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DGF / DONG Energy
Future monopile design
Alastair Muir Wood MEng CEng MICE MInstRE
1 April 2014
Future monopile design
Do monopiles have a future?
Recent developments by DONG Energy to monopile design
Future development to monopile design – The PISA Project
2
The P-y model
3
p
p
H
M
S
Offshore foundations - 2011
4
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80
Tu
rbin
e S
ize /
MW
Maximum Water Depth / m LAT
Gravity Base
Jacket/Tripod
Monopile
The limit of the monopile?
UK ROUND III PROJECTS
Water depths at Hornsea
5
0
200
400
600
800
1000
1200
1400
15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60 60-65 65-70 70-75
Fre
qu
en
cy o
f avera
ge w
ate
r d
ep
th in
1km
by 1
km
sq
uare
Water Depth
Whole Hornsea Zone
Hornsea Project 1
Offshore foundations - 2011
6
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80
Tu
rbin
e S
ize /
MW
Maximum Water Depth / m LAT
Gravity Base
Jacket/Tripod
Monopile
The limit of the monopile?
UK ROUND III PROJECTS
Offshore foundations - 2014
7
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80
Tu
rbin
e S
ize /
MW
Maximum Water Depth / m LAT
Gravity Base
Jacket/Tripod
Monopile
Gunfleet sands III
Westermost
Rough
Gode Wind
The limit of the monopile?
Offshore foundations - 2014
8
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80
Tu
rbin
e S
ize /
MW
Maximum Water Depth / m LAT
Gravity Base
Jacket/Tripod
Monopile
Gunfleet sands III
Westermost
Rough Gode Wind
• Monitoring of existing
monopiles
• Refining existing
design methods based
on results from
monitoring
• Optimisation of
monopiles during
design
UK ROUND III PROJECTS
9
Can we go further?
Maximum measured load
10 10
Academic Work Group
University of Oxford Principal Investigator: Dr Byron Byrne
Professor Guy Houlsby, Dr Harvey Burd, Dr Chris Martin, Dr Ross McAdam
Imperial College London Professor Richard Jardine, Professor David Potts,
Professor Lidija Zdravkovic, Dr David Taborda
University College Dublin Dr Ken Gavin, Dr Paul Doherty
Independent Technical Review Panel
Chairman: Professor Gudmund Eiksund
Liv Hamre Dr Fabian Kirsch
Tim Camp Professor Werner Rucker
Discretionary Project Steering Committee
Jan Matthiesen
Morten Liingaard
Chris Leach
Daniel Bartminn /
Emmet Donegan
Alan Smith / Mike Rose Pål Johannes Strøm Eivind Sønju Kasper Roed Jensen
Project Partner Technical Experts
Marc Costa Ros
Christian Le Blanc
Pedro Barbosa Moreira
Volker Herwig / Emmet
Donegan / Daniel Bartminn
Alan Smith / Mike Rose Pål Johannes Strøm
-
Wolfeckart Semm
Manouchehr Hassanzadeh
Miguel Lanca Coelho
Lead Partner
Project Manager: Jesper Skov Gretlund
Technical Manager:
Alastair Muir Wood
Assisting Consultants
UXO Consultant
Structural designer
Advanced
numerical
modelling
Testing Contractors
Project plan
Numerical simulations
Field tests Draft lateral load
methodology
Validated design
methodology
Design of field
tests
Validation
Parametric study of
geometry and soils
Preliminary results of the numerical analysis
12
0
10
20
30
40
50
60
70
80
0 0,5 1 1,5 2
H (
MN
)
δground (m)
FE
Basic API
*P-y + S-y spring model
*
Planning the tests…
13
Cowden
Dunkirk
10m
Pile geometry
14
Steel
Mult
Displacement
Mom
ent
Failure of soil
before steel
Failure of steel
before soil
0.1D
What test geometry?
15
10 20 30 40
Length / Diameter
150
100
50
Existing tests Jackets
Current
Monopiles
Future
Monopiles
Diameter /
thickness*
* t is the average buried thickness
STEEL LIMITING
SOIL LIMITING
16
Aging
Creep
Locked in Thermal Stresses
Bacterial corrosion
Bacterial leaching
Carbonation
Curing
Plasticity
Stre
ss
Strain
Peak compressive
stress
Peak tensile stress
Test
results
Design
model
Conclusion: The analogy with concrete
17
Unload reload behaviour
Accumulated deformations
Densification
Pore pressure development and dissipation
Damping
Creep
Various L/D ratios
Different diameters
Load
Displacement
Current
Design model
Conclusions
Reality
Age hardening
Other installation methods
Post PISA
