Tutorial

POSEIDON ND Contents

POSEIDON Tutorial 1

POSEIDON ND Tutorial 2006 / 2007

1 Introduction 3

2 A Midship Section - from Concept to Sizing 6 2.1 Design Parameters and Concept Sketch 7 2.2 Principal Dimensions and Material 9

2.2.1 Input of the Principal Dimensions 9 2.2.2 Material definition 10 2.2.3 Storing the Project 11 2.2.4 End connections of stiffeners 12

2.3 Frame Table 14 2.3.1 Generation of a Frame Table 14 2.3.2 Changes in the Frame Table 16

2.4 The Wizards of POSEIDON 17 2.5 Modeling of Longitudinal Members 19

2.5.1 Definition of the Frame Table (Y and Z Dir) 19 2.5.2 Definition of Geometry and Topology 20 2.5.3 Plates, Stiffeners and Holes of Longitudinal Members 25 2.5.4 Arrangement of Transverse Stiffeners on Longitudinal Members 44 2.5.5 Arrangement of Transverse Girders on Longitudinal Members 46

2.6 Modeling of Transverse Members 48 2.6.1 Cells 48 2.6.2 Transverse Members 53

2.7 Design Criteria or Loads 61 2.7.1 Tanks 61 2.7.2 Design Criteria Stillwater Bending Moments and Shear Forces 68

2.8 Sizing of a Transverse Section 70 2.8.1 Sizing of all Members at Frame 154 in accordance with the GL Rules 70

2.9 Permissible Stillwater Values 72 2.9.1 Stresses for Deck and Bottom Structures 72

2.10 Assessment of the results of a Transverse Section 73 2.10.1 Correction of the Transverse Section 73 2.10.2 Duplicate calculations in the GL Rules program 75 2.10.3 Result lists for all Longitudinal Plates and Stiffeners 77 2.10.4 Evaluation of lifetime 81

Contents

POSEIDON ND

2 POSEIDON Tutorial

3 Generation of a Further Transverse Section 90 3.1 New shell description at Frame 68 and 76 90 3.2 Automatically generated Frame Shapes 91 3.3 Definition of a cross section with new structural information 92 3.4 Fitting the Plate and Stiffener Arrangement to the changed cross section 94

4 A Transverse Bulkhead at Frame 76 97 4.1 Description of Bulkhead components 97 4.2 Geometry of Cells for Bulkheads 100 4.3 Plate Arrangement 101 4.4 Stiffener definition on a bulkhead 102 4.5 Definition of girders on a bulkhead 104 4.6 Sizing of the Bulkhead Members 105

5 Generation of a FE – Model 107 5.1 Naming of FE-Models 107 5.2 Parameters of mesh generation 108 5.3 Boundary conditions 109 5.4 Definition of the loads to generate 110 5.5 Mesh generation in longitudinal direction 112 5.6 Start the model generation 113

POSEIDON ND Introduction

POSEIDON Tutorial 3

1 Introduction

The purpose of this tutorial is to present a method of using POSEIDON ND accompanied by examples. To this end, the individual work steps and inputs to complete the given tasks are presented.

The user is led through the individual program sections and can easily understand the solution to the tasks. There are many cross references to the Reference Manual and to the Online Help function that clarify the various input alternatives.

At the beginning of each section of the tutorial the problem to be solved is described. Furthermore the prerequisites from previous sections which are necessary for its solution are presented.

The POSEIDON ND TreeView reflect, in its order, the fundamental work steps.

General

Please follow the advice for the configuration of the POSEIDON ND program, which is to be found in the POSEIDON ND User's Guide, in order to print POSEIDON ND files, properly install the example files onto your hard disk and to use the individual settings for colors, typefaces, etc.

POSEIDON ND’s Online Help may be invoked at any point within the program using the F1 function

key or the 'Help for active view'-Button . The help description, which corresponds to the current display, will be shown.

Printing

For a direct printout of the actual window, please use the Print-Button . The print command can be used in all POSEIDON ND displays.

Note: If you use the Print Preview Button ,the printer output will be displayed on the screen. Here you can set your own individual settings for printer-and page layout.

Graphical output

An active preview plot window is available in most POSEIDON sections.

Note: By clicking the right mouse button on the plot preview window, you can choose the print command or the print preview command.

Use the plot button to view all graphics on the screen in a separate window. By pressing 'p' on the keypad, the actual content of the plot window will be send to the printer.

Plot all plates and profiles, for example, in Section Hull Structure, Longitudinal Members: Plate Arrangement. There, you have additional control over determining what is to be plotted.

Input

POSEIDON ND is using WindowsTM

standard functions. It is possible to use the commands cut, copy, paste in all child windows by clicking the right mouse button or using the corresponding buttons

of the toolbar.

A star in the left column of the input grids marks a new input line, containing proposals. A pencil

marks a line in edit mode. A plus marks a line of a 'Super-Grid'. By clicking the plus you get the second input level of this grid. (see: definition of 'Functional Elements' for example)

Introduction

POSEIDON ND

4 POSEIDON Tutorial

Figure 1: TreeView

How to use this manual

The experienced user may possibly find the descriptions in the individual chapters to be too detailed. Therefore, a short instruction of the work steps to be followed is given in the text lines marked with an

⇒.

Several definitions and conventions, which are frequently used within the tutorial, follow:

Definition:

Section. The sections of POSEIDON ND are shown by folders in the TreeView on the left part of the main window. A selection has to be made in order to reach the actual input display. This process is described with the help of sections. So the example: Switch to Section 2.1.1 ' Wizards � Transverse Section � Container Ship' ' means the selection of folder no 2 in the main-tree and, following that, the choice of folder no 1 in the sub-tree.

Conventions:

Italics Inputs, which the user has to make, are printed in italics.

Frame No Name of a column or input field

⇒ Summary of the inputs described in the following section.

The tutorial describes the typical procedure for sizing a container ship in accordance to the GL Rules with the help of POSEIDON ND. The generation mechanism of POSEIDON and the various input techniques are introduced. It is shown how the sizing can be accelerated considerably by working efficiently with POSEIDON. It is recommended that the users themselves practice using the computer and follow the work steps, which are given in the tutorial.

POSEIDON ND Introduction

POSEIDON Tutorial 5

Figure 2: POSEIDON ND main window

A Midship Section - from Concept to Sizing POSEIDON ND

6 POSEIDON Tutorial

2 A Midship Section - from Concept to Sizing

This chapter describes the modeling and the sizing process of a midship section.

The process is subdivided into the following individual steps:

• concept sketch for a midship section,

• input of the characteristic ship data / principal dimensions,

• generation of a frame table in the ship’s longitudinal direction (X axis),

• geometric and topologic description of the shell, inner bottom, bulkheads, decks, girders, transverse members, etc. for various frames,

• arrangement of plates, stiffeners and holes on these Functional Elements,

• input of the design-loads, which have an influence on the sizing of plates and stiffeners in accordance with the GL Rules (cargo static, dynamic, tanks with corresponding medium etc.),

• input of the permissible design bending moments and shear stresses,

• iterative sizing in accordance with the GL Rules, varying loads and corrections on members.

The complete input described in this tutorial is also contained in the file TUTOR_ND.POX that is loaded on the POSEIDON ND CD-Rom.

POSEIDON ND A Midship Section - from

Concept to Sizing

POSEIDON Tutorial 7

2.1 Design Parameters and Concept Sketch

Problem

Collection of the characteristic ship’s data, which are necessary for the sizing of the transverse section.

Requirements

This step does not require the prior completion of any POSEIDON ND program section.

In this example the ship’s characteristic dimensions and design parameters are as follows:

Ship Type: Container Ship „CONTEST“ Class: 100 A5 Germanischer Lloyd

Lpp: 230 m

LwL: 234 m

B: 32,25 m

H: 18,3 m

T: 13,5 m

TB : 6,6 m

cB : 0,65

V0 : 23 kn

Floor spacing: 3.060 mm

Transverse frame spacing: 765 mm

Deadweight: 35000 to

XA: Fr. 76

Even when only roughly known the deadweight entry is strongly recommended due to static torsion for container ships in this example and for tankers to control the design principles.

The abbreviations conform to the syntax in the Germanischer Lloyd Rules, Part 1 Chapter 1. For more information call the Online Help for this section.


8 POSEIDON Tutorial

For the first pictorial representation of the midship section, a concept sketch has been made up.

Figure 3: Concept Sketch of a Ship design


Concept to Sizing

POSEIDON Tutorial 9

2.2 Principal Dimensions and Material

Problem

Input of the principal dimensions, allocation of a project name, saving of the input in a file.

Requirements

POSEIDON is individually configured (see the Installation Manual).

2.2.1 Input of the Principal Dimensions

⇒ Switch to Section 1 'General' and enter a project name, project description and the Principal Dimensions according to the values given above.

After starting POSEIDON, choose in the TreeView Section 1.1 General Data.

You see a tabbed form for project data, principal dimensions, additional principal dimensions in case of ice class and a description of the waterline in damage condition. Please enter a project name and the authors name. The description field makes it possible to give a detailed description of the project. Choose the second tab 'Principal Dimensions' and enter the values given above (see Figure 4) POSEIDON ND automatically calculates the GL scantling length L. In our example inputs for ice class and for waterline of damage are not necessary here. If, for example, entries are made in classification symbol E2 for ice strengthening, the formulas for ice strengthening in accordance with the GL Rules automatically flow into the scantling of the transverse section. You can find more information on this topic by calling the Online Help function with F1.

Figure 4: Input mask for Principal Dimensions


10 POSEIDON Tutorial

2.2.2 Material definition

⇒ Check the default material number

Choose in the TreeView the Section 1.2 materials and familiarize yourself with the definitions of the material numbers. The first four rows are predefined and not changeable. Post it is possible to define your own material numbers.

Figure 5: The pre-defined material values

When displaying the section 'Show with plate thickness' ( by using the show button ) or the ToolTips of the preview-plot-window (by moving the mouse pointer on a Functional Element) the three

primary materials are indicated by stars. Members with Mat.No. 1 contain no stars; members with

Mat.No. 2 and 3 contain 1 and 2 stars, respectively. Higher material numbers (user defined materials also) are indicated by the # sign. This display convention allows the user to identify graphically areas of the hull using higher tensile materials.


Concept to Sizing

POSEIDON Tutorial 11

2.2.3 Storing the Project

⇒ Save the data and reload the data.

Now, save your first project by clicking the save-button in the toolbar. POSEIDON ND launches a WINDOWS

TM dialog box where you have to enter the path and the name of the project file. Save the

project under the name MYEXAMPLE.POX. If you repeat this command later, POSEIDON ND save your work direct under the given project file name. Please use the 'Save As' command in the File menu, if you want to assign a new project file name.

Figure 6: POSEIDON ND File pull down menu

To reload a project file, please use the ‘open’ command in the File menu or the Load Button in the toolbar.

Advice: If you start POSEIDON ND, the latest stored project file will be loaded automatically.



2.2.4 End connections of stiffeners

Problem

The modeling of the standard local connections for the longitudinal stiffeners with respect to a more detailed life-cycle analysis.

Requirements

⇒ Switch to Section 1.4 'End connection of stiffeners'

Now two examples for a heeling stiffener with bracket and a normal bracket should be modeled.

The explanation of the entry fields is done with the following sketch.

Figure 7: Explanation of entry fields in this mask

hs: height of heeling stiffener

lb: length of bracket

hb: height of bracket

h1: Height of bracket at 0,3*hb ( 0 for straight )

c: height of noose

t: thickness of bracket


Concept to Sizing


First end connection type is the example with the heeling stiffener. In a second step the normal bracket will be modeled. The dimension of the heeling stiffener should be 100mm. The bracket dimensions should be 300*200*12 mm. The height h1 at hb/3 is 140mm and noose should be 20mm high.

The second end connection type is only modeled without the heeling stiffener.

Figure 8: Input mask for typical end connections of stiffeners



2.3 Frame Table

Problem

Generation of a frame table in the ship’s longitudinal direction.

Requirements

The principal dimensions exist in POSEIDON ND, Section 'General � General Data'.

2.3.1 Generation of a Frame Table

⇒ Switch to Section 1.5 and enter the aft perpendicular (frame 0, offset 0 mm) in the frame table.

Choose the Section 1.5 Frame Table (X-Dir) of the TreeView of POSEIDON ND. The forward perpendicular resides at frame 300+500mm. Check the entries of the aft perpendicular in the head of the table.

⇒ Choose 'AFT' in the field 'Keep PP' and check the entry of the field 'at Frame' If the value is not 0, please enter 0. The calculated forward perpendicular should be frame no. 230 now.

From the entries for the aft perpendicular, the given frame spacings and Lpp, POSEIDON ND automatically calculates the forward perpendicular and shows it in the grey shadowed field in the head of the window. If you know the position of the forward perpendicular it is also possible to enter the position of the forward perpendicular. Then the aft perpendicular will be calculated by POSEIDON ND.

The table is to be filled out with frame numbers from -9 to 302. The frame spacing is 765 mm.

⇒ Enter in Line 1 of the frame table: Frame No. -9, Frame Spacing 765.

⇒ Enter in Line 2 of the frame table: Frame No. 302, Frame Spacing 765.


Concept to Sizing


POSEIDON ND makes two input rows with a useful proposal available. Next, change the proposals of

Frame No. 1 and overwrite this with -9. Next, overwrite Frame No. 2 with 300. Enter 765 for both

Frame Spacings.

Figure 9: Input mask for Frame Table

Advice: POSEIDON does not extrapolate beyond the last frame number, therefore the highest occurring frame number must be given.

After concluding the input by leaving the last input row, POSEIDON generates the complete frame table. With this, the position of the forward perpendicular is also defined and the value of 300+500 should be displayed in the head of the table.

The program calculates both of the last two columns of the table. Xp-Coordinate fr. aft PP gives

the spacing of the frame from the aft perpendicular. X/L contains the relative spacing of the frame from the starting point of length L, which for its part is taken from the forward perpendicular to the aft (see Figure 9).

With the 'toggle to all lines ON / OFF ' button of the toolbar, you can activate or deactivate the display of a list of all generated frames. Use the scroll bars to scroll up or down through the table.

Save your work using the pull-down menu File, Save or the Save-button . The changes that follow in the next section are not necessary input for our example; they serve only as further practice in dealing with the frame table display.



2.3.2 Changes in the Frame Table

The frame table can also be modified. For example, here is how to change the spacing to 750 mm in the range between frame 3 and frame 109.

For this, first conceal the display of the generated frame list (toggle to all lines off ). Place the

cursor on Frame No. -9 and twice insert, by using the F6 function key, two new input lines. Overwrite

the first generated input line in Frame No. with 3 and the second generated input line in Frame No. with 110. Next, overwrite the Frame Spacing for Frame No. 3 with 750. Complete the input by leaving the edited line.

Display the list of generated frames (toggle to all lines on ) and scroll through the new frame table and check the results. Observe also that the position of the forward perpendicular has changed, because of the input of the new, diminished frame spacing, and that the forward perpendicular also has been newly calculated.

Now, re-establish the original values. Highlight the row of Frame No. 3 by placing the mouse pointer on the left grey column of the window and press the F5 function key or by clicking the right mouse button to get the pop-up menu which show all possible commands (see Figure 10). Delete both rows,

so that now only two rows exist, one with Frame No. -9 and one with Frame No. 300.

Figure 10: Delete a row of the frame table


Concept to Sizing


2.4 The Wizards of POSEIDON

Problem

Definition of a typical cross-section with the help of a POSEIDON-Wizard.

Requirements

The principal dimensions and the frame table have been entered.

The built-in Wizards of POSEIDON allow much faster generation of the midship section than the standard way of manually describing each functional element. For example a midship section of a container ship can be generated in a few minutes with the help of the Wizard. This generated section has to be modified afterwards to reflect the design idea or the actual design in all details.

The input displays of the wizards are largely self-explanatory. The input fields are described in online-help.

Choose the Section 2.1 Wizards � Transverse Section in the POSEIDON ND TreeView. Choose Point 1 Container Ship .

As shown in the concept sketch the midship section should include a ballast tank and only 9 containers

in the bottom layer. To change the number of containers in the bottom layer, overwrite the No. of Cont. in Y-/Z-Dir - parameter with 9;11 and complete the input with the ENTER key. Look at the graphical output, a ballast tank is defined now.

By clicking the OK button, a typical POSEIDON-description of the cross section is generated.

Figure 11: Cross section wizard for Container Ships

Advice: Notice that the Wizard always generates (and also overwrites) complete cross sections. For this reason do not use the Wizard to edit regions of a cross section.



To check the result, look at the sections 3.3.1 Hull Structure � Longitudinal Members: and 3.3.2 Hull Structure � Transverse Web Plates. To have an overview about the defined midship section press the

'3D geometry' button .

To learn about the detailed input possibilities of POSEIDON ND, you should now define structural cross section of the example using the input displays described in the following sections. Therefore you should reload your file MYEXAMPLE.POX newly. Close the file without saving (Close command in the

file menu) and use the function Open File in the POSEIDON ND toolbar to reload the file.

Advice: The last loaded files are listed in the history of the file menu (Figure 12). This gives you a fast access to your last used files.

Figure 12: File menu with history


Concept to Sizing


2.5 Modeling of Longitudinal Members

Problem

Definition of the individual structural elements of the transverse sections and the description of the geometry and the topology.

Requirements

The principal dimensions and the frame table have been entered.

New feature: Frame Table (Y and Z Dir)

A new powerful feature in POSEIDON ND is the possibility to define a frame table in y-z direction. The names of the longitudinal frames can be used as references in the description of transverse and longitudinal members. The longitudinal frames are shown as horizontal or vertical dotted lines in a transverse section of the vessel.

2.5.1 Definition of the Frame Table (Y and Z Dir)

The Name of the longitudinal frame can have a maximum of 6 characters. The name must begin with up to four letters followed by a number. The number is necessary for the generation of frames.

Choose the Section 1.5 in the TreeView. Overwrite the field Frame No. with 154. In our example, the

name of the longitudinal frames will be L_0 up to L_n. Activate the grid cell Name by the mouse pointer and use the proposal L_0 of the pull down menu (see Figure 13). Jump into the next grid cell

No by using the Tab key. Here you use the proposed 1 to get the definition of one longitudinal frame. Use also the proposed value 0,0 to define the spacing and the y-coordinate. The grid cell of the z-coordinate has to be empty for definitions of frames in y-direction. Choose P for the symmetry of this frame, because it is defined in the center line of the vessel.

Figure 13: Use of the frame table in y-z direction

154



The input of the next line is similar, but you have to change the name to L_1, the y-coordinate to

720,0 mm and the symmetry to P+S. In the third line we want to define 12 frames. Change the

name to L_2, the value of no to 12, the spacing to 855,0 and the y-coordinate to 1440,0. The preview displays the actual defined frames. It is possible to highlight the defined frames in the preview

window and POSEIDON ND shows a ToolTip containing the actual name and the actual coordinate of the highlighted frame. With this function you have fast access to the name and the coordinate of the last generated frame. With the all lines on command, you can see the names of all generated frames. The complete input of the frame table is shown below in Figure 14: .

Figure 14: Frame table in y-z direction

Save your work and close the frame table window.

Advice: Files containing the definition of a 'frame table in y and z Dir' do not work correctly with older versions of POSEIDON!

2.5.2 Definition of Geometry and Topology

Choose the section 3.1.1 'Hull Structure � Longitudinal Members � Functional Elements. In this input display, the so-called Functional Elements, which are involved in the transverse section, are defined.

POSEIDON ND's Functional Elements describe the geometry and the topology (i.e. the connection between the elements) of the longitudinal members of a ship steel structure. They are entirely independent of the plate arrangement or a possible finite element grid. For example, the entire shell shape is defined as one Functional Element, just as the entire inner bottom is one other element. Functional Elements connecting to other Functional Elements must be described by naming the connecting members (reference), as demonstrated in the following example.

In POSEIDON ND, a Functional Element is identified by an abbreviation (name of the Short Cut), which is always used and recognized in other program parts.


Concept to Sizing


POSEIDON ND interpolates geometric information between frames. If, for example, a Functional Element is described at frame 100 and labeled with the attribute F or F+A and if the same Functional Element is also defined at frame 130 and labeled with the attribute A or F+A, then the geometry of the Functional Element will be interpolated between these two cross sections. That means:

F : The geometric information is also valid for frames located further forward and will be utilized for interpolation.

A : The geometric information is also valid for frames located further aft and will be utilized for interpolation.

F+A : The geometric information is also valid for frames located further forward and further aft and will be utilized for interpolation.

2.5.2.1 Generation of the Functional Element SHELL

⇒ Switch to Section 3.1.1 and generate the Functional Element SHELL at frame 154, Attribute F+A.

Establish your first Functional Element. Activate the grid cell Func.Ele and use the proposal SHELL of

the pull down menu. Using the Tab key or the mouse pointer activate the next column Frame No. and

enter 154. and accept the standard value of F/A. F+A means, that the shell will be interpolated at all

cross sections (forward and aft) between the definition at frame 154 and the next direct definition.

Accept also the standard of P+S for symmetry and the y and z-coordinates (0,0/0,0).

In the right hand column LT of the line, a 1 for a straight or a 2 for a circular connection (e.g.: bilge radius) of the shape points has to be entered. Accept the 1 and complete the input by leaving the edited line. Now the second line is activated and you have only to change the y / z-coordinates and the line type. If a value remains constant from one line to the next, that field should be left empty. The definition of the Functional Element SHELL is shown in Figure 15.

The description field can be used for a any description of the Functional Element.

⇒ Enter the Functional Element of the SHELL according to the following figure.

Figure 15: Functional Element SHELL



The preview display you get a visual control of the actual definition of the functional element .Try to highlight the sections of the functional element by the mouse pointer and you will see the coordinates

in the ToolTip also the description line will be highlighted by an additional arrow

It is also possible to use the Plot button to take a look at your complete shape representation for the Functional Element SHELL. You will recognize the orientation of the SHELL description by the small, black arrow at the beginning of the shape. This orientation will later be the basis for the positioning of the plates and the stiffeners on the Functional Element SHELL.

Advice: Orient the Functional Elements from center line to outside and from below to above. This simplifies the overview for you. Symmetrical members intersecting the midship plane must start at the symmetry-line (e.g. SHELL at Y= 0).

By pressing the minus button now the rows containing the coordinates will be closed. Now enter the

text description whole shell in the field Description. As previously mentioned above, Functional Elements may be referenced by means of your short cut. The term used here only serves the purpose of simplifying the distinction between the Functional Elements for you.

2.5.2.2 Generation of further Functional Elements

⇒ Definition of Functional Element IB at frame 154 with attribute F+A, refer to the following figure.

Establish the Functional Element inner bottom with the abbreviation Func.Ele. IB and the F/A

attribute F+A by activating the last line beginning with the star . Overwrite SHELL with IB and enter the following values:

Figure 16: Definition of the Functional Element IB

The entries for the first line are copied automatically to the second line, only changes have to be overwritten, choose the third line (Shell) in the pull down menu which is available in the coordinate grid

cells. This is automatically opened, if you press the arrow button of the active cell. This pull down menu contains references to all defined Functional Elements. The y-value Shell can also easily be given by highlighting the Functional Element Shell in the preview and a right click on the mouse. A pop up menu will be launched where you can choose the command: Set current grid cell to Shell (see Figure 17).

Use the Plot button, to take a look at your complete Functional Elements IB and SHELL.

Press the minus button to close the rows containing the coordinates.

Advice: Older versions of POSEIDON ND and automatic tools as the wizard use another way for description. Instead of repeating a Y/Z-value the next line is left blank and known as “no change happened”.


Concept to Sizing


Figure 17: Use preview plot functions to define functional elements

⇒ Enter the Functional Element DK_1, description weather deck, attribute F+A at frame 154. For the shape, refer to the following Figure . (Note the usage of the SHELL for the description).

Next, establish the new Functional Element with the description weather deck, the Short Cut DK_1 and the F/AF/AF/AF/A attribute F+A. Enter the following values in the input mask.

Figure 18: Definition of the Functional Element DK_1 (main deck)

Advice: DK_1 and IB are now connected with the functional element SHELL, marked by the red colored circles. It is an advantage to use this style of description, because if the description of SHELL changes, the deck (DK_1) and the innerbottom (IB) always remain attached to the SHELL and change their geometry automatically.

You always have visual control of your actual input in preview window.

⇒ Enter further Functional Elements.

Now, by using the coordinates given below (see Figure 19), enter all other Functional Elements.



Figure 19: List of all defined Functional Elements

The coordinates for the other elements are given below. By clicking on the arrow button of a grid cell, you get the pull down menu containing all existing functional elements.


Concept to Sizing


2.5.2.3 View of the Transverse Section at Frame 154

With the Plot button , you can view the results of your work. Choose Frame No. 154 and Show Geometry /Topology in the following dialog box.

Figure 20: View of the transverse section at frame 154 with topologic connections

The points shown in circles indicate that POSEIDON has realised a physical connection between the Functional Elements at each of these points. Therefore, be certain to check that all physical element connections are marked with a circle.

2.5.3 Plates, Stiffeners and Holes of Longitudinal Members

Problem

In this section, the purely geometric/topologic description of the model is supplemented by the arrangement of plates and also by the description of stiffeners and holes on a Functional Element.

This includes also decisions regarding strength and lifecycle behavior even when POSEIDON ND sets most of the criteria automatically!

Requirement

At least one Functional Element exists at the frame.

In POSEIDON ND the plates and profiles can be defined with or without given dimensions. If no dimension are given, a preliminary thickness (1.0 mm) or profile dimension (minimum dimension from the profile table) will be assumed. The required values according the GL Rules can be determined during sizing.



2.5.3.1 Automatic Plate Arrangement for Longitudinal Members

⇒ Switch to Section 3.1.2, plate arrangement at frame 154.

Select the section 3.1.2 Hull Structure � Longitudinal Members � Plate Arrangement. In this input task the plates on the existing Functional Elements at a defined frame range (around frame 154) will be generated.

POSEIDON ND offers the choice to generate standard plate and stiffener arrangement automatically

or to copy such an arrangement from another frame.

Press the magic button . The following dialog box (see Figure 21) will be displayed, where you can enter the valid x-range for the plate fields.

Figure 21: Magic Wand Dialog box for X-Range of Plate Arrangement

⇒ Overwrite the proposed values according to your demands.

Please enter for x-Start -9 and for x-End 302.

The Plates for all Functional Elements will be generated for the entire range of cross sections.

By default POSEIDON ND generates five plates for the SHELL (from keel to sheerstrake) and one plate for all other Functional Elements.

Advice: In order to arrange plates on a Functional Element automatically, the current frame has to be well defined. That is, either it has to be described by explicit input, or it must be possible to

interpolate it by means of the attribute F/A of other frames.

Now, use the Plot button and activate the hook plate dim. in the dialog. Take a look at the transverse section you have just generated.


Concept to Sizing


Figure 22: Input mask for plate arrangements

Fitting the Plate Arrangement of the Shell Plating

As an initial configuration, the automatic plate arrangement is very effective, however, it has to be further refined and adapted to the design concept. Modifying the arrangement is the subject of this section.

All plates, which belong to the shell, carry the Short Cut SHELL. In order to achieve a better overview,

you should describe the individual plates in greater detail with the help of Item. In our example, we name the first plate SHELL;FK (for flat keel) and all others as SHELL;A to SHELL;J.

Flat Keel

⇒ Overwrite the description keel with FK

First, overwrite the description keel with FK (flat keel).

POSEIDON determines the starting point Y-Z Start of the plate FK (BEGIN) directly from of the starting point of the geometry. Plate arrangements always have the same orientation as the geometric description of the corresponding Functional Element.

A plate width of 900 mm is defined with B=900.0 and, with that, the Y-Z End is determined; POSEIDON ND "proceeds" 900 mm further along the geometry and so determines the end coordinates.



The moulded line is to the right as seen from the start point of the plate, so leave RIGHT as it is. Here, you can choose between right and left by using the pull down menu of the grid cell.

Leave the field for minimum thickness t[mm] empty. The symmetry input P+S is already correctly filled in, because our model is symmetrical.

Material No. 1 is also appropriate. Compare it with the above given material table.

The Design Criteria S corresponds on the consideration of shell load, in accordance with the GL Rules. The relevant design criterion must be assigned to every plate. If you press the pull down menu button, the following dialog box (see Figure 21) will be displayed, where you can choose between all possible design criteria.

Advice: If you use the standard naming for the functional elements (SHELL, IB, LB_n, LG_n, DK_n, CO_n) it is easier to follow up the relevant design criterions given for the Rule Check!

Figure 23: Dialog box of design criteria


Concept to Sizing


The Attributes dialog box contains several additional information for the plate i.e. a corrugated plate for longitudinal bulkheads may be defined as well as longitudinal strength attributes, unsupported lengths and actual detail categories.

Figure 24: Dialog box for Plate Attributes

The longitudinal strength behavior for all plates is predefined to Full Effective and this is appropriate for this shell plate. Other examples are plates with small longitudinal extension, massive cut-outs or structural discontinuities that should be excluded from the longitudinal strength calculation by marking the buttons Non effective shear (NES), Non effective bending (NEB) or excluding both attributes shear and bending by marking Non effective shear and bending (NEX).

The span of a plate field is calculated internally by POSEIDON ND. To suppress this function the unsupported span in both directions (dx for longitudinal direction, dyz in the cross section plane) may be entered directly. A special example is the ‘not modelled buckling stiffener’ but the not to be neglected consideration of it.

The lifetime analysis has to be performed with the actual detail category in accordance with the GL Rules. POSEIDON ND makes automatically proposals for the correct detail category when a blank line (default) is shown in the select box. The default value for a plate is usually 80. This value may be changed by clicking the select box and choosing another appropriate value according to the following figure as an excerpt of the GL-Rules. (See Figure 25)

Advice: In some cases and for work saving reasons models are sometimes described without any transverse members. In this case POSEIDON ND is not able to calculate according to the default setting the actual detail categories!



Figure 25: Excerpt of GL-Rules, Fatique Strength

Please leave the description line with the down arrow. Your first plate has now been fitted to the functional element SHELL.

Advice: The orientation of the plates on a Functional Element must correspond to the orientation of the geometric description of the Functional Element. Also, several plates have to be described according to the order given by this orientation.


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Bottom Plating

⇒ Overwrite the description bottom with A and Y-Z End with B=3000.

⇒ Insert further rows for the shell and overwrite the description with B, C and D.

In the example, the bottom plating should be made of the plates "A" to "D".

For the bottom plating, overwrite the description bottom with A and Y-Z End with B=3000.

Highlight the line of SHELL;A and, with F6 (New) or a right mouse click, generate a further input line for plate B. Overwrite A with B. Carry out the same for plates C and D.

With AUTO as the starting point of each following SHELL plate, the end-point of the previous plate of SHELL will be automatically fitted.

Bilge Plates

⇒ Overwrite the Description bilge with E and Y-Z End with z=3800.

The bilge strake is represented by plate E.

For the bilge strake, overwrite the description bilge with E and Y-Z End with z=3800. This time, you

have used a Z coordinate value for the Y-Z End. POSEIDON overwrites it with ;Z= 3800.0 and calculates the required Y coordinate from the geometric description.

Side and Sheerstrake Plates

⇒ Overwrite the description side with F and Y-Z End with B=3000.

⇒ Generate further lines from SHELL;F with the descriptions G, H and I.

The side plates are described with a letter from F to I.

For the side plate F, overwrite the description side with F and Y-Z End with B=3000.

Highlight the line of SHELL;F and, with F6 (New) or a right mouse click, generate a further input line for plate G. Overwrite F with G. Carry out the same for plates H, I and J.

⇒ Overwrite the description sheerstrake with K, material no. with 3 and the minimum thickness with 30mm.

For sheerstrake plate, overwrite the description sheerstrake with K.

Material no. 3 is assigned to this plate (in accordance with section 1.2 Materials) and a minimum thickness of 30 mm. The end point END is already correctly filled in. POSEIDON calculates the end of

the shape representation of the SHELL and uses these coordinates internally for Y-Z End.

The preview displays generated plates. Check particulary the plate butts. Highlight the plates by the mouse pointer to see the ToolTip containing the name of the plate and the defined thickness.

Advice: The plate description of a Functional Element (for example SHELL) frequently consists of several rows. In order to ensure that plates always describe the complete Functional Element, the first plate of the element should always start with BEGIN and the last plate should always finish with END.

Fitting of the Plates for the Inner Bottom

In our example, the inner bottom plates are sequentially numbered from 1 to 4.



⇒ Overwrite Y-Z End with B=3150, t[mm] with 18 mm and Mould. Line with left of the plate IB;pl.1

Plate IB;pl.1 lies opposite to plate SHELL;FK. Overwrite Y-Z End with B=3150.

In the field t[mm], enter a minimum thickness of 18 mm. In the field Mould. Line, choose left by using the pull down menu.

Check the field Design Criteria and enter IB if there is no entry.

⇒ Generate a new plate from IB.pl.1 and overwrite the description with pl.2 and Y-Z End with B=3150.

Generate IB;pl.3 with the same data, and IB;pl.4 with Y-Z End END.

For inner bottom plate pl.2, now insert a new line. For this, place the cursor on IB;pl.1 and execute the F6 (New) command. POSEIDON inserts a new line and assumes the values.

Overwrite the description pl.1 with pl.2 and Y-Z End with B=3150.

Also generate a new line for inner bottom plate pl.3. The width should be 3150 mm as well.

Use the F6 (New) command and overwrite the description with pl.4 and, select LB_2+50 for Y-Z End. POSEIDON ND internally calculates the end coordinates from the geometric description.

Fitting of the Longitudinal Bulkhead Plates

⇒ Overwrite Y-Z End of plate LB_1;pl.1 with Z=6800.

The longitudinal bulkhead plates are named with digits from 1 to 5. The fifth plate (above) consists of higher tensile steel.

The first plate LB_1;pl.1 starts with BEGIN (= beginning of the geometry) and ends at ;Z=6800.0. Overwrite the old values. If you imagine the end point of the plate as being the coordinate values Y ; Z, then you have now internally referenced the Y coordinate of the LB_1 shape representation and explicitly assigned the Z coordinate 6800 mm. This is useful, because, by doing this, you have placed the plate butts on the shell plating and on the longitudinal bulkheads at the same height.

The moulded lines for all longitudinal bulkhead plates are located left as seen from the start of the

Functional Element; therefore, the entry left in the field Mould. Line is already correctly filled in.

⇒ Generate three more plates from LB_1;pl.1 and overwrite the description with pl.2 to pl.4 and Y-Z End with B=3000.

⇒ Generate a further plate and overwrite the description with pl.5, the Y-Z End with END, t[mm] with 30

mm and Mat.No. with 3.

For plates 2 to 4, insert a new line and enter B=3000 for Y-Z End for each.

For plate 5, insert a new line as well and, select End for Y-Z End. The Material No. is 3 for higher tensile steel and the minimum thickness is 30.0 mm.

Fitting the Plates for Deck 1, Deck2 and Deck6

⇒ Change the data for Deck1 to Design Criteria WD, t[mm] 40 mm, Material No. 3 and Moulded Line left.

⇒ Check the data of Deck2 and Deck6 to Moulded Line left.

For the plate assignment for Deck 1, enter the Design Criteria WD for weather deck as design load. Additionally, enter the minimum thickness as 50.0 mm and the Material No. 3.

The moulded lines for all three decks are located left as seen from the start of the Functional Element.


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2.5.3.2 Overview of the Plates for the Longitudinal Members

⇒ Fit further plates according to the following table or the concept sketch. Save the file.

Following, you will find an overview of all plate arrangements at frame 154. Now enter the data for the plates, which have not yet been fitted (particularly CO_1 and CO_2 and LG_0 to LG_14), and compare these with the concept sketch found at the beginning of the tutorial. As descriptions, the longitudinal girders use the longitudinal frame number.



Check the results of your work by using the Plot button. Observe the placing of the stars behind the thickness values used to identify members with Material No.3.

Figure 26: View of plate arrangement at frame 154

Save your work .

2.5.3.3 Arrangement of Longitudinal Stiffeners

In POSEIDON ND you can define several stiffeners with the same spacing and of the same type in one input line. If one of the stiffeners is located at the position of an adjoining Functional Element, then this stiffener will not be generated by POSEIDON ND!

To find the input display for stiffeners switch to section 3.1.3.

POSEIDON ND offers the choice to generate standard plate and stiffener arrangement automatically

or to copy such an arrangement from another frame.

Press the magic button . The following dialog box (see Figure 27) will be displayed, where you can enter the valid x-range for the longitudinal stiffeners.

Advice: It is useful to use the new function of the 'frame table in y and z dir'.


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Figure 27: Magic Wand Dialog box for X-Range of longitudinal stiffeners

Stiffeners at the Shell Plating

⇒ Switch to the display of the Longitudinal Stiffeners, (Section 3.1.3). Overwrite the Description 1 of the

SHELL with 1, Y-Z Start with L_1, Y-Z End with n=1, the Profile Type with HP, Moulded Line

with MF, Material No. with 3 and a with 0.

Use the item indicator 1, for this row will describe the first stiffeners on the shell. In the column Y-Z Start (position of the 1st stiffener), Y or Z coordinates, or a reference to the geometry, will be

requested. Choose L_1. Enter Y-Z End with n=1. The stiffener type HP is already correctly filled in, otherwise the desired type can be chosen by the pull down menu. Leave the dimension columns empty. The stiffeners should lie on the moulded line of the SHELL, with the profile bulbs pointing towards mid-ship. Therefore, select MF by the pull down menu in the field Moulded Line. The angle of rotation is to be given relative to the SHELL with R90.0 degrees. The profile on the outer shell bottom should be of higher tensile steel and contain the Material No. 3. The stiffeners should be arranged on both sides and should contain the Symmetry Designation P+S.

Advice: The value l should be 0, if transverse members (e.g. floor plates ) are defined. For economized input it is possible to enter the distance of the transverse members here. Then it is not necessary to define the transverse members for the dimension procedure of the longitudinal members. Attention: the given values in this field are used by POSEIDON ND in every case, also if there are defined transverse plates with smaller or larger distances!

The following figure shows how the angle of rotation and the position on and opposite to the moulded line and the orientation of the plates determine the orientation of the stiffeners. The value of the relative angle of rotation is within the range from 0 to 180 degrees related to the orientation of the Functional Element.

Figure 28: Orientation of stiffeners



The Attributes dialog box contains several additional information for the longitudinal stiffener as longitudinal strength attributes, coupling with struts, length of brackets, actual detail categories and the factor for asymmetrical profiles.

Figure 29: Attributes dialog box for longitudinal stiffeners

The longitudinal strength behavior for all longitudinal stiffeners is predefined to Full Effective and this is appropriate for this stiffener. Other examples are stiffeners with small longitudinal extension, structural discontinuities or stiffener located on non effective plates that should be excluded from the longitudinal strength calculation by marking the buttons Non effective shear (NES), Non effective bending (NEB) or excluding both attributes shear and bending by marking Non effective shear and bending (NEX). An additional example is the full modeled and connected buckling stiffener etc. that is real to neglect.

The span of each stiffener is calculated internally by POSEIDON ND as the frame distance. To suppress this function the unsupported span may be reduced by entering reducing bracket lengths or couples with struts. It has to be observed that in opposition to the use of l ,as described before, the benefit is that different frame distances and the size of connecting stiffeners are considered automatically!

The lifetime analysis for the longitudinal stiffeners has to be performed with the actual detail category in accordance with the GL Rules. Only with the use of End-Connection-Types (EC) a second select box is activated. The benefit is an automatical consideration of fore and aft connection type. POSEIDON ND in both cases makes automatically a proposal for the correct detail category when a blank line (default) is shown in the select box/boxes (the entry default is changed to blank after leaving the input mask!!) and if all transverse members are modeled. The default value for a stiffener depends on the used profile type and the way it is touched by other or additional members. This value may be changed by clicking the select box and choosing another appropriate value according to the GL-Rules, an excerpt of the most common is given in the next figure (See Figure 30). The result is displayed after calculation as an extended lifetime in years.


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The additional local stresses caused by the use of asymmetric profiles are observed with the factor ksp. POSEIDON ND does the calculation according to default values when the entry is ‘0’. The default values for ksp are:

• Flat bars, T-profiles 1,00

• Bulb profiles 1,03

• Asymetric T-profiles 1,05

• Rolled angels (L-profiles) 1,15 Please refer to GL-Rules, chapter 1, section 3.

Advice: In some cases and for work saving reasons models are sometimes described without any transverse members. In this case POSEIDON ND is not able to calculate according to the default setting the actual detail category! For economical calculation of only cross sections set actual detail category manually according to actual GL-Rules!



Figure 30: Excerpt of GL-Rules (Example for various intersections)

⇒ Start to enter more stiffeners in the described way

Highlight the line SHELL and create a new input line by pressing F6 (New). Overwrite Item with 3-13,

Y-Z Start with L_3, Y-Z End with L_13 and a with a.

Zoom the preview by pulling open a window with the left mouse button and observe how POSEIDON has generated the stiffeners. Recognize, that the stiffeners of the SHELL which are located on the position of the longitudinal girders, consequently will not be generated.


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Now, enter the remaining profiles on the SHELL and use, as Item-description, the numbering of the stiffeners (see Figure 31). The number of input rows depends on the number of changes in the

stiffener types and stiffener spacing. For all stiffeners in the double bottom area choose Material No. 3, which is equivalent to the use of higher tensile steel.

In the area of the uppermost plate (SHELL;J), enter the dimensions for the flat bar as 300*30.. Enter

Material No. 3. With this, all of the stiffeners on the shell plating are completely described.

⇒ Enter further stiffeners of the SHELL according to the following figure. (for a complete profile data table � see below )

Figure 31: Input mask for longitudinal stiffener arrangements

Stiffeners on Longitudinal Bulkheads LB_1

⇒ Change the data of LB_1 in the same way as the stiffeners on shell.

Overwrite the item description of LB_1 with 25-27. In the column Y-Z Start, Y or Z coordinates are

asked for. Enter L_25 in this column. Enter L_27 in the column Y-Z End and n=3 for a. Select Type

HP and leave the Dimensions empty. The stiffeners should be located on the moulded line of LB_1,

with the profile bulbs pointing towards the bottom. Therefore, select MF in the field M. Line. The angle of rotation is to be given relative to LB_1 with R90.0 degrees. The profile should be made of normal tensile steel and contain Material No.1. The stiffeners should be arranged on both sides and should contain the symmetry designation P+S. Enter the same definitions as used in definition of SHELL stiffeners. (for detailed coordinates see the table below). Afterwards change the input of LB_2.



Stiffeners on Decks

Redefine the input line of DK_1. In the column Y-Z Start, enter L_18, in the column Y-Z End enter

L_19 and n=2 for a. Select Type FB and fill the field of the Dimensions with 400*50. Use material no. 3. Change the values of DK_2 and DK_6 according the table below.

Stiffeners on all other Functional Elements

Use the 'Proposal Line' marked by the to generate a new input line in the display of the stiffeners.

Select LG_14 in the column Funct. Element. Next, overwrite the Item with 1-2. Let the stiffeners begin at z=575.0. The end of the stiffener position is adequately described by means of the number of

stiffeners n=2 and the spacing a. According to the concept sketch, enter 650 for a. Select the Type HP

and leave the Dimensions empty. The stiffeners should be located opposite to the moulded line (opposite side) of LG_14 and with the view on the front side of the profile. Therefore, select OF by the pull down menu in the field M. Line. The angle of rotation is to be given relative to LG_14 with R90.0 degrees. Thus, the profile bulbs point downwards. The profiles should be of normal tensile steel and should contain the Material No. 1. The stiffeners should be arranged on both sides and therefore should contain the symmetry designation P+S.

Complete the entries for the stiffeners according to the following table.

⇒ Generate further stiffeners according to the data in the following table. Save the data.


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A view of the entered stiffeners can be produced by pressing the Plot button. Activate the hook profile dim. In the following dialog box. Zoom into the plot by pulling open a window with the left mouse button in the Plot Window (see the Reference Manual). Below, as an example, a zoomed view of the upper hull flange is shown. Zoom out by clicking into the window once.

Figure 32: Zoomed view of a transverse section showing profile description


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2.5.3.4 Hole Arrangement

You have access to the input display for holes in section 3.1.4. Hull Sructure � Long. Members � Holes and Cut Outs.

⇒ Generate four holes with a diameter of 600 mm in the longitudinal girders 5, 8, 11 and 14 at frame 154 at half of the girder height

Activate the first line.

Use the pull down menu of the column Funct. Element, select LG_05. The Item-description can be

1. In First F. No. and Last F. No. the definition range for the definition of holes can be entered.

Enter 154 in both columns. In the column Description, the position relative to the Functional Element (or, alternatively, an absolute coordinate) and the hole dimensions are asked for. The standard value is Y=.0;B=0.0;L=0.0. Overwrite it with F=.5;B=600.0;L=400.0 (half of the girder height, width =400 mm, height=600 mm).

The pre-setting of Spacing is a. This means that the hole is defined on every frame in the definition range.

Use the 'Proposal Line' and change the column Funct. Element with LG_08, LG_11 and LG_14.

Check whether your hole display is filled out according to the figure.

Figure 33: Input mask for hole arrangements with preview plot

Use the Plot button and zoom in to visualize your input.(see Figure 34: Zoomed view of a cross section with holes)



Figure 34: Zoomed view of a cross section with holes

Now, leave the plot window and save your data.

Keep in mind that - in contrast to the manual input described here - the input of Functional Elements is greatly simplified when using one of the wizards to generate a standard structure with few inputs. This standard structure can then be modified with the techniques described here. Of course, direct input of the Functional Elements gives you the greatest possible flexibility.

2.5.4 Arrangement of Transverse Stiffeners on Longitudinal Members

⇒ Description of a Transverse Stiffener on the center-line girder. Switch to Section 3.1.5.'Transverse Stiffener Arrangement'. Generate a new row by using the values given in the following figure. Save your data.

In POSEIDON the description of stiffeners which are located perpendicular to the ship’s longitudinal direction is different than the description of longitudinal stiffeners. Therefore these transverse stiffeners have a separate input mask. They typically exist only on one frame or on a sequence of frames (for example, every second frame). Therefore, such members may be described on several frames at the same time, which do not have to directly follow one another.

In order to enter the transverse stiffeners on longitudinal members, switch to the Section 3.1.5 'Hull Structure � Longitudinal Members � Trans. Stiffener Arrangement '.

A HP profile should be placed on the center-line girder LG_00. The stiffener should be arranged on frame 43 up to frame 176 not at every frame.


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Select the Functional Element LG_00 by using the pull down menu . Overwrite Item with SHELL-IB.

In the column Start of Stiffener, Y or Z coordinates or a reference to geometry are asked for. Click

the grid cell and select BEGIN; the position End of Stiffener is described with END, i.e. the stiffener extends over the whole length of the functional element.

Enter 43 as First Frame No., 176 as Last Frame No. and a;a;2a in the column Spacing (in which a stands for the frame spacing). The stiffeners are now defined from frame 43 up to frame 176 repeated in the order stiffener, stiffener, no stiffener, (stiffeners at frames 43, 44, 45, 47, 48, 49, 51...).

The Type is already correctly filled out with HP; the Dimensions are to be left empty (POSEIDON choose automatically the smallest profile from the active profile table). The stiffener should be located on the moulded line of the LG_00, with the profile bulbs pointing towards the front side. MF in the field

M.Line is already correctly filled out. Compare your entries with those shown in Figure 35.

Figure 35: Input mask for transverse stiffener arrangement

Check the correctness of the definition by zoom in the plot view near the center line girder.

Figure 36: View of a longitudinal with vertical stiffeners.



2.5.5 Arrangement of Transverse Girders on Longitudinal Members

⇒ Description of a Transverse Girder on the coaming. Switch to Section 3.1.6.'Transverse Girder'. Generate a new row by using the values given in the following figure. Save your data.

The input of a transverse girder is similar to the input of transverse stiffeners. To enter a transverse girder on a longitudinal member, switch to the Section 3.1.6 'Hull Structure � Longitudinal Members � Trans. Girder' . Choose frame no. 76.

A transverse girder used as a coaming stay should be placed on the coaming CO_1. The girder should be arranged on frame 76 up to frame 180 at every 8

th frame.

Select the Functional Element CO_1 by using the pull down menu . Overwrite Item with STAY. In

the column Start of Girder, select DK_1, the position End of Stiffener is described with CO_2.

Fill in 76 for First Frame No. and 180 for Last Frame No., the Spacing is defined with 8a. Use

the following figure to define the next values hweb, bflg, tweb and tflg .

The meaning is: height of web at Dk_1, height of web at CO_2, breadth of the flange at DK_1 and CO_2, thickness of the web and thickness of the flange.

Figure 37: Input of transverse web frames.

Figure 38: Preview of the coaming stay.

Compare your preview with the Figure 38 and save your work.


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2.6 Modeling of Transverse Members

The cross section oriented geometry and topology of a plate will be defined with the help of a so-called 'cell'. Though cells are basic for the plate definition (each plate needs exactly one cell, which describes the plate contour), the cell generation is completely separate from the plate definition because the cells may also be used for the definition of tanks.

For all structural components in the ship’s transverse direction, it is possible to define several of them (in a range of frames) with one statement. To simplify the input, there is also a generation hierarchy for transverse structural components in POSEIDON. If several components use the same frame position, then a transverse member overwrites a girder and a girder overwrites a simple stiffener.

2.6.1 Cells

Problem

Definition of the geometry and the topology of transverse members with the assistance of longitudinal members.

Requirements

Main dimensions, frame table and the longitudinal members (long. Plate arrangement) have been entered.

Cells in POSEIDON are enclosed topological areas in a cross section. The description of cells by reference to Functional Elements offers the advantage that the geometry of the cell is automatically adjusted when the description of one of the Functional Elements (e.g.: SHELL) changes. Cells are not tied to just one frame. They are available at every frame at which the described contour constitutes an enclosed area. POSEIDON distinguishes between various types of cells:

• elementary cells are cells that enclose no other cells,

• permanent cells are defined by the user and may enclose several elementary cells. The user can easily define permanent cells, by using the predefined temporary cells. Only permanent cells can be used for the description of transverse members.

• temporary cells are cells that are newly generated by POSEIDON for each actual cross section. Temporary cells are named CE_1 ... CE_n . This type of cell will not be listed in the input mask. They will be shown in the plot preview by moving the mouse pointer on it and serves the fast input of the geometry description of permanent cells.



2.6.1.1 Definition

Now select the Menu Point 3.2.1 'Transverse Web Plates � Geom. of Cells in the Section Hull Structure. In this display, the cells for the description of the transverse members are created.

For an easier input, please change the properties of the preview plot window by a right mouse click on it. Choose 'Properties' from the shown pop up menu.

Figure 39: Change preview plot properties by a right mouse click

Choose the tab 'Cross Section' and change the option 'View on' from both to portside .

Figure 40: Preview plot Properties

Next, close the plot properties window by a click on the cross .

The plot properties of every preview window can be individual adjusted by the user.

Please move the mouse pointer on the empty cell near the center line girder in the preview plot window. The active cell will be shown red colored and if you stop the motion of the mouse pointer, a yellow ToolTip shows the name of the 'Temporary Cell' ; here: 'CE_1'. Use the right mouse button to launch a Pop Up Menu and choose the command 'Insert permanent cell with geometry of CE_1' (see Figure 41). A new window will be launched containing a proposal for the name of the permanent cell (see Figure 42). This name can be given at the user's choice or he accept POSEIDON's proposal. Overwrite WF_1 (the meaning is: WebFrame_1) by FL_1 (Floorplate_1) and change the symmetry


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from P to P+S. (see Figure 42 and Figure 43) Then press the OK button. A new cell named FL_1 should be generated by POSEIDON.

Figure 41: Definition of permanent cells.

Figure 42: Enter a name for a new cell.

Figure 43: The new name FL_1.

If a new cell is defined, POSEIDON ND shows the definition of the cell in the input table. The new permanent cell FL_1 is described by the functional elements SHELL, LG_02, IB and LG_00 (see Figure 44). It is possible to adjust the cell description by using other functional elements or coordinates. For example, please try to change the input IB to Z=900 and see what happens in the preview. A half floor plate will be shown. After that, please redefine the input to IB because we need a complete floor plate in the example.



Figure 44: The Input to define the cell FL_1.

⇒ Define the other four cells of the bottom area in the same way. The result are 5 permanent cells named FL_1 up to FL_5.

Advice: Please note that a symmetry designation for each Functional Element in the cell description of FL_1 is given - which, in this case, is always set to P (port side) - although the cell is symmetric. Here, the symmetry designation of the Functional Elements is important only in special cases, for instance for the explicit description of cells crossing the line of symmetry. In such a case, the described Functional Elements which are located on the port side have to be given and also those located on the starboard and, in particular, those which cross the line of symmetry and run from starboard to port or the other way around.


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It may be, that the input rows are not in order. POSEIDON ND gives the user the possibility to sort the rows in the most input windows. Move the cursor on the header of the column 'Short Cut'. The cursor changes to a small black arrow. Now double click the left mouse button and the input rows will be sorted.

Figure 45: Sort the input by the column 'Short Cut'.

⇒ Define the absent cells in the same way and compare to the list below.Save your work .

Figure 46: Definition of cells of transverse web plates.



2.6.1.2 Overview of all Cells

The display of your definition of Cells should look like the following, although perhaps in a different order:

Figure 47: Overview of cells at frame 154

2.6.1.3 Automatically generated Cells

Use the Show command and have a look at frame 60, 140 and 150 one after the other in the display 'Show Transverse Member (Geometry)' and choose the hook 'perm. cells' only.

POSEIDON interpolates and generates the geometry at frames which are not described and automatically fits the cells for the transverse plates.

2.6.2 Transverse Members

Problem

This section describes the definition of transverse members and the arrangement of plates, stiffeners and holes.

The transverse plates for the previously defined cells are to be created. The floors are located in the range of frame 76 to 184 symmetrical at every fourth frame. The docking plates are located at every frame.

Requirements

The cells, which exist in the range of frame 76 to 184, are defined.


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2.6.2.1 Plate arrangement

⇒ Switch to Section 3.2.2 and enter 76 as Frame No.. Define a new plate FL1:76, valid from frame 42 to

176. Select the cell FL_1 by using the pull down menu of Cell and define the Spacing with a.

In the Section Hull Structure, select the Menu Point Trans. Web Plates � Plates (Section3.2.2). In this display, transverse members are defined by Short Cuts. The geometry-description of a plate is done through the assignment of a cell.

Next, press the 'Toggle on / off' button . This means that all defined transverse members are shown, independent of the frame on which they are defined. This setting is generally useful for the input or changing of members, because it can otherwise occur that a component that was just defined will not be displayed, since it is not defined at the current frame.

Enter the name FL1:76 in the first input field Short Cut. This name is the name of the actual

transverse floor plate. The default-setting in the field Item is 1. The frame numbers indicate the range

in which the transverse component is valid. Here, enter 76 as First Frame No and 184 as Last Frame No .

The assignment of the component to a cell is done by using the pull down menu of the field Cell. Select the cell WF_1 from the list that is offered. The molded line (ML) is already lying correctly with Aft and material and symmetry designation can also be left as they are. Thereby, the component is generated symmetrically on both sides.

The adjustment of the field Spacing follows as the last step. In this field, you define at which frames in

the range from First Frame No. to Last Frame No. the component is to exist. The default setting in this field is a. This means that the component is defined on every frame from frame 76 to 184. Leave the a in this field, which corresponds to a definition at every frame.

The field Spacing is very flexible; it is also possible to enter complicated definitions. In this example, we will not make use of this, but, as needed, you can find exact instructions in the POSEIDON Reference Manual or in the Online Help function.

To define the other plates, overwrite the name of the Short Cut' and change the name of Cell in the

proposed input row at each case. Change the Spacing from a to 4a.

Define the transverse members according to values in the following table.

Figure 48: Definition of transverse plates.



Compare your input values with the following figure again and save your data.

Figure 49: Input Table 'Floors and Transverse Web Plates at frame 76.

By entering individual frame numbers in the field Frame No above (e.g. at frame 77, 78 and 80), have a look at the components. You will see that the components are defined at the first and the last frame of the range and, additionally, at every fourth frame in between - also at frame 80. Check that the component is not defined at frame 77 and frame 78 (only FL1:76 is defined at every frame), as well as at frame 79 (only every fourth frame). Depending upon the frame number, the definition line of the component is either shown in the input table or not. Compare also the gray colored plates in the preview plot at these frame numbers.

The transverse stiffeners on LG_00, which are given in chapter 2.5.4, will be deleted by POSEIDON automatically at the frame numbers, where a web plate is defined.

Advice: When selecting cells by the pull down menu of the field Cell, the temporary cells are shown as well. If such a cell is selected, POSEIDON ND automatically changes it into a permanent cell, names it WF_n and uses the proposed name in the Short Cut field. Change the proposed name into the new name of our example. We do not use this "Standard-Abbreviation“ in our example due the better way of 3D-description.

2.6.2.2 Arrangement of Stiffeners on Transverse Members

⇒ Switch to the section 3.2.3 'Stiffeners on Floors and Transverse Web Plates'. Use the 'Proposal Line' to

choose FL_1:76 from the Short Cut pull down menu. Enter LG_00+50 and SHELL+350 at Start of Stiffener , LG_02-50 and SHELL+350 at End of Stiffener , enter 2 at n , 1100 at a and FB at the

column Type .

Switch to the display of Stiffeners on Floors and Transverse Web Plates in Section 3.2.3.

Use the pull down menu of the column Short Cut and choose FL_1:76 to generate a new input line. The next two fields describe the starting point and the ending point of the stiffener. In this example, the first stiffener should run parallel to SHELL at a distance of 350 mm from LG_00 to LG_02. The values

of the y-coordinates LG_00+50 (Start of stiffener) and LG_02-50 (End of stiffener). Now, give SHELL+350 for both fields of the column of z-coordinate (see Figure 50 ).


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A Functional Element (+ value) can be selected in all input cells for the description of the coordinates of stiffeners.

The field n gives the number of the stiffeners to be generated. Enter a 2 here. The field a defines the distance between the 2 stiffeners. Use the value 1100. The molded line is already correctly filled out with MR.

In the field Type, select flat bar .

Figure 50: Input of the first stiffener on a transverse web plate.

⇒ Use the 'Proposal Line' and enter 2 in the column Item, define the coordinates Start of Stiffener at

270.0;SHELL+350, End of Stiffener at 270.0 ; IB-350, n as 2 and a as 900.

Choose FL_1:76 again from the pull down menu of the column Short Cut in the 'Proposal Line'.

POSEIDON uses a copy of the previous line and you can change the values. Overwrite Item with 2,

Start of Stiffener with 270.0;SHELL+350, End of Stiffener with 270.0;IB-350, n with 2 and a with

900. The column a describes the spacing. Now you have created the stiffeners of a Cut Out of a pipe duct, which will be defined under section 3.2.4 later.

⇒ Use the 'Proposal Line' and enter of Item as 3-4, Start of Stiffener at L_3;SHELL, End of Stiffener at L_3;IB, n as 2 and a as 855. Use connected in the column End Connection.

Choose FL_2:76 from the pull down menu of the column Short Cut in the 'Proposal Line'. Overwrite

Item with 3-4, Start of Stiffener with L_3;SHELL, End of Stiffener withL_3;IB, n with 2 and a with 855. Now you have created two stiffeners with a spacing of 855 mm between each other. Choose C

from the pull down menu of the column End Connection. This creates stiffeners on the web plate which are connected to the longitudinals. The value lK will be considered in the calculation of the dimensions of the longitudinal stiffeners.

Advice: The value lK reduces the free length of the longitudinal and will only be taken into account if the y-coordinate of the buckling stiffener is exactly the same as the y-coordinate of the longitudinal!



Compare and complete your inputs with the following table.

Figure 51: Definition of stiffeners on transverse members

It is noteworthy that no frame range can be entered in this display. With the help of the Short Cut, the stiffener is assigned to the transverse component of the same name and automatically contains the same range of validity as this one.

Use the preview to have a look at your definitions, zoom in to see details. Save your work.

Figure 52: Arrangement of the stiffeners on transverse web plates.


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2.6.2.3 Hole Arrangement

⇒ Switch to the section 3.2.4 'Holes & Cut Outs. Use the 'Proposal Line' and enter the name of the Short Cut FL_1:76 and the dimensions Y=720; Z=0,5L; DY=800; DZ=1000; R1=200.

Switch to the section 3.2.4 'Hull Structure � Transverse Web Plates � Holes and Cut Outs'.

Choose FL_1:76 in the column Short Cut this is the name of the associated transverse component.

For the definition of the dimensions of the hole, please enter the following data in the fields: Y-Pos: 720; Z-Pos : 0,5L; DY: 800; DZ: 1000 and R1: 200. With both of the two values DY = 800 and DZ =

0,5L, the middle of the hole is defined. DZ = 0,5L denotes the center of the cell height. The two

following values establish the width (DY) and the height (DZ) of the hole. The value R1 define the

radius of all four edges of the cut out, if the values R1, R2 and R3 are defined with 0. It is possible to define different variants of cut outs. Please press the F1 function key to learn more about the definition of different cut outs.

Create new input lines for holes by using the pull down menu of the column Short Cut and enter the values according to the data in the following figure:

Figure 53: Definition of Cut Outs on transverse web plates.



Use Plot button to take a look at the results of your input, for example at frame 76.

Figure 54: Arrangement of holes and cut outs on transverse members

Save your work!


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2.7 Design Criteria or Loads

Problem

All different loads or load combinations have an influence on the later sizing in accordance with the GL Rules. By using Design Criteria, loads are associated to plates and stiffeners.

Requirements

There are no special requirements.

2.7.1 Tanks

For the geometry definition of tanks three different methods with their own benefits and purposes are available:

• The compartment method is for complex tanks with different cross-sections over its length due to Functional Elements which cause different cell arrangements in the X-Extension. Such tanks are defined with the help of the menu Compartments.

• The cell method is for tanks which have a constant hull shape and continuous Functional Elements in the tank area at all X-Positions. An elementary cell inside the tank is selected by right clicking in the preview plot and choosing “Insert tank with cell…”. The launched dialog box asks for the new name. Another possibility is by choosing in the “Comp.Name” column the corresponding cell out of the select box. If there are cut-outs defined in the cell boundary, the tank is automatically extended to the next watertight longitudinal.

• The manual method is used for special descriptions such as open holds, where no enclosed area exists. The “Comp.Name” column is left empty and the Design Criteria is assigned manually to the plates where the pressure is to be considered.

The first two descriptions will be followed in the next chapters. The third is rarely used but self-explanatory.

2.7.1.1 Tank Description with Compartments (Compartment method)

The tanks on the port side will be described in our example by using compartments, even when this is not necessary given a simple contour and continuous Functional Elements which guarantee an identical cell arrangement over the entire X-Extension.

⇒ Choose the Menu Point 4. Design Criteria/Loads in the POSEIDON Menu and select Compartments.

Use the 'Proposal Line' and enter TK_1P in the column Short Cut , highlight the starting cell on the port side, click the right mouse button and choose “Insert permanent cell with geometry of CE_n” from the launched popup window (See Figure 55). The compartment border will be highlighted in dark blue, the active cell area in light blue.



Figure 55: Choosing cells to arrange the compartment

Repeat the process with the next cells in the intended tank area according to Figure 56 and exit after completing the last column with the down arrow. Enter 302 in the column Frame No. (the end of the compartment in this example).

Note: Due to the parallel ship body in this example the main benefit of compartments are not highlighted as it should be. At every changed cell arrangement due to the ending or beginning of functional elements, you have to name the point of change in the X-Extension and repeat the description process for a new valid range of cell arrangements until the end of compartment is reached. This will usually happen in the fore- and aft-ship areas.

Figure 56: Completed Compartment


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Move the mouse pointer to the Preview Plot and see the highlighted cell that belongs to the Compartment TK_1P shown in the ToolTip by holding the pointer for a moment over the defined compartment (see Figure 56).

⇒ Generate the next compartment for the port wing tank!

Use the 'Proposal Line' and change ‘TK_1P’ into ‘TK_2P’ in the column Short Cut , highlight the cell on the port side, click the right mouse button and choose “Insert permanent cell with geometry of CE_n” from the launched popup window as before. End the compartment description by leaving the line with the down arrow and enter 302 as ending frame in the column Frame No. See Figure 57.

Figure 57: Completed compartments for the starboard side

⇒ Copy the last compartment TK_2P to the starboard side and name it TK_3S.

Select the compartment TK_2P as shown in the figure before. Use the ‘copy’-button in the upper task line to copy the compartment TK_2P to TK_3S.

Figure 58: Copy button of upper task line

The following warning for deleting the ‘Undo-buffer’ will be launched. Click ‘Yes’ or if you are not quite sure cancel this process and save your data before you proceed in the same way.

Figure 59: Warning window



Change the following mask according to the entries of Figure 60 and hit ‘Ok’.

Figure 60: Compartment dialog box for symmetry and destination

Figure 61: Completed compartments

Check your display for the new compartments with the Figure 61 and save your data.

⇒ Switch to Section 4.2. Tanks and use the compartments to describe the tanks.

Click the select box in the column Comp. Name and choose ‘Comp:TK_1P’. Leave the line with the down arrow. See next figure.

Figure 62: Tank description with the help of compartments.


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Repeat this procedure for the next tanks and use ‘Comp:TK_2P’ and ‘Comp:TK_3S’ instead.

Figure 63: Completed tank description with compartments in this section.

Check your display for the tanks with the Figure 63 and save your data.

Note: Some items such as the symmetry in this mask seem to be incorrect. This will be fixed automatically after the calculation in the next step.

The default input of the Medium is Ballast. The other parameter Rho, Frame No.Aft / Forward

and Height of overflow will be calculated by the given main dimensions. Different values are only needed, if cargo tanks (Tanker) are defined. All values with 0,00 will be calculated by POSEIDON,

except pv which must be given for cargo tanks.

2.7.1.2 Tank Description with Cells (Cell method)

The last missing tank on our starboard side should be described in this example with the use of the cell method to demonstrate the self-extending capability of cells when holes and cut-outs are defined on longitudinal members.

⇒ Generate with the help of the 'Preview Plot', one permanent cell and the corresponding Tank TK_4S.

Your tank no. 4 should be limited by the longitudinal girder LG_02, the SHELL, the deck DK_6, the bulkhead LB_2 and the inner bottom and be located on the port side.

Move the mouse pointer over the 'Preview Plot'. The temporary cells of the cross section should be red if you move your mouse pointer over them (if not, set the preview plot properties to 'default'). Activate the first cell beside the pipe duct and press the right mouse button. Choose 'Insert tank with cell CE_n' from the pop up menu (see Figure 64). The window 'Enter name for new cell' will be shown. Rename the proposal TK_1 to TK_4S and press the OK button (see Figure 65). The geometry of the 'Tank 4' is now defined by using the newly created permanent Cell TK_4S.

Note: Self extending to watertight longitudinal boundaries is only automatically done when holes and cut-outs are defined !



Figure 64: Choose the cell for the tank description.

Figure 65: Renaming of the temporary cell.

Figure 66: The ToolTip shows the Tank No.

Move the mouse pointer to the Preview Plot and see the name Tank 4 in the ToolTip by holding the pointer for a moment over the defined tank (see Figure 66).

Note: If the tank is deleted, the cell TK_4S will not automatically be deleted with it.


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2.7.1.3 Calculation of generated Tanks

With the Calc command, you now have possibility to calculate the edge points and the expansion of the liquid surface at frame 154. According to the position of the "capture cell“ or compartment, POSEIDON automatically sets the symmetry description.

Mark all lines of tanks to be calculated in the input table by pressing the ‘Ctrl’-button on the keyboard

while holding dump the left mouse button, then press the Calc button

Figure 67: Tanks marked for calculation.

The tank dimensions for all tanks will be automatically calculated. Compare your results with Figure 68. The input of a corrected free length is only needed for partially filled tanks (cargo tanks).

Figure 68: Definition of tanks.

The plates and stiffeners which lie in or on Tank No. 1 to 4 will be calculated later during the sizing in accordance with the GL Rules for the design loads for tank structures. The load assignment happens automatically!



Figure 69: Tanks according to both methods.

Save your work!

2.7.2 Design Criteria Stillwater Bending Moments and Shear Forces

⇒ Switch to Section 4.5.1

Choose the menu point Design Criteria/Tanks in the POSEIDON ND TreeView and select Hull Girder Bending � Stillwater. Here you may enter stillwater values at selected locations along the ship’s length. The values will be interpolated linearly. Default values will be provided resulting from GL Construction Rules.


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Figure 70: Input mask for stillwater bending moments, shear forces and torsional moments.

As you have not entered any own values so far, you can see the standard values. They are given relative to scantling length L. At 0.3*L and 0.7*L the maximum and minimum stillwater bending moments and shear forces are calculated, according to the GL Rules (part 1, chapter 1, section 5).

The bending moment, shear force and torsional moment curves will be shown in the preview plot of the input window.

Close all subordinate windows and save your work. Check your vessel by pressing the button for 3D Geometry.



2.8 Sizing of a Transverse Section

Problem

Generation, sizing and display of the members of the transverse section.

Requirements

The transverse section is described with Functional Elements, plates, stiffeners and holes. The loads exist. Design criteria / loads have been entered and checked.

2.8.1 Sizing of all Members at Frame 154 in accordance with the GL Rules

⇒ Switch to Section 3.1.2. Press the dimens button , named: 'Determine Scantlings at the actual frame'. Save the data.

With the diMens command, it is possible to size all members (longitudinal and transverse) of the current frame in accordance with GL Rules. The diMens command automatically carries out all steps necessary for sizing.

POSEIDON performs a sizing in several iteration steps. Beginning with their definition, the members incrementally approach the dimensions which finally conform to the requirements of the GL Rules. In this, all of the sizing criteria from cargo, tank load, inner bottom load, shell load, etc. are internally taken into consideration. At last, a buckling check will be performed.

Members with preset dimensions are retained during the process. Presetting the dimensions of plates and profiles, for example in the upper flange area, assists the program to fulfill the longitudinal Stillwater Bending Moment and Shear Force criteria (see Figure 71).

Figure 71: Predefined members in the upper Flange of the vessel.


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The dimensioning calculation is completely documented in the POSEIDON INFOFILE. Possible error messages or warnings for each calculated plate or stiffener will be reported there.

Section values like section moduli, moments etc. are written at the end of the POSEIDON INFOFILE.

Have a look at INFOFILE in the bottom area of the main window of POSEIDON ND and compare the values.

Figure 72: Summary of scantling results at frame 154

Scroll through the INFOFILE to see the reported messages or warnings and errors during the sizing.

The preview shows a colored plot of the section. If you see any red colored member, then the dimension does not meet the requirements of the GL Rules.

Figure 73: Colored preview of the dimensioned cross section.

Get a detailed overview about the calculated scantlings by pressing the plot button and activate the hook plates dim. or the hook stiffener dim.



2.9 Permissible Stillwater Values

Problem

Check of stillwater values and section moduli resulting from the sizing of the structure.

Requirements

The structure has been defined and sized.

2.9.1 Stresses for Deck and Bottom Structures

⇒ Switch to section 5.3. Check bending and shear stresses and resulting permissible stillwater bending moments and shear forces.

Choose Section 5.3.1 'Results � Hull Girder Bending � Section Moduli BM and SF (input)' in the TreeView of POSEIDON ND.

The editable lists the input values for the calculation of the stillwater values. These are the vertical moment of inertia, the maximum shear stress for a unitary shear force of 1 kN (per kN Shear Force), the distance of the neutral axis above base line, the Z-coordinate of the bottom, the Y- and Z-coordinates of the top of continuous strength member, k-factors of the top and the bottom area, Cs factors according the GL Rules the actual Cs factors, the permissible bending stresses / shear forces and the actual / required section moduli at the deck and the bottom.

The values are calculated according to the rules of the Germanischer Lloyd, but it is possible to change the values manually.

Figure 74: Input mask for necessary values to calculate permissible stillwater values

Switch to section 5.3.1 'Results � Hull Girder Bending � BM and SF (output)' to check the permissible stillwater bending moments and shear stresses.

Figure 75: Permissible stillwater values


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2.10 Assessment of the results of a Transverse Section

Problem

Interpretation of the calculated dimensions and the applied load criteria. Sizing of the members so that the bending stress requirements of the transverse section are fulfilled.

Requirements

The members have been generated and sized.

2.10.1 Correction of the Transverse Section

⇒ Switch to Section 5.1.

Choose the Menu Point 'Results � Hull Cross Section � Long. Plates' in the POSEIDON TreeView. An overview about the results of the sized cross section will be shown.

Figure 76: Results of the cross section at fr. 154 (longitudinal plates).

Here the applied design criteria and longitudinal stresses (acc. Section 5.B.1 of the GL Rules) are given for each part. POSEIDON has automatically supplied the tank and outer shell plates with the correct design criteria. The plate thickness is rounded to 0,5 mm in accordance with the GL Rules and

combined with a + or - symbol (green colored background). The symbol ++ indicates that the required

dimensions are greatly exceeded (blue colored background); -- indicates substantially too small

(inadequate) dimensions (red colored background). If + or - is displayed, the sized dimensions lie

within the tolerances.

If # - symbols (magenta colored background) are displayed in the column Assessment, POSEIDON has terminated the sizing of a part of an element or of a plate, because of buckling problem, often caused by an improper input.



After pressing the button, POSEIDON ND shows the calculated plate dimensions in a plot window.

Figure 77: Calculated results for each plate field.

If all dimensions are acceptable, press the OK button to copy the calculated scantlings to section 3 of POSEIDON ND. This is also necessary for the transverse members.

With the All lines on/off command , you can observe that POSEIDON has subdivided the plates according to stiffener spacing. A sizing is effected for every subdivision. It is also possible to click the

to get the results of the subdivisions for one member (see Figure 78). The header line shows the worst case of all subdivisions of a plate, which is the used result.

Figure 78: Result list for each subdivision.


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A click on the button leads to the sizing only for this part and will show a detailed protocol of this process in the INFOFILE (see Figure 79).

If you want to try some variations of the structure to decrease the actual scantlings, it is possible to

change the white backgrounded values in the result list and press the button again.

Change the frame spacing a=855 to a=800 of SHELL Plate D, subdivision 1 for example and press the

button again. You can see, that this change results in a lower plate thickness of 17,9 mm for this subdivision. Please restore the original frame spacing a=855 and recalculate the values.

Figure 79: Detailed result protocol of the shell plate D, subdivision1.

After a calculation command , the applied input values of the actual subdivision are now in the memory and it is possible to check them very detailed or to calculate some variations in the GL Rules program.

2.10.2 Duplicate calculations in the GL Rules program

⇒ Switch to the GL Rules program by using the tab GL-Rules of the TreeView. To check the calculated scantlings of SHELL Plate D, Part 1, choose Section 6.1 of the GL Rules program 'Shell Plating � bottom plating and flat plate keel'. Check the values and try to understand the input.



Switch to the GL Rules program by using the tab GL-Rules of the TreeView. The SHELL Plate D is calculated by the design criteria S (bottom pressure), Ti1 (tank pressure of tank1, member in tank) and a buckling check was performed for any subdivision of this plate. Check the results in Section 3 (buckling), Section 6 (shell plating) and Section 12 (tank structures).

In our example; we check the results of the criterion shell plating. Choose Section 6.1 of the GL Rules TreeView.

All input values agree with the values used for the calculation in POSEIDON.

Switch back to POSEIDON and save your work.

Any variations in the result part of POSEIDON (Section5) or in the GL RULES program take no effect on the accepted / stored results. If you want to realize a variation of the structure, it has to be made in Section 3 of POSEIDON 'Step by Step by hand'!

It is possible to create a GL Rules result file by pressing the result-file

button. The output is shown in the INFOFILE and can be printed by pressing the printer button beside the result file button.

Figure 80: GL Rules TreeView

Figure 81: GL Rules input / result mask (bottom plating).


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2.10.3 Result lists for all Longitudinal Plates and Stiffeners

⇒ Switch to 5.6. in the Poseidon main menu and choose Shear stress.

A complete summary of the Shear stresses TauL and Normal Stresses SigmaL as well as a summary table for all stresses due to hullgirder loads according to section 5 of the GL-Rules will be generated for the actual calculated frame 154. This allows an identification of the relevant loadcases considering aspects of dimensioning, buckling or fatigue. In addition the advanced user obtains a powerful tool for the evaluation of the results (e.g. stress plots). This will be shown later on.

Figure 82: Result table and detailed overview for Shear stresses TauL of all components.

The abbreviations according to the GL-Rules valid for Figure 82 are:

• QV vertical shear force

• QH horizontal shear force

• MTor torsional moment

• SW stillwater

• Wave wave load

• St.V. St. Venant

• Warp. Warping

• LC loadcase acc. to section 5 of GL-Rules

• SWmax max. stillwater

• SWmin min. stillwater



Figure 83: Result table and detailed overview for Normal stresses SigmaL of all items.

The abbreviations according to the GL-Rules valid for Figure 83 are:

• MSW vertical stillwater bending moment

• MWV vertical wave bending moment

• MWH horizontal wave bending moment

• MTor torsional moment

• DeltaSig max. stress range due to hullgirder loads (LC3 multiplied with ff for fatigue)

• Mean mean stress due to hullgirder loads

Please note that

As you can see in Figure 83 the table for the normal stress contains additional information. The stresses marked in:

• Red max. stresses for calculation of scantlings

• Blue max. stresses for buckling evaluation

• Dashed max. stresses for fatigue evaluation (ff for fatigue is considered)

With this additional information you can easily identify the loadcase relevant for your special evaluation.

For the shell plate F, for example, the maximum stresses for scantling calculation are represented in red in loadcase ‘LC3 a’ in combination with the maximum Stillwater ‘SW max’, the maximum stresses for the buckling evaluation are represented in blue in loadcase ‘LC2 b’ in combination with the maximum stillwater ‘SW max’ and the maximum stresses for the fatigue evaluation are represented dashed in loadcase ‘LC3 a’ in combination with the minimum stillwater ‘SW min’. See Figure 83.

Advice: When the maximum stresses of stress evaluation and buckling evaluation belong to the same loadcase the result will be colored blue.


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Figure 84: Detailed summary of stresses for each item.

Additional abbreviations according to the GL-Rules valid in the stress summary table are:

• PS local bending stress due to sea pressure at shell

• PS+PT combination of local bending stress due to sea pressure and tank pressure

• PT/PC local bending stress due to tank pressure or cargo deck load

• Dim.(global) SigmaL and TauL acc. section 5, D of the Rules

• US SigV utilization factor SQRT(Sig²+3*Tau²)/ (190/k))

• Buckling (global) max. stresses of buckling evaluation acc. section 5,D and section 5,C 7.

• Fatigue (incl.local) Min stress, max stress, mean stress and stress range (Delta) for fatigue analysis due to hullgirder and local loads.

⇒ Plot as one example the Shear Stress Distribution of loadcase ‘LC1a max’.

All the stresses of the shown result tables can be plotted within the menu points 5.1.1 and 5.1.2. Switch to 5.1.1 and use the ‘Show’ command in the end of the line for Shell plate D:

Figure 85: Use of the result list for plot purposes.



Select the point ‘Stresses, Pressure’ to activate the select box for stresses in the launched popup window. See Figure 86.

Figure 86: Dialog box for plotting of results.

Choose ‘TauL LC1a max’ and hit the ‘Ok’-button to plot the chosen stress distribution.

Figure 87: Plot of the Shear stresses according to loadcase LC1a max


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2.10.4 Evaluation of lifetime

Problem

Evaluating a lifetime analysis for longitudinal plates and stiffeners using the actual detail categories according to Section 20 Fatigue Strength of GL-Rules.

Requirements

The scantlings of longitudinal members have been determined and the actual detail category has been applied for every plate and stiffener. The lifetime analysis has been done in conjunction with the sizing calculation using default values for the probability level in accordance to GL-Rules

⇒ Switch in the Poseidon main menu to section 1.1 General Data and choose the Options-tab.

The next figure shows the ‘Probability Level’ in the ‘Options’-tab. The default values can be modified, if ‘use special probability level’ is hooked. The provided ‘Lifetime in years’ and the sea conditions ‘Days per year at sea’ and ‘Waveperiod’ can be changed to your project requirements.

Figure 88: Options card in Poseidon main menu 1.1 General Data

The following values have been calculated during the sizing process and can be plotted for the evaluation of the lifetime:

• Predicted lifetime

• Required detail category

• Usage factor detail category.

Additionally the ‘actual detail category’ can be plotted as shown in the next sections.



2.10.4.1 Lifetime of longitudinal plates

⇒ Switch in the Poseidon main menu to section 5.1.1 Long. Plates and right mouse click to launch the popup dialog box. Choose ‘Properties’ and the next dialog box will be launched (See Figure 90).

Figure 89: Result preview plot.

Choose first the point ‘Detail Category (req.)’ and hook ‘plates’ as seen in Figure 90.

Figure 90: Plot properties for the result preview window.

The required detail category calculated by POSEIDON ND is shown in Figure 91.


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Figure 91: Required Detail Categories for the plates according to calculation.

You can see the actual detail categories for each plate in Figure 92. The actual detail categories are to be taken in accordance to GL-Rules, chapter 1, section 20. If no detail category is given in table ‘3.1.2 Plate Arrangement’, POSEIDON takes default values ( 80 for plates ).

Figure 92: Actual detail categories for the plates as ‘intended or built’

The next step is to compare the required with the actual values for detail category. See Figure 91 and Figure 92. In our example all actual values are above the required values. The calculated usage factor is given in Figure 93.



Figure 93: Usage calculated with the actual detail category

The predicted lifetime is finally seen in Figure 94.

Figure 94: Calculated Lifetime for plates.

In this example the ‘actual detail categories’ are above the required, the ‘Usage’ is below 1.0 and the ‘Lifetime’ is over 50 years. This is OK, but what to do if values are not sufficient?

In this case the scantlings or the design has to be changed. Please refer to the section 2.5.3.1 on page 26.


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2.10.4.2 Lifetime of longitudinal stiffeners

⇒ Change the ‘Plot Properties’ as in the section before, choose ‘Detail Category (req.)’, unhook the ‘Plates’ and hook the ‘Profiles’ as shown in Figure 95.

Figure 95: Plot Properties

The procedure is exactly the same as in the last section ‘Lifetime of longitudinal plates’. POSEIDON has calculated the ‘required detail categories’ in accordance to the given design values.

Figure 96: Required Detail Categories for profiles of frame 154.

The actual detail categories are to be taken in accordance to GL-Rules, chapter 1, section 20. If no detail category is given in table ‘3.1.3 Stiffener Arrgmt.’, POSEIDON takes default values as described before in section 2.5.3.3 on page 34.



Figure 97: Actual Detail Categories for profiles of frame 154

The comparison of Figure 96 and Figure 97 turns out that all ‘actual detail categories’ are above the ‘required detail categories’. Another view to the Usage factor in the figure below shows that the side tank is the critical in this area. The highest values are 0,95.

Figure 98: Usage of the actual detail category of profiles


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The minimum predicted Lifetime is 25 years. See Figure 99 for the green values on the longitudinal stiffeners on the shell in the side tank area.

Figure 99: Calculated Lifetime for the profiles of frame 154

For this example the lifetime design seems to be acceptable on the first view. The results show the sensitivity of longitudinal profiles, especially the local design at cross sections where web-/bulkhead plates and their stiffeners have to be connected.

A close look at Figure 97 shows that the proposal for the ‘Actual detail category’ in the passage way is 80, because the stiffeners of the web plate are not connected with the longitudinal stiffeners. See Figure 100.

Figure 100: Passage way without connection of web stiffeners



The proposal for the actual detail category in the side tank region is 63, with respect to used bulbous profiles connected with heel stiffener and integrated bracket and additional backing bracket. For details see GL-Rules, chapter 1, section 20.

Figure 101: Side tank with connected heel stiffener

The figure below shows the description of the floor plate stiffeners in ‘3.2.3 Stiffeners’ in the double bottom. The ‘flat bar’ is connected to the longitudinal bulbous profile as seen in the opened select box without any bracket.

Figure 102: Stiffeners on floor plates

The proposal for the actual detail category is therefore 56. See Figure 103.

Figure 103: Double Bottom with connected heel stiffener and shown ‘actual detail category’

Please reference to previous section 2.5.3.3 in this ‘Tutorial’.

POSEIDON ND Generation of a Further

Transverse Section


3 Generation of a Further Transverse Section

Problem

Definition of Functional Element SHELL on further frames to realize the hull shape.

3.1 New shell description at Frame 68 and 76

⇒ Use F6 or the right mouse button to generate another SHELL element at frame 76 and frame 68. Adjust the shape representation of frame 76 corresponding to the following figure. Save the data.

Switch to section 3.1.1 'Functional Elements'. Further frames, partly with altered hull shape, are to be established. For this purpose, place the cursor on the Functional Element SHELL and activate the line. Use the (F6) function key or the right mouse button. In the newly opened window, enter 76 as the

Frame No. and press the OK Button. POSEIDON has established a new line for the element SHELL and assumes the shape of frame 154. Now the parallel midship is defined between the frames 76 and 154 because the coordinates between these two frames are exactly the same. Close the new input by

clicking the minus button .

Repeat the same procedure again and enter 68 in the field Frame No.. Now, change the coordinates according to the following figure:

Figure 104: additional definitions of the Functional Element SHELL

Save your work!

Generation of a Further Transverse Section POSEIDON ND


3.2 Automatically generated Frame Shapes

⇒ Use the plot button to show the interpolated cross sections at frame 68 and 72.

Check the cross section at frame 68 with the Show command. POSEIDON has accepted the new frame shape and all other elements. It interpolates and generates the geometry at frames which are not explicitly described. Since all associations of Functional Elements with the shell are used as a reference, the geometry of the Functional Elements automatically conforms to the altered shape.

Figure 105: View of the new transverse section after definition of the Functional Element SHELL at frame 68.

Check also the other cross sections between frame 68 and 76 with the Show command.

POSEIDON now supports the creation of interpolated Functional Elements. For this, activate one input

line of the Functional Element SHELL and press the right mouse button. Change the Frame No. to 68

and activate the hook Interpolate in the pop up window 'New Functional Element'. After pressing the OK button, an interpolated shell contour will be created. This is also possible for all other Functional Elements.

It is not necessary to input a lot of frames, because POSEIDON ND can interpolate automatically between two defined frames.

The more the contour of a Functional Element changes, the more input definition is needed.

Save your work!


Transverse Section


3.3 Definition of a cross section with new structural information

⇒ Description of a cross section at the end of the hold (frame 76)

Now generate a cross section at the end of the hold, at frame 76. Therefore aft of frame 76 the decks DK_1 and DK_2 must be defined non-stop from centerline to the shell. The definition of the coaming starts at frame number 75.

You still are in section 3.1.1 'Longitudinal Members � Functional Elements'. Activate the functional

element DK_1 and press the F6 function key. Overwrite Frame No. with 76 and F/A with F in the

'New Functional Element' mask. Press OK and use the button of the input table to accept the

values. Now repeat the process and enter F/A with A. Overwrite the Y - value of the first point with 0.0

in the input table and close the input by using . Use the same procedure to create DK_2.

The coaming CO_1 and the coaming top CO_2 has to be defined in the same manner. The values are listed in the figure below.

Figure 106: new topologic definition at frame 75/76.

Press the 3D button (without options) to see the geometry in a 3D view (see Figure 107) or the plot button to check the cross section (see Figure 106).



Figure 107: 3D geometry (clipped, above), Figure 108: view on geometry at fr. 76 A+F (below).


Transverse Section


3.4 Fitting the Plate and Stiffener Arrangement to the changed cross section

⇒ Generate the new plate arrangement at DK_1 and DK_2 on fr.76.

Switch to the section 3.1.2 'Longitudinal Members � Plate Arrangement'. The frame 76 will be

displayed by using the Frame No. 154, where the original plate description is made with the X-

Extension from -9 to 302. Correct the x-Start value -9 for the items DK_1 and DK_2 into 76.

Choose the value 154 in Frame No. and hit Return on the keyboard. Use the Copy button and

overwrite the field x-Start of Destination in the dialog 'Copy members of FrameNo 154 (F)' with -9

and the field x-End of Destination with 76. Then press OK.

Figure 109: Dialog 'Copy members'

After that, the new dialog window 'Copy Functional Elements' will be launched. Select the Functional Elements DK_1 and DK_2 and press OK.

It is also possible to activate all Functional Elements by pressing the button ALL.

Figure 110: Choose DK_1 and DK_2 from dialog.

The new input for DK_1 and DK_2 in the X-Extension in between frame -9 and 76 will be displayed in the mask ‘Plate Arrangement’ on frame -9.



Complete the input mask Plate Arrangement according to the data in the following figure by using the line copy function. Mark the item DK_1 and press two times ‘F6’, then fill in the changed data. DK_2 is changed analogous but only one time. Control your entries with the help of the following figure:

Figure 111: Corrected input of section 3.1.2 at fr. -9, view forward with highlighted deck plate.

Use the same procedure for the longitudinal stiffeners in the input mask Longitudinal Stiffener Arrangement (Section 3.1.3), make three line copies for each item DK_1 and DK_2. Change the values given as an excerpt of the input mask.

Figure 112: Stiffener arrangement in the X-Extension between frame -9 and 76

When you have copied and entered the changes of the plates and stiffeners according to Figure 111 and Figure 112 fix the long list of warnings in the Info bar with a right mouse click and choose from the launched pop up display ‘Clear’.


Transverse Section


Control your work by using the plot button and click in the launched popup window the hook for plate and for stiffener dimension. Zoom the applicable deck area in the plot window to get a closer view.

Figure 113: Plot window with zoomed deck area of DK_1 and DK_2.

Save your work.

A Transverse Bulkhead at Frame 76 POSEIDON ND


4 A Transverse Bulkhead at Frame 76

Problem

Definition of a three-piece watertight transverse bulkhead at frame 76.

Requirements

The principal dimensions, the frame table, the shell and the longitudinal members at this frame have been entered.

4.1 Description of Bulkhead components

⇒ Generation of functional elements, assignment of geometry data and assignment of a frame number

A definition of a bulkhead in POSEIDON is a composition of several components (Functional Elements). These Functional Elements for bulkheads are not the same as Functional Elements defined in section 3.1.1! Each component can be assigned to one or more bulkheads. The geometry information for a component is given by one or more cell descriptions. One cell description (definition of geometry) can be assigned by different components (Functional Elements) of different bulkheads. It is possible to share one cell description (definition of geometry) by several plate definitions.

Select Section 3.3.1 'Transverse Bulkheads � Overview' from the TreeView. Enter the following values in the grid of the input line:

Bulkhead Name: BHD1

Frame No.: 76 and A

Functional Element: BF_1 (Bulkhead Functional Element)

Cell: BC_1 (Bulkhead Cell)

Figure 114: Definition of bulkhead components.

Note: The cells in Figure 114 above are marked in red. This can temporary be accepted due to the fact that the Bulkhead cells will be described later on. Also the view on F+A causes overlapping plates and profiles due to both description on frame 76.

POSEIDON ND A Transverse Bulkhead at

Frame 76


In the proposal line , overwrite the value BC_1 of Cell by BC_2 and leave.

So we have defined the bulkhead (BHD1) by one Functional Elements (BF_1) and two cell descriptions. (see the following table)

Note: The cells used by one Functional Element have to be defined in the same plane, because stiffeners and girders will be defined later by using the Functional Elements.

⇒ Define the transverse coaming plate in section 3.2 Transv. Web Plates

The advanced user will be a little disturbed to define this plate in the section Transverse Web Plates. The reason is the calculation according to GL-Rules, the water pressure for the bulkhead (without the collision bulkhead) is defined to a level 1m above bulkhead deck and would cause faulty results.

The transverse coaming plate will be defined in section 3.2 'Hull Structure � Trans. Web Plates' as described in chapter 2.6 'Modeling of Transverse Members'.

Switch to Section 3.2.1 and define the cell between DK_1, CO_1 and CO_2 as permanent cell COA_1.

Then switch to Section 3.2.2 and define a plate CO_1:76.Choose the design criteria Ae (superstructure aftend bulkhead) and CO (coaming).

After that, switch to Section 3.2.3 and define the stiffeners.

Save your work and close all child windows. Control your work with the plot preview!

Figure 115: Preview Plot for the transverse coaming



4.2 Geometry of Cells for Bulkheads

⇒ Generation of the geometrical and topological information of the bulkhead components.

Switch to Section 3.3.2 'Trans. Bulkheads � Geometry of Cells'. Use the pull down menu of the proposal line and select the cell BC_1.

Fill in the values of the following table by using the pull down menus of the input window and describe the corners of the cell BC_1.

Figure 116: Definition of the bulkhead cell BC_1.

Now you have generated the geometry and topology of a bulkhead component between center line, inner bottom, longitudinal girder LB_2, deck DK_6, longitudinal girder LB_1 and deck DK_2. For all

points the column X relative to Xref [mm] contains 0.0, because of the component is defined on the

X plane of the defined frame number 76. The input value 3 in LT (Line Type) defines the connection of an edge (given by straight line between two points), along a given longitudinal Functional Element.

Generate the geometry for the cell BC_2 in the same manner (see the following table):


Frame 76


4.3 Plate Arrangement

⇒ Generation of the plates with thickness of 12.0, 10.0 and 8.0

Switch to section 3.3.3 'Trans. Bulkheads � Plates' Choose BF_1 from the pull down menu of

Functional Element. Next choose the needed cell BC_1 from Cell . Do not change the value in

Start of Plate , but choose BH= from the pull down menu of End of Plate and enter the value 5380.

Enter 13.0 in column t (thickness). All other values can be left on default. The default input of the

column Design Criteria is WT (watertight) , but it can be changed by the user, if required.

Now you have created the first part of plating by using geometry of the cell BC_1. To define the next

part, use the AUTO command in Start of Plate.

Create the further plates in the same manner by using the following table. Now you have defined a transverse bulkhead with three bulkhead plates (only two cells) and one transverse plate for the transverse coaming.

Figure 117: Input mask for plates at transverse bulkheads.



4.4 Stiffener definition on a bulkhead

⇒ Definition of the vertical stiffening at bulkhead BHD1 with HP-profiles.

Switch to Section 3.3.4 'Trans. Bulkheads �Stiffeners'. Choose the Functional Element BF_1.

The stiffener definition will be valid for the whole bulkhead. The first stiffener should be defined at the

center-line, between the inner bottom and DK_1. The two input fields of the column Start of Stiffener / End of Stiffener refers to the y- and z coordinate of the starting point and the ending

point of the stiffener. Enter on the left input cell 0, on right input cell IB (Start of Stiffener) and 0 and

DK_1 in the second row of this column (End of Stiffener). Change Item to CL and the column Sym. to P. Do not change the other default values.

The definition of the following two stiffeners starts at L_1 with a spacing of 720mm. Overwrite Item

with 1, Start of Stiffener with YL_1;IB , End of Stiffener with L_1;DK_1. Enter nnnn with 2 and a with

720. Change the column Sym. to P+S.

Use the following table to define the following stiffeners.

Figure 118: The input mask for stiffeners at transverse bulkheads.

Figure 119: Preview Plot of the bulkhead stiffeners.

Note: See the highlighted stiffeners of the second line Figure 118 blue coloured in Figure 119.


Frame 76


Use the Plot button to check the result at frame 76. Choose A in the field F/A !

Figure 120: Plot Dialog

Figure 121: The transverse bulkhead

Note: If you choose A+F in the F/A-field for this special example you will get warnings for overlapped plates and stiffeners of DK_1 and DK_2. This is reasonable due to the fact that the joint is modelled exactly on frame 76 (This will never occur in reality). With this entry you have chosen to display both parts in the same plot area and the warning has to be observed as a reminder.



4.5 Definition of girders on a bulkhead

If you size the cross section of frame 76 now as described in Chapter 4.6, POSEIDON calculates very large profile dimensions, because of the free length of the profiles is 12920 mm from inner bottom up to deck 2. We need some girders to shorten the free length.

Switch to Section 3.3.5 'Trans. Bulkheads � Girders'. The input is similar to the stiffener definition, but you have to give the scantlings of the girders. Enter the values in the same manner as the stiffeners before and use the following table.

Figure 122: Input mask for girders on bulkheads.

If some girders or tweendecks are defined, the correct free length will be used for the profile

calculation. Check your input by the preview or by using the plot button . Save your work!

Figure 123: Preview of the complete bulkhead at frame 76.

Note: See the highlighted girder of the second line Figure 122 blue coloured and marked by an arrow in Figure 123. The ToolTip on the right side shows the complete dimensions of the girder 3. Another left mouse click highlights it in the table.


Frame 76


4.6 Sizing of the Bulkhead Members

⇒ Switch to Section 5.2. or press the dimens button , named: 'Determine Scantlings at the actual frame'.

Please enter in the launched window for the Frame No. 76, for the F/A A and choose for the Rule Check Determine.

Figure 124: Rules Check mask

Figure 125: Result mask for the Transverse Members.

Advice: If all dimensions are acceptable, press the OK button to copy the calculated scantlings to section 3.2 and 3.3 of POSEIDON ND. Otherwise go further on as seen in Chapter 2.10.1

Generation of a FE – Model

POSEIDON ND


5 Generation of a FE – Model

This section deals with the automatic generation of Finite Element Models of the ship structure. Mesh generation in POSEIDON also is cross section oriented. Generation starts by specifying parameters for the node distribution of at least one reference cross section. This node distribution is also used for the other cross sections, until a new reference cross section will be found. It is possible to divide a reference cross section into areas of different levels of refinement. We will now generate a mesh between frames 76 and 92 and define a mesh refinement around the holes in the floor and in the web frame.

Problem

Input of the principal mesh generation parameters in a cross section.

Input of the necessary boundary conditions.

Input of the modeling area in the longitudinal direction.

Generation and check of the Finite Element model.

Requirements

The structure to be modeled has to be defined completely and without topological errors.

5.1 Naming of FE-Models

⇒ Switch to section 7.1 in the Poseidon main menu and give a name for your first model.

The mask 7.1 FE-Models of the POSEIDON ND main menu provides the possibility to name your different FE-Models. For this example we use the simple name ‘Model 1’.

Figure 126: Mask for naming different FE-Models

POSEIDON ND Generation of a FE – Model


5.2 Parameters of mesh generation

⇒ Fixing of the mesh generation parameters for a cross section

Select the Menu Point 7.2 Net Tolerances in the TreeView. POSEIDON ND creates a proposal input

row with defaults. Enter the number of the desired cross section in the first column Frame No. , in this

case 76. Thus, you have defined the reference cross section. If you enter 3 in Mode, you have chosen, the plates to be modeled as shell elements, nodes are generated on trace curves of the stiffeners and the stiffeners are modeled as Beam Elements, when POSEIDON generates the FE model. (for more information about the different modes, see the Reference Manual or press F1 for Online Help!)

In case definition ranges intersect, later lines of meshing parameters overrule earlier definitions (see Reference Manual). Therefore define the basic meshing parameters at first.

POSEIDON should model the half cross section. Enter 0 in column ymin , do not overwrite the entry

AUTO in ymax, zmin and zmax. The entries in min.l and max.l limits the edge length of elements between 350 mm and 2000 mm. But note: in Mode 3 the positions of the stiffeners have the first priority for the meshing.

Use the new proposal input row to define a fine meshed area in the model. Overwrite the values in

ymin with 0, ymax with 6570, zmin with 0 and zmax with 1800, min.l with 200 and max.l with 650. Now you have redefined the element size in an area between the shell, the inner bottom and the longitudinal girder LG_08 on portside.

Figure 127: Input of mesh generation parameters at a cross section

This mesh description is valid for the whole model until the next input, if existing.

With the Show command , take a look at the result of the mesh generation in the cross section to check the correctness of parameters (see Figure 128).

Have a look at the fine generated mesh in the double bottom area.


POSEIDON ND


Figure 128: Nodes on frame 76 A+F.

5.3 Boundary conditions

⇒ Define the boundary conditions in section 7.3 Boundary Condition of Poseidon main menu.

Select Section 7.3 ‘Boundary condition’ in the POSEIDON main menu. We want to create a FE model of the half structure of the vessel between frames 76 and 92 (only for example!), which is clamped on

fr. 76. Overwrite the entry ‘152 +230’ in Location of section by 76. Next, we have to define the

symmetry condition in the X-Z plane. Choose x-z plane from the pull down menu of the column Kind of Section and leave the field with a click on the right arrow to Location of section with 0. Define the symmetry condition of the nodes in the center line. Fix the degrees of freedom as shown below.

Figure 129: Input of boundary conditions.

Save your work!



5.4 Definition of the loads to generate

⇒ Switch to Section 7.4.1 'Tank Loads' in the Poseidon main menu.

Activate the hooks for static pressure like shown in Figure 130. The further possibilities in this mask will be used for cargo tanks.

Figure 130: Tank Loads.

Note: The sections 'Cargo Loads' and ‘Container Loads’ are only available if there are loads defined in section 4.3 and 4.4 of POSEIDON ND.

⇒ Switch next to section 4.5.3.3 ‘Definition of Waves’, then to 7.4.4 ‘External Sea Loads’.

Enter in the proposal line for xp/LPP the crest position 0,0 for the sagging wave. Leave the line with the down arrow and enter for the hogging wave in the same column 0,5. Control your work with the Figure 131:

Figure 131: Mask for the Definition of Waves


POSEIDON ND


⇒ Switch to Section 7.4.4 'External Sea Loads' in the Poseidon main menu

In the menu 'External Sea Loads' the user has the possibility to create two draughts. Enter Tmin with 5,0m and Tscantl..with 13,5m. Activate also the checkbox 'Weather Deck' to generate the weather deck load. Hook both of the additional Wave pressures analogous to the previous defined waves for hogging and sagging.

Figure 132: External Sea Loads

Save your work!



5.5 Mesh generation in longitudinal direction

⇒ Fixing of the mesh generation parameters in the longitudinal direction.

Now select the Menu Point 7.5 'Generate FE Model' in section 'Preprocessor' and define a new input

row to fix the model boundaries. Overwrite the entry in column From with 76 and in To with 77. It is necessary to get the bulkhead girders in the FE model. Define the location and the numbering of cross

sections in the FE-model with the input of a (every frame starting with frame 76) in Step . It is not necessary to overwrite the entries in the other columns. (see the Reference Manual or the Online Help)

In the second input row overwrite the values as shown in the figure below. Note, that the employed frames and frame spacing (4a) are chosen on the defined web frames. POSEIDON creates the nodes of the FE model only from the defined members on the defined cross sections.

Figure 133: Define the mesh generation parameters in longitudinal direction


POSEIDON ND


5.6 Start the model generation

Finally, use the Generate command to start the FE model generation. This will launch the following popup window. Please hook ‘Generate Loads’ and ‘Include All Transverse Members’ as shown in Figure 134. Click OK to start finally the generation.

Figure 134: Dialog box for FE Model creation

To check the result, have a look at the POSEIDON INFOVIEW.

Figure 135: Info View: Generation of the FE Model without errors.

Now POSEIDON has done the work, the next steps in GLFrame are described to give you a short overview and how to control and handle your generated model.



⇒ Switch to GLFrame in the Poseidon main menu.

Press the GLFrame Plot command for 3D-FE models in the task line.

Figure 136: The generated FE model in GL-Frame

You can simply rotate the whole model via the arrow buttons on the keyboard and zoom model details.

To control your model do a right mouse click in the plot window. This will launch the following dialog box. Choose ‘Properties’ to launch the ‘Fempl Properties’.


POSEIDON ND


Figure 137: Fempl Properties

Choose the tab ‘Clipping Ranges’ and hook frame 76, then press the Refresh-button.

As an example we have clipped frame 76. Check your model!



Figure 138: Clipped frame 76

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