = Mohr-Coulomb Failure criteria = Mohr-Coulomb Two increment blocksTwo increment blocks First load increment block – Pile self-weight as 9 equal First load increment block – Pile self-weight as 9 equal

nodal forces on the top cap of the caisson applied in 5 nodal forces on the top cap of the caisson applied in 5 equal incrementsequal increments

Second load increment block – Total Resultant load of Second load increment block – Total Resultant load of 18MN applied in 50 equal increments on full model18MN applied in 50 equal increments on full model

Load attachment point – 7.425 m below the top of the Load attachment point – 7.425 m below the top of the caisson on the sidecaisson on the side

Load angle – 15 degrees to HorizontalLoad angle – 15 degrees to Horizontal

Deformed mesh with load=7.2MN for CALM loadingDeformed mesh with load=7.2MN for CALM loading

Deviatoric stresses with load=7.2MN for CALM loadingDeviatoric stresses with load=7.2MN for CALM loading

TLM analysisTLM analysis

Load is applied at the side of the caisson wall in 55 equal Load is applied at the side of the caisson wall in 55 equal load increments for a Taut Leg Anchor Mooring Line (TLM) load increments for a Taut Leg Anchor Mooring Line (TLM) as follows:as follows:

Failure criteria - Mohr-Coulomb Failure criteria - Mohr-Coulomb Two increment blocksTwo increment blocks First load increment block – Pile self-weight as 9 equal First load increment block – Pile self-weight as 9 equal

nodal forces on the top cap of the caisson in 5 equal nodal forces on the top cap of the caisson in 5 equal incrementsincrements

Second load increment block – total Resultant load of Second load increment block – total Resultant load of 18000 kN in 50 equal increments on full model18000 kN in 50 equal increments on full model

Load attachment point – 7.425 m below the top of the Load attachment point – 7.425 m below the top of the caisson on the sidecaisson on the side

Load angle – 45 degrees to Horizontal Load angle – 45 degrees to Horizontal

Deformed mesh with load=12.6MN for TLM loadingDeformed mesh with load=12.6MN for TLM loading

Deviatoric stresses with load=12.6MN for TLM loadingDeviatoric stresses with load=12.6MN for TLM loading

TLP AnalysisTLP Analysis The load has been applied on top of the rigid cap of the caisson in 55 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 load increments for a Tension Leg Platform Tether (TLP) / Riser anchor as follows:anchor as follows:

Failure criteria = Mohr-Coulomb Failure criteria = Mohr-Coulomb Two increment blocksTwo increment blocks First load increment block – Pile self-weight as 9 equal nodal forces on First load increment block – Pile self-weight as 9 equal nodal forces on

the top cap of the caisson in 5 equal incrementsthe top cap of the caisson in 5 equal increments Second load increment block – Total Resultant load of 18MN in 50 Second load increment block – Total Resultant load of 18MN in 50

equal increments on top at the middle of the anchorequal increments on top at the middle of the anchor Load attachment point – Middle node of the top cap of the caissonLoad attachment point – Middle node of the top cap of the caisson Load angle – 71.55 degrees to Horizontal Load angle – 71.55 degrees to Horizontal

Deformed mesh with load=8.4MN for TLP loadingDeformed mesh with load=8.4MN for TLP loading

Deviatoric stresses with load=8.4MN for TLP loadingDeviatoric stresses with load=8.4MN for TLP loading

Design of Suction caissons for a Jacket platform Design of Suction caissons for a Jacket platform

for a typical Indian Offshore soil profilefor a typical Indian Offshore soil profile SUCTION CAISSON CONFIGURATION

10800 mm30 mm THICK10500 mm

11300 mmSeabed

Aims of Caisson AnalysesAims of Caisson Analyses

To obtain the limit collapse load due to immediate (undrained) static To obtain the limit collapse load due to immediate (undrained) static loadingloading

To obtain horizontal contact stresses acting on the caisson sides. These To obtain horizontal contact stresses acting on the caisson sides. These are used for the design of the caissonare used for the design of the caisson

Failure criteria = Mohr Coulomb Failure criteria = Mohr Coulomb 2 increment blocks2 increment blocks Total increments 55Total increments 55 I st increment block – Pile self weight – 5 equal incrementsI st increment block – Pile self weight – 5 equal increments 2 nd increment block –Moment and Resultant force in 50 Unequal 2 nd increment block –Moment and Resultant force in 50 Unequal

increments increments smaller load increments towards the end of the increment blocksmaller load increments towards the end of the increment block Iterative solution, tolerance - 0.005Iterative solution, tolerance - 0.005 PRes = 20000 kN in 1H to 3VPRes = 20000 kN in 1H to 3V M = 6000 kN-MM = 6000 kN-M

FE mesh for jacket platform caissonFE mesh for jacket platform caisson

Deformed mesh due to self weight onlyDeformed mesh due to self weight only

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

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