Evaluation of Foundation Settlement under Various Added Loads in ...
Hydrodynamic Loads and their Impact on Foundation Design · Hydrodynamic Loads and their Impact on...
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![Page 1: Hydrodynamic Loads and their Impact on Foundation Design · Hydrodynamic Loads and their Impact on Foundation Design Harris King – Senior Structural Engineer Harris.King@woodgroup.com](https://reader030.fdocuments.us/reader030/viewer/2022040908/5e800048aa4d9e633c5ffbc7/html5/thumbnails/1.jpg)
Hydrodynamic Loads and their Impact
on Foundation Design
Harris King – Senior Structural Engineer
Subsea Expo 2017
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• Introduction
• The Problem
• Foundation Design
• Current Methodologies
• Refinement
• Outcome
Agenda
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• Inspiration came from experiences with a recent
project
• SSIV structure within 500m zone
Introduction – Past Experience
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• Challenging geotechnical conditions
– Close to 3 different soil formations
Introduction – Past Experience
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2 kPa
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• Initial plan to install 2 structures in 1 campaign – no
longer feasible
Introduction – Past Experience
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• Obtain site specific soils info
• Generate a more complex design incorporating
retractable mudmats
• Use CFD to better quantify applied loads
Introduction – Past Experience
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• Gravity based subsea structures subject to
environmental loads
• Can lead to increased weight/footprint to achieve on
bottom stability
• Potential increases in fabrication and installation
complexity
• Cost saving opportunity
The Problem
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• Installation complexity
The Problem
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Background – Foundation Design
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• Methodologies outlined in API, ISO and DNV codes
• Develop a design that avoids:
– Sliding failure (horizontal)
– Bearing failure (vertical)
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Background – Foundation Design
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• Bearing failure (vertical)
• Eccentricity - M
Fv
Fv
M
Fv
Fh Fh
Extract from API RP 2GEO/ISO 19901-4
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Background – Foundation Design
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• Sliding failure (horizontal)
• Increased area (clay) or increased weight (sand)
Fv
Fh
Fv
Fh
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Current Methodologies
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• Morison’s Equation
• L = 4.46m, D = 7.46m, H = 4.05m. A = 30.2m2
• Lateral Load = 306kN @ 3.0ms-1
• Approximate 30% reduction accounting for solidity –
242 kN
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Current Methodologies
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• Assessment within beam FE Model
• Lateral Load = 229 kN @ 3.0 ms-1
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Current Methodologies
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• Reduced drag loads for shielded members using
guidance from DNV RP H103
• Lateral Load = ~200 kN @ 3.0 ms-1
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Current Methodologies
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• 306 kN – Solid Body
• 242 kN – Solid Body (accounting for solidity)
• 229 kN – Assessment within beam FE Model
• 200 kN – Assessment within beam FE Model (with
shielding)
• ?
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Refinement
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• CFD Results
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Refinement
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• CFD Modelling of structure
• Lateral Load = 80 kN @ 3.0 ms-1
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Refinement
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• 67% load reduction compared
to solid body (with solidity
reduction)
• 35% Reduction compared to
solid body (with solidity
reduction)
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Refinement
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• 306 kN – Solid Body
• 242 kN – Solid Body (accounting for solidity)
• 229 kN – Assessment within beam FE Model
• 200 kN – Assessment within beam FE Model (with
shielding)
• 80 kN – CFD approach
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• Foundation capacity on Sand
– Sliding resistance generally proportional to on
bottom weight
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Outcome – Foundation Design
Lateral Load (kN) Minimum Required on
bottom weight (t)
306 100
242 79
229 75
200 66
80 26
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Outcome – Foundation Design
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• Foundation capacity on clay
– Generally proportional to mud mat area
10.0m
6.0m
6.0m
3.6m
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• Potential to achieve
– Lighter, smaller structure
– Reduce fabrication quantity
– Reduce deck space, crane size on installation
vessel
– Circa. £10ks vs £100ks
– Lower cost
Conclusions
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Questions ?
Summary
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