Steel Structures In Offshore
Applications
Constança Rigueiro
Hämeenlinna 24th of January 2018
Institute for Sustainability and Innovation in Structural Engineering
2|Steel Structures In Offshore Applications Constança Rigueiro
Contents
• Overview of the @ISISE UC
• Advanced Education @ DEC.UC
• Brief Outline of R&D on Offshore domain
Overview of the
@ISISE UCConstança Rigueiro
Hämeenlinna 24th of January 2018
Institute for Sustainability and Innovation in Structural Engineering
4|Steel Structures In Offshore Applications Constança Rigueiro
University of Coimbra
Founded in 1290 by King D. Dinis, it is the 5th oldest in
Europe with approx. 23000 students
Located in Coimbra with 3 campuses
Faculty of Science and Technology
• 8000 students, 600 lecturers, 11 departments
Department of Civil Engineering (2017 world rank 100-
150 (QS), best at UC):
• 600 students in 2 Integrated MSc’s (Civil and
Environment, 5 years);
• Advanced MSc’s: Erasmus Mundus European Master
SUSCOS, MSc in Steel Construction, MSc in Acoustics
and Energy Efficiency for Sustainable Construction, MSc
in Rehabilitation of Buildings, MSc in Fire Safety
Engineering, MSc in Sustainable Urban Water Management,
MSc in Geotechnics and Soil Mechanics
• Doctoral Programs: Steel Construction; Fire Safety
Engineering; Transportation Systems, Territorial Planning,
Civil Engineering; Environmental Eng.
Coimbra
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5|Steel Structures In Offshore Applications Constança Rigueiro
ISISE is a Research, Development & Innovation Unit
formed in 2007 and involving the Structural Groups
from the Civil Engineering Departments of the
Universities of Coimbra and Minho.
In the 2014 Research Assessment Exercise (2008-
2014), ISISE was rated as Excellent
60 PhD members; 107 PhD students; >10 M€ of
competitive funding currently granted ; 2 European
Master Courses; International leadership.
Guimarães
Coimbra
ISISE – Institute for Sustainability and
Innovation in Structural Engineering
Institute for Sustainability and Innovation in Structural Engineering
6|Steel Structures In Offshore Applications Constança Rigueiro
ISISE: Scope of activityThe vision of ISISE is to increase the structural and functional performance of Civil
Engineering Works, from a perspective of advanced technology, innovation and a
knowledge based economy with a wide focus that ranges from materials to integral
systems with a life cycle approach.
Despite the ISISE focus on structural engineering, it is clearly recognized that progress
and innovation in Civil Engineering Works require a holistic approach whereby the
structural performance cannot be separated from the functional performance and
other related aspects, such as social, environmental and business considerations.
(excerpt from Strategic Programme 2015-2020)
ISISE aims at promoting innovation and sustainability, with a link to the construction
sector industry, focusing on: REHABILITATION: Reshaping the built environment
and INDUSTRIALIZATION: Construction as an advanced industrial process: from
material to system
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7|Steel Structures In Offshore Applications Constança Rigueiro
ISISE: Productivity Indicators and
Internationalization
0
20
40
60
80
100
120
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
44
62
75 75
88
108 108 110
9396
Non-PhD Researchers
0
10
20
30
40
50
60
70
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
18
22
2830 29
3129
45
63
66
Phd Members
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8|Steel Structures In Offshore Applications Constança Rigueiro
ISISE: Productivity Indicators and
Internationalization
0
20
40
60
80
100
120
140
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
18
28
3643
35
49
70
92
117122
ISI journals
0
2
4
6
8
10
12
14
16
18
20
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
14
8
12
6
4
9
17
13
17
19
Phd theses
0
2
4
6
8
10
12
14
16
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
4
3
0
6
4 4
11
16
12
14
Books
0
20
40
60
80
100
120
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
3
3237
81
5449
93
54
107
93
Msc theses
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9|Steel Structures In Offshore Applications Constança Rigueiro
ISISE Management and Research Groups
• 18 full-time researchers with PhD
• 12 collaborators from other areas
• 43 PhD students and grant holders
• 8 full-time researchers with PhD
• 9 collaborators from other areas
• 13 PhD students and grant holders
Historical and
masonry
structures
(Paulo B. Lourenço)
Steel and mixed
construction
technologies
(Luís Simões da Silva)
Structural
composites
(Joaquim Barros)
DIRECTOR
Luís Simões da Silva
CO-DIRECTOR
Paulo B. Lourenço
Functional
performance
(Luís Godinho)
GROUPS
• 11 technical and administrative staff @ISISE UC
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10|Steel Structures In Offshore Applications Constança Rigueiro
R&D Projects
(2005-)
Completed
(2009-2016)Ongoing + starting in 2017
€ (Total /
ISISE-UC)
RFCS – TGS8 15 9+3 75 511 670€
Other Intern. 7 2 15 721 144 €
Other national 15 8
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11|Steel Structures In Offshore Applications Constança Rigueiro
ISISE Research Clusters
Steel and mixed construction technologies
A Fire safety
B Earthquake engineering
C Blast and impact
D Connections
E Nonlinear design and stability
E.1 Advanced design
E.2 Cold-formed and modular construction
F Composite and mixed construction
F.1 Steel-concrete composite
F.2 Steel & glass
G Wind towers & renewables
H Offshore and naval engineering
H.1 Offshore
H.2 Naval engineering
I Timber construction
Functional Performance
J Energy efficiency
K Integral lifetime design
L Dynamics and acoustics
Advanced Education
@ DEC.UC
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13|Steel Structures In Offshore Applications Constança Rigueiro
Educational Offer from ISISE SMCT
• PhD Programmes (1)
• Advanced MSc Programmes (4)
• Core Integrated MSc’s (2)
• Short Courses
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Erasmus Mundus European Master Program:
Sustainable Constructions under Natural
Hazards and Catastrophic Events
A partnership involving top European Universities in the
steel construction area:
Czech Technical University at Prague, Prague, Czech Republic
University of Coimbra, Coimbra, Portugal
Technical University of Lulea, Lulea, Sweden
University “Politechnica” Timisoara, Timisoara, Romania
University of Liège, Liège, Belgium
University of Naples “Federico II”, Naples, Italy
WWW.SUSCOS.EU
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PARTNERS
Lulea University of technology
Czech Technical University in Prague
(coordinator)
University of Coimbra
University of Liège
"Politehnica" University of Timisoara
University of Naples "Federico II“
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Short Courses from ISISE SMCT (on offhsore structures domain)
Brief Outline of R&D on
Offshore domainConstança Rigueiro
Hämeenlinna 24th of January 2018
Institute for Sustainability and Innovation in Structural Engineering
18|Steel Structures In Offshore Applications Constança Rigueiro
Portugal
Total surface: 92,090 km²
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19|Steel Structures In Offshore Applications Constança Rigueiro
Actual Exclusive Economic Zone of Portugal 1,727,408 km²
Portugal is 95% of Water!!
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20|Steel Structures In Offshore Applications Constança Rigueiro
Future Exclusive Economic Zone of Portugal 4 M km²
Then we will be 97% of Water!!
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21|Steel Structures In Offshore Applications Constança Rigueiro
National strategy for the sea
“….A wide commitment was then
established to promote, on the one
hand, knowledge-based economic
development and innovation, enabling
more efficient use of resources and, on
the other hand, a more competitive,
sustainable, growth, to ensure social
and territorial cohesion….”
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22|Steel Structures In Offshore Applications Constança Rigueiro
• Improve S&T capacity for Sustainable Development;
• Increase R&I capacity;
• Induce knowledge;
• Spread scientific excellence
OCEAN ENGINEERING
Ocean Environment Offshore Structures
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23|Steel Structures In Offshore Applications Constança Rigueiro
Areas of
Research
Bottom Founded Platforms
Materials For Offshore And
Subsea Engineering
Risk Reliability
And Safety Assessment
Wind Structures
Energy Infrastructures
Floating Platforms
Ocean Environment
Offshore Geotechnical Engineering
Computational Dynamics Of
Offshore Structures
Accidental Collapse Limit
State (Fire; Blast And Collisions)
OCEAN ENGINEERING
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24|Steel Structures In Offshore Applications Constança Rigueiro
Offshore Structures: Finished And Ongoing PhD And MsC
Thesis• Tiago Manco, “Behaviour of steel members subjected to hazardous loading in support
offshore structures”. PhD in Construção Metálica e Mista, Universidade de Coimbra.
(ongoing 2018).
• João Nuno Ribeiro, “Characterization of damage behaviour of structural steel”. PhD in
Construção Metálica e Mista, Universidade de Coimbra. (ongoing 2018).
• Daniel Alexandre Simoes Oliveira, “Fluid-structure interaction in offshore structures”.
PhD in Construção Metálica e Mista, Universidade de Coimbra. (ongoing 2019).
• Damjan Čekerevac, “Characterization of blast action and structural mitigation
measures in offshore environment”, PhD in Construção Metálica e Mista, Universidade
de Coimbra. (ongoing 2020).
• Filip Ljubinkovic, “Optimization of bridge superstructures using curved shaped plated
elements: aesthetics and structural concepts”. PhD in Construção Metálica e Mista,
Universidade de Coimbra. (ongoing 2019).
• Mohammad Reza Shah Mohammadi, “Hybrid High-Rise Wind Turbine Tower Aeroelastic
Load, Dynamic Response, and Fatigue Assessment”, PhD in Construção Metálica e
Mista, Universidade de Coimbra. (ongoing 2019).
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25|Steel Structures In Offshore Applications Constança Rigueiro
Offshore Structures: Finished And Ongoing PhD And MsC
Thesis• Slobodanka Jovašević, “In-situ bolted connections in lattice towers for wind energy
converters”, PhD in Construção Metálica e Mista, Universidade de Coimbra. (ongoing
2019).
• Miguel Moya: “Assessment of tubular connections of offshore structures according to
Norsok N004, ISO 19902 and Eurocode 3 “, Mestrado integrado em Engenharia Civil da
Universidade de Coimbra, 2014.
• Tiago Manco: “Comparative Assessment of Standards for offshore applications
(API,ISO,NORSOK,EC3)“, Mestrado integrado em Engenharia Civil da Universidade de
Coimbra, 2014.
• Francisco Arede, “Numerical safety assessment criteria for subsea components”,
Mestrado integrado em Engenharia Civil da Universidade de Coimbra 2015.
• Daniel Oliveira, “Fluid interaction / structure in offshore environment”, Mestrado
integrado em Engenharia Civil da Universidade de Coimbra, February 2016.
• Lucas Ferreira, “Dynamic behaviour of Offshore structures”, Mestrado integrado em
Engenharia Civil da Universidade de Coimbra 2015.
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• Aleksandra Mielcarek: "CFD Analysis of a pool fire in an offshore platform";
Mestrado em Construção Metálica e Mista, Universidade de Coimbra, February 2016.
• Filipe Miranda: ”Behaviour of tubular offshore joints under static and tubular joints”;
Mestrado Integrado em Engenharia Civil, Universidade de Coimbra 2017.
• Tiago Ribeiro, “Fatigue Life Extension Of Fixed Offshore Structures Formed By Tubular
Elements”, Mestrado em Construção Metálica e Mista, Universidade de Coimbra,
September 2017.
• Miguel Correia, “Robustness and progressive collapse in offshore structures: a case
study”, Mestrado em Construção Metálica e Mista, Universidade de Coimbra. (ongoing
2018).
Offshore Structures: Finished And Ongoing PhD And MsC
Brief Outline of R&D on
Offshore domain
National and International Projects
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28|Steel Structures In Offshore Applications Constança Rigueiro
National ProjectsFunding: 0.2 M€ Jul 2011 – Jun 2014
IMPACTFIRE - Robust Connections for
Impact and Fire Loading
• Finite Element Modeling (ABAQUS)
• Calibration & Parameterization
• Connection tests
• Impact Loading
• Fire situation
Scope: Eurocode 1, Part 1.7, Accidental actions
Connection behaviour characterization
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Funding: 0.2 M€, Abril 2011 – Mar 2014
IMPACTFIRE
ROBUST CONNECTIONS FOR IMPACT AND FIRE LOADING
• Accidental Actions, Standards, Material Behaviour
• Experimental Assessment Of Connections Subject To Accidental Actions (Impact, Fire)
• Non-linear Dynamic Analysis Of Connections
• Analytical Methodology For Design Connections Subject To Accidental Actions
OBJECTIVES:
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• Finite Element Modeling (ABAQUS)• Connection tests under impact
Scope: Eurocode 1, Part 1.7, Accidental actions
Connection behaviour characterization
Robust connections under impact
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Funding: 0.175 M€ 3 Partners Jul 2016 – Jun 2019
ULTIMATE PANEL
Curved thin panels for
structural application(PTDC/ECM-EST/1494/2014)
(i) Univ ersity of Coimbra
(ii) Univ ersity of Lisbon
(iii) State Univ ersity of Rio de Janeirol
OBJECTIVE:
The objective of this research project is the
development of advanced knowledge about the
behaviour of curved panels that results in practical
application rules and in a standardised FEM
procedure for analysing curved panels. In fact,
curved panels, either for aesthetic or structural
reasons, are often used in bridge structures, ship
structures, aircraft and submarines
National Projects
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32|Steel Structures In Offshore Applications Constança Rigueiro
Oliveira De Frades
Luleå
Hämeenlinna
Aachen
Hamburg
Coimbra Thessaloniki
RFSR-CT-2006-00031 HISTWIN
High strength tower in steel for wind turbines
RFSR-CT-2010-00031 HISTWIN 2
FCT – PTDC-64217/2006
RFS2-CT-2014-00023 HISTWIN+
RFSR-CT-2015-00021 SHOWTIME
Steel Hybrid Onshore Wind Towers Installed with
Minimal Effort
H2020-MSCA-ITN-2014: 643167
AEOLUS4FUTURE - Efficient harvesting of the wind energy
International Projects
SHOW IME
Brief Outline of R&D on
Offshore domain
Some Outputs
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Offshore Structures: Publications
• João Ribeiro, Aldina Santiago A., Constança Rigueiro, Luís Simões da Silva, Analytical
model for the response ofT-stub joint component under impact loading, Journal of
Constructional Steel Research, 106, pp. 23-34, 2015
(http://dx.doi.org/10.1016/j.jcsr.2014.11.013)
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva
Comparative assessment of the design of tubular elements according to offshore design
standards and Eurocode 3, presented on 15th International Symposium on Tubular
Structures, 27 to 29 of May 2015, Rio de Janeiro, Brazil.
• João Ribeiro, Aldina Santiago, Constança Rigueiro, Pedro Barata, Milan Veljkovic,
“Numerical assessment of T-stub component subjected to impact loading”, Engineering
Structures, 106, 450-460, 2016. (doi.org/10.1016/j.engstruct.2015.10.047).
• Barata P., Santiago A., Rodrigues J-P., Rigueiro C., “Development of an experimental
system to apply high rates of loading”. International Journal of Structural Integrity, Vol. 7
No. 2, pp. 291-304. 2016. (doi.org/10.1108/IJSI-05-2014-0027)
• Ribeiro J., Santiago A., Rigueiro C., “Material modelling of Tensile steel component under
impulsive loading”, International Journal of Structural Integrity, Vol. 7 No. 2, pp.323-342.
2016. ( DOI 10.1108/IJSI-05-2014-0026)
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Offshore Structures: Publications
• Ribeiro J., Santiago A., Rigueiro C., “Damage model calibration and application for S355
steel”, 21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy.
Journal Procedia Structural Integrity, No. 2, pp.656-663. 2016.
(10.1016/j.prostr.2016.06.085)
• Manco T., Rigueiro C., Martins J.P., Simões da Silva L., “Comparative assessment of the
design of tubular Elements according to offshore design standards and Eurocode 3”,
Steel Construction 9, 2016. (DOI: 10.1002/stco.201610031)
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva, Analysis of
pre-compressed steel tubular members under impact: a parametric study. The
International Colloquium on Stability and Ductility of Steel Structures – SDSS’2016 30
May – 01 June 2016, Timisoara, Romania.
• Daniel Oliveira, Aldina Santiago, Constança Rigueiro, Fluid Structure Interaction in
Offshore Environment, 5th International Conference on Integrity - Reliability – Failure.
Porto (Portugal), 24-28 July 2016
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva, Numerical
analysis of stiffened curved panels under compression. The 8th International Conference
on Steel and Aluminium Structures (ICSAS 2016). December 7 to 9, 2016, Hong Kong.
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Offshore Structures: Publications
• Rigueiro C., Ribeiro J., Santiago A., “Numerical assessment of the behaviour of a fixed
offshore platform subjected to ship collision”, X International Conference on Structural
Dynamics, EURODYN 2017, September 201, Roma, Italy. Journal Procedia Engineering,
No. 199, pp.2494-2499. 2017. (DOI: 14)
• Damjan Čekerevac, Constança Rigueiro e Eduardo Pereira, “Assessment Of Blast Loads
On Offshore Topsides Using Analytical Models: Case Study”, XI Congresso de Construção
Metálica e Mista, Coimbra, Portugal, (2017).
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva, Semi-
analytical model for the prediction of the post-buckling behaviour of unstiffened
cylindrically curved steel panels under uniaxial compression, Accepted Journal: Marine
Structures.
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva, "Semi
analytical behaviour of isotropic and orthotropic curved panels under
combined in-plane and out-of-plane loading" submitted in December 2017.
• Tiago Manco, João Pedro Martins, Constança Rigueiro e Luís Simões da Silva, Semi-
analytical orthotropic model for the prediction of the post-buckling behaviour of
stiffened cylindrically curved steel panels under uniaxial compression, submitted in
December 2017
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Numerical assessment of the behaviour of a
fixed offshore platform subjected to ship
collision
Constança Rigueiro | João Ribeiro | Aldina Santiago
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1. Framework
Bottom founded platforms Floating platforms
Jacket and tower
structuresTension Leg Platforms
Flexible or compliant
tower structures
SPAR and Semi-
submergible platforms
shallow waters
(<900 m)
high depths
(up to 3000 m)
Rigid Risers Flexible Risers
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Accidental actions are actions caused by abnormal operation or technical
failure. They include for instance:
• Fires;
• Explosions;
• Impacts from ships;
• Dropped objects, helicopter crash among others.
1. Framework
http://www.nydailynews.com/news/national/oil-rig-sinks-massive-
explosion-11-workers-missing-article-1.165869
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1.1 General background - Collisions with jacket platforms
Impact actions may be caused by:
• Vessels in service to and from the installation (including supply
vessels);
• Tankers loading at the field;
• Ships and fishing vessels passing the installation;
• Floating installations;
• Aircraft on service to and from the field;
• Falling or sliding objects;
• Icebergs or ice.
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The requirements to design
structures exposed to accidental
actions, here presented, are given
in Norsok – N003 Actions and
Actions Effects, Norsok – N004
Design of steel structures
accidental loads.
1.1 General background - Collisions with jacket platforms
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Qvale K. H., (2012)
✓ Overall deformation of
the platform;
Elastic
behaviour
✓ Global deformation of
bracing and leg
element;
Plastic
behaviour
Plastic
behaviour
✓ Local deformation of
bracing/leg at impact
point (local denting);
1.1 General background - Collisions with jacket platforms
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Ship collisions with offshore
structures may be critical to the
ship, installation or both.
Accurate analyses are thereforeimportant to ensure that the
installation can withstand a high-
energy ship impact.
It is required that the platformsurvives to initial impact but
progressive collapse shall not
occur.
Ship collision load
1.1 General background - Collisions with jacket platforms
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1.2 Design principles
Design values by Norsok-N003
• The ship mass should not be normally considered with less than 5000
tons.
• Ship speed should not be considered below 2 m/s for the ALS design
check.
• Hydrodynamic (added) mass can be assumed to be 40% of the ship mass for sideways impacts and 10% for bow/stern impacts.
Supply vessel impact on an offshore installation:
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The Norsok-N004 distinguishes between three different design categories for
strain energy dissipation:Strength design: The installation is
strong enough to resist the
collision-force with minor
deformation. This means that the
ship is forced to deform and
dissipate most of the collision
energy.
DNV_RP_C204 (2010)
Structure
Ship
Ship
Structure
1.2 Design principles
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Ductility design: The installation undergoes large plastic deformations and
absorbs most of the collision energy. In this case, the striking ship will be
strong and undergo minor deformations.
DNV_RP_C204 (2010)
Ship
Structure
Structure
Ship
1.2 Design principles
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Shared-energy design: This implies that both the installation and ship
contribute significantly to the energy dissipation.
DNV_RP_C204 (2010)
Structure
Ship
• The analysis is complex compared
to strength or ductility design and a
nonlinear analysis with finite element is
necessary.
1.2 Design principles
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• The structure is designed to operate at an average depth of 130 m.
• The deck consists in three levels with a total area of 1915 m2.
2. Platform description
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Storage area complete
Residential
Quarters
2. Platform description
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+9.75 m
+14.33 m
+19.74 m
Storage area
Residential Quarters
Heliport
Drilling area
2. Platform description
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✓ Material Modeling:
• Steel with fy= 355 MPa;
• E=210 GPa
• Estiff_ship=100x Esoft_ship
• Strain rate effects were
neglected.
Steel grade cr H
S235 20% 0,0022
S355 15% 0,0034
S460 10% 0,0034
3. Finite Element Model
Material model
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L=46 m
D= 1676 mm
t=32 mm
• The calculation procedure for ship
collision was implemented in the
ABAQUS software
• The mesh size is maintained within 5 to 10 times the member thickness to
obtain sufficiently accurate
predictions of the strain;
3. Finite Element Model
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Corpo 1
Corpo 2
A B
C
D
Corpo 1
Corpo 2Superfície
“Target” S21
S12 (Superfície “Contactor”)
Tempo t
Tempo t
Tempo 0
Tempo 0
Sct do Corpo 1
e Corpo 2
S12
S21
Sct do Corpo 1 e
Corpo 2
c t12f
c t21f
Implicit \ Dynamic
Moderate Dissipation Application
Uses Hilber-Hughes-Taylor (HHT) integration procedure
• 𝛼 = −0.41421;
• 𝛽 = 0.5 and
• 𝛾 = 0.91421
Therefore unconditionally stable with respect to the time-
increment
Contact algorithm: Penalty – hard
contact - to model the contact between
the ship and the platform. No static
friction coefficient is used in this
contact formulation.
No Damping
Non linear dynamic analysis3. Finite Element Model
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• Only the side of the hull was included
in the model for the sake of saving
computation time.
• The ship mass= 5000 tons (more 10%
for the added mass);
• Ship speed: 2 m/s (for the ALS
design check) and 0,5 m/s.
3. Finite Element Model
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• A stiff vessel model was constructed since, by definition, this model would
not experience any structural deformation;
• And a soft ship
stiff vessel model soft vessel model
3. Finite Element Model
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4. Collision Scenarios
4.1 Stiff ship: 2 m/s vs 0,5 m/s
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57|Steel Structures In Offshore Applications Constança Rigueiro
4.2 Stiff vs soft ship
Stiff ship Soft ship
4. Collision Scenarios
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✓ The numerical tools (non-linear FE) available for advanced strength assessments of
structures have reached a level of robustness and efficiency making them attractive for
evaluating the structural integrity;
✓ Detailed model of the structure can be analysed under a given scenario in order to
simulate the response: the damage levels and the residual strength.
✓ The 2 m/s recommended velocity may cause severe damage on the jacket’s legs; this is
very pronounced particularly when comparing to a velocity 0,5 m/s, as the 2 m/s ship
carries 16 times the kinetic energy of the same ship travelling at 0,5 m/s (assuming
constant mass);
✓ Both impacts due to soft or stiff ships (Shared design situation vs. a Ductile - design
one), the energy dissipated by the remaining structure is much higher than that from
the sum of the leg and ship.
5. Conclusions
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59|Steel Structures In Offshore Applications Constança Rigueiro
Analysis Methodologies of the Interaction
Fluid-Structure (FSI) in Offshore Structures
Daniel Oliveira | Aldina Santiago | Constança Rigueiro
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60|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
Analysis of the Fluid Structure Interaction (FSI) !!!!!!
1. Introduction
Extreme
environmental
conditions
Waves Actions
Current Actions
Wind Actions
Loss of human life
Economic losses
Environmental Contamination
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61|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
Analytical
Conservation
law of Energy
Equations of Navier-Stokes (1822)
Conservation law of
Quantity of Motion
2. Analysis Methodologies of FSI Problems
Conservation
law of Mass
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62|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
Analytical
Tests with reduced
scale and real scale models
Waves Tanks
Study of Phenomena
resulting from Fluid-Structure Interaction
2. Analysis Methodologies of FSI Problems
Development and
validation of
empirical formulas
(eg Morison formula)
Experimental
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63|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
Analytical
Partial differential
equations to solve the Navier-Stokes eq.
Computational Fluid Dynamics – CFD
(1950/60)
Analysis of complete
structures with full scale models
2. Analysis Methodologies of FSI Problems
Increase of the
computational power
Experimental
Numerical
Integration/Interaction with Computational
Solids Mechanics (CSM) models
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64|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
3. Numeric Model of FSI
3.1 Types of Models
Monolithic Approach Partitioned Approach
𝑆𝑓 𝑡𝑛
𝑆𝑆 𝑡𝑛
Interface
𝑆𝑓 𝑡𝑛+1
𝑆𝑆 𝑡𝑛+1
Interface (…)𝑆𝑓 𝑡𝑛𝑆𝑆 𝑡𝑛
𝑆𝑓 𝑡𝑛+1𝑆𝑆 𝑡𝑛+1
(…)
𝑆𝑓- Fluid Model (Actions)𝑆𝑆- Solid Model (Structure)
Unique Model with fluid and
structure
Aplicable for any type
of interaction
Times-step is
important for the convergence of
results
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Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
3. Numeric Model of FSI
3.2 Partitioned Approximation: Results Interaction Methods
Unidirectional
(Poor Coupling)
CSM Model CFD Model
𝒕𝒏
𝒕𝒏+𝟏
1 iteration
Bidirectional Explicit
(Poor Coupling)
𝒕𝒏
𝒕𝒏+𝟏
1 iteration
Bidirectional Implicit
(Strong Coupling)
𝒕𝒏
𝒕𝒏+𝟏
Interaction after
Convergence
Rigid Structures
(Small deformations)
Deformable
structures (Large
deformations)
Deformable
structures (Large
deformations)
1
2
3
4
CSM Model CSM ModelCFD Model CFD Model
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66|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
3. Numeric Model of FSI
3.3 Application to Singular Elements
Wave_Structure
interaction
Partitioned
Approach
CFD-CSM
Unidirectional Coupling (Explicit)
Rigid
Cylindrical Element
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67|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
3. Numeric Model of FSI
3.3 Application to Singular Elements
Wave_Structure
interaction
Partitioned
Approach
CFD-CSM
Bidirectional Coupling Implicit
Deformable
Cylindrical Element
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68|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
3. Numeric Model of FSI
3.3 Application to Singular Elements
Wave_Structure
interaction
Partitioned
Approach
CFD-CSM
Bidirectional Coupling Implicit
Deformable
Rectangular Element (Plate)
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69|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
4. Case Study
4.1 Structural Definition
Dimensions
Base - 65 x 62 m2
Altura - 150 m
Material: Steel A500
Legs
1676 x 32 (mm)
Legs
1219 x 25 (mm)
Bracing System
800 x 25 (mm)
Other Elements
650 x 19 (mm)
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Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
4. Case Study
4.2 Model CFD (STAR – CCM+)
Geometry definition
Construction of Simulation Topology
Physical models Mesh GenerationPreparation of
the analysis
Surface Remesher
Trimmed Remesher
Prism Layer Mesher
Control zones
8 132 809 cells
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71|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
4. Case Study
4.3 Model CSM (Abaqus)
FEM – Shell
Elements
Square Elements
– 25 cm
360 000
Elements
Linear Elastic
Material
Dynamic Implicit
Analysis
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72|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
4. Case Study
4.4 Results (CFD and CSM)
Unidirectional
Coupling
Definition of
the Wave
H= 24 m
T= 13,6 s
Co-simulation
7 s
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73|Steel Structures In Offshore Applications Constança Rigueiro
Metodologias de Análise da Interação Fluido-Estrutura (FSI) em Estruturas offshore Daniel Oliveira
4. Case Study
4.4 Results (CFD and CSM)
Unidirectional
Coupling
Definition of
the Wave
H= 24 m
T= 13,6 s
Co-simulation
7 s
von Mises Stress Displacements
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5. Conclusions
1. The hydrodynamic action, mainly the wave action, is the most determinant
in the design of offshore structures, the application of interaction (FSI)
could be very important;
2. The partitioned approach is the most used FSI numerical modelling method,
being the most practical to apply in the offshore industry;
3. There are different interaction methodologies with CFD and CSM models,
and the most appropriate must be chosen according each type of structure
(as demonstrated in the examples presented with the singular elements);
4. The results obtained with the application of FSI in the Case Study - Jacket
Structure confirm the ability of this methodology to provide the necessaryinformation for the analysis and verification of the safety of the structure.
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Characterization of blast action and structural
mitigation measures in offshore environment
Damjan Čekerevac | Constança Rigueiro | Eduardo Pereira
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76|Steel Structures In Offshore Applications Constança Rigueiro
▪ The jacket type of offshore platforms experienced the largest number of
accidents
Type of UnitNo. of fatal accidents / % of total no. of
fatal accidents
No. of fatalities / % of total no. of
fatalities
Helicopter offshore duty 113 / 20,4 646 / 29,8
Jacket platform 202 / 36,5 509 / 23,4
Semi-submersible platform 47 / 8,5 292 / 13,5
Jackup platform 66 / 11,9 233 / 10,7
Drill ship 47 / 8,5 236 / 10,9
1. Accidental Scenarios For Offshore Platforms
▪ Jacket structures are often
constructed in groups
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▪ Explosions on offshore oil and gas platforms represent the most
devastating accident that may occur during the life time of this
structure
Type of unit Operation mode Event Sequence Damage level
Jacket platform Development drilling Blowout-Fire-Explosion Significant
Repair work Explosion and fire Severe
Production Collision-Release-Fire Severe
Helicopter collision Minor
Release-Explosion-Fire Total loss
1. Accidental Scenarios For Offshore Platforms
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78|Steel Structures In Offshore Applications Constança Rigueiro
▪ Fire and explosions on offshore oil and gas platforms represent the
most devastating accident that may occur during the life time of this
structure
https://www.oilandgaspeople.com/news/6240/at-least-32-dead-in-worst-offshore-disaster-since-
piper-alpha/
1. Accidental Scenarios For Offshore Platforms
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1. Accidental Scenarios For Offshore Platforms
• The offshore platforms are typically associated with a vapour
cloud explosion (VCE)
• Size of the explosion depends on many parameters:
o Characteristics of gas cloud
o Congestion
o Confinement level
o Ventilation
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80|Steel Structures In Offshore Applications Constança Rigueiro
• Thickness usually varies between 1 mm and 6 mm
• Allows for energy dissipation
• Characterized by large deformations
• Usually made of carbon or stainless steel
Bulkheads
Corrugated walls:
• Strong plate supported by stiffeners
• Thickness usually varies between 5 mm and 16 mm
• Less flexible and characterized by brittle failure
• Usually made of carbon steel
2. Types of blast walls
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Elements
Connections
2. Types of blast walls
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Two analytical approaches recommended in the literature were considered
In order to study their limitations for use in offshore environment :
• Biggs (Structural Dynamics, John M. Biggs, 1964)
• DNV (DNV RP C204: Design Against Accidental Loads)
Both Biggs and DNV provide resistance functions and charts for the flat
plate under blast impact for various boundary conditions and shape
ratios
DNV proposes guidelines for design of stiffened plates
The guidelines for corrugated plates do not exist.
3. Limitations of analytical approaches
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83|Steel Structures In Offshore Applications Constança Rigueiro
Two types of plates (1,2 x1,2 m2) are modelled in order to study the
suitability of analytical approaches:
• Plate without stiffeners and with thickness 16 mm
• Plate without stiffeners and with thickness 8 mm
Typically, explosions on offshore structures are deflagration type
so the blast pressure curve was modified as follows:
Time [s]
Pressure [MPa]
0,10
0,4
0,05
3. Limitations of analytical approaches
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First plate was expected to respond in elastic and the second plate in
elasto-plastic way
The maximum values of displacements in the center of the plate are
shown in the table below and compared with the numerical results:
Displacements
BiggsDNV
(RP C204)
Abaqus(Explicit)Constant velocity
integration
Wmax (tp = 16 mm) 14 mm 13,5 mm 11,3 mm
Wmax (tp = 8 mm) >>500 mm 70 mm 23,2 mm
It is observed that the existing analytical approaches estimate very
successfully the response of the plate as long as the plate behaves
elastically
Displacements calculated for the plate that undergoes certain
plastification under high strain rate loading showed not to be reliable
3. Limitations of analytical approaches
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Plate typologies in consideration
• Carbon steel S355
• Strain rate and strain hardening defined based on experimental
tests (National Project ImpactFire)
Material
4. Numerical analysis
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Boundary conditions
• Deflagration type of an explosion with the same pressure curve
as the one used for the study of analytical approaches
• Peak overpressure: 0,4 MPa
• Rise and fall time equal to 50 ms
Load
• Plates (t=16 mm and t=4 mm) with fully fixed edges
• Corrugated plates (t=4 mm and t=2 mm) with fixed edges
Time [s]
Pressure
[MPa]
0,10
0,4
0,05
4. Numerical analysis
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Displacements (frame 70, corresponding to max disp.)
0
0,005
0,01
0,015
0,02
0,025
0,03
0,035
0 0,2 0,4 0,6 0,8 1 1,2 1,4
Dis
pla
cem
en
t [m
]
Position along x support [m]
Comparison of displacements in the middle section
Corrugated t= 2mm
Corrugated t= 4mm
Flat t = 16 mm
Flat t = 4 mm
5. Results
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Displacements
0
0,005
0,01
0,015
0,02
0,025
0,03
0,035
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35
Dis
pla
cem
en
t [m
]
Time [s]
Comparison of displacements in the central node
Corrugated t= 2mm
Corrugated t= 4mm
Flat t = 16 mm
Flat t = 4 mm
5. Results
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Reactions (frame 70, corresponding to max disp.)
0
5000
10000
15000
20000
25000
0 0,2 0,4 0,6 0,8 1 1,2 1,4
Re
acti
on
fo
rce
[N
]
Position along x support [m]
Comparison of reaction forces along x support
Corrugated t= 2mm
Corrugated t= 4mm
Flat t = 16 mm
Flat t = 4 mm
5. Results
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✓ Corrugated plates have much lower deflections than flat plates without
stiffeners; 2 mm thick corrugated plate has the same deflection as the 16
mm thick flat plate
✓ Thin corrugated plate is characterized by large permanent deflections
✓ Thinner corrugated plate has around 30% lower reaction forces in thenodes than the thick, but higher than the thicker flat plate
✓ Thin corrugated plates allow for significant plastic dissipation which is
even two times higher than for the thin flat plates
6. Conclusions
Thanks for your
attention
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