analysis and design

Analysis and Design of Marine Structures–Guedes Soares & Das eds© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9 Table of Contents Methods and tools for loads and load effec

ANALYSIS AND DESIGN OF MARINE STRUCTURES

PROCEEDINGS OF MARSTRUCT 2009, THE 2nd INTERNATIONAL CONFERENCE ON MARINESTRUCTURES, LISBON, PORTUGAL, 16–18 MARCH 2009

Analysis and Design of Marine

Cover photograph: Bulk carrier INA from Portline, Portugal

MARSTRUCT Book Series

1 Advancements in Marine Structures (2007)

Edited by Carlos Guedes Soares & P.K Das

ISBN: 978-0-415-43725-7 (hb)

2 Analysis and Design of Marine Structures (2009)

Edited by Carlos Guedes Soares & P.K Das

ISBN: 978-0-415-54934-9 (hb)

ISBN: 978-0-203-87498-1 (e-book)

CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business

©2009 Taylor & Francis Group, London, UK

‘The importance of welding quality in ship construction’ by: Philippa Moore

© 2009 TWI Ltd

Typeset by Vikatan Publishing Solutions (P) Ltd., Chennai, India

Printed and bound in Great Britain by Antony Rowe (A CPI-group Company), Chippenham, WiltshireAll rights reserved No part of this publication or the information contained herein may be reproduced, stored

in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying,recording or otherwise, without written prior permission from the publisher

Although all care is taken to ensure integrity and the quality of this publication and the information herein, noresponsibility is assumed by the publishers nor the author for any damage to the property or persons as a result

of operation or use of this publication and/or the information contained herein

Published by: CRC Press/Balkema

P.O Box 447, 2300 AK Leiden, The Netherlands

e-mail: Pub.NL@taylorandfrancis.com

www.crcpress.com – www.taylorandfrancis.co.uk – www.balkema.nl

ISBN: 978-0-415-54934-9 (hbk+CD-ROM)

ISBN: 978-0-203-87498-1 (e-book)

Analysis and Design of Marine Structures–Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Table of Contents

Methods and tools for loads and load effects

A study on the effect of heavy weather avoidance on the wave pressure distribution along the

Zhi Shu & Torgeir Moan

Comparison of experimental and numerical sloshing loads in partially filled tanks 13

S Brizzolara, L Savio, M Viviani, Y Chen, P Temarel, N Couty, S Hoflack, L Diebold,

N Moirod & A Souto Iglesias

T.W.P Smith, K.R Drake & P Wrobel

Estimation of parametric rolling of ships—comparison of different probabilistic methods 37

Jelena Vidic-Perunovic & Jørgen Juncher Jensen

Š Malenica, F.X Sireta, S Tomaševi´c, J.T Tuitman & I Schipperen

Methods and tools for strength assessment

Finite element analysis

Methods for hull structure strength analysis and ships service life evaluation, for a large LNG carrier 53

Leonard Domnisoru, Ionel Chirica & Alexandru Ioan

Parametric investigation on stress concentrations of bulk carrier hatch corners 67

Dario Boote & Francesco Cecchini

A study on structural characteristics of the ring-stiffened circular toroidal shells 77

Qing-Hai Du, Zheng-Quan Wan & Wei-Cheng Cui

Application developments of mixed finite element method for fluid-structure interaction

Jing Tang Xing, Ye Ping Xiong & Mingyi Tan

Marc Wilken, G Of, C Cabos & O Steinback

Finite element simulations of ship collisions: A coupled approach to external dynamics

Ingmar Pill & Kristjan Tabri

Ultimate strength

Claude Daley & Apurv Bansal

Ultimate strength characteristics of aluminium plates for high speed vessels 121

S Benson, J Downes & R.S Dow

Improving the shear properties of web-core sandwich structures using filling material 133

Jani Romanoff, Aleksi Laakso & Petri Varsta

Jacob Abraham & Claude Daley

Ultimate strength of stiffened plates with local damage on the stiffener 145

M Witkowska & C Guedes Soares

Approximate method for evaluation of stress-strain relationship for stiffened

panel subject to tension, compression and shear employing the finite element approach 155

Maciej Taczala

Residual strength of damaged stiffened panel on double bottom ship 163

Zhenhui Liu & Jørgen Amdahl

Assessment of the hull girder ultimate strength of a bulk carrier using nonlinear

Zhi Shu & Torgeir Moan

Ultimate strength performance of Suezmax tanker structures: Pre-CSR versus CSR designs 181

J.K Paik, D.K Kim & M.S Kim

Coatings and corrosion

Pawel Domzalicki, Igor Skalski, C Guedes Soares & Yordan Garbatov

Anticorrosion protection systems—improvements and continued problems 199

Anders Ulfvarson & Klas Vikgren

Prospects of application of plasma electrolytic oxidation coatings for shipbuilding 207

Alexander N Minaev, Natalie A Gladkova, Sergey V Gnedenkov & Vladimir V Goriaynov

Corrosion wastage statistics and maintenance planning of corroded hull structures of bulk carriers 215

Yordan Garbatov & C Guedes Soares

Numerical simulation of strength and deformability of steel plates with surface pits

Md Mobesher Ahmmad & Yoichi Sumi

Effect of pitting corrosion on the collapse strength of rectangular plates under axial compression 231

S Saad-Eldeen & C Guedes Soares

Fatigue and fracture

Fracture mechanics procedures for assessing fatigue life of window and door corners in ship structures 239

Mika Bäckström & Seppo Kivimaa

Experimental and numerical fatigue analysis of partial-load and full-load carrying fillet welds

O Feltz & W Fricke

Global strength analysis of ships with special focus on fatigue of hatch corners 255

Hubertus von Selle, Olaf Doerk & Manfred Scharrer

Structural integrity monitoring index for ship and offshore structures 261

Bart de Leeuw & Feargal P Brennan

Effect of uncertain weld shape on the structural hot-spot stress distribution 267

B Gaspar, Y Garbatov & C Guedes Soares

A study on a method for maintenance of ship structures considering remaining life benefit 279

Yasumi Kawamura, Yoichi Sumi & Masanobu Nishimoto

Impact strength

L.S Sutherland & C Guedes Soares

Impact damage of MARK III type LNG carrier cargo containment system due

J.K Paik, B.J Kim, T.H Kim, M.K Ha, Y.S Suh & S.E Chun

Simulation of the response of double bottoms under grounding actions using finite elements 305

I Zilakos, M Toulios, M Samuelides, T.-H Nguyen & J Amdahl

Fire and explosion

J.K Paik, B.J Kim, J.S Jeong, S.H Kim, Y.S Jang, G.S Kim, J.H Woo, Y.S Kim,

M.J Chun, Y.S Shin & J Czujko

The effects of reliability-based vulnerability requirements on blast-loaded ship panels 323

S.J Pahos & P.K Das

Structural monitoring

Giovanni Carrera, Cesare Mario Rizzo & Matteo Paci

Assessment of ice-induced loads on ship hulls based on continuous response monitoring 345

B.J Leira, Lars Børsheim, Øivind Espeland & J Amdahl

Materials and fabrication of structures

Welded structures

Philippa L Moore

A data mining analysis to evaluate the additional workloads caused by welding distortions 365

Nicolas Losseau, Jean David Caprace, Philippe Rigo & Fernandez Francisco Aracil

3D numerical model of austenitic stainless steel 316L multipass butt welding and comparison

A.P Kyriakongonas & V.J Papazoglou

Adhesive joints

Fabrication, testing and analysis of steel/composite DLS adhesive joints 379

S Hashim, J Nisar, N Tsouvalis, K Anyfantis, P Moore, Ionel Chirica, C Berggreen, A Orsolini,

A Quispitupa, D McGeorge, B Hayman, S Boyd, K Misirlis, J Downes, R Dow & E Juin

The effect of surface preparation on the behaviour of double strap adhesive joints with

K.N Anyfantis & N.G Tsouvalis

J.A Nisar, S.A Hashim & P.K Das

Buckling of composite plates

B Hayman, C Berggreen, C Lundsgaard-Larsen, A Delarche, H.L Toftegaard, R.S Dow,

J Downes, K Misirlis, N Tsouvalis & C Douka

Buckling strength parametric study of composite laminated plates with delaminations 413

N.G Tsouvalis & G.S Garganidis

Buckling behaviour of the ship deck composite plates with cut-outs 423

Ionel Chirica, Elena-Felicia Beznea & Raluca Chirica

Buckling behaviour of plates with central elliptical delamination 429

Elena-Felicia Beznea, Ionel Chirica & Raluca Chirica

Methods and tools for structural design and optimization

Structural design of a medium size passenger vessel with low wake wash 437

Dario Boote & Donatella Mascia

Multi-objective optimization of ship structures: Using guided search vs

Jasmin Jelovica & Alan Klanac

José M Varela, Manuel Ventura & C Guedes Soares

Structural reliability safety and environmental protection

Still water loads

Probabilistic presentation of the total bending moments of FPSO’s 469

Lyuben D Ivanov, Albert Ku, Beiqing Huang & Viviane C.S Krzonkala

Stochastic model of the still water bending moment of oil tankers 483

L Garrè & Enrico Rizzuto

Joško Parunov, Maro ´ Corak & C Guedes Soares

Ship structural reliability

Structural reliability of the ultimate hull girder strength of a PANAMAX container ship 503

Jörg Peschmann, Clemens Schiff & Viktor Wolf

Sensitivity analysis of the ultimate limit state variables for a tanker and a bulk carrier 513

A.W Hussein & C Guedes Soares

Ultimate strength and reliability assessment of laminated composite plates under axial compression 523

N Yang, P.K Das & Xiong Liang Yao

Environmental impact

I.S Carvalho, P Antão & C Guedes Soares

Fuel consumption and exhaust emissions reduction by dynamic propeller pitch control 543

Massimo Figari & C Guedes Soares

Analysis and Design of Marine Structures–Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Preface

This book collects the papers presented at the second International Conference on Marine Structures,MARSTRUCT 2009, which was held in Lisbon 16 to 18 March This Conference follows up from the ini-tial one that was held in Glasgow, Scotland two years before and aims at bringing together researchers andindustrial participants specially concerned with structural analysis and design Despite the availability of severalconferences, it was felt that there was still no conference series specially dedicated to marine structures, whichwould be the niche for these conferences

The initial impetus and support has been given by the Network of Excellence on Marine Structures(MARSTRUCT), which is now in its 6th year of funding by the European Union and brings together 33European research groups from Universities, research institutions, classification societies and industrial compa-nies that are dedicated to research in the area of marine structures However this Conference is not meant to berestricted to European attendees and a serious effort has been made to involve in the planning of the Conferenceparticipants from other continents that could ensure a wider participation, which is slowly happening.The conference reflects the work conducted in the analysis and design of marine structures, in order to explorethe full range of methods and modelling procedures for the structural assessment of marine structures Variousassessment methods are incorporated in the methods used to analyze and design efficient ship structures, as well

as in the methods of structural reliability to be used to ensure the safety and environmental behaviour of theships This book deals also with some aspects of fabrication of ship structures

The 60 papers are categorised into the following themes:

• Methods and tools for establishing loads and load effects

• Methods and tools for strength assessment

• Materials and fabrication of structures

• Methods and tools for structural design and optimisation

• Structural reliability, safety and environmental protection

The papers were accepted after a review process, based on the full text of the papers Thanks are due tothe Technical Programme Committee and to the Advisory Committee who had most of the responsibility forreviewing the papers and to the additional anonymous reviewers who helped the authors deliver better papers byproviding them with constructive comments We hope that this process contributed to a consistently good level

of the papers included in the book

Carlos Guedes SoaresPurnendu Das

Analysis and Design of Marine Structures–Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Organisation

Conference Chairmen

Prof Carlos Guedes Soares, IST, Technical University of Lisbon, Portugal

Prof Purnendu K Das, Universities of Glasgow & Strathclyde, UK

Technical Programme Committee

Prof N Barltrop, University of Glasgow & Strathclyde, UK

Dr N Besnard, Principia Marine, France

Dr M Codda, CETENA, Italy

Prof L Domnisoru, UGAL, Romania

Prof R.S Dow, University of Newcastle upon Tyne, UK

Prof W Fricke, TUHH, Germany

Prof Y Garbatov, IST, Technical University of Lisbon, Portugal

Prof J.M Gordo, IST, Technical University of Lisbon, Portugal

Dr B Hayman, DNV, Norway

Prof A Incecik, University of Newcastle upon Tyne, UK

Prof T Jastrzebski, TUS, Poland

Prof J.J Jensen, DTU, Denmark

Prof B.J Leira, NTNU, Norway

Prof V Papazoglou, NTUA, Greece

Prof P Rigo, University of Liège, Belgium

Prof E Rizzuto, University of Genova, Italy

Prof R.A Shenoi, University of Southampton, UK

Prof P Temarel, University of Southampton, UK

Prof A Ulfvarson, Chalmers University of Tech., Sweden

Prof P Varsta, Helsinki University of Technology, Finland

Dr A Vredeveldt, TNO, The Netherlands

Advisory Committee

Dr R.I Basu, ABS, USA

Prof F Brennan, Cranfield University, UK

Dr F Cheng, Lloyd’s Register, UK

Prof Y.S Choo, Nat Univ Singapore, Singapore

Prof W.C Cui, CSSRC, China

Prof C Daley, Memorial University, Canada

Prof A Ergin, ITU, Turkey

Prof S Estefen, COPPE, Brazil

Prof M Fujikubo, Osaka University, Japan

Prof D Karr, University of Michigan, USA

Prof H.W Leheta, Alexandria University, Egypt

Dr O Valle Molina, Mexican Inst of Petroleum, Mexico

Prof J.K Paik, Pusan National University, Korea

Prof P.T Pedersen, DTU, Denmark

Dr N.G Pegg, DND, Canada

Prof M Salas, University Austral of Chile, Chile

Prof Y Sumi, Yokohama National University, Japan

Prof V Zanic, University of Zagreb, Croatia

Conference Secretariat

Ana Rosa Fragoso, IST, Technical University of Lisbon, PortugalMaria de Fátima Pina, IST, Technical University of Lisbon, PortugalSandra Ponce, IST, Technical University of Lisbon, Portugal

ANALYSIS AND DESIGN OF MARINE STRUCTURES

PROCEEDINGS OF MARSTRUCT 2009, THE 2nd INTERNATIONAL CONFERENCE ON MARINESTRUCTURES, LISBON, PORTUGAL, 16–18 MARCH 2009

Analysis and Design of Marine

Cover photograph: Bulk carrier INA from Portline, Portugal

MARSTRUCT Book Series

1 Advancements in Marine Structures (2007)

Edited by Carlos Guedes Soares & P.K Das

ISBN: 978-0-415-43725-7 (hb)

2 Analysis and Design of Marine Structures (2009)

Edited by Carlos Guedes Soares & P.K Das

ISBN: 978-0-415-54934-9 (hb)

ISBN: 978-0-203-87498-1 (e-book)

CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business

©2009 Taylor & Francis Group, London, UK

‘The importance of welding quality in ship construction’ by: Philippa Moore

© 2009 TWI Ltd

Typeset by Vikatan Publishing Solutions (P) Ltd., Chennai, India

Printed and bound in Great Britain by Antony Rowe (A CPI-group Company), Chippenham, WiltshireAll rights reserved No part of this publication or the information contained herein may be reproduced, stored

in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying,recording or otherwise, without written prior permission from the publisher

Although all care is taken to ensure integrity and the quality of this publication and the information herein, noresponsibility is assumed by the publishers nor the author for any damage to the property or persons as a result

of operation or use of this publication and/or the information contained herein

Published by: CRC Press/Balkema

P.O Box 447, 2300 AK Leiden, The Netherlands

e-mail: Pub.NL@taylorandfrancis.com

www.crcpress.com – www.taylorandfrancis.co.uk – www.balkema.nl

ISBN: 978-0-415-54934-9 (hbk+CD-ROM)

ISBN: 978-0-203-87498-1 (e-book)

Analysis and Design of Marine Structures – Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Table of Contents

Methods and tools for loads and load effects

A study on the effect of heavy weather avoidance on the wave pressure distribution along the

Zhi Shu & Torgeir Moan

Comparison of experimental and numerical sloshing loads in partially filled tanks 13

S Brizzolara, L Savio, M Viviani, Y Chen, P Temarel, N Couty, S Hoflack, L Diebold,

N Moirod & A Souto Iglesias

T.W.P Smith, K.R Drake & P Wrobel

Estimation of parametric rolling of ships—comparison of different probabilistic methods 37

Jelena Vidic-Perunovic & Jørgen Juncher Jensen

Š Malenica, F.X Sireta, S Tomaševi´c, J.T Tuitman & I Schipperen

Methods and tools for strength assessment

Finite element analysis

Methods for hull structure strength analysis and ships service life evaluation, for a large LNG carrier 53

Leonard Domnisoru, Ionel Chirica & Alexandru Ioan

Parametric investigation on stress concentrations of bulk carrier hatch corners 67

Dario Boote & Francesco Cecchini

A study on structural characteristics of the ring-stiffened circular toroidal shells 77

Qing-Hai Du, Zheng-Quan Wan & Wei-Cheng Cui

Application developments of mixed finite element method for fluid-structure interaction

Jing Tang Xing, Ye Ping Xiong & Mingyi Tan

Marc Wilken, G Of, C Cabos & O Steinback

Finite element simulations of ship collisions: A coupled approach to external dynamics

Ingmar Pill & Kristjan Tabri

Ultimate strength

Claude Daley & Apurv Bansal

Ultimate strength characteristics of aluminium plates for high speed vessels 121

S Benson, J Downes & R.S Dow

Improving the shear properties of web-core sandwich structures using filling material 133

Jani Romanoff, Aleksi Laakso & Petri Varsta

Jacob Abraham & Claude Daley

Ultimate strength of stiffened plates with local damage on the stiffener 145

M Witkowska & C Guedes Soares

Approximate method for evaluation of stress-strain relationship for stiffened

panel subject to tension, compression and shear employing the finite element approach 155

Maciej Taczala

Residual strength of damaged stiffened panel on double bottom ship 163

Zhenhui Liu & Jørgen Amdahl

Assessment of the hull girder ultimate strength of a bulk carrier using nonlinear

Zhi Shu & Torgeir Moan

Ultimate strength performance of Suezmax tanker structures: Pre-CSR versus CSR designs 181

J.K Paik, D.K Kim & M.S Kim

Coatings and corrosion

Pawel Domzalicki, Igor Skalski, C Guedes Soares & Yordan Garbatov

Anticorrosion protection systems—improvements and continued problems 199

Anders Ulfvarson & Klas Vikgren

Prospects of application of plasma electrolytic oxidation coatings for shipbuilding 207

Alexander N Minaev, Natalie A Gladkova, Sergey V Gnedenkov & Vladimir V Goriaynov

Corrosion wastage statistics and maintenance planning of corroded hull structures of bulk carriers 215

Yordan Garbatov & C Guedes Soares

Numerical simulation of strength and deformability of steel plates with surface pits

Md Mobesher Ahmmad & Yoichi Sumi

Effect of pitting corrosion on the collapse strength of rectangular plates under axial compression 231

S Saad-Eldeen & C Guedes Soares

Fatigue and fracture

Fracture mechanics procedures for assessing fatigue life of window and door corners in ship structures 239

Mika Bäckström & Seppo Kivimaa

Experimental and numerical fatigue analysis of partial-load and full-load carrying fillet welds

O Feltz & W Fricke

Global strength analysis of ships with special focus on fatigue of hatch corners 255

Hubertus von Selle, Olaf Doerk & Manfred Scharrer

Structural integrity monitoring index for ship and offshore structures 261

Bart de Leeuw & Feargal P Brennan

Effect of uncertain weld shape on the structural hot-spot stress distribution 267

B Gaspar, Y Garbatov & C Guedes Soares

A study on a method for maintenance of ship structures considering remaining life benefit 279

Yasumi Kawamura, Yoichi Sumi & Masanobu Nishimoto

Impact strength

L.S Sutherland & C Guedes Soares

Impact damage of MARK III type LNG carrier cargo containment system due

J.K Paik, B.J Kim, T.H Kim, M.K Ha, Y.S Suh & S.E Chun

Simulation of the response of double bottoms under grounding actions using finite elements 305

I Zilakos, M Toulios, M Samuelides, T.-H Nguyen & J Amdahl

Fire and explosion

J.K Paik, B.J Kim, J.S Jeong, S.H Kim, Y.S Jang, G.S Kim, J.H Woo, Y.S Kim,

M.J Chun, Y.S Shin & J Czujko

The effects of reliability-based vulnerability requirements on blast-loaded ship panels 323

S.J Pahos & P.K Das

Structural monitoring

Giovanni Carrera, Cesare Mario Rizzo & Matteo Paci

Assessment of ice-induced loads on ship hulls based on continuous response monitoring 345

B.J Leira, Lars Børsheim, Øivind Espeland & J Amdahl

Materials and fabrication of structures

Welded structures

Philippa L Moore

A data mining analysis to evaluate the additional workloads caused by welding distortions 365

Nicolas Losseau, Jean David Caprace, Philippe Rigo & Fernandez Francisco Aracil

3D numerical model of austenitic stainless steel 316L multipass butt welding and comparison

A.P Kyriakongonas & V.J Papazoglou

Adhesive joints

Fabrication, testing and analysis of steel/composite DLS adhesive joints 379

S Hashim, J Nisar, N Tsouvalis, K Anyfantis, P Moore, Ionel Chirica, C Berggreen, A Orsolini,

A Quispitupa, D McGeorge, B Hayman, S Boyd, K Misirlis, J Downes, R Dow & E Juin

The effect of surface preparation on the behaviour of double strap adhesive joints with

K.N Anyfantis & N.G Tsouvalis

J.A Nisar, S.A Hashim & P.K Das

Buckling of composite plates

B Hayman, C Berggreen, C Lundsgaard-Larsen, A Delarche, H.L Toftegaard, R.S Dow,

J Downes, K Misirlis, N Tsouvalis & C Douka

Buckling strength parametric study of composite laminated plates with delaminations 413

N.G Tsouvalis & G.S Garganidis

Buckling behaviour of the ship deck composite plates with cut-outs 423

Ionel Chirica, Elena-Felicia Beznea & Raluca Chirica

Buckling behaviour of plates with central elliptical delamination 429

Elena-Felicia Beznea, Ionel Chirica & Raluca Chirica

Methods and tools for structural design and optimization

Structural design of a medium size passenger vessel with low wake wash 437

Dario Boote & Donatella Mascia

Multi-objective optimization of ship structures: Using guided search vs

Jasmin Jelovica & Alan Klanac

José M Varela, Manuel Ventura & C Guedes Soares

Structural reliability safety and environmental protection

Still water loads

Probabilistic presentation of the total bending moments of FPSO’s 469

Lyuben D Ivanov, Albert Ku, Beiqing Huang & Viviane C.S Krzonkala

Stochastic model of the still water bending moment of oil tankers 483

L Garrè & Enrico Rizzuto

Joško Parunov, Maro ´ Corak & C Guedes Soares

Ship structural reliability

Structural reliability of the ultimate hull girder strength of a PANAMAX container ship 503

Jörg Peschmann, Clemens Schiff & Viktor Wolf

Sensitivity analysis of the ultimate limit state variables for a tanker and a bulk carrier 513

A.W Hussein & C Guedes Soares

Ultimate strength and reliability assessment of laminated composite plates under axial compression 523

N Yang, P.K Das & Xiong Liang Yao

Environmental impact

I.S Carvalho, P Antão & C Guedes Soares

Fuel consumption and exhaust emissions reduction by dynamic propeller pitch control 543

Massimo Figari & C Guedes Soares

Analysis and Design of Marine Structures – Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Preface

This book collects the papers presented at the second International Conference on Marine Structures,MARSTRUCT 2009, which was held in Lisbon 16 to 18 March This Conference follows up from the ini-tial one that was held in Glasgow, Scotland two years before and aims at bringing together researchers andindustrial participants specially concerned with structural analysis and design Despite the availability of severalconferences, it was felt that there was still no conference series specially dedicated to marine structures, whichwould be the niche for these conferences

The initial impetus and support has been given by the Network of Excellence on Marine Structures(MARSTRUCT), which is now in its 6th year of funding by the European Union and brings together 33European research groups from Universities, research institutions, classification societies and industrial compa-nies that are dedicated to research in the area of marine structures However this Conference is not meant to berestricted to European attendees and a serious effort has been made to involve in the planning of the Conferenceparticipants from other continents that could ensure a wider participation, which is slowly happening.The conference reflects the work conducted in the analysis and design of marine structures, in order to explorethe full range of methods and modelling procedures for the structural assessment of marine structures Variousassessment methods are incorporated in the methods used to analyze and design efficient ship structures, as well

as in the methods of structural reliability to be used to ensure the safety and environmental behaviour of theships This book deals also with some aspects of fabrication of ship structures

The 60 papers are categorised into the following themes:

• Methods and tools for establishing loads and load effects

• Methods and tools for strength assessment

• Materials and fabrication of structures

• Methods and tools for structural design and optimisation

• Structural reliability, safety and environmental protection

The papers were accepted after a review process, based on the full text of the papers Thanks are due tothe Technical Programme Committee and to the Advisory Committee who had most of the responsibility forreviewing the papers and to the additional anonymous reviewers who helped the authors deliver better papers byproviding them with constructive comments We hope that this process contributed to a consistently good level

of the papers included in the book

Carlos Guedes SoaresPurnendu Das

Analysis and Design of Marine Structures – Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Organisation

Conference Chairmen

Prof Carlos Guedes Soares, IST, Technical University of Lisbon, Portugal

Prof Purnendu K Das, Universities of Glasgow & Strathclyde, UK

Technical Programme Committee

Prof N Barltrop, University of Glasgow & Strathclyde, UK

Dr N Besnard, Principia Marine, France

Dr M Codda, CETENA, Italy

Prof L Domnisoru, UGAL, Romania

Prof R.S Dow, University of Newcastle upon Tyne, UK

Prof W Fricke, TUHH, Germany

Prof Y Garbatov, IST, Technical University of Lisbon, Portugal

Prof J.M Gordo, IST, Technical University of Lisbon, Portugal

Dr B Hayman, DNV, Norway

Prof A Incecik, University of Newcastle upon Tyne, UK

Prof T Jastrzebski, TUS, Poland

Prof J.J Jensen, DTU, Denmark

Prof B.J Leira, NTNU, Norway

Prof V Papazoglou, NTUA, Greece

Prof P Rigo, University of Liège, Belgium

Prof E Rizzuto, University of Genova, Italy

Prof R.A Shenoi, University of Southampton, UK

Prof P Temarel, University of Southampton, UK

Prof A Ulfvarson, Chalmers University of Tech., Sweden

Prof P Varsta, Helsinki University of Technology, Finland

Dr A Vredeveldt, TNO, The Netherlands

Advisory Committee

Dr R.I Basu, ABS, USA

Prof F Brennan, Cranfield University, UK

Dr F Cheng, Lloyd’s Register, UK

Prof Y.S Choo, Nat Univ Singapore, Singapore

Prof W.C Cui, CSSRC, China

Prof C Daley, Memorial University, Canada

Prof A Ergin, ITU, Turkey

Prof S Estefen, COPPE, Brazil

Prof M Fujikubo, Osaka University, Japan

Prof D Karr, University of Michigan, USA

Prof H.W Leheta, Alexandria University, Egypt

Dr O Valle Molina, Mexican Inst of Petroleum, Mexico

Prof J.K Paik, Pusan National University, Korea

Prof P.T Pedersen, DTU, Denmark

Dr N.G Pegg, DND, Canada

Prof M Salas, University Austral of Chile, Chile

Prof Y Sumi, Yokohama National University, Japan

Prof V Zanic, University of Zagreb, Croatia

Conference Secretariat

Ana Rosa Fragoso, IST, Technical University of Lisbon, PortugalMaria de Fátima Pina, IST, Technical University of Lisbon, PortugalSandra Ponce, IST, Technical University of Lisbon, Portugal

Methods and tools for loads and load effects

Analysis and Design of Marine Structures – Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

A study on the effect of heavy weather avoidance on the wave

pressure distribution along the midship transverse section

of a VLCC and a bulk carrier

Z Shu & T Moan

CeSOS and Department of Marine Technology

Norwegian University of Science and Technology, Trondheim, Norway

ABSTRACT: This paper is concerned with the effect of heavy weather avoidance on the long-termwave-induced pressure along the midship transverse section of a VLCC and a bulk carrier A practical model isproposed to consider the effect of the heavy weather avoidance on the wave pressure along the midship trans-verse section This model is based on the modification of the wave scatter diagrams according to the operationallimiting criteria The wave pressure distributions of a VLCC and a Bulk carrier are investigated in the casestudy using the computer code WASIM with linear analysis option Two different wave scatter diagrams fromIACS and OCEANOR were considered for the long-term predictions of wave pressures The results show thatthe influence of heavy weather avoidance on the extreme values of wave pressure along the midship transversesection is dependent on how the heavy weather avoidance is accounted for

1 INSTRUCTIONS

Wave induced loads are very important for the safety

of seagoing vessels From the design point of view, the

wave induced loads can generally be categorized into

two classes, (1) global loads, i.e hull girder bending

moments and shear forces; (2) local loads, i.e wave

pressures

The main external loads on the seagoing vessels

are the wave induced hydrodynamic pressures With

the hydrodynamic pressures, the motions and global

hull girder loads in waves can be directly obtained

by integrating the hydrodynamic pressure and

iner-tia forces over the ship hulls In order to evaluate

the structural strength of the vessels under the wave

induced loads, a finite element analysis of the midship

region or the entire ship model is generally required

in the direct calculation The accuracy of structural

response analysis is highly depends on prediction of

extreme values of the wave induced hydrodynamic

pressure distributions, acceleration and the hull girder

bending moments

The extreme values of wave induced loads can be

obtained either from the ship rules or direct

calcula-tions The ship rules express the loads by simplified

formulas obtained based on experience with different

kinds of vessels However, these formulas are only

functions of the ship’s length, breath, and block

coef-ficients without explicit consideration of the effect of

heavy weather avoidance such as the route, scatter

diagram, operational profiles

In reality, ship masters are expected to operatethe ship to avoid heavy sea states by adopting speedreduction, course change and even fully stop in order

to decrease the hull damage and ease the motions.This means that the probability of the severe waveclimate encountered by the ships will be reduced tosome extent compared with the planned route Hencethe wave induced loads are expected to be reduced as adirect consequence of the vessel operation Since seastates with large significant wave height contributemost to the extreme loading, it is particularly impor-tant to consider the effect of avoiding those sea states

on the extreme loading Some researchers have tigated the effect of heavy weather avoidance on theglobal loads such as wave induced vertical bendingmoment Guedes Soares (1990) performed a study

inves-on the effect of heavy weather maneuvering inves-on thewave-induced vertical bending moments by assumingnon-uniform distribution heading under different seastates Shu & Moan (2008) proposed a practical model

to consider the effect of the heavy weather avoidance

on the wave induced hull girder loads This model

is based on the modification of the wave scatter grams according to the operational limiting criteria.Various wave scatter diagrams exist for the long-termprediction of extreme wave induced loads Two possi-bilities are wave scatter diagrams from IACS (2000)and OCEANOR (2005) The IACS wave scatter dia-gram describes the wave data of the North Atlantic,covering the area as defined in the Global Wave Statis-tics (GWS) (1980) with more realistic considerations

dia-of the wave steepness Moreover, the IACS data have

been smoothed by fitting an analytical probability

density function to the raw data OCEANOR data

are hindcast data of the North Atlantic in the last 12

years from 1994 to 2005 based on satellite data and

calibrations to wave buoy measurements Compared

with the wave scatter diagram from IACS, it should be

noted that OCEANOR wave data were not obtained by

the on-board observations and measurements Hence

for sure, OCEANOR data do not reflect any

influ-ence of heavy weather avoidance Therefore these

data have more probability in the tail of the marginal

distribution of the significant wave height

In this paper, this model is adopted to evaluate the

effect of heavy weather avoidance on the wave

pres-sure along the midship transverse section The wave

pressure distributions along the midship transverse

sections of a VLCC and a Bulk carrier are

investi-gated in the case study The long term predictions of

wave pressure distributions along the midship

trans-verse section will change depending on the heavy sea

states that are avoided by modifying the wave

scat-ter diagram The characscat-teristic values corresponding

to exceedance probability of 10−8from direct

calcu-lation are compared with those from rule simplified

formulae

2 HEAVY WEATHER AVOIDANCE

When sailing on a seaway, the shipmasters will in

gen-eral try to avoid severe sea states by adopting actions

such as reducing speed, changing course or both of the

formers according to certain limiting operational

cri-teria relating to the safety and comfort of passengers

and crew, to the safety and capacity of the vessel or

to operational considerations Operational restrictions

for high speed and light craft (HSLC) on coastal

voy-ages of short duration with short distance to shelter

can be fulfilled based on relevant sea state forecasts

For voyages of long duration without the opportunity

to seek shelter, fulfillment of operational restrictions

depends upon additional information about on-board

monitoring of responses and sea state forecast as

well as time to carry out the necessary change of

operation: speed reduction and change of heading or

generally a combination of both These actions will

generally be based on the observations and

measure-ments of the waves and vessels responses On the

other hand with the development of forecast

tech-nology of wave climate, most sea-going vessels have

installed facilities to receive weather data onboard

The shipmaster will have an advanced knowledge of

what kind of sea states are ahead on the planned route

and what kind of actions should be adopted to avoid

running directly into the severe sea states according to

the corresponding operational restrictions The

suc-cess of these actions depends on how fast the sea

state changes and the time available The operationalcriteria can be expressed in terms of allowable signif-icant wave height Hs However when and how theseactions should be taken is also greatly dependent onthe shipmasters experiences

It has been reported by Sternsson (2002) that ance of heavy weather can significantly reduce theprobability of encountering large waves according toon-board measurements However so far, this kind ofon-board measured data usually have only covered avery short period such as 1–2 years or even less Forthis reason it can not be directly used to perform thelong term prediction to investigate the effect of heavyweather avoidance on wave-induced loads

avoid-Systematic studies of bulk carriers, tankers and tainerships have been performed by ISSC CommitteeV.1 (Moan et al 2006) and it is found that the opera-tional envelopes can be transformed into operationalcriteria on significant wave height Hs vs ship length.Therefore, a simplified estimate of the effect of heavyweather avoidance can be obtained by identifying theoperational limiting boundaries which for simplicitymay be expressed by Hs ≤ Hslim The limiting sig-nificant wave height is approximated in this study

con-by a constant Hslim, independent of Tp If severe seastates are avoided by ships, the occurrences of actualsea states encountered by ships during its service lifemust be different from those given by the scatter dia-grams for the geographical area in which the ship isoperating This especially must be true for high seastates It is also known that high sea states usuallycontribute most to the long term prediction values.Moe et al (2005) had compared the wave observationsfrom a bulk carrier (Lpp= 285 m) with meteorologi-cal data and found that the probability of encounteringwaves with Hs> 6 m was less for the ship observa-

tions which indicates the effect of avoidance of heavyweather on the actual encountered sea states Despitethe uncertainty in these observations and comparisons,they support the assumption that the effect of opera-tional restrictions can be modelled by modifying theoriginal wave scatter diagram according to the limitingsignificant wave height

The operability limiting boundaries are obtainedfrom short term statistics combined with seakeepingcriteria The limiting curves can be presented as theenvelope curves which are functions of the limitingsignificant wave height Hslimand corresponding peakperiod Tp

Shu & Moan (2008) proposed a practical model

to consider the effect of the heavy weather ance on the wave induced hull girder loads Thismodel is based on the modification of the wave scatterdiagrams according to the limiting significant waveheight determined by operational limiting criteria.Three simplified methods as shown in Table 1 are used

avoid-to carry out this kind of modification of wave scatterdiagram

Table 1 Methods about modification of wave scatter

diagram.

Descriptions of the method

and add the probability of the truncated

area directly to the areas just below Hslim.

and add the probability of the truncated

area uniformly to all the areas below Hslim

the tail above Hslim and an inflation factor

β greater than 1.0 for the part below Hslim

Method 1 can be comparable to a situation where the

shipmasters avoid the heavy weather by maneuvering

the vessel into a just calmer sea state If the shipmasters

have some knowledge of the wave climate ahead under

the help of wave climate forecast, he will be sure to

take some actions in advance to avoid running directly

into those severe sea states Then an alternative way

is to add the probability of truncated area uniformly

to the all the areas below the limiting significant wave

height Hslim This approach is denoted by Method 2

However, due to the uncertainty of the wave climate

forecasts and the decision of the shipmaster, the severe

sea sates with significant wave height greater than

Hslim can not be perfectly avoided in reality This is

supported by the wave data measured onboard (Olsen

et al 2006) Method 3 accounts for this situation in a

simplified manner by using a reduction factor,α less

than 1.0, for the tail above Hslimand an inflation factor

β greater than 1.0 for the part below the limiting

sig-nificant wave height After these modifications, the

total probability should still be unit

3 CASE STUDY

3.1 Vessel particulars

In this case study, two representative vessels, including

a VLCC and a bulk carrier are considered to study

the effect of avoidance of heavy weather on the wave

induced pressure along the midship transverse section

The main dimensions of the relevant vessels are listed

in Table 2 The body plans are shown in Figure 1 and

Figure 2

3.2 Hydrodynamic analysis

The linear version of WASIM, DNV (2006) is used to

calculate wave induce pressures with zero speed

WASIM is a 3D time-domain hydrodynamic code

base on Rankine panel method The theory core of

WASIM is based on the method developed by Kring

et al (1998) The wave induced pressures are

cal-culated at 24 locations as shown in Figure 3 from

p13 to p36 along the midship transverse sections of

Table 2 Main particulars of vessels.

Figure 2 The body plan of a Capesize bulk carrier.

both the VLCC and the bulk carrier Although it isusually accepted that the heave and pitch motionscan be reproduced very well by potential theory, theroll motion predicted by potential theory consideringonly wave making damping is questionable The wavepressure distributions along the midship transversesection are consequently subjected to great uncer-tainty due to the questionable prediction of roll motion

in beam sea A sensitivity analysis was carried out toassess the influence of the roll damping on the waveinduced pressures Four damping levels in roll as apercentage of the critical damping are considered forthe hydrodynamic calculation by WASIM, namely2.5%, 5%, 7.5% and 10%, respectively (Ferrari &Ferreira, 2002)

The damping coefficient in roll motion is crucialespecially for the roll motion around the resonancefrequency

P14 P13 P1-P12

Figure 3 The pressure locations along the midship cross

section.

3.3 Long term prediction considering heavy

weather avoidance

The characteristic extreme value of the wave pressure

can be conveniently obtained by a linear long-term

response analysis The long-term predictions is

per-formed according to the procedure recommended by

IACS (2000) The procedure is generally based on the

North Atlantic wave condition, uniform distribution

of mean wave heading, Pierson-Moskowitz wave

spec-trum, and short-crested waves with spreading function

cos2θ The speed is assumed to be zero since the ship

masters are expected to just keep a very slow speed

for steering or even fully stop in order to decrease

the hull damage and ease the motions in severe sea

states

Two wave scatter diagrams for the North Atlantic

are considered for the long term prediction in this

study They are those provided by IACS and

OCEANOR Wave scatter diagram from IACS is

issued by classification society and recommended for

evaluation of extreme loads of hull girder OCEANOR

data are hindcast data of the last 12 year from 1994–

2005 and have more probability in the upper tail with

Hs>14 m compared to the classification society

scat-ter diagrams It is noted that the IACS procedure does

not describe explicitly that heavy weather avoidance

should be accounted for However, since the IACS

scatter diagram is mainly based on onboard

observa-tions and measurements, they could have implicitly

included the effect of heavy weather avoidance

com-pared with the OCEANOR data which describe the

real wave condition on sea

In the long term analysis of the wave pressures,

these wave scatter diagrams are modified at four

lim-iting significant wave heights, i.e., 8 m, 10 m, 12 m

and 14 m, Shu & Moan (2008), to account for heavy

weather avoidance

4 RESULTS AND DISCUSSIONS

4.1 Comparison of wave pressure between direct

calculation and Common Structural Rule

The comparison of the wave pressure distribution

envelop along the midship transverse sections obtained

by simplified rule formulas and that obtained by long

term prediction with different roll damping for thefull load condition of a VLCC and a bulk carrier

at exceedance probability level of 10−8 are shown

in Figure 4 and Figure 5, respectively The tions of wave pressure are different between CommonStructural Rules (CSR) for tankers (IACS 2006a) andCommon Structural Rules for bulk carriers (IACS2006b) In the CSR, simplified formulas are given

calcula-to calculate the dynamic wave pressure ing to CSR for tankers, the wave pressure is taken

Accord-as the greater one resulting from simplified

formu-lae p 1 and p 2 denoted as CSR p 1 and CSR p 2 in

Figure 4 p 2 is dominant in the midship region InCSR for bulk carriers, the wave pressure is assignedthe maximum value from the simplified formulas

for load case F, H, R and P where F represents

load case with equivalent design wave in

follow-ing sea, H head sea, R beam sea with maximum roll motion and P beam sea with maximum wave

pressure at the waterline on the weather side, tively The detailed simplified formulas for dynamicwave pressure can be found in the CSR The nonlin-ear effects in large waves are not considered in thelong termprediction based on linear hydrodynamicanalysis Therefore, the nonlinear correction factors

-20 -10 0 10 20 30 40

Dp0025 Dp005 Dp0075 Dp01 CSR P1

-20 -10 0 10 20 30

Dp0025 Dp005 Dp0075 Dp01 Case F Case R

Table 3 Comparison of wave pressure distributions between

those obtained by long term prediction and simplified

for-mulas (IACS 2006a) with different roll damping for typical

locations along the midship transverse section for a VLCC

with IACS wave data.

Wave pressure Location along

the cross section

* Percentage of critical damping.

Table 4 Comparison of wave pressure distributions between

those obtained by long term prediction and simplified

for-mulas (IACS 2006b) with different roll damping for typical

locations along the midship transverse section for a bulk

carrier with IACS wave data.

Wave pressure Location along

the cross section

* Percentage of critical damping.

used in the rule simplified formulas are not included

The envelop of the dynamic wave pressures

rep-resents the maximum dynamic wave pressure

dis-tribution The wave pressure is proportional to the

distance from the envelop to the corresponding point

on the hull

From Figure 4, it is observed that the long term

predictions with roll damping of 5% agree well with

the values from p 2according to CSR-tanker for this

VLCC For the bulk carrier, it is seen from Figure 5

that load case P is dominant for the wave pressure

at the midship transverse section except the area near

the centre bottom which is dominant by load case

H according to CSR-bulk carrier and the long term

predictions with roll damping of 5% seems to agree

well with those obtained by simplified formulas The

comparisons of the wave pressure between the

sim-plified formulae and those by long term predictions

at 5 typical locations with different roll dampings are

summarized in Table 3 and Table 4 corresponding to

a VLCC and a bulk carrier, respectively From Table 3

and Table 4, it can be seen that the roll damping has a

significant influence on the wave pressures especially

at area around the bilge keel while the wave pressure

at the centre bottom is almost not affected by the rolldamping

4.2 Extreme wave pressure considering the effect

of heavy weather avoidance

The heavy weather avoidance is considered by ing the wave scatter diagram according to the limitingsignificant wave height It has been seen that the rolldamping is of importance for the wave pressures alongthe midship transverse section and the determination

modify-of the accurate roll damping is subjected to a largeuncertainty For illustrative purpose, the long termpredictions of wave pressure with consideration ofheavy weather avoidance are based on the hydrody-namic analysis with 5% of linear critical roll dampingfor both the VLCC and the bulk carrier in the presentstudy Figure 6 and Figure 7 show the wave pres-sures considering heavy weather at typical locationsalong the midship transverse sections of the VLCCand the bulk carrier, respectively In the legend of

Figures 6 and 7, original represents no consideration

of heavy weather avoidance add, cut and alfa010

represent consideration of heavy weather avoidance

by method 1, method 2 and method 3, respectively.From Figure 6, it is noted that if the heavy weatheravoidance is not considered, the direct calculationsusing the 3D program with IACS wave scatter diagramagree very well with the rule values for the VLCC atvarious typical locations except P21 along the mid-ship transverse sections P21 is about in the middle

of the bilge keel and centre bottom At this location,the wave pressure obtained by long term prediction

is 29% larger than that by simplified formula Forbulk carrier without consideration of heavy weatheravoidance, it is observed that the direct calculationsusing the 3D program with IACS wave scatter dia-gram generally give lower extreme values of wavepressure than rule simplified formulae as shown inFigure 7

The underestimation increases from the water line

to the centre bottom It is noted that wave pressure

at the centre bottom obtained by long term predictionwith IACS wave data is 27% lower than that obtained

by simplified formulas

The IACS wave scatter diagram is conditioned onthe presence of the vessel to some extent and has beensmoothed from 103to 105by fitting an analytical dis-tribution to the raw data It may be argued that theobservations on board would imply non-conservativepredictions of severe sea states, because they mayhave been avoided by the vessel On the other hand,fitting of an analytical probability density function

to the raw data represents a smoothing and possibleextrapolation and may increase the probability con-tent in the distribution tail The OCEANOR data arebelieved to be more severe than the IACS wave scatterdiagrams

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

a

0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave da

ta

original add cut alfa010

c

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45

Pru

Limiting significant wave height Hs

IACS W ave data original add cut alfa010 Oceanor W ave data original add cut alfa010

d

0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20

Limiting significant wave height Hs

e

Figure 6. Wave pressure considering the effect of heavy weather avoidance for a VLCC in the full load condition a P13,

b P15, c P18, d P21, e P24 original: with full scatter diagram; add: method 1; cut: method 2; alfa010: method 3.

7 8 9 10 11 12 13 14 15 16 0.65

0.70 0.75 0.80 0.85 0.90 0.95 1.00

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

c

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

Limiting significant wave height Hs

IACS Wave data original add cut alfa010 Oceanor Wave data original add cut alfa010

d

0.50 0.55 0.60 0.65 0.70 0.75 0.80

Limiting significant wave height Hs

e

Figure 7. Wave pressure considering the effect of heavy weather avoidance for a bulk carrier in the full load condition a P13,

b P15, c P18, d P21, e P24 original: with full scatter diagram; add: method 1; cut: method 2; alfa010: method 3.

The OCEANOR data is found to yield wave

pressures at various locations along the midship

trans-verse section which are about 5–18% higher than those

obtained from the IACS wave scatter diagram issued

by classification society by using the full scatter

dia-gram for this VLCC while the overestimations are

3–9% for bulk carrier This may indicate that the

IACS scatter diagram has inherently included the

effect of heavy weather avoidance compared with

OCEANOR scatter diagram However this fact does

not lead to the conclusion that the rule formulae

give non-conservative results and should be increased

to have enough safety margins since the effect of

heavy weather avoidance is expected to reduce the

characteristic extreme value

In the present work, the heavy weather

avoid-ance has been modeled by modifying the original

wave scatter diagram according to operational

restric-tions expressed as limiting significant wave height

As expected it is found that Methods 1 and 2 (see

Table 1), in general result in a larger reduction in wave

pressure than Method 3 Method 1 and Method 2

imply that the operational restrictions are perfectly

satisfied by proper action adopted by the shipmaster

and the wave climate forecast available is absolutely

correct It is also found that the long term predictions

at exceedance probability of 10−8based on Method 1

were very close to Method 2 independent of the wave

scatter diagram applied Moreover it is found that the

characteristic extreme values of wave pressure can

be reduced significantly when the limiting significant

wave height is less than Hs= 12 m for the VLCC and

bulk carrier compared with those using the full scatter

diagram In case of Hs= 14 m, the extreme values

from Method 1 and Method 2 agree very well with

those extreme values without consideration of heavy

weather avoidance

However due to the uncertainty in the forecast

and shipmaster’s decision, the ship can not avoid those

severe sea states with Hs> Hslimabsolutely The sea

states experienced by passing ship are expected to have

a smaller probability in the upper tail as compared

with the scatter diagrams issued by the classification

societies and meteorological data Method 3 is

estab-lished to account for this fact with a reduction factor of

α = 0.1 to reduce the tail above the limiting significant

wave height Compared to Method 1 and Method 2,

Method 3 yields much higher extreme values at

lim-iting significant wave height of 8 m and 10 m If the

sea states with significant wave height above 8 m are

avoided, the 10−8predictions of wave pressure at

var-ious locations along the midship transverse section

are approximately 90% of the values using the full

scatter diagram for both vessels independent of wave

scatter diagrams adopted The factorα in Method 3 is

expected to have an important influence on the extreme

values

5 CONCLUSIONSThe effect of the avoidance of heavy weather on thewave pressure along the midship transverse section hasbeen assessed in this paper The hydrodynamic analy-sis of the wave pressure with various roll damping hasbeen run by WASIM with linear analysis option Theheavy weather avoidance is accounted for by modify-ing the wave scatter diagram according to the limitingsignificant wave height

It is found that the roll damping is of significantimportance for the long term prediction values of wavepressures along the midship transverse section of bothVLCC and bulk carrier, especially for the area betweenthe bilge and the centre bottom The extreme value ofwave pressure at the centre bottom is not affected bythe roll damping

Compared with OCEANOR wave data, which arebelieved to describe the real wave condition on sea,the IACS wave data usually yields lower extreme val-ues of wave pressures along the midship transversesection, which indicate to some extent that the IACSwave data has implicitly included the effect of heavyweather avoidance

The influence of heavy weather avoidance on theextreme values of wave pressure along the midshiptransverse section is dependent on how the heavyweather avoidance is accounted for For both Method 1and Method 2, the sea states above the Hslim areassumed to be absolutely avoided As expected,Method 1 and Method 2 can effectively reduce theresponse when Hslim is less than 12 m Method 3accounts for that the vessel can not completely avoidthe heavy weather In this case, if the sea states withsignificant wave height above 8 m are avoided, the

10−8 predictions of wave pressures along the

mid-ship transverse section are approximately 90% of thevalues using the full scatter diagram The reduc-tion factor α in Method 3 is expected to have an

important influence on the characteristic extremevalues

ACKNOWLEDGMENTSThe work has been performed in the scope of theproject MARSTRUCT, Network of Excellence onMarine Structures, (www.mar.ist.utl/marstruct/), whichhas been financed by the EU through the GROWTHProgramme under contract TNE3-CT-20030-506141.The authors wish to give thanks to the support fromthis project The authors acknowledge the finan-cial support from the Research Council of Norway(RCN) through the Centre for Ship and Ocean Struc-tures (CeSOS) The authors also wish to thank FugroOCEANOR for providing the valuable wave climatehindcast data

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effec-tiveness of the bilge keel as an anti-roll device in

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maneuver-ing on the wave induced vertical bendmaneuver-ing moments in ship

structures, Journal of Ship Research, Vol 34: 60–68.

Hogben, N., Dacunha, N.M.C & Oliver, G.F 1986 Global

wave statistics, British Maritime Technology Ltd., Feltham.

IACS 2000 Recommendation, No 34, Standard Wave

Data, International Association of Classification

Soci-eties, http://www.iacs.org.uk/publications.

IACS 2006a Common Structural Rules for double hull oil

tankers, International Association of Classification

Soci-eties, http://www.iacs.org.uk/publications.

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carri-ers, International Association of Classification Societies,

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Moe, E., Holtsmark, G & Storhaug, G 2005 Full scale surements of the wave induced hull girder vibrations of

mea-an ore carrier trading in the North Atlmea-antic, International Conference on Design and Operation of Bulk Carriers.

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Analysis and Design of Marine Structures – Guedes Soares & Das (eds)

© 2009 Taylor & Francis Group, London, ISBN 978-0-415-54934-9

Comparison of experimental and numerical sloshing loads

in partially filled tanks

S Brizzolara, L Savio & M Viviani

Department of Naval Architecture and Marine Engineering, University of Genoa, Italy

Y Chen & P Temarel

Ship Science, School of Engineering Sciences, University of Southampton, UK

N Couty & S Hoflack

Principia, France

L Diebold & N Moirod

Bureau Veritas, France

A Souto Iglesias

Naval Architecture Department (ETSIN), Technical University of Madrid (UPM), Spain

ABSTRACT: Sloshing phenomenon consists in the movement of liquids inside partially filled tanks, whichgenerates dynamic loads on the tank structure Resulting impact pressures are of great importance in assessingstructural strength, and their correct evaluation still represents a challenge for the designer due to the highnonlinearities involved, with complex free surface deformations, violent impact phenomena and influence of airtrapping In the present paper a set of two-dimensional cases for which experimental results are available areconsidered to assess merits and shortcomings of different numerical methods for sloshing evaluation, namely twocommercial RANS solvers (FLOW-3D and LS-DYNA), and two own developed methods (Smoothed ParticleHydrodynamics and RANS) Impact pressures at different critical locations and global moment induced by watermotion for a partially filled tank with rectangular section having a rolling motion have been evaluated and resultsare compared with experiments

1 INTRODUCTION

The sloshing phenomenon is a highly nonlinear

movement of liquids inside partially filled tanks with

oscillatory motions This liquid movement

gener-ates dynamic loads on the tank structure and thus

becomes a problem of relative importance in the

design of marine structures in general and an

espe-cially important problem in some particular cases

(Tveitnes et al 2004)

In some cases, this water movement is used for

dampening ship motions (passive anti-roll tanks),

especially for vessels with low service speed

(fish-ing vessels, supply vessels, oceanographic and

re-search ships, etc.) and for which active fin stabilizers

would not produce a significant effect (Lloyd

1989)

The sloshing problem has been to a great extent

investigated in the last 50 years, with increasing levels

of accuracy and computational efforts

First attempts were based on mechanical models

of the phenomenon by adjusting terms in the monic equation of motion (Graham & Rodriguez 1952,Lewison 1976) These types of techniques are usedwhen time-efficient and not very accurate results areneeded (Aliabadi et al 2003)

har-The second series of investigations solves a tial flow problem with a very sophisticated treatment

poten-of the free-surface boundary conditions (Faltinsen

et al 2005) that extends the classical linear wavetheory by performing a multimodal analysis of thefree-surface behavior This approach is very timeefficient and accurate for specific applications but

it does not allow to model overturning waves andmay present problems when generic geometries and/orbaffled tanks are considered

The third group of methods solves the nonlinearshallow water equations (Stoker 1957) with the use ofdifferent techniques (Lee et al 2002, Verhagen & VanWijngaarden 1965)

The fourth group of techniques used to deal with

highly nonlinear free-surface problems is aimed at

solving numerically the incompressible Navier—Stokes

equations Frandsen (2004) solves the nonlinear

poten-tial flow problem with a finite difference method in

a 2-D tank that is subjected to horizontal and

verti-cal motion, with very good results, but this approach

suffers from similar shortcomings to the multimodal

method Celebi and Akyildiz (2002) solve the

com-plete problem by using a finite difference scheme

and a VOF formulation for tracking the free-surface

Sames et al (2002) present results carried out with

a commercial finite volume VOF method applied to

both rectangular and cylindrical tanks Schellin et al

(2007) present coupled ship/sloshing motions with

very promising results

In general, numerical techniques present

signif-icant problems when considering highly nonlinear

waves and/or overturning waves, the effect of air

cushions and fluid-structure interactions Considering

the first problem, Smoothed Particle

Hydrodynam-ics (SPH) meshless method appears as a promising

alternative to standard grid based techniques because

of their intrinsic capability to capture surface

defor-mations Literature about SPH applications to typical

marine problems is not very abundant; in Colagrossi

et al 2003 one of the first applications is shown In

successive years, a certain number of applications

devoted to the assessment of slamming phenomenon

(Oger et al 2006, Viviani et al 2007a, b 2008) are

found Sloshing phenomenon is considered by Souto

Iglesias et al 2006 and Delorme et al 2008b, in which

a comprehensive series of calculations is performed,

focusing attention on resulting global moment and its

dependence with tank oscillating frequency, but

prob-lems related to the evaluation of local impact pressures

are still considerable, with presence of significantly

oscillating results

The activity described in the present paper, which

was carried out in the framework of the EU funded

MARSTRUCT Network of Excellence, covered three

two-dimensional (or infinite length) cases, focusing

on impact pressures and global moments into a

par-tially filled tank with rectangular section, which has an

oscillatory rolling motion with different periods and

different water levels For these tests, experimental

measurements were carried out by the Model Basin

Research Group (CEHINAV) of the Naval Architecutre

Department (ETSIN) of the Technical University of

Madrid (UPM), in the context of a comprehensive

analysis of sloshing phenomenon, as reported by

Delorme et al (2007 and 2008a)

A series of numerical techniques has been applied

by various participants to assess their merits and

short-comings, and in particular:

– a RANS code own-developed by UoS (University

of Southampton)

– two available commercial software for the solution

of RANS equations, namely FLOW-3D applied by

BV (Bureau Veritas) and LS-DYNA applied by PRI(Principia)

– a SPH code own developed by DINAV (University

of Genoa)

2 EXPERIMENTAL SET-UPThe experimental tests which are used for benchmark-ing the various numerical techniques were performed

by CEHINAV-ETSIN-UPM, as reported in Delorme

et al 2007 and 2008a

In particular, a rectangular tank having dimensions(in centimeters) reported in Fig 1 was considered Thetank is cylindrical, and the dimension perpendicular tothose reported in Fig 1 is 62 mm; a sinusoidal rollingmotion has been imposed during experiments, with arolling axis located 18.4 cm over the bottom line, anamplitude of 4◦in all cases and different periods.

The tank was fitted for a series of sensors in ferent locations, as indicated in Fig 1 During exper-iments, pressures in correspondence to the two mostcritical positions were recorded The sensors areBTE6000—Flush Mount, with a 500 mbar range

dif-In parallel to pressure measurements, global torquemeasurement were conducted In particular, torquetime history was measured during experiments withwater inside the tank and with empty tank, then thefirst harmonic of the moment response of the liquidwith respect to the tank rotating centre for every casewas obtained postprocessing data

In table 1, the two water levels considered in presentanalysis are reported, together with the correspondentnatural period of oscillation

Figure 1 Tank geometry and position of the sensors Table 1 Water levels considered.

Table 2 Test Cases description.

For both water levels, experiments carried out in

correspondence to the resonance period have been

considered (case 1 and 3 for level A and B

respec-tively), to have large free surface deformation and

analyse codes’ capability to capture it Moreover, for

case B a lower oscillating period (90% of the

reso-nance one) has been analysed (case 2), in which a

marked beating phenomenon has been observed

In table 2, main characteristics of cases analysed

are briefly summarized for a better understanding

In correspondence to case 1, pressure sensors are

located at positions 1 and 6, and impacts were recorded

on sides in correspondence to lower sensor, as

pre-sented in following Fig 2

In correspondence to cases 2 and 3, pressure

sen-sors were located at positions 3 and 6; as anticipated,

case 2 is interesting for the presence of beating type

kinematics and pressures, with peak values

oscillat-ing, as presented in following Fig 3 for sensor 6

Regarding case 3, pressure peaks were recorded in

correspondence to both locations as reported in Fig 4,

with impact events at the tank top (sensor 3) and

pres-sure rises due to the incoming wave and to water fall

after impact at sensor 6

In addition to pressure measurement, in

follow-ing table 3 the resultfollow-ing first harmonic of the liquid

moment is reported

In particular, M0 is the first harmonic amplitude

and φ is the phase lag with respect to oscillating

motion, resulting in equation (1) for time history,

considering the motion period T:

25 20 15 10 5 0

Rolling motion during experiments was a pure soidal motion apart at the very beginning of the exper-iment to avoid infinite accelerations

sinu-Finally, a proper uncertainty analysis has not beenconducted yet since it is hard to find a consistentapproach to it in this case This is due to the strongchaotic character of the pressure peaks, as discussed

in Delorme et al 2008, where the initial steps to suchanalysis were given

3 DESCRIPTION OF METHODSMethods used for modeling the sloshing phenomenonare summarized in Tables 4 and 5 for test case 1 and