steel structures in offshore applications - hamk · 122 isi journals 0 2 4 6 8 10 12 14 16 18 20...

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




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



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



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



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



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



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



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



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



Educational Offer from ISISE SMCT

• PhD Programmes (1)

• Advanced MSc Programmes (4)

• Core Integrated MSc’s (2)

• Short Courses



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

http://www.suscos.eu/



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“



Short Courses from ISISE SMCT (on offhsore structures domain)

Brief Outline of R&D on

Offshore domainConstança Rigueiro




Portugal

Total surface: 92,090 km²



Actual Exclusive Economic Zone of Portugal 1,727,408 km²

Portugal is 95% of Water!!



Future Exclusive Economic Zone of Portugal 4 M km²

Then we will be 97% of Water!!



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….”



• 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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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



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).




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.



• 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 domain

National and International Projects



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



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:



• Finite Element Modeling (ABAQUS)• Connection tests under impact

Scope: Eurocode 1, Part 1.7, Accidental actions

Connection behaviour characterization

Robust connections under impact



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



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


Offshore domain

Some Outputs



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)




• 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.




• 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



Numerical assessment of the behaviour of a

fixed offshore platform subjected to ship

collision

Constança Rigueiro | João Ribeiro | Aldina Santiago



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



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



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.



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.




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);




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




1.2 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:



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




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




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.




• 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



Storage area complete

Residential

Quarters




+9.75 m

+14.33 m

+19.74 m

Storage area

Residential Quarters

Heliport

Drilling area




✓ 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



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;




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



• 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.




• 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




4. Collision Scenarios

4.1 Stiff ship: 2 m/s vs 0,5 m/s



4.2 Stiff vs soft ship

Stiff ship Soft ship

4. Collision Scenarios



✓ 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



Analysis Methodologies of the Interaction

Fluid-Structure (FSI) in Offshore Structures

Daniel Oliveira | Aldina Santiago | 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




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




Analytical

Tests with reduced

scale and real scale models

Waves Tanks

Study of Phenomena

resulting from Fluid-Structure Interaction


Development and

validation of

empirical formulas

(eg Morison formula)

Experimental




Analytical

Partial differential

equations to solve the Navier-Stokes eq.

Computational Fluid Dynamics – CFD

(1950/60)

Analysis of complete

structures with full scale models


Increase of the

computational power

Experimental

Numerical

Integration/Interaction with Computational

Solids Mechanics (CSM) models




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





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





3.3 Application to Singular Elements

Wave_Structure

interaction

Partitioned

Approach

CFD-CSM

Unidirectional Coupling (Explicit)

Rigid

Cylindrical Element






Wave_Structure

interaction

Partitioned

Approach

CFD-CSM

Bidirectional Coupling Implicit

Deformable

Cylindrical Element






Wave_Structure

interaction

Partitioned

Approach

CFD-CSM

Bidirectional Coupling Implicit

Deformable

Rectangular Element (Plate)




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)




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




4. Case Study

4.3 Model CSM (Abaqus)

FEM – Shell

Elements

Square Elements

– 25 cm

360 000

Elements

Linear Elastic

Material

Dynamic Implicit

Analysis




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




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



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.



Characterization of blast action and structural

mitigation measures in offshore environment

Damjan Čekerevac | Constança Rigueiro | Eduardo Pereira



▪ 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



▪ 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




▪ 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/





• 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



• 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



Elements

Connections

2. Types of blast walls



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



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




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




Plate typologies in consideration

• Carbon steel S355

• Strain rate and strain hardening defined based on experimental

tests (National Project ImpactFire)

Material

4. Numerical analysis



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



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



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



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



✓ 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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