Lande Andrade, S. 2016

147 Pages·2016·6.14 MB·English

Master’s degree thesis

IP501909 MSc thesis, discipline oriented master

Parametric Structural Analysis for a Platform Supply
Vessel at Preliminary Design Phase – A Sensitivity
Study via Design of Experiments

1103/Sthéfano Lande Andrade

Number of pages including this page: 147

Aalesund, 03/06/2016
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ECTS credits: 120

Supervisor: Henrique Murilo Gaspar / co-supervisor: Sören Ehlers

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Date: 03/06/2016

Master Thesis 2016
For
STUD.TECHN. Sthéfano Lande Andrade

Parametric Structural Analysis for a Platform Supply Vessel at Preliminary Design
Phase – A Sensitivity Study via Design of Experiments

The offshore market has been severely affected by the sudden drop in oil prices, affecting the
support vessels industry. This challenged both shipyards and ship designers to find possible
solutions that will raise their competitiveness, as structural optimization.

The objective of the project is to create a method capable of performing a sensitivity analysis
focusing on the structural optimization of Offshore Support Vessels from the PX family. The
sensitivity analysis will be performed according to requirements defined by Ulstein.

Master Thesis’ project plan:
 Develop a structural Optimization Routine;
o Optimization Model based on design of experiments;
o Structural Analysis to be performed with FEM capable software (Ansys);
 Apply routine to a simple case;
o Loaded stiffened plate;
o Different topology configurations;
 Create Finite Element models of PSV;
o Parametric Model;
o Define a representative model (section vs entire vessel);
 Run the routine on the model.

Optimization results:
 Propose effective solutions to minimize mass according to the requirements.

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Supervisor - Henrique Murilo Gaspar (NTNU)
Co-Supervisor - Sören Ehlers (TUHH)

Finish: 3rd June 2016
Supervisor Signature:
Henrique Murilo Gaspar

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Abstract

Parametric structural design analysis is a promising alternative to diminish the hull’s structural
mass, resulting in a vessel with higher payload capacity as well as lower construction and
maintenance costs. The challenge of investigating a large space of alternatives, e.g. testing
topology and materials, is caused by the high amount of engineering time required to model,
analyse and evaluate each of the possible configurations. The objective of this paper is to
demonstrate the application of a structural sensitivity study for a parametrically model global
structure of a platform supply vessel, focused on mass reduction during the preliminary design
phase. The methodology starts with the CAD/FEM creation of a parametric model,
representing the vessel’s middle sectional region. The focus on early design stages allows for
simplifications in the structural model, gaining computational time when bypassing local
details that would require finer mesh, which is not desirable for any kind of fast analyses
procedures. Strength analyses are performed, following procedure of design of experiments
methodology, which serves as a tool to understand mass efficiency based on the initially
defined variables. The method gathers knowledge on impact of variables on various combined
responses, and these are used to map the most efficient parameters and determine a viable
solution space that better material usage in comparison to the original design.
Keywords: Parametric Model; Structural Sensitivity Analysis; Response Surface
Methodology.

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Acknowledgements

Primarily, I would like to thank my family, who always backed me up in my decisions. They
encourage me to go beyond and to not doubt myself. Their continuous support and care has
always been unparalleled.
I also must thank my friends who were always present to help me in times of need and to
commemorate accomplishments together.
I must express my gratitude towards my supervisor, Henrique Gaspar. Beyond supervising,
correcting and providing information for the thesis, he showed trust in my capabilities, helped
me develop new skills, aided at moments of need and pushed me always do better.
Sören Ehlers, my co-supervisor, provided a large amount of knowledge towards ship structural
design and software based finite elements analysis, always with utmost patience. Moreover,
during the initial stages of my thesis, Sören offered me the opportunity to study these topics
directly at TUHH.
I would like to thank Ulrikke Brandt and Ulstein, who provided technical knowledge about
PSV’s structural design and helped me outline the boundaries of the case.

Candidate Signature:
Sthéfano Lande Andrade

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Table of Contents
List of figures ........................................................................................................................ xi
List of tables ........................................................................................................................ xiv
Abbreviations ...................................................................................................................... xvi
1 Introduction ........................................................................................................................ 1
1.1 Project background ...................................................................................................... 1
1.2 Research Question ....................................................................................................... 2
1.3 Literature Review ........................................................................................................ 3
1.4 Thesis Scope ................................................................................................................ 4
2 Structural Design of Platform Supply Vessels at Early Design Stages ............................. 7
2.1 Conceptual Structural Design...................................................................................... 7
2.1.1 Global Loads ........................................................................................................ 8
2.1.2 Longitudinal Strength .......................................................................................... 9
2.1.3 Finite Elements applied to Ship’s Structural Design ......................................... 11
2.2 Platform Supply Vessel ............................................................................................. 14
2.3 Structural Optimization ............................................................................................. 15
2.3.1 Optimization of Shape ....................................................................................... 15
2.3.2 Optimization of Topology.................................................................................. 15
2.3.3 Optimization of Dimensioning .......................................................................... 16
3 Experimentation and Sensitivity Analysis ....................................................................... 17
3.1 Design of Experiments .............................................................................................. 18
3.2 Introduction to Response Surface Method ................................................................ 21
4 Methodology .................................................................................................................... 25
4.1 FE Model Creation Guidelines .................................................................................. 27
4.2 Design of Experiments applied to simulations .......................................................... 34
4.2.1 Central Composite Design ................................................................................. 35
4.2.2 D-Optimal Overdetermined. .............................................................................. 36
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