Structural optimization of AMELS LE luxury yachts

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Structural Optimization of AMELS Limited

Edition Luxury Yachts

A comparison of the optimal transverse, longitudinal and hybrid constructed mid-ship section, with respect to production costs, mass and interior space, from the

AMELS Limited Edition luxury yachts.

Sita Verburg January 2014 SDPO.14.001.m

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Thesis for the degree of MSc in Marine Technology in the specialization of Ship Design

Structural optimization of AMELS LE

luxury yachts

By

Sijke Anita Verburg

Performed at

AMELS Holland B.V.

This thesis (SDPO.14.001.m) is classified as confidential in accordance with the general conditions for projects performed by the TUDelft.

January 10th₂₀₁₄

Company supervisors

Responsible supervisor: Maarten Slegers

E-mail: m.slegers@amels-holland.com

Daily Supervisor(s): Leen Koole, Pieter Korevaar

E-mail: l.koole@amels-holland.com, p.korevaar@amels-holland.com Thesis exam committee

Chair/Responsible Professor: Prof. Ir. J.J. Hopman

Staff Member: X. Jiang

Staff Member: Dr. Ir. R. Hekkenberg Company Member: Ir. M. Slegers

Author Details

Studynumber: 1307347

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Abstract

At AMELS, a yacht design and building company in the Netherlands, there is a desire to get a complete and systematic overview of the preferable construction method of the yachts with respect to production costs, mass and inside space over the complete range of ship sizes. The current ‘Limited Edition’ luxury yachts vary in stiffening method and stiffener spacing, or are almost identical for different ship sizes. This research is meant to shed some light on the optimal structural design.

In order to make an even comparison of the ship’s construction costs, mass, and available interior space for the owner, a simplified basic mid-ship section will be applied for all ship sizes. The mid-ship section is based on the mid-ship sections of the AMELS Limited Edition luxury yachts. Together with the length of the ship, basic dimensions such as the breadth, depth and deck height will be adjusted. A large number of models, with three different construction methods, longitudinal, transverse and hybrid stiffening, three different stiffener spacings (500, 600 and 700 mm) and three ship sizes (50, 67.5 and 85 m) have been created and analyzed.

The main variables are plate thickness, scantlings and spacing of longitudinal members and scantlings and spacing of transversal members for every chosen ship size and construction method. The class rules from Lloyds Register for Special Service Crafts are applied.

The comparison of the models show a decreasing trend for the production cost versus stiffener spacing, an increasing trend in the mass versus stiffener spacing and a rather undetermined trend for the clear height versus stiffener spacing. These trends are the same for all investigated ship sizes. Per ship size, the production costs, mass, and clear height are normalized, to allow for the use of coefficients.

For choosing the optimal design, weighting factors have been set. The production costs have a weighting factor of 0.25, the mass a factor of 0.375 and the clear height also has a factor of 0.375. These numbers are chosen because at AMELS, the building of the hulls is outsourced to shipyards in Eastern Europe, where they calculate the production cost in euro per tons. Therefore, the production costs are currently a little less important. For Dutch shipyards that do build the hulls in the Netherlands, the weighting factors are estimated as follows: production costs have a weighting factor of 0.5, the mass a factor of 0.25 and the height also a factor of 0.25. The production costs are much more important when the hulls are built in the Netherlands due to the fact that the wages are at present much higher than in Eastern Europe.

The calculation of the optimal design is performed by multiplying the weighting factor with the specific coefficients, for all variations. The resulting objective function is used to rank the models, for which the lower, the better. When taking the AMELS weighting factors into account, for a ship length between 50 and 67.5 m, the longitudinal stiffened method with a spacing of 600 mm and the hybrid framed method with a spacing of 600 mm are equally good. For the larger range of yachts, between 67.5 and 80 m, the longitudinal framed method with a spacing of 600 mm is preferable.

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After applying these results to the natural frequency test and a second optimization cycle with respect to the deck heights, for each ship size a single optimal solution is found:

• For the 50 m model: the hybrid stiffened variation with a 600 mm stiffener spacing • For the 67.5 m model: the longitudinal stiffened variation with a 600 mm stiffener spacing • For the 85 m model: the longitudinal stiffened variation with a 600 mm stiffener spacing In case of the weighting factors for hull building in the Netherlands, a slightly different result is reached: for the ships of 50 and 67.5 m the hybrid stiffened method is preferred, with 600 mm stiffener spacing. The largest yacht, of 85 m, has as longitudinal stiffening as optimal method, with 700 mm stiffener spacing.

Except these standard variations in which the frame distance is three times the stiffener spacing, a small study on frame distance variation has been conducted. Resulting in the conclusion that the frame distance, in most cases, is optimal around 1.8 m.

AMELS can use the results of this study to get a good insight in the drivers of the optimal design. When in the future the building strategy of the company changes, the weighting factors can be adjusted and the results change accordingly.

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Introduction

Nomenclature

Acronym Meaning

B Breadth

BBS Breadth Between Stiffeners BPF Blade Passing Frequency

D Depth

db Double bottom

FEM Finite Element Method

GM Distance between the center of gravity and the metacenter height GRT Gross Register Tonnage

HVAC Heat Ventilation Air Conditioning

L Length

Loa Length over all Lwl Waterline length

ld Lower Deck

LE Limited Editions LR Lloyd’s Register

md Main Deck

SSC Special Service Craft STF Number of Stiffeners

T Draught

tt Tanktop

VCG Vertical Centre of Gravity

wt Water tight

Term Meaning

Ducts Pipes, for example HVAC-ducts Limited Edition Serie of yachts

MAESTRO Structural optimization software modeFRONTIER Optimization software

Scantlings Dimensions of the stiffeners

Spec Specification, refers to the building specification Strake Plate field, often separated by girders, decks or floors. Tween deck Deck between the main deck and the tank top. Lower deck.

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Introduction

This thesis describes the optimization of the construction of super yachts. The yachts that will be optimized are based on the Limited Edition luxury yachts of AMELS.

At the engineering department of AMELS there is a desire to get a complete and systematic overview of the preferable construction method of the yachts with respect to production costs, mass and inside space over the complete range of ship sizes. The three main construction methods will be researched: transversely, longitudinally and hybrid stiffened.

The structure of this thesis follows the design process. In the first part an introduction about super yachts, the problem definition and construction methods is given. Then, in part two, an analysis of the scope of the research, optimization methods and the mid-ship section including loads and production costs is performed.

Part three, the synthesis, combines the gained knowledge in order to make the mid-ship models. The design part, part four, contains apart from the realization of the models, also the consequences of structural choices in the design. Furthermore, a consideration of the different objectives is made. In the

evaluation the validity of the model and the results are checked. Apart from that, some

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Introduction

Part 1. Introduction

The introduction is not only intended as an introduction into the research problem, but also to give some background information for people who are unfamiliar with the super yacht industry, AMELS or the construction of ships in general.

In chapter 1 an introduction about super yachts and the company, AMELS, is given. The second chapter contains the design brief, with the problem statement, the research questions and the research method. Chapter 3 explains the basics of ship construction.

1 AMELS Limited Edition luxury yachts

1.1 Super yachts

A super yacht is a very luxurious, expensive, and often privately owned yacht with a professional crew. It can be either a sailing or a motor yacht. At the moment, the world wide super yacht fleet exists of 3.572 yachts between 24 and 200 meter, and another 225 super yachts are under construction.1_{From the} fleet, over 400 yachts are available for chartering and around 650 are for sale.

Super yacht owners have very different backgrounds, from movie stars or fashion designers, to royalties, successful business people and professional athletes. They have one thing in common, all are very wealthy.

Figure 1. AMELS LE 180; Step One

When a client decides to buy a yacht, and already has an idea about a yard or specific ship, the connected broker is contacted. The broker will form together with the future captain, the ‘owner’s representative’ and a few others the ‘client team’. The client does most of the negotiations with the shipyard about the progress of the yacht. The owner’s representatives represent the interests of the owner towards the designers and the shipyard.

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Introduction

Figure 2. AMELS LE 171; Bel Abri

Apart from the yacht itself the accompanying “toys” are very important. In Figure 2 some RIBs can be seen. Furthermore, jet-skis, sea-bobs, a mini submarine and a helicopter are necessary extras to make the yacht complete.

Figure 3. AMELS; Lady in Blue

1.2 AMELS

AMELS Holland B.V. has established itself as a specialized yacht designer and builder in 1982, after being founded in 1918 in Makkum. Since 1982 AMELS has been building custom yachts in Makkum. In 1991 AMELS became part of the DAMEN SHIPYARD GROUP and with the growing order book, another building location in Vlissingen was established. However, in the years after, a decrease in projects was seen and all AMELS’s activities were moved to Vlissingen.

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Introduction

With becoming part of DAMEN and the relocation to Vlissingen, the ‘Damen Standard’ business model was adopted. Meaning a shift took place from completely custom building to semi-custom building. The hull and technical systems are already determined and designed before the client enters the project. This saves a lot of time on designing, engineering and also on delivery of components. Furthermore, a learning effect takes place; problems that occur during building can be adapted for the next vessel of a series. This makes the quality rise and the price decrease. This method is called the “proven platform”, at AMELS these series are called “Limited Editions” (LE). The different series are named after the length in foot. For example, the LE 180.

The initial design for a new series is made at the design department. The engineering department uses the initial design to make a detailed design. The building of the hulls is often outsourced to a Romanian or Polish shipyard. From there the hulls are shipped to the site in Vlissingen as can be seen in Figure 5. Here, the further assembly takes place, as well as the sea trials and the delivery.

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Introduction

2 Design brief

In paragraph 2.1 the problem is defined, after which the research questions that result from the problem definition are described in paragraph 2.2. In paragraph 2.3 the applied method will be discussed.

2.1 Problem definition

Currently AMELS offers five types of Limited Editions. The structural design of a Limited Edition is either made by AMELS employees, by a subcontractor, or is based on a previous design. This has led to a variation of structural solutions.

The cross sections off all Limited Editions are depicted in this paragraph (from the smallest to the biggest), in order to deduct the similarities and differences in the structural design.

Figure 6. AMELS LE 180 cross section

The AMELS LE 180 is the smallest limited edition; it has a waterline length of 49.6 m. The LE 180 is transversely stiffened with a spacing of 500 mm. It is based on the AMELS 171, which has the same cross section. The left side of the picture shows a normal frame, the right side a web frame.

Figure 7. AMELS LE 199 cross section

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Introduction

mm. This cross section differs from the others with respect to non-uniformity of the stiffeners in the sides. There is an extremely large difference in the dimensions of the stiffeners above the tanktop deck and the stiffeners above the lower deck.

The LE 199 has an overall length of 60 m, and a waterline length of 59.7 m. The bow is, therefore, almost vertical.

Figure 8. AMELS LE 212 and 242 cross section

The AMELS LE 212 and the LE 242 have the same general stiffening properties and the same cross section. They are hybrid framed with longitudinal stiffening at 500 mm in the decks and transverse stiffening in the sides, also at 500 mm. The tanktop is transverse stiffened at 500 mm, as well as the part of the lowerdeck which is located behind the engine room. Furthermore, these yachts do not have one specific framing method in the lowerdeck. This is due to the fact that there are many local objects that need space or cut out a part of the hull (for example the numerous doors).

The LE 212 has a waterline length of 59.3 m, while the LE 242 with a waterline length of 67.2 m, 7.9 m longer is.

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Introduction

The AMELS LE 272 is longitudinal framed with a stiffener spacing of 500 mm in the bottom, the decks, and the side shell up to the lower deck. Above the lower deck the stiffener spacing in the side is 400 mm. The LE 272 has a waterline length of 76.7 m.

Between the five Limited Editions are a few similarities to name, for example: • Four out of five yachts have a stiffener spacing of 500 mm

• The LE 212 and the LE 242 are in general the same The differences are, for example:

• All three stiffening methods are applied

• The ration between the dimensions of the web frames on the tanktop deck and the lower deck • Number of struts (often placed around a staircase)

For the stiffening methods a trend can be found with regard to ship length: the two smallest yachts are transversely stiffened, the 212 and 242 are hybrid stiffened and the longest yacht is longitudinal stiffened.

The goal of this research is to make a complete and systematic overview of the preferable construction method of the yachts with respect to production costs, mass and available living space over the complete range of ship sizes.

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Introduction

2.2 Research questions

The problem stated in the previous section leads to the following research question:

What are the relations between production costs, mass and available space for different sizes of the AMELS LE, for an optimized transverse, longitudinal and hybrid constructed slice of approximately 9 meters long?

The main research question is divided into eight smaller questions: • What are the constraints of the project?

• Is there a mid-ship section that is applicable for most AMELS LE luxury yachts and how can it be scaled?

• How should the production costs be defined?

• What are the most important and critical classification rules?

• For minimizing space between ceiling and deck, should the piping be routed through or underneath the girders?

• Which optimization method and which software suit the problem best?

• What are the optimal deck thicknesses, stiffener spacings, frame spacings and scantlings for a transverse, longitudinal and hybrid constructed slice of approximately 9 meters long for certain ship sizes, while optimizing the box dimensions, weight and production costs?

• Would it be possible to reduce the depth of the ship if the box dimensions are higher than specified, and would that reduce the production costs and steel weight further?

2.3 Method

In order to make an even comparison of the ship’s construction costs, mass, and available interior space for the owner, a simplified basic mid-ship section will be applied for all ship sizes. With the length of the ship, basic dimensions such as the breadth, depth and deck height of the mid ship section will be adjusted. The space available for the interior should be as large as possible, since this is what the future owner will use. On both sides of the mid ship section a watertight bulkhead is placed. The mid-ship section will be designed and compared in 3 ways: with a transverse, a longitudinal and a hybrid framing system.

In order to gain a good insight in the required height of the structural parts above the interior ceiling, a comparative optimization of a deck structure with pipes underneath and through the girders will be performed. This will be done in both MAESTRO and modeFRONTIER, both optimization software packages, so that at the same time a comparison of the optimization software is made and the most suitable software will be used for the optimization of the mid-ship section.

The loads, to which the ship is subjected to, are determined by the classification rules of Lloyds Register for Special Service Crafts (SSC Rules). Other loads, like for example, the still water bending moment, are deducted from the current Limited Editions. These loads will formula wise be implemented in Excel, because an integration of SSC in the model will not be possible. Other class criteria with regard to strength, practical matters, noise and vibrations will be modeled as constraints.

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Introduction

The optimization objectives are cost and mass reduction, and increase of the interior space. The main variables are plate thickness, scantlings and spacing of longitudinal members and scantlings and spacing of transversal members for every chosen ship length and construction method. For the standard variations a fixed frame distance of three times the stiffener distance will be used, for a small selection of variations the influence of the frame distance will be investigated.

The desired result of this research will be a series of graphs in which it can be easily seen for which length, transverse, longitudinal and hybrid framing has the least production costs, mass and the most height.

In order to gain a large space inside the ship, with the smallest depth possible, the deck heights of the models will be evaluated, and if needed adjusted.

A schematic overview of the research method is given in Table 1.

Table 1. Research design

Input Processing Examples of desired output

Data from the AMELS Limited Editions

Objectives

• Cost reduction • Box increase • Mass reduction Scaled basic mid-ship

section • Transverse • Longitudinal • Hybrid Criteria • Strength • Classification rules • Noise / vibrations Special Service Craft

Rules by Lloyd’s Register

Variables • Distances between stiffeners • Plate thicknesses • Stiffener /frame / girder dimensions Locations of the wt bulkheads

Several ship lengths Method

• Optimization • Strength

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Introduction

3 Construction of ships

The structure and the shell of a ship is an essential part to provide the necessary strength and to keep the water outside. Different construction methods have different influences on the overall design. At first the basic principles and calculations of the construction are explained. In paragraph 3.2 it will be discussed how a structural design is realized. In paragraph 3.3 the different framing methods are considered, and in paragraph 3.4 the specific structural design problems for super yachts are discussed. Finally, paragraph 3.5 describes the consequences of certain structural solutions on the overall design. 3.1 Basic principles and calculations

The hull structure of a ship is constantly subjected to a variety of loads, stresses and strains caused by forces from within and outside the ship. For yachts, the internal forces vary less than for merchant ships and are mainly caused by the mass of the structure, the machinery and operating the machinery. The plating of the hull is supported by stiffeners in order to be able to resist the loadings on the structure. Beams are the secondary stiffeners for the decks and frames are the secondary stiffeners for the shell and bottom. While webframes and girders are respectively the primary stiffeners for the sideshell, bottom and decks.

The ships structure will experience three kinds of basic deformation when subjected to simple hydrostatic loads2_:

• Hull girder bending – bending of the whole ship, as a result of the difference in buoyancy caused by the wave pattern and the ships own loading

• Deformation of panels between bulkheads and between the frames – induced by the hydrostatic pressure

• Shell plate bending between adjacent transverse and longitudinal stiffeners – also induced by the hydrostatic pressure

In this paragraph several important loads that the ships structure should be able to withstand are explained.

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Introduction

3.1.1 Bending moment / longitudinal strength

The wave bending moments that work on the ship are calculated by empirical formulas in SSC Rules. The wave bending moments (hogging and sagging, see Figure 10) together with the still water bending moment make the rule bending moments.

The stresses caused by the bending moments are the largest in the material which is the furthest away from the neutral axis, the deck and the bottom. By calculating the inertia moments of all parts in the cross section that contribute to the longitudinal strength, the moment of

inertia of the section can be found, as well as the section modulus. The section modulus follows from the moment of inertia by this formula: . With I being the moment of inertia, and z the distance from the material to the neutral axis.

The maximum stresses, σmax, that will occur can be calculated using:

∙

. In which M is the bending moment according the Rules. The maximum stress should not exceed the allowable maximum stress.

Besides the bending moments the buoyancy and structural forces also cause shear forces to act on the structure.

3.1.2 Local forces

The local forces acting on the structure are, from the outside of the structure the water pressure, and, from the inside of the structure, foundations for the superstructure, equipment or cargo.

3.1.3 Noise and vibrations

Especially for yachts and cruise ships there are strict limits on noise and vibrations. Noise and vibrations are caused by excitation sources like engines, propellers and encountering waves hitting (parts of) the structure in their natural frequency, which causes these parts to vibrate. When the frequency is high enough this causes noise, and when the frequency is lower this can cause damage because of the shaking or an uncomfortable feeling. It is even possible that the structural design of yachts can be driven by stiffness requirements rather than strength requirements.3

3_{Roy, J., Munro, B., Walley, S., Meredith-Hardy, A., (2009): Longitudinal vs Tranversely framed structures for large displacement}

motor yachts.

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Introduction

3.2 Structural design

When a new ship is designed, at first a concept design is made. In this stage the structural design is often not taken into account at all. At the moment that the basic design cycle is started the structural design is

also taken up.

When making a structural design it is very common to first decide on the framing system (longitudinal, transversal or hybrid, see paragraph 3.3) and then choose a distance between the frames. This is mostly done on experience. An overview of the structural design methodology is given in Figure 11. The next step is to include the mid-ship cross section and comply it with the rules for local loads. At AMELS, all yachts have to comply with the Lloyds Rules for Special Service Crafts. The computer program SSC is used to design the scantlings according to the rules. Some practical constraints are already included in this program, it gives for example a database with profiles that are common to use.

After that, the scantlings will be checked for the global loads and increased if they are not sufficient. At AMELS, the current structure will be drawn in Nupas, from which the weight of the sections will be deducted.

In shipbuilding often a previous design is used as starting point for a new design, this makes that it is not unusual that the first two steps are skipped.

3.3 Longitudinal, transverse and hybrid framed structures

The directions, in which the secondary stiffeners are aligned, determine if the ship is longitudinally or transversely supported. A combination of longitudinal and transverse supports is called a hybrid framed structure. An example of a transverse and a longitudinal framed structure can be seen in Figure 12. Most often a hybrid structure has longitudinals in the double bottom and underneath the deck(s), while the side shell is transverse supported.

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Introduction

Figure 12. Framing methods; transverse left, longitudinal right5.

When the SSC Rule length of a yacht is less than 50 m the longitudinal strength will not be examined, because the global strength will be sufficient when the scantlings are calculated according the local strength.4

The transition between transverse and longitudinal framed structures occurs between 50 and 90 meter yachts.5_{The study conducted by Roy et al (2009) on an 80 m yacht concludes that longitudinally framed} structures are lighter, require less welding length and have fewer parts then transverse framed

structures. Also from a vibration perspective and practical construction point of view, longitudinally framed structures are preferred over transverse framed structures for this specific 80 m yacht. A hybrid structure however, would be a good compromise for yachts of this size. It has to be noted that in this study the structures were not optimized; only 3 versions were calculated.

In Figure 13 a picture of a transversely framed AMELS LE yacht is shown.

4_{Malinowski, W., Blanchard, T., (2009): Structural Plan Appraisal of Large Yachts.}

5_{Roy, J., Munro, B., Walley, S., Meredith-Hardy, A., (2009): Longitudinal vs Tranversely framed structures for large displacement}

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Introduction

Figure 13. Example of an AMELS LE under construction

3.4 Design considerations for super yachts

With regard to super yachts, the main design consideration is luxury. Luxury is difficult to define since it is very personal, however most people agree on the following general definition: the state of great comfort and extravagant living. In order to reach this state of comfort and allow for the extravagant living, space, quietness, entertaining systems, interior, exterior and ‘toys’ are essential.

The demands on space and quietness are often the most challenging since they conflict with the other requirements named above and the basic demands on a ship, being; ability of sailing and keeping an intact platform to carry the luxury (hull structure). In order to sail, the ship is equipped with engines and propellers, which are the most noise and vibration generating machinery on board. The available space is in the first place bounded by the dimensions of the ship, and secondly on the dimensions of the structural parts of the ship.

The client is only interested in the luxury; therefore the available space within the hull should be as large as possible. The quality of the finishing of the yacht is of vital importance too. Everything should look perfect and therefore the fairness of the hull, the superstructure and the decks is one of the main focus points. Any unfairness left in the steel has to be smoothed by stretching the plates or by applying filler; both methods require a large amount of man-hours.

For the client the mass of the ship is not of importance. Off course the mass has influence on the required power to reach the design speed, but for most super yacht owners the fuel consumption of the yacht is not interesting.

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Introduction

3.5 Design consequences of construction choices

Every construction method has consequences on the final design. The secondary stiffener spacing can have a significant effect on the initial deformations of the yacht. With an increasing distance between the stiffeners the deformations will be (and are also allowed to be) larger. One of the biggest problems in the structural design, are the brackets that inevitably collide with the luxury area. This problem occurs in all framing methods.

3.5.1 Longitudinal

When longitudinal stiffeners are applied the web frames tend to be relatively large. This either makes the indoor space smaller, or the rooms need to be strategically placed with interior walls on the same line as the web frames. Web frames surrounding windows could be used to create a cozy ‘sit-in-window frame’.

Most piping in the sides of the yacht is routed horizontally, therefore, the amount of penetrations are very small in a longitudinal stiffening method.

The fairness of the yacht is very good when longitudinal stiffeners are applied, because the spacings are less, the deformations will be small.

3.5.2 Transverse

Since both the stiffeners and the web frames are transversely applied, there is a lot of space for the vertical routing of cables and ducts. Furthermore, at some points the frames have the same height as the secondary stiffeners, this ensures that best use of the available space.

3.5.3 Hybrid

Hybrid framing is believed to combine the best of longitudinal and transverse framing: material where you need it. The combination however, could lead to a fairness problem because of the different shrink directions.

It has the advantage of transverse stiffeners and frames in the side which gives excellent vertical routing opportunities and when the frames and stiffeners have the same dimensions the best use of the

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Analysis

Part 2. Analysis

In the analysis the boundaries of the research project are set, the research method is worked out in detail and all necessary data is gathered.

Chapter 4 defines the scope of the project. In chapter 5 the optimization method and software is chosen and explained. Subsequently, will, in chapter 6, the scalable mid-ship section be defined. From there the loads, where the mid-ship section is subjected to, can be determined. This is explained in chapter 7. And finally the production costs will be discussed in chapter 8.

4 Scope

In order to define the area of interest and the boundaries of this thesis, the important aspects are discussed in this chapter.

Paragraph 4.1 starts off with the consideration of the superstructure. In the second paragraph, the particulars of the mid-ship section are discussed. Paragraph 4.3 will elaborate on the structural

constraints. While the classification rules are considered in paragraph 4.4. Considerations that not have been addressed yet in this chapter, are shortly discussed in paragraph 4.5. Finally a schematic overview of the most important boundaries is given in paragraph 4.6.

4.1 Superstructure

It is assumed that the aluminum superstructure does not contribute to the global strength. Therefore, it is not modeled.

4.2 Mid-ship section

For comparison purposes a scalable mid-ship section will be used. However, some aspects as the head room, deck height, compartment length, double bottom etc. require incremental steps. In this paragraph the boundaries and choices are described. A detailed description of the scalable mid-ship section will be given in chapter 6, and of the final mid-ship models in chapter 9.

AMELS yachts are known for their slender appearance; therefore the depth and breadth of the ship are kept as small as possible without cutting down the internal volume.

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Analysis

4.2.1 Box

The box is the space directly available for the client. It is called a box because it usually has a box shape: the space is bounded between the inner walls, ceiling and floors. All pipes and cables are hidden behind the inner walls and ceiling. In Figure 14, an overview of a frame is given in which the different boxes can be distinguished very well. While Figure 15 shows the definition of a single box.

The clear height (the ceiling height as specified in the building specification) within the box is measured between the decorative floor and the base ceiling. The space between the ceiling and the deck above is filled with ceiling components, structural elements, piping, wiring, etc.

When the required height for these systems will be reduced, the height of the box can be raised. This is either possible by reducing the height of both the secondary stiffeners and the girders, with the other systems running underneath the structure, or by increasing the girder height and decreasing the stiffener height, while the pipes are routed through the girders.

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Analysis

4.2.1.1 Deck and box height

The space between ceiling and floor can differ from deck to deck, and also even on the same deck; for instance between owner space, crew space and function of the room. The clear height is determined in the yacht specification. In the owners accommodation it varies from 210 up to 260 cm. This is due to the fact that either the routing of the cables and pipes is through the stiffeners or underneath. The crew accommodation is often somewhat lower.

When routing through the stiffeners, holes have to be cut, which requires the stiffeners to be larger. However, the total space required for the stiffeners, cables and pipes is often less. In order to create enough space for the HVAC between the secondary stiffeners and the deck girders, the size of the secondary stiffeners will be minimized and the size of the deck girders will be maximized. However, in previous ships build by AMELS the girder depth with cut outs is considerably smaller. Details of these cut outs are shown in Figure 16.

Figure 16. Details of cutouts in girder webs

The depth of the ship increases with length, and with increasing depth it is possible to insert an extra deck. In this project the lower deck will be inserted from a total hull length of 60 m.

Domes are created out of esthetic considerations and for the air conditioning to blow fresh air in the rooms. An example of the domes can be found in Figure 14.

The distance between the lower side of the deck and the top of the floor in the cabins above is 100 mm.

4.2.1.2 Space between box and shell

The insulation on the side shells is approximately 200 mm thick and covers the stiffeners as well. Between the inner walls and the insulation covering the stiffeners there is a cavity of on average 200 mm at half the deck height, this cavity is filled with pipes and electrical wires. In Figure 17 part of a drawing can be seen in which the construction is depicted together with the ceiling, floor and walls, including a window.

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Analysis

4.2.2 Double bottom

For ships with a Rule length less than 50 meter a double bottom is not mandatory. When the Rule length is larger than 50 m, a double bottom has to be fitted in the hull, located between the collision bulkhead and the forward watertight bulkhead for the machinery space. When the Rule length exceeds 61 m the double bottom is also applied outside the machinery space; from the collision bulkhead up to aft peak bulkhead. Finally, when the Rule length exceeds 76 m, the double bottom is to be fitted throughout the whole length of the ship.6

For this comparison the double bottom is considered part of the mid-ship section for all ship sizes. The center girder will be as high as the double bottom. The minimum height of the double bottom of the model is 1100 mm, because of accessibility reasons.

4.2.3 Section length

The watertight bulkheads are taken as boundaries of the mid-ship section. In most cases this is between 8 and 11 meter. For this project a distance of 9 meter is chosen, because that fits both with 500 and 600 mm stiffener spacing. Although 700 mm stiffener spacing will be considered as well, for this spacing a model with the length of 8.4 m will be used.

4.3 Constraints on the structural parts The constraints on structural parts are based on materials, strength and vibration

requirements as well as practical considerations.

4.3.1 Material

For all calculations the material properties of mild steel are applied.

Property Quantity Unit

Youngs modulus E 200 GPa

Yield strength σ 235 MPa

Poisson’s ratio ν 0.3

Table 2. Material properties.

4.3.2 Strength

The maximum allowable stresses are defined in Part 6 Chapter 7 Section 3 of the SSC Rules. Different maxima are used for global and local loads.7

6_{SSC Rules P3 Ch2 S6.6.1-3} 7_{SSC Rules P6 Ch7 S3}

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Analysis

4.3.3 Vibrations and noise

Regarding the vibrations and noise onboard ships we can consider two types: global vibrations in the order of 1 – 10 Hz and local vibrations in the order of 5 – 100 HZ.8 The exciting loads are for instance the propeller, the engines, generators and the wave encounters. Wave excitation frequencies are typically 1 – 2 Hz, the shaft excitation frequencies 4 – 5 Hz and the blade passing frequency of the propeller is between 18 – 27 Hz. The blade passing frequency can be calculated by the ratio of the engine versus propeller speed and the number of blades of the propeller. The natural frequencies of the engines and generators are much higher.

Global vibrations are not considered in this study, since determining the natural frequencies of the whole ship would demand that the whole ship will be modeled and FEM analyzed. This is beyond the scope and time path of this thesis.

For local vibrations all bulkheads, decks and shells, the natural frequencies can be calculated by differential equations. Local plate fields which have a frequency below 10 Hz are considered too low in stiffness and therefore have a too high mobility.9_{Plates should therefore be designed with natural} frequencies of 10 – 18 Hz or higher than 27 Hz.

Floating floors can be ordered in every combination of springs and masses, therefore it is not necessary to put restraints on the natural frequency of plates because of floating floor considerations.

4.3.4 Practical considerations

To minimize the initial deformations due to welding a minimal plate thickness of 4 mm is applied. This is in general higher than the prescribed rule minimum plate thicknesses in the decks and the sideshell, which are listed in appendix A.

The AMELS standard on fairness of plating and construction is more stringent than the SSC Rules and will therefore be applied. The standard prescribes a maximum allowable deformation of: 3∙

.10

Plates made of steel can be straightened in order to reduce the deformations. The dimensions of the scantlings used are rounded to millimeters. For all stiffeners, T-profiles are used. Dimensions of longitudinal stiffeners and plates on the same height do not change between watertight bulkheads (equality constraints), as well as the dimensions of the transverse stiffeners and frames. The bulkheads are modeled, but not optimized.

The frames are placed at every third stiffener, meaning at respectively 1500, 1800 and 2100 mm. For a small number of variations the influence of the frame spacing is investigated by making three variations based on a 600 mm stiffener spacing: 1200 mm, 1800 mm and 2400 mm.

8_{Lloyd’s Register (July 2006): Ship Vibration and Noise – guidance notes.}

9_{Wijnen, J, (12/11/2012): Memo Natural frequency plate vibration AMELS 8300. Damen Research.}

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Analysis

4.4 SSC Rules

The SSC Rules are applicable for yachts that are subjected to the MCA Large Commercial Yacht Code, the limit of this code is 3000 GRT or 12 guests. Yachts that have a higher GRT or more guests are subjected to SOLAS passenger ship rules, these rules have a higher demand on global strength and local loads, which are not accounted for in SSC Rules. Besides more demanding structural rules, SOLAS requires a greater amount of safety equipment. For this research SSC Rules are used.

The specific rules about the loads acting on the yacht are discussed in chapter 7. 4.5 Other considerations

4.5.1 Costs

At the moment the price for having the hull build on a yard is determined by the mass of the hull. The price differs per yacht, and is mainly based on experiences with the previous yacht of a series.

Because of the ‘price per ton’-calculation method, there is no internal data at AMELS about welding length, materials and man-hours. The currency used in this research, will be euros, since most of the ship will be built and bought in Europe.

Chapter 8 will go deeper into the production costs.

4.5.2 VCG

The VCG is not optimized since other systems have a large influence on the total VCG as well, and they cannot be generalized for the range of vessel lengths. For example, large swimming pools or the position and volume of tanks differ from ship to ship. While a lower VCG is not always preferable due to a large GM and associated high accelerations.

4.5.3 Mass

In commercial vessels a reduced weight of the ship itself results in a bigger payload. For yachts however, a reduction of weight could lead to a reduced resistance and therefore fuel savings or a higher speed.

4.5.4 Volume

All volume that is used on construction parts is a loss for the owner of the ship. In this case also the area of the lower decks is important because the amount of crew determines the service level of the vessel.

4.5.5 Filler

The amount of filler that is needed is difficult to predict, since welding deformations can be

straightened, but the insertion of, for example, doors and hawse holes can cause large deformations too. The filler is applied above the waterline until 500 mm below the waterline.

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Analysis

4.6 Schematic overview

In Table 3, a schematic overview of the boundaries, as discussed in this chapter, is given.

Table 3. Boundaries and constraints of the project

Quantity Min Max Unit Comments

Ship length 50 85 m Determined by 3000 GRT limit

Section length 8.4 9 m Length between WTBH, 9 m fits 500 and 600 mm frame spacing, 8.4 m fits 700 mm

Tanktop height 1100 mm

Deckheight 2250 3000 mm

Space between inside wall and stiffeners

200 mm

Minimum plate thickness 4 mm And as defined in SSC Rules Max allowable plate

deformation

3 mm For 500 mm frame spacing (otherwise apply ratio)

Wave excitation frequency 1 2 Hz

Shaft excitation frequency 4 5 Hz AMELS project 8300 (typical) Blade passing frequency 18 27 Hz AMELS project 8300 (typical)

Natural frequency plates 10 Hz Outside excitation frequencies, no limitations regarding floating floors

Material Mild Steel

Superstructure Not contributing to global strength

Allowable stresses As defined in SSC Rules

Global loads As defined in SSC Rules (excl. dynamic loads)

Local loads As defined in SSC Rules

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Analysis

5 Optimization

At first a general introduction on optimization and optimization algorithms is given. Subsequently in the second paragraph the different optimization methods and software are discussed. In paragraph 5.3 the selection of the method and software that is used for this research is explained. Paragraph 5.4 will elaborate on the chosen optimization method and software. Where after, respectively, in paragraph 5.5, 5.6 and 5.7 the design variables, the objective function and the constraints will be discussed.

5.1 Introduction

According to the business dictionary the definition of optimization is:

“Finding an alternative with the most cost effective or highest achievable performance under the given constraints, by maximizing desired factors and minimizing undesired ones. In comparison, maximization means trying to attain the highest or maximum result or outcome without regard to cost or expense. Practice of optimization is restricted by the lack of full information, and the lack of time to evaluate what information is available (see bounded reality for details). In computer simulation (modeling) of business problems, optimization is achieved usually by using linear programming techniques of operations research.” 11

Performing a structural optimization is more than a recalculation of the structure two or three times and choosing the lightest alternative, because in this case not all alternatives are considered. For conducting a real optimization as many parameters as possible need to be varied. Optimization algorithms solve problems by finding a combination of design variables in the design vector which gives the best result for the objective function. The design variables are subjected to constraints.

In formulae, optimization algorithms are structured as follows; 12131415 • Design variable Xi i = 1, 2, …, N • Objective function F(Xi)

• Constraint Cj(Xi) ≤ CMj j = 1, 2, …, M • Side constraint Xi min ≤ Xi ≤ Xi max

As already visible in the above enumeration, there are multiple sorts of constraints:

• Technological constraints (earlier called side constraints) determine the upper and lower bounds of the design variables.

• Geometrical constraints connect design variables in order to create a structure without large discontinuities.

11_{Businessdictionary.com visited at 19-6-2013}

12_{Rigo, P., (2001): A module-oriented tool for optimum design of stiffened structures – Part I}

13_{Sekulski, Z., (2009): Least-weight topology and size optimization of high speed vehicle-passenger catamaran structure by}

genetic algorithm

14_{Caprace, J.D., Bair, F., Rigo, P., (2010): Scantling multi-objective optimization of a LNG carrier}

15_{Augusto, O.B., Kawano, A., (1997): A mixed continuous and discrete nonlinear constrained algorithm for optimizing ship hull}

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Analysis

• Structural constraints contain, among others, the allowable stress and deflection limits in order

to avoid buckling, yielding and cracks.

• Global constraints impose limitations for the ship as a system, for example the center of gravity or total fabrication costs.

5.2 Methods and software

In this paragraph a few different optimization methods and associated software that are used more often in structural optimization research are discussed briefly. Also an overview of the advantages and disadvantages is given. As well as the criteria used for selecting a software.

5.2.1 Linear programming in SHIPOPT and MAESTRO

In 1980 Owen Hughes was one of the first to come with an optimization method for ship structures. The optimization (or redesign as he called it) was achieved by means of a sequence of linear programming solutions.16 Linear programming is basically a mathematical way of allocating resources to activities. Where programming is another word for planning, and does not necessarily need computer

programming. Simple linear programming problems can easily be solved by hand.

In linear programming every function and constraint needs to be linear. In order to do that Hughes applied a linearization based on the first- and second order terms of Taylor expansion in his Sequential Linear Programming. Using a first-order approximation has the disadvantage that when all the

derivatives are small, or when the constraint function has a high curvature, the obtained tangent plane becomes a poor representation of the actual constraint. The second-order derivative gives on the other hand a more accurate result.

The simplex method is a general method of solving linear programming problems. It is based on the geometric representation of the mathematical problem. One can draw a graph with the constraint boundaries. The points were the constraints intersect are the corner point solutions. The corner point solutions that lie in the feasible region are the corner point feasible solutions (CPF). The optimum solution is the CPF that has no adjacent CPF that is better17.

Hughes developed SHIPOPT and MAESTRO (Method for Analysis, Evaluation and STRuctural Optimization). From which MAESTRO is the most sophisticated, as it models directly with FEM. Advantages of linear programming

• Linear programming is fast

• Linear programming is easy understandable Disadvantages of linear programming

• Constraint functions need to be linear and continuous

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Analysis

• Once the objective function and all constraints are completely defined the results will be

inflexible

5.2.2 An algorithm based on convex linearization and a dual approach in LBR-5

The algorithm based on convex linearization and a dual approach is based on linear programming, but has some additional features. The method is called CONLIN and is developed by Fleury.18 In order to reduce the calculation time, the non-linear and implicit functions are replaced by the convex approximation (a linearization in a convex set, an object is convex when for every pair of points in the object, every point on the straight line that connects the pair of points is also within the object). The linearization of the design variables is based on the first term of the Taylor expansion.

By a dual approach it is meant that the primal constrained problem with N unknowns is replaced by an unconstrained problem with M unknowns. This second problem is called the dual problem, and will be a Lagrange function.

The only application of this method in optimizing ship structures is in LBR-5. LBR-5 is a program

developed by Philippe Rigo of the University of Liege.19 The program is a tool that links standard design tools to each other in order to ease and improve the preliminary studies of naval and floating hydraulic structures by optimization. LBR-5 consists of 3 modules: CONSTRAINT, COST and OPTI. In the

CONSTRAINT module the user can implement and/or select the constraints. The proposed constraints are retrieved from databases for structural and geometrical constraints. The COST module is optional and needs, when used, input on the unit costs of materials, productivity rates and labour costs. The OPTI module contains the optimization algorithm.

Advantages of the CONLIN method in LBR-5

• Efficient optimizer, only 10 to 15 iterations are necessary to find the optimum • Large structures can be studied

• Initial scantling is not mandatory, and if it is provided it does not have to be feasible Disadvantages of the CONLIN method in LBR-5

• No integration of CAD or FEM programs

• Not yet capable of solving multi-objective problems

18_{Rigo, P., Fleury, C., (2001): Scantling optimization based on convex linearizations and a dual approach – Part II} 19_{Rigo, P., (2001): A module-oriented tool for optimum design of stiffened structures – Part I}

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Analysis

5.2.3 ModeFRONTIER combined with ANSYS workbench

ModeFRONTIER is an optimization program which offers multiple optimization algorithms. Not only linear optimization can be used, but for instance, also genetic algorithms. What makes modeFRONTIER different from many other programs is that it basically is a platform, that allows the user to implement other software (for example ANSYS workbench, Excel, Fluent, etc.) that is not meant for optimization in an optimization loop. It has a very clear interface which shows directly all input and output variables, the integrated software and the optimization method. However, every single block needs information in order for the model to work, which creates many input fields and not an easy overview of the settings. The post processing possibilities are excellent, all solutions can be seen, different graphs can be made and objective importance can be changed.

Advantages of modeFRONTIER

• Clear overview of the optimization environment • Many choices for optimization algorithms • Excellent post processing possibilities Disadvantages of modeFRONTIER

• Many input and data fields and, in combination with ANSYS workbench, even more • Model has to be made in ANSYS workbench

• Calculation methods have to be programmed from scratch 5.3 Selection of method and software

5.3.1 Selection criteria

The software should satisfy the following criteria: • Capable of

o FEM analysis

o production cost and mass calculation o multi-objective optimization

o imposing restrictions on height of parts o natural frequency analysis

• Workable

• Oriented on ships and ship structures • Available

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Analysis

5.3.2 Considerations

With the selection criteria in mind the optimization methods and software, named in paragraph 5.2, are considered.

Since the workability is hard to judge if you have not tried the software, both software packages that showed a good capability and were available for testing, MAESTRO and modeFRONTIER, have been tried. The workability is based on that experience.

MAESTRO: Satisfies all criteria

• The workability is not optimal due to the software being in a transition phase from a non-interface program to an non-interface program

• Simple geometry input

• Known and available at the TU Delft LBR-5: Does not satisfy all criteria

• It is not possible to do a FEM analysis

• It is not possible to solve multi objective problems

• LBR-5 is not used within the TU Delft and the availability is unknown modeFRONTIER: Satisfies the capability criteria

• Both GA and Linear programming optimization possibilities

• Due to the large amount of input fields, rather unclear, even though the general overview of the model and the interface are excellent (workability)

• Due to the generality of the software all desired calculations have to be programmed from scratch

• Not known at the TU Delft but a trial license was obtained and the software was tried

5.3.3 Conclusion

A schematic overview based considerations with regard to the choice for the optimization software are given in Table 4. The capability weights twice as much as the other requirements.

Criteria MAESTRO LBR-5 modeFRONTIER

Capability ++ -- ++

Workability 0 ? -

Orientation + + -

Availability + ? 0

Conclusion ++++ - 0

Table 4. Selection optimization software

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Analysis

5.4 MAESTRO

For the structural optimization of the AMELS LE luxury yachts the computer program MAESTRO will be used. MAESTRO is an optimization program for ship structures which uses FE Analysis to check the structure for the loads and boundaries and redesigns it if necessary. In Figure 20 an overview of the program is given. The geometrical model can be either a whole ship or part of the ship. In the older versions the geometrical model was created in a preprocessor called SHIPMESH, in the 11th_(beta) version the pre- and postprocessor are integrated in MAESTRO. The preprocessor, however, still creates a .dat-file where all commands for the solver are combined, and which is modifiable by hand.

Figure 20. MAESTRO overview

5.5 Design variables

The design variables can be divided in two categories: the optimization variables and the model

variations. The first are optimized within the model, and for the second different models will be created on forehand.

5.5.1 Optimization variables

The variables within the optimization model are the scantlings of the stiffeners, frames and girders and the thicknesses of the plates. In Table 5 all variables can be found. The BBS and STF are related by the following formulas (respectively for longitudinal and transverse stiffening): !!" #

$%&'( and !!" ) ∙

$%&'(. In which B is the width of the strake, d is the section spacing and n is the number of sections per bay.

Not all optimization variables are unique; some are coupled by a ratio. For example the height of the web or the flange is often linked to the thickness of the web or the flange.

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Analysis

Though the breadth between stiffeners is a optimization variable, in this research it will be used as a variable in the model variation.

Table 5. Variables in MAESTRO

5.5.2 Model variations

For the different ship sizes, distances between frames and construction methods will be created. In Table 6 the model variations and the total number of models can be found.

Number of models Specification

Stiffening methods 3 Longitudinal, transverse and hybrid

Hybrid model 3 Comparison tween deck transverse or longitudinal, for L = 67.5 m, BBS = 500 mm Transverse model 4 Comparison number of girders in the decks,

for L = 67.5 m, BBS = 500 mm Stiffener spacing’s

(breadth between stiffeners)

3 500, 600, 700 mm

Lengths 3 50, 67.5 and 85 m

Frame spacing 6 Comparison web frame spacing, for L= 67.5

m, BBS = 600 mm

Total number of models 37 Number of stiffening methods * number of stiffener spacing’s * number of ship sizes + extra models

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Analysis

5.6 Objective functions

MAESTRO contains options for objective functions with respect to cost, weight and VCG. Furthermore, a penalty function for the stiffener web height is incorporated.

In case of multi objective optimization the objective function in MAESTRO is: * +₍ ,

, + +. + /+ +01,21,2 With: U = the result of the objective function

P1 = the weight parameter to indicate the relative importance of cost reduction P2 = the weight parameter to indicate the relative importance of weight reduction P3 = the weight parameter to indicate the relative importance of reduction of the VCG C, C0 = production costs and reference value of the production costs

W, W0 = the weight of the structure and the reference weight / = +/ _3$3$ ₄ .

P4 = the weight parameter for the stiffener web height penalty function HSW, HSW0 = stiffener web height and reference stiffener web height VCG = vertical center of gravity20

For this research only the cost and weight objectives will be used. P1 = 0.6, P2 = 0.4, P3 = 0 and P4 = 0.

5.6.1 Production costs

Within the model volumetric cost coefficients for stiffened panels and for stiffeners and girders has to be entered, as well as lineal cost coefficients for a stiffened panels and for stiffeners and girders. The volumetric cost coefficient represents all costs which are proportional to the volume of material, for example steel costs. While the lineal cost coefficient represent all costs that are proportional to the total length of frames and girders in each strake, this is a measure for, for example, the weldingcosts. The formulas below show the relations.21

, = 56, + , + , 7 8$

Stiffened panel costs

, = 9(:;!< + ;_{= >? 6ℎ < + A < 7B + 9}. ;_{= >?} In which: s = number of stiffeners tp, hsw, tsw, bsf, tsf = panel scantlings A = module length d = section spacing B = width of the strake

l = stiffener length in each panel (l = B if transversely stiffened)

ρ1 = volumetric cost coefficient (cost per unit volume) for a stiffened panel

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Analysis

ρ2 = lineal cost coefficient (cost per unit length of stiffener) for a stiffened panel

Girder costs

, =C [9₀ 6ℎ < + A < 7 + 9_/ ] In which:

Ng = number of girder segments in the strake CF = ;/= hgw, tgw, bgf, tgf = girder scantlings

ρ3 = volumetric cost coefficient for fabricated beams ρ4 = lineal cost coefficient for fabricated beams Frame costs

, = C [90 6ℎ < + A < 7 + 9/] In which:

Nf = number of frames per strake hfw, tfw, bff, tff = frame scantlings

The values of the cost coefficients ρ1 to ρ4 are explained in paragraph 9.1.1.

5.6.2 Weight

The total weight, W, is the accumulated weight of all the parts:

= ) + + H + ? × H

5.6.3 Box size

Box size is not an integrated objective function in MAESTRO. Therefore constraints are put on girder-, frame- and stiffener height. In the evaluation phase, box size from the different model variations will be compared. And, if possible, the deck height will be adjusted.

5.7 Constraints

The constraints are divided in technological, geometrical and structural constraints. The first two types are to be defined by the designer, whereas the structural constraints are already incorporated in the software. The safety factor of the loads can be adjusted by the designer.

5.7.1 Technological constraints

The upper and lower bounds of the design variables are listed in a dataset, according the following format:

0.004 < TPL < 0.020 0.060 < HSW < 0.200 Etc.

This is where the minimum requirements from the SSC Rules will be incorporated. These requirements can differ from strake to strake.

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Analysis

5.7.2 Geometrical constraints

For creating a structure with sensible proportions, relations between design variables can be declared like this:

TPL / TSW < 2.0 TPL / TSW > 0.5 Etc.

Other relations can also be entered, for example: 1.0 HFW - 1.0 HSW > 0.040

This type of relations is usually to set a minimum distance between parts, for example to ensure a good accessibility.

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Analysis

5.7.3 Structural constraints

The different failure modes that are distinguished can be found in Table 7.

The capacity of the structure to overcome a failure mode is given by adequacy parameters. For calculating the adequacy parameters at first a strength ratios is calculated:

J K∙L LM

In which γ is the safety factor, Q the load and QL the maximum load. Then the requirement becomes: J N 1. However, such a requirement cannot be handled by MAESTRO, it has to be defined in the form < or >. Therefore another parameter is added, being: F PJQ R 0.

With FPJQ (TK∙U ('K∙U The optimal value of the adequacy parameters is just above zero. Since a negative value means that capacity of the structure for that

particular failure mode is not high enough, whereas a

value of almost 1 means that there is an overcapacity. When the adequacy parameter is 1, the specific failure mode does not occur within that structure.

Where in the SSC Rules safety factors are used in defining a maximum stress allowance of the yield stress, are safety factors in MAESTRO defined as a load factor that increase the expected load.

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Analysis

6 Mid-ship section

In order to design a scalable mid-ship section the current AMELS LE are analyzed, results from this analysis can be found in paragraph 6.1 and are used for determining the scaling properties which are explained in paragraph 6.2.

6.1 Reference vessels

All first ships of the LE series are used for reference; 171, 180,199, 212, 242 and 272 feet.

Name Deniki Step One Event Imagine ? ?

Series 171 180 199 212 242 272 L (m) 52.35 55 60 65.5 74 83 Lwl (m) 47.16 49.6 59.67 59.32 67.2 76.67 B (m) 9.0 9.0 10.3 11.88 12.25 14.6 D (m) 4.9 4.9 5.6 6.45 6.45 7.3 T (m) 3.14 3.14 3.41 3.66 3.85 3.85 V (kn) 15.5 15.5 16.5 17.0 16.5 17.0 GRT 642 656 1070 1503 1725 2800 Year 2007 2012 2013 2011 ? ?

Table 8. Reference vessels

The 171 series evaluated into the 180 series. Except ‘Event’ all yachts have a waterline length that is approximately a factor 0.91 of the length over all. ‘Event’ has a vertical bow and therefore the waterline is almost the same length as the length over all.

In the tables below a detailed overview is given on the clear heights of the 180 and the 212.

Table 9. Specification on clear heigths (AMELS LE 177)

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Analysis

CONSTRUCTION HEIGHT

The clear height in the interior is measured between the unfinished hard floor and unfinished ceiling outside any domes. Special Interior styling elements, coves, doorframes, ceiling armatures for lighting, speakers, fire detection, sprinkler heads etc. and floor-covering materials are not included in the clear height.

The following clear heights are approximately measured in the interior of the Yacht:

- Laundry, staff cabin and corridor at tank deck :2000 mm.

- Crew accommodation at lower deck :2100 mm

- Guest accommodation at lower deck :2200 / 2335 mm

- Dining and Main saloon main deck :2125 / 2335 mm

- Corridor main deck :2200 mm

- Owner’s Cabin main deck :2140 / 2260 mm

- Sky Lounge :2200 / 2335 mm

- Guest accommodation at bridge deck :2120 / 2255 mm

- Beach club Lower deck :2000 mm

Table 10. Specification on clear heights (AMELS LE 212)

The clear heights of the 212 will be used for the ships that do have a tween deck.

When making the structural design, the function of the spaces has to be kept in mind. For different spaces different clear heights are demanded, as shown in Table 10. The mid-ship section most often contains on the tanktop deck the engine room and on the lower deck another part of the engine room, guest accommodation and crew accommodation. Therefore corresponding clear heights should be used for the design.

Structural optimization of AMELS LE luxury yachts

Structural Optimization of AMELS Limited

Edition Luxury Yachts

Structural optimization of AMELS LE

luxury yachts

Sijke Anita Verburg

AMELS Holland B.V.

Abstract

Contents

Introduction

Nomenclature

Introduction

Introduction

Introduction

Part 1. Introduction

1

AMELS Limited Edition luxury yachts

Introduction

Introduction

Introduction

2

Design brief

Introduction

Introduction

Introduction

Introduction

Introduction

3

Construction of ships

Introduction

Introduction

Introduction

Introduction

Introduction

Analysis

Part 2. Analysis

4

Scope

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

5

Optimization

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

Analysis

6

Mid-ship section

Analysis