container ship guidelines - gl

Rules for Classification and Construction V Analysis Techniques

1 Hull Structural Design Analyses

1 Guidelines for Global Strength Analysis of Container Ships

Edition 2011

The following Guidelines come into force on 1 February 2011.

Alterations to the preceding Edition are marked by beams at the text margin.

Germanischer Lloyd SE

Head Office Brooktorkai 18, 20457 Hamburg, Germany

Phone: +49 40 36149-0 Fax: +49 40 36149-200

[email protected]

www.gl-group.com

"General Terms and Conditions" of the respective latest edition will be applicable (see Rules for Classification and Construction, I - Ship Technology, Part 0 - Classification and Surveys).

Reproduction by printing or photostatic means is only permissible with the consent of Germanischer Lloyd SE.

Published by: Germanischer Lloyd SE, Hamburg

Table of Contents

Section 1 Basic Principles

A. Application, Scope ..................................................................................................................... 1- 1 B. Strength Analysis ....................................................................................................................... 1- 1 C. Structural Modelling .................................................................................................................. 1- 2 D. Loads and Loading Conditions ................................................................................................... 1- 3 E. Calculation and Evaluation of the Results .................................................................................. 1- 4

Section 2 Global Strength Analysis

A. General ....................................................................................................................................... 2- 1 B. Structural Idealization ................................................................................................................ 2- 1 C. Boundary Conditions .................................................................................................................. 2- 5 D. Design Loads .............................................................................................................................. 2- 6 E. Model Check .............................................................................................................................. 2- 13 F. Evaluation .................................................................................................................................. 2- 13 G. Documentation ........................................................................................................................... 2- 14

V - Part 1 GL 2011

Table of Contents Chapter 1

Section 1

Basic Principles

A. Application, Scope

1. These Guidelines specify the procedure for strength assessment of container ship structures by means of Finite Element (FE) Analysis. Application of this advanced analysis method, amending the standard Rule scope, allows verification of complex structures under a more refined approach, thus enabling further optimisation of structural design and material utilisa-tion.

2. A container ship is defined as a ship intended for the carriage of containers and equipped with the appropriate facilities.

3. The structural analysis is to be carried out on the basis of permissible stresses in accordance with the GL Structural Rules for Container Ships (I-1-5).

4. Section 1 of these Guidelines outlines the basic principles governing FE analysis.

5. Section 2 provides detailed guidance for global strength analysis of container ships using a finite element model of the entire vessel. The focus of a global FE analysis is on global stress and deforma-tion under particular consideration of torsional re-sponse which is significant due to large hatch open-ings. Such an analysis is mandatory for all container ships of novel design, exceptional size, or complex structural arrangement.

6. Computer programs used for finite element analysis have to be recognised. As recognised soft-ware is considered all finite element programs that can show results to the satisfaction of Germanischer Lloyd.

7. Required fatigue strength assessment is to be based on the GL Guidelines for Fatigue Strength Analyses of Ship Structures (V-1-2).

B. Strength Analysis

1. In general, strength analysis comprises the following steps:

– determination of the objective, type and extent of the analysis

– structural modelling and specification of bound-ary conditions

– determination of load cases and load application

– solving of the equation system

– evaluation and assessment of the results

2. Regarding structural modelling, boundary conditions and loading, certain simplifications are possible or necessary, depending on the objective of the analysis and the type of structure.

3. In ship structures the deformations and stresses can usually be subdivided into the following categories, depending on the structural conditions:

– global deformations and stresses of the hull girder and the primary structural members

– local deformations and stresses of the primary and secondary structural members

– locally increased stresses at structural details and discontinuities

4. Global deformations and stresses

4.1 The structural response of the hull girder and the primary structural members under normal, shear, bending and torsional loads results in global (i. e. large-area) deformations and stresses.

4.2 The primary structural members, in this sense, are the floors, bottom girders, side and deck trans-verses, stringers, longitudinal and transverse deck strips, deck girders and comparable components, each including the effective part of the plating and stiffeners.

4.3 The resulting stresses are nominal stresses, i. e. stresses which would also result from integral quantities of the sectional forces and moments and of the cross-sectional properties. Global nominal stresses generally include the effective breadths, but not lo-cally increased stresses.

5. Local deformations and stresses

5.1 In secondary structural members local loads can give rise to additional local deformations and stresses.

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Section 1 Basic Principles Chapter 1Page 1–1

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5.2 The secondary structural members include all frames, stiffeners, longitudinals, beams and the plating with their bending, shear and torsional stiffness as well as the associated tripping and supporting brack-ets.

5.3 Effective plate breadth shall be taken into account.

5.4 The resulting stresses are nominal stresses which are superimposed on the global stresses.

6. Locally increased stresses

6.1 Locally increased stresses at structural details and discontinuities have to be assessed especially in respect of fatigue strength. Here a distinction is made between three types of stresses:

– maximum stress in the notch root

– structural or hot spot stress, defined alternatively for welded joints

– special parameters for assessing the stress at crack tips

6.2 The maximum stress in the notch root, e. g. of the rounded edges of cut-outs, can already exceed the elastic limit of the material for realistic load as-sumptions in typical structural details of shipbuilding. Instead of the nonlinear notch stress σ and strain ε, the notch stress σk can be determined and assessed for normal cases under the assumption of linear-elastic material behaviour. In the case of very sharp notches, the local supporting effect of the material can be con-sidered with a correspondingly enlarged notch radius.

6.3 In complex welded structures, only the stress increase as a result of the structural geometry is gener-ally considered in the analysis, whilst that caused by the weld toe is considered during the assessment. This leads to the structural or hot spot stress σs at welds, and this is determined under the assumption of elastic material behaviour.

6.4 Apart from a direct calculation of the locally increased stresses, it is possible to use catalogued stress concentration factors or detail categories. When using concentration factors and detail categories, the associated nominal stresses have to be determined with sufficient accuracy in accordance with their defi-nition. Moreover, the ranges of application and valid-ity for the catalogued data are to be observed.

6.5 Fatigue strength requirements are given in the GL Structural Rules for Container Ships (I-1-5), Sec-tion 20. Assessment procedures are specified in the GL Guidelines for Fatigue Strength Analyses of Ship Structures (V-1-2)

C. Structural Modelling

1. Types of structural models

1.1 Global model of the hull

A global model of the hull girder is normally used for the global strength analysis of the entire hull girder and its primary structural components. For 3D model-ling of all the primary structural components, the loads can be applied realistically, and the structural behav-iour of complex ship structures, including the interac-tions between the individual components, can be taken into account, see Section 2.

1.2 Partial model of the hull

Partial models of the hull girder are used for the analy-ses of global and local stresses of the respective part and its primary structural components, e.g. midship cargo hold area. Like 3D global models, hold models are generally used to analyse the complex, three-dimensional strength behaviour of the primary struc-tural components.

1.3 Local models

Local models are used for the strength analysis of secondary or special components as well as structural details. The main focus of the investigations is usually on the analysis of the local structural behaviour and/or the locally increased stresses at structural details and discontinuities

2. Elements used for structural modelling

2.1 Selecting the type of element used primarily depends on the objective of the analysis. The charac-teristics of the selected element type have to be able to reflect with sufficient accuracy the stiffness of the structure and the stresses to be analysed.

2.2 Usually, the following types of elements are used for strength calculations of ship structures:

– truss elements (1D elements with only axial stiffness)

– beam elements (1D elements with axial, shear, bending and torsional stiffness)

– plane stress elements (2D elements with mem-brane stiffness in the plane, but without bending stiffness about the axes lying in the plane)

– plate and shell elements (2D elements with membrane, bending and torsional stiffness)

– solid elements (3D elements)

– boundary and spring elements.

When using different element types, attention shall be paid to the compatibility of the displacement functions as well as the transferability of the boundary loads and

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Section 1 Basic Principles V - Part 1GL 2011

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stresses, particularly for the coupling of elements with and without bending stiffness at the nodes.

3. Checks of the model

Geometry of the modelled structure, chosen elements and associated material characteristics as well as ap-plied boundary conditions have to be checked system-atically for errors.

D. Loads and Loading Conditions

1. General notes

1.1 The relevant loads for the strength analyses of ship structures can generally be classified into the following types:

– static (stillwater) loads from the deadweight of the ship and cargo and from the hydrostatic pressure caused by the buoyancy and tank con-tents

– wave-induced loads, i.e. dynamic pressure, loads from accelerated masses and tank con-tents, as well as internal and external hydrody-namic impact forces

– other variable loads from the ship's operation, e.g. from the action of the engines or the rudder, and also wind loads and ice loads

– loads due to container handling or special cargo types

– loads in case of accidents, e.g. collision, ground-ing or flooding of compartments

1.2 The selection and generation of the load cases to be analysed shall be done in such a way that, with respect to the sum of the forces and moments, either fully balanced load cases are created or clearly de-fined, realistic sectional forces and/or deformations are obtained at the model boundaries or supports.

1.3 Since several of the load components men-tioned are of a stochastic nature, and because the se-lection and determination of the relevant load cases might be very complex, there are simplified proce-dures which can be used for practical cases. Moreover, there are special procedures which refer particularly to wave-induced loads, but can also be applied to other stochastic load effects.

2. Simplified procedures

2.1 Under this approach selected (deterministic) load cases are considered that are decisive for the strength of the structural areas under analysis. In gen-eral, these load cases consist of unfavourable, but physically meaningful, combinations of diverse load effects. For assessments of the fatigue strength, those

load cases are to be selected that generate both maxi-mum and minimum stresses at the critical points.

2.2 Load cases represent unfavourable loading conditions combined with the following unfavourable wave situations:

– wave from astern and ahead (with respect to the vertical hull girder bending and loads on the forebody)

– oblique waves from astern and wave from ahead when the ship is upright (relevant for container ships which react sensitively to horizontal bend-ing moments and torsional moments in the hull girder)

– oblique waves from astern and wave from ahead when the ship is rolling (insofar as this is rele-vant for the ship structure or component under consideration).

2.3 Application of the load components and load combination factors are specified in the GL Structural Rules for Container Ships (I-1-5).

2.4 With respect to the loading conditions, condi-tions with uniform and non-uniform cargo distribution at maximum draught should generally be considered. Furthermore, the relevant loading conditions with single holds or tanks loaded to the maximum or empty, as well as ballast conditions, have to be in-cluded in the computations.

2.5 With regard to the situation of waves from astern and/or ahead, the load cases "ship on wave crest" and "ship in wave trough" have to be analysed, whereby the position of the crest or trough is to be varied. The external pressure shall correspond to the phase relations between ship and wave. Moreover, vertical and longitudinal acceleration components shall be applied that have an unfavourable effect on the masses of the ship and the cargo or tank contents.

2.6 The situations with oblique wave from astern or ahead, when the ship is upright, has to be chosen so that the maximum torsional or horizontal bending moments are applied at various positions of the hull girder, whilst the vertical bending moment exhibits values that are generally reduced in relation to the peak value. Furthermore, the relevant vertically and longitudinally oriented acceleration components that have an unfavourable effect on the masses of the ship and the cargo or tank contents shall be applied.

2.7 The situations for rolling of the ship are to be selected so that the maximum transverse accelerations actually occur. The vertical and horizontal accelera-tion components that have an unfavourable effect on the masses of the ship and the cargo or tank contents shall be applied.

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3. Special procedures

3.1 As an alternative to the simplified procedure with selected (deterministic) load cases, there are also special procedures which are especially suited for consideration of the wave-induced ship motions and loads. For specified irregular waves, there are two possibilities for calculating the motions and loads:

– computation in the frequency domain and assess-ment with the aid of the spectral method

– computation in the time domain by simulation

The natural seaways are usually characterized by energy spectra. Here, the use of the Pierson-Moskowitz spectrum is recommended. The results shall be as-sessed statistically, whilst considering the frequency of occurrence of the seaways, cargo distributions, ship's courses and speeds.

3.2 For computations in the frequency domain, the first step is to determine the structural response to harmonic elementary waves, in the form of transfer functions which apply for each case of a particular cargo distribution, ship speed and heading relative to the wave direction. Here a sufficient number of wave frequencies shall be taken in order to consider the resonance peaks of the structural response with suffi-cient accuracy. For a specified natural seaway, the spectrum of the structural response is obtained from the transfer function and the wave spectrum.

3.3 For computations in the time domain, the loading process shall be generated in a suitable man-ner from the characteristic data of the wave spectrum. The time domain for analysis of the structural re-sponse shall be selected to be large enough, so that the subsequent statistical evaluation can be performed with sufficient accuracy with respect to the expected values.

3.4 The structural response for a natural seaway is to be determined for a representative selection of waves, container distributions, ship's headings and speeds, and these shall be selected with reference to their frequency of occurrence and the structural re-sponse to be assessed. For the waves, the long-term statistics of the North Atlantic should be used in gen-eral. If the examination is not to be performed in de-tail, a uniform distribution for the ship courses and 2/3 of the maximum speed can be assumed. For the load-ing conditions see 2.4. In the statistical assessment of the structural response, the probability level specified in the GL Structural Rules for Container Ships (I-1-5) is to be used as the basis.

4. Modelling the loads

4.1 The loads have to be modelled realistically. Distributed loads shall be converted to the equivalent nodal forces. If necessary, the modelling of the struc-ture has to be adapted to the modelling of the loads.

4.2 If the boundary deformations derived from coarse models of large structural areas are applied to local models, the correspondingly interpolated values shall be specified for the intermediate nodes. In addi-tion, the loads acting within the local structural area are to be applied, insofar as they are relevant.

5. Load input check

5.1 The input data on the loads shall be checked thoroughly for errors. As is the case for the structural geometry, here the effectiveness of the check can be increased considerably with the aid of suitable check-ing programs and visualization of the data.

5.2 It is particularly important to check the sums of the forces and moments. For balanced load cases, it is to be ensured that the residual forces and moments are negligible.

5.3 The checks performed have to be docu-mented.

E. Calculation and Evaluation of the Results

1. Plausibility of the results

1.1 Before and during the evaluation, the results shall be examined for plausibility. This involves, in particular, the visual presentation and checking of the deformations to see whether their magnitudes lie within the expected range and whether their distribu-tions are meaningful with respect to the loads and boundary conditions or supports.

1.2 Furthermore, it should be checked whether the forces and moments at the supports lie within the expected order of magnitude or can be neglected, as appropriate for the modelling used.

1.3 For local models with specified boundary deformations from the models of large structural ar-eas, it is necessary to check whether the stresses near the boundaries correspond for the two models.

2. Deformations

2.1 The deformations of the structure should generally be plotted so that other persons can perform a plausibility check of the results. Here it has to be observed that in a three-dimensional representation the direction of the deformation is not clearly defined.

2.2 A further evaluation of the deformations is generally performed with a view to special questions for certain structures, e.g. for deformations of the foundations of propulsion plants or supports of hatch covers.


Section 1 Basic Principles V - Part 1GL 2011

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3. Stresses

3.1 Stresses have to be checked with respect to the permissible values, as defined in the GL Structural Rules for Container Ships (I-1-5). The corresponding stress category is to be observed, see B.3. - B.6. If necessary, stress components that are missing because of the selected models and element types shall be superimposed.

3.2 For the stress evaluation simplifications in the model in relation to the real structure have to be included in the assessment.

3.3 In models with relatively coarse meshes, the reduced effective breadth has to be considered, if applicable. Furthermore, local stress increases at exist-ing structural details and discontinuities shall be in-cluded in the assessment, if their effect is not consid-ered separately.

3.4 To improve the clarity, it is recommended that the assessment be carried out with the aid of utili-sation factors, which are obtained from the relation-ship between the existing and the permissible stress. Result tables should be set up and sorted according to the utilisation factors.

3.5 For analyses that are nonlinear with respect to materials, the local strain shall generally also be de-termined and assessed in addition to the local elastic-plastic stress.

4. Buckling strength

The safety with respect to buckling failure is to be determined by considering all calculated stress com-ponents in the member area under assessment, on the basis of the criteria given in the GL Structural Rules for Container Ships (I-1-5), Section 3. In the buckling analysis of stiffeners, the effective breadth of the asso-ciated plating has to be taken into account.

5. Fatigue strength

5.1 Fatigue strength aspects shall generally be taken into account in the assessment of ship structures, owing to the cyclic stresses that are usually present. In strength analyses for specified load cases, a simplified assessment can be performed if the load cases accord-ing to D.2. are chosen such that the maximum stress ranges are approximately attained in the components under consideration. Calculation of fatigue strength is then to be carried out on the basis of the GL Structural Rules for Container Ships (I-1-5), Section 20.

5.2 Container ship structural members to be as-sessed for fatigue strength have to be selected accord-ing to the structural arrangement characteristics of the individual ship. In general fatigue strength calcula-tions have to be carried out for hatch corners, side shell longitudinals, large openings and cut-outs in members subjected to cyclic loads and to the welded joints of these members.

5.3 In the assessment of the stresses with regard to fatigue strength, the stress type has to be consid-ered, i.e. whether nominal stresses or locally increased notch or structural stresses are calculated with the chosen model.

5.4 For the assessment, it is recommended that utilisation factors are applied; these are obtained from the ratio of the maximum actual stress range to the permissible stress range for an equivalent stress spec-trum of the same shape and number of load cycles, see also the GL Guidelines for Fatigue Strength Analyses of Ship Structures (V-1-2).

6. Presentation of the results

6.1 The results obtained and the conclusions made on the basis of these results shall be clearly and completely documented.

6.2 The documentation can take the form of plots and lists. Lists are necessary for the case that a graphi-cal presentation of results is not sufficiently accurate. Extensive lists shall be sorted, for example, according to utilisation factor.

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Section 2

Global Strength Analysis

Fig. 2.1 Global FE model of a container ship

A. General

1. The objective of the global strength analysis is to obtain a reliable description of the overall hull girder stiffness and to calculate and assess the global stresses and deformations of all primary hull members for specified load cases resulting from realistic loading conditions and the wave-induced forces and moments.

2. Generally, the purpose of the global analysis is not to judge on local stresses due to stiffener- or plate bending, whereas the focus is at realistic stiffness and deformation characteristic of the hull girder par-ticularly under consideration of the torsional moments.

3. The finite element analysis of the entire ship shall verify the structural adequacy of the longitudinal and transverse primary structure. Particularly the scantlings of members which are influenced mainly by the torsional moment i.e. the side shell longitudinals, radii of the hatch corners as well face plates and hori-zontal girders of the transverse bulkheads shall be checked by a global analysis.

4. Stresses in all primary members will be as-sessed with respect to yield strength and buckling. Hatch corners and side shell longitudinals are subject to fatigue strength analysis.

5. The applied tools for the finite element calcu-lations shall be based on recognised software. As recognised software is considered all finite element programs that can show results to the satisfaction of Germanischer Lloyd.

B. Structural Idealization

1. Model size, coordinate system and units

1.1 The global FE model is to represent the entire ship including the deckhouse. Due to the asymmetric loading in seaway half models cannot be accepted.

1.2 A right-handed cartesian coordinate system according Fig. 2.9 should be used with:

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Section 2 Global Strength Analysis Chapter 1Page 2–1

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– X measured in the longitudinal direction, posi-tive forward from the aft perpendicular

– Y measured in the transverse direction, positive from the centreline to port

– Z measured in the vertical direction, positive upwards from the baseline

1.3 With respect to unified evaluation software developed at GL the following units and material properties shall be used:

Table 2.1 Units of GL software

Length m

Mass t

Force kN

Table 2.2 Material properties

Young’s Modulus [kN/m2]

PoissonValue

Shear Modulus [kN/m2]

Density

[t/m3] Steel 2,06 ⋅ 108 0,30 0,792 ⋅ 108 7,80

Alu 0,69 ⋅ 108 0,33 0,259 ⋅ 108 2,75

1.4 The minimum yield stress ReH has to be re-lated to the material defined as indicated in Table 2.3. Consequently for every used steel a separate data set for the material has to be defined regardless the fact of same Young’s Modulus. Elements have to refer to this material data set as the materials are defined in the structural drawings. Later used evaluation routines refer to these material data sets when permissible stresses and buckling strength will be checked.

Table 2.3 Minimum yield stresses for steel

1 2 3 4 5

ReH [N/mm2] 235 315 355 390 460

2. Element types

2.1 The global strength calculation will deliver the global stress state resulting from hull girder bend-ing and torsion. Local effects like bending of stiffened plates under water pressure will not be analysed with the global model. The membrane stress state will be the dominating result.

2.2 All primary structural members, i.e shell, inner skin, girders, web frames, horizontal stringers and vertical girders of transverse bulkheads, are to be idealized preferably by 4-node plane stress or shell elements.

2.3 Secondary stiffening members may be ideal-ized by 2-node truss or beam elements. High trans-

verse and longitudinal girders can either be idealized by use of beam elements or by use of plane stress elements (PSE) for the webs and truss elements for the flanges. In case the FE-model shall be used for a sub-sequent vibration analysis beam elements are to be preferred. For beam elements the effective breadth has to be carefully evaluated when defining the bending stiffness. For the axial stiffness, however, only the sectional area of the profile shall be considered.

2.4 The characteristics of the selected element type shall reflect the stiffness of the structure with sufficient accuracy. When carrying out a strength analysis, adequate knowledge of the characteristics of the elements used is a prerequisite

2.5 When using different element types, attention shall be paid to the compatibility of the displacement functions as well as the transferability of the boundary loads and stresses, particularly for the coupling of elements with and without bending stiffness at the nodes.

2.6 In the coarse meshes used for global analyses it is beneficial that the plane stress or shell element's shape functions include "incompatible modes" which offer improved bending behaviour of the modelled member, as illustrated in Fig. 2.2. This type of element is required for the modelling of web plates with a single element over the full web height, in order to calculate the bending stress distribution correctly. Disadvantage of the incompatible mode is that the element edges could be diverged and reproduce a lower stiffness. But in combination with the used coarse mesh these elements reproduce the stiffness of the hull girder in a realistic way.

Fig. 2.2 Improved bending of web modelled with one element over height

2.7 Triangular elements with a linear shape func-tion shall be avoided where possible. These 3-node elements can only represent constant strain or stress. They have no in-plane bending characteristic and are therefore too stiff in areas of significant stress gradi-ents. As well 4-node elements with inner angles below 45° or above 135° between the edges shall be avoided.

2.8 The element edge aspect ratio shall generally not exceed the value 3. This aspect ratio may be ex-ceeded in areas of low stress gradients or where a constant stress distribution over the element width can be expected.

2.9 Elements should be preferably oriented ac-cording to Fig. 2.3 In case the specification regarding the ij-direction and the ij-edge cannot be followed, at


Section 2 Global Strength Analysis V - Part 1GL 2011

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least the orientation of the normal vector has to be according to Table 2.4 and Fig. 2.3. This convention facilitates load application and the idealisation of corrugated walls as well as the evaluation of the ele-ment stresses.

Table 2.4 Element orientation

ij-Direction ij-Edge Normal vector direction to

Decks Transverse Aft Top Longitudinal walls Longitudinal Bottom Inside

CL-walls Longitudinal Bottom PS Transverse walls Transverse Bottom Fore

Shell Longitudinal Inwards/ Bottom Inwards

3. Modelling the structure

3.1 Mesh size shall be determined according to proper stiffness representation and load distribution. The distance between the longitudinal girders and transverse floors is taken as the standard length of the elements. If the spacing of primary members deviates much from normal, the mesh arrangement described above shall be re-considered to provide a proper meshing of the global FE-model.

Typical meshes used for global strength analysis are shown in Fig. 2.5 for the foreship and Fig. 2.6 for the midship section.

3.2 The FE-model is to be based on the gross scantlings of the hull structures. For buckling evalua-tion the corrosion addition will be deducted.

3.3 Due to the complexity of the ship structure, simplifications are generally necessary in modelling.

These simplifications are permissible, provided that the results are only impaired to a negligible extent.

3.4 Small secondary components or details that only affect the stiffness to a lesser extent can be neg-lected in the modelling. Examples are brackets at frames, sniped short buckling stiffeners and small cut-outs.

3.5 Man holes or cut-outs of significant size shall always be considered to calculate realistic shear stresses. The reduction in stiffness can be considered by a corresponding reduction in the element thickness. Even larger openings which correspond to the element size such as pilot doors are to be considered by delet-ing the appropriate elements.

Plate thickness reduction in way of cut-outs:

a) Web plates with several adjacent cut-outs, e.g. floor plates, longitudinal bottom girder:

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red 0H ht (y) t

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Fig. 2.5 Typical foreship mesh used for global FEA



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Fig. 2.6 Typical midship mesh used for global FEA

3.6 Steps in the plate thickness or scantlings of profiles, insofar as they are not positioned on the ele-ment boundaries, shall be taken into account through correspondingly adapted element data or characteris-tics to obtain an equivalent stiffness.

3.7 The plane elements shall generally be posi-tioned in the mid-plane of the corresponding compo-nents. For thin-walled structures, the elements can also be arranged at moulded lines, as an approximation.

3.8 Plane 2D elements in inclined or curved surfaces shall be positioned at the geometrical centre of the modelled area if possible, in order that the global stiffness behaviour can be reflected as correctly as possible.

3.9 Translatory singularities in PSE structures can be avoided by arranging so-called singularity-trusses as indicated in Fig. 2.7. The FE program GL-Frame suppresses these singularities internally.

singularity node(z-direction)

singularity truss

zy

x

Fig. 2.7 Singularity trusses

3.10 For coarse meshes stiffeners have to be as-sembled to trusses or beams by summarising relevant cross-section data. They have to be arranged at the edges of the plane stress or shell elements. Fig. 2.8 shows an example of a part of a deck structure with an adjacent longitudinal wall with longitudinal stiffeners. In this case the stiffeners at the longitudinal wall and stiffeners at the deck have to be idealized by two truss elements at the intersection of the longitudinal wall and the deck. Each of the truss elements has to be assigned to different element groups: One truss to the group of the elements representing the deck structure the other truss to the element group representing the longitudinal wall. In the example of Fig. 2.8 at the intersection of the deck and wall the deck stiffeners are assembled to one truss representing 2 x 1.5 × FB 100 ⋅ 8 and the wall stiffeners to an additional truss representing 1.5 × FB 200 ⋅ 10.

C. Boundary Conditions

To eliminate rigid body motion of entire global finite element models 6 supports or boundary elements (springs with high stiffness) have to be arranged. As ship and cargo weight are in equilibrium with buoy-ancy and wave loads these boundary elements get no loads. This has to be checked. A typical arrangement is indicated in Table 2.5 and Fig. 2.9. Care shall be taken to place pairs of boundary elements on a single plane to avoid unrealistic deformation plots, e.g. three z-constraints on bottom level.

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Table 2.5 Global support

Location Direction

SB Z CL Y Engine Room

Front Bulkhead PS Z CL X CL Y Collision Bulkhead CL Z

D. Design Loads

1. General

A direct wave load analysis shall be carried out to calculate hull girder forces and moments which in turn have to be in compliance with the rule requirements.

The global FE-model needs to include the masses, because the inertia forces counteract the external sea pressures. All force components obtained from the direct wave load analysis are to be in a state of equi-librium.



D

GL offers the computer program GL Ship Load. This software tool enables efficient determination of loads for the global FE analysis.

2. Mass model

The hydrodynamic analysis needs a correct mass dis-tribution to generate correct motions and forces. The mass models applied in the global FE analysis and the wave load analysis need to be complete and represent the considered loading conditions.

The lightship weight components such as hull struc-ture, machinery and equipment, outfitting, etc. are the same for every considered loading condition. Likewise consumables, effects and stores will vary little if at all.

The other weight groups such as containers and ballast water shall be defined according to each loading con-dition.

2.1 Light ship weight

The weight of the hull structure is obtained by apply-ing a material density to the FE-elements. It is com-mon practice to use an increased value to account for structural components not included in the model, such as brackets. To match a specified centre of gravity position for the hull structure weight, different mate-rial densities can be used for the individual element groups.

The remainder of the lightship weight (such as ma-chinery, hatch covers, and outfitting) and consumables will be represented by a distribution of nodal masses in relevant regions according to their locations and centres of gravity.

The mass of each weight group will be adjusted in order to achieve the correct mass distribution and the position of the centre of gravity. The use of negative nodal masses is not acceptable. The whole mass model shall be in compliance with the considered lightship weight distribution.

2.2 Water ballast and tank contents

The liquid mass in tanks will be represented by distri-bution of nodal masses to the surrounding structure. It is not necessary to include the local pressure distribu-tion of the tanks in the global FE-analysis.

2.3 Container loads

The inertia forces of the containers have to be trans-ferred to the appropriate nodes in the hull structure. Load transfer can be carried out in two different ways:

2.3.1 If the forces are transferred to ship interface nodes prior to a Finite-Element calculation, no explicit auxiliary model to account for the containers is re-quired for the finite-element calculation itself.

2.3.2 If auxiliary systems are used for load applica-tion and load transfer, they shall not influence the stiffness of the FE model. This shall be checked by

test calculation without loads on the auxiliary systems. Deformations of the hull have to result into stresses and strains within the auxiliary systems equal to zero. On-deck containers can be modelled by using plane stress, shell or solid elements, which may be con-nected directly or via the hatch covers to the hull structure by either truss elements. The containers or the hatch covers have to be supported on the coaming by use of a vertically oriented truss element. At the location of the transverse and longitudinal stoppers the structure of the hatch covers will be supported either in transverse direction only or in transverse and longi-tudinal direction, respectively. The centre of gravity for the on-deck containers has to be correctly repre-sented to get realistic heeling moments. If the contain-ers in the holds are modelled by an auxiliary system, again special attention shall be paid to the vertical and horizontal force transfer to the appropriate nodes in the hull structure in order not to influence the stiffness of the ship.

3. Loading conditions In general 2 loading conditions are investigated:

3.1 Max SWBM Maximum displacement at scantling draught with maximum permissible vertical hogging still water bending moment (Max SWBM) shall be considered. If possible with respect to stability, a homogenous weight distribution in all bays with a high stack load for the containers on the deck shall be used for this loading condition. The maximum used charge for water ballast, fuel etc. is limited to around 30 % of the total cargo weight. With the exception of the hold of the midship area, where 40’ containers are to be loaded, the use of 20’ or 40’ containers is optional. A relatively low GM (metacentric height) for the ves-sel’s size will be achieved with this loading condition.

3.2 Min SWBM

Maximum displacement at scantling draught with minimum possible vertical hogging/ maximum sag-ging still water bending moment (Min SWBM) shall be considered. For the hold containers all bays shall be used. The deck containers are to be arranged in the midship area as it is necessary to achieve the Min SWBM. For hold and deck containers a relatively high uniform weight shall be used. The maximum used charge for water ballast, fuel etc. is limited to 20 % of the total cargo weight. The use of 20’ or 40’ contain-ers in the hold and on the deck is optional. A relatively high GM (metacentric height) for the vessel’s size will be achieved with this loading condition.

3.3 One bay empty

This condition is optional for investigation depending on the scope of analysis agreed between yard and ship owner

Similar as the Max SWBM condition but one 40’ bay in a hold of the midship area is to be empty.

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4. Wave load analysis

The ship motions and the pressure distribution on the shell have to be calculated for different wave lengths, heights and heading angles. The design wave ap-proach is based on the following assumptions:

– For every loading condition the hydrodynamic pressure and ship motions are calculated for dif-ferent heading angles by a linear analysis. Ap-plication of the so-called strip theory is suffi-cient. In this approach pressure distribution is determined by linear analysis up to the still wa-ter line only.

– For different sea states the hydrodynamic pres-sure is then adjusted to the real wave contour by a non-linear correction. These non-linear load effects due to the characteristic hull form of con-tainer ships, i.e. pronounced bow and stern flare are significant. The load magnitude including non-linear effects differs considerably from the linear response.

– Since the ship motions are based on the results of the linear analysis, the imbalances of forces due to the non-linear correction of pressures have to be compensated by adjustment of the ship accelerations. Inertia forces of the ship and hydrodynamic pressure shall be in equilibrium.

– In a "simulation in regular waves", numerous wave situations are systematically analysed vary-ing wave lengths, wave crest positions and head-ings in a first step, taking the hull shape fully into account. With these load cases the vertical and horizontal wave bending and the torsional moments according to the GL Structural Rules for Container Ships (I-1-5), Section 5 are to be covered.

– Consideration of pressure and acceleration loads caused by free (resonant) rolling is also neces-sary. Here the additional torsional moment due to inertia forces from the containers during roll-ing may play an important part. The maximum rolling angle is to be determined on the basis of a refined ship motion analysis including rolling in a realistic way or on design values given in this Section.

– For every loading condition around 20 load cases are finally selected for the finite element analy-sis. Selection of these load cases generally results in envelope curves of bending and torsional mo-ment over the ship length, approximating the curves found in the systematic variation of wave situations and considering also other design load parameters such as acceleration and rolling.

The applied tools for calculation of wave loads shall be based on recognised software. All wave load programs that can show results to the satisfaction of Germani-scher Lloyd will be considered recognised software.

The wave load analysis shall be carried out for a ship's speed corresponding to 2/3 of the service speed. Addi-

tionally, non-linear effects have to be included in the wave load analysis.

4.1 Design wave amplitude

The length and height of the design wave have to be chosen with respect to the vertical design bending mo-ment of the GL Structural Rules for Container Ships (I-1-5), Section 5.

As a first step, the most sensitive wave length for the vertical wave bending moment has to be found for the wave crest condition (hogging) and the wave trough condition (sagging). The most sensitive wave configu-ration (length and crest position) is defined as the condition where the vertical bending moment accord-ing to the Rule is achieved with a wave height as small as possible. This wave configuration is the so-called design wave.

For head and following seas a variation of the wave length from 0,8 to 1,2 LW/Lpp is to be considered. During this variation process and during the system-atic "simulation in regular waves", the relevant wave amplitude A depends on the considered wave length.

ji3 3W,i pp W, j pp

AAL / L L / L

=

To compare the relevant amplitudes from different wave lengths, they shall be scaled on the wave length Lw/Lpp = 1

For each wave length, a full period is considered. Therefore, 50 equidistant positions of the wave crest along the ship length are recommended.

4.2 Reference wave amplitude

The reference wave amplitude is the corresponding amplitude of the design wave scaled on the wave length LW/Lpp = 1.

The ratio of the reference wave amplitude for sagging and hogging condition corresponds to a reduction factor for the sagging amplitude.

saggred

hogg

AW

A=

For positions of the wave crest between amidships (hogging condition) and the ship ends (sagging condi-tion) following formula has proved to be useful to adjust the dynamic wave amplitude Adyn.

( ) ( )( )2dyn (x / L 0,5) red ppppA A 1 1 W cos x / L== ⋅ − − ⋅ π ⋅

For beam sea (60° – 120°) the sagging reduction of the amplitude shall be neglected.

4.3 Simulation in regular waves

For ships with a high deck opening ratio, situations in oblique waves and by free rolling have been found to be decisive for several structural components.



D

4.3.1 Additional roll angle

Conventional wave load analysis cannot simulate the roll motion adequately. To solve this problem, GL requires the method of additional roll angle to simu-late realistic distribution of the torsional moment over the ship length.

In order to avoid severe load combinations, which are unlikely to occur, the additional roll angle shall be applied under the assumption that maximum wave amplitude A and extreme roll angle ϕ do not act si-multaneously.

2 2

( 0) max

A 1A ϕ=

⎛ ⎞ ⎛ ⎞ϕ+ =⎜ ⎟ ⎜ ⎟⎜ ⎟ ϕ⎝ ⎠⎝ ⎠

This interaction formula assumes statistical independ-ence between wave amplitude and additional roll angle.

Generally two combinations of additional roll angle and wave amplitude have to be considered.

max max0,5 A 0,866 A andϕ = ⋅ϕ ⇒ = ⋅

max maxA 0,50 A 0,866 or= ⋅ ⇒ ϕ = ⋅ϕ

max max maxA 0, 25 A 0,97= ⋅ ⇒ ϕ = ⋅ϕ ≈ ϕ

The maximum roll angle ϕmax in degrees for a prob-ability level of Q = 10-6 can be derived by:

max 02160 f (GM )

B 60ϕ = ⋅

+

f(GM0) = 1,0 – exp (–GMdyn/GMmin)

GMdyn = GM0 + 0,01 ⋅ B

GMmin = B2/(8 ⋅ Lpp)

GM0 = metacentric height of the actual loading condition

ϕmax is not to be less than 17,5°, reflecting the in-creased sensitivity in beam wind loads at low meta-centric heights.

4.3.2 Variation of the wave parameters

In the "simulation in regular waves", a large number of wave situations is systematically analysed with different wave lengths, wave heading angles, addi-tional roll angles and wave crest positions. Each addi-tional roll angle, positive (starboard side immersed) and negative (port side immersed), shall be combined with 6 wave heading angles. The necessary wave length depends on the wave heading angle. Table 2.6 shows the relevant combinations of the wave parame-ters, which have be to analysed for each loading con-dition. Head and following seas correspond to 180 and 0 degrees respectively. Due to the symmetry of the ship geometry, it is sufficient to consider wave direc-tions from one side. The heading angles 30, 60, 120 and 150 degrees correspond to waves from starboard.

Table 2.6 Variation of the wave parameters

additional roll angle ϕ 0° ±50 % ϕmax ±87 % ϕmax or ±ϕmax wave Amplitude A 100 % 87 % 50 % or 25 %

wave heading angle φ 0, 180 30, 150 60, 120 0, 180 30, 150 60, 120 0, 180 30, 150 60, 120 wave lengthship length

0,35 2 × 50 4 × 50 4 × 50 0,40 2 × 50 4 × 50 4 × 50 0,45 2 × 50 4 × 50 4 × 50 0,50 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 0,55 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 0,60 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 0,65 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 0,70 2 × 50 4 × 50 4 × 50 0,80 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 0,90 2 × 50 2 × 50 4 × 50 4 × 50 4 × 50 4 × 50 1,00 2 × 50 4 × 50 4 × 50 1,10 2 × 50 4 × 50 4 × 50 1,20 2 × 50 4 × 50 4 × 50

analysed wave situations 500 700 700 1000 1400 1400 1000 1400 1400

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For each combination of additional roll angle and heading angle a full wave period is considered. Also here 50 equidistant positions of the wave crest over the entire ship length are recommended. The resulting wave amplitude is to be based on the design wave amplitude and the corrections for the additional roll angle, the wave length and the wave crest position. In total, 9500 situations of the vessel in regular waves are to be analysed.

4.4 Load case selection

The relevant load cases for FE analysis are to be se-lected by evaluation of sectional forces and moments along the ship's length for all analysed wave situ-ations. In these load cases the vertical and horizontal wave bending and the torsional moments have to match the design values defined in the GL Structural Rules for Container Ships (I-1-5), Section 5.

Additionally critical combinations of the sectional forces and moments have to be considered, such that the largest stress values and stress ranges for fatigue are obtained. Table 2.8 shows the moment’s distribu-tion of the dominant sea conditions.

Table 2.7 shows the ratio of the maximum considered moments to the design values.

For the torsional moments the zero-crossing point is also of prime importance. In upright conditions or conditions with 50 % additional roll angle the tor-sional moment has a zero-crossing about at 0,5 x/L.

In conditions of free rolling (with either 0,87 ϕmax or ϕmax) the point of zero-crossing depends on the load-ing condition. For the Max SWBM it is positioned about at 0,3 x/L and for the Min SWBM at 0,7 x/L.

The applied bending and torsional moments shall approximately represent the envelope curves accord-ing to the GL Rules. Therefore it is necessary to select several load cases of the dominant sea conditions.

For each loading condition about 20 load cases are finally selected for the finite element analysis.

Note

fQ is a function of the design lifetime. For a design lifetime of n > 20 years, fQ may be determined by the following formula for a straight-line spectrum of sea-way-induced stress ranges:

⎛ ⎞

− ⎜ ⎟⎜ ⎟⎝ ⎠

5

Q2 10f 0,125 log

n

−⋅= ⋅

5. Loads on bow and stern structures

Consideration of slamming loads is crucial for con-tainerships with excessive bow flare and stern over-hang. Since direct calculation of slamming loads is extensive and time consuming, GL require the genera-tion of load cases from rule-based slamming pressures pe. The concept used to obtain balanced load cases comprises the following steps:

– Consider static loads that represent the loading condition Max SWBM. No hydrostatic loads are applied to elements where slamming pressures are at least as large as the static pressure.

– Pressures pe on shell elements are computed from GL Structural Rules for Container Ships (I-1-5), Section 4, B.2.2 or B.2.3 for bow area and stern areas, respectively.

– Pressures pe on bow and stern areas are applied in a way that, in combination with hydrostatic and weight loads, the resulting vertical bending moment (incl. stillwater loads) does not exceed the rule wave sagging bending moment (without stillwater loads). This restriction is imposed be-tween 10% and 90% of the ship’s length. For typical vertical bending moment distributions, see Fig. 2.10.

– For this purpose, bow and stern areas are di-vided into several vertical areas. Load cases are generated by adding slamming loads, area by area, until the required vertical bending moment is reached. If necessary, the slamming pressure

Table 2.7 Moment factors

Still Water Static Moments

Wave-Induced Dynamic Moments

Vertical Torsion Vertical Horizontal Torsion

Head and follow sea 1 1 0,75 * 0 0

Oblique sea 1 1 0,50 0,75 * 0,75 *

Free rolling 1 1 0,25 0,75 * 0,75 *

* fQmin = 0,75 for n = 20 years

fQ = probability factor according to GL Structural Rules for Container Ships (I-1-5), Section 4, Table 4.2



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Table 2.8 Load case selection

Max Stillwater Bending Moment Min Stillwater Bending Moment

Still

wat

er

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

Max

Hog

ging

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

Max

Sag

ging

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

Vertical

Torsion

Obl

ique

sea

in w

ave

cres

t

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent

VerticalHorizontalTorsion

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


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Table 2.8 Load case selection (continued)

Max Stillwater Bending Moment Min Stillwater Bending Moment

Obl

ique

sea

in w

ave

trou

gh

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


Free

rol

ling

in w

ave

cres

t

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


Free

rol

ling

in w

ave

trou

gh

0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


0 0.2 0.4 0.6 0.8 1

x/L

Mom

ent


on the last added area is scaled by a factor less than one, so that the resulting vertical bending mo-ment does not exceed the rule bending moment.

– In this way, several load cases are generated until at each z-position above the ballast water-line the pressure pe is applied.

Each slamming load case results from the combination of pressures pe, hydrostatic loads, and weight loads. These loads are balanced by adjusting the acceleration factors for the weight loads.

This procedure represents the slamming condition for global strength analyses in a simple but realistic way and enables dimensioning of fore and aft ship areas. The evaluation is limited to permissible stresses and buckling strength only. The fatigue criteria are ignored for slamming load cases.

� ��

��

��

��

��

��

��

�

��

��

��

Fig. 2.10 Vertical bending moments without and with slamming loads



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E. Model Check

The FE-model shall be checked systematically in respect of the following possible errors:

– fixed nodes

– nodes without stiffness

– intermediate nodes on element edges, not con-nected to the element

– trusses or beams crossing shells

– double shell elements

– extreme element shape (element edge aspect ration and warped elements)

Additionally verification of the correct material and geometrical description of all elements is required. Also the moments of inertia, section moduli and neutral axes of the complete cross sections shall be checked.

For each load case, the sum of forces and the reaction forces of the boundary elements shall be negligibly small.

To check the boundary conditions and detect weak areas as well as singular sub-systems, a test calcula-tion run is to be performed. The model should be loaded with a unit force to all nodes for each coordi-nate direction. This will result in 3 load cases – one for each direction. The calculation results have to be checked with respect to maximum deformations in all directions. This test helps to find areas of improper connections between adjacent elements or gaps be-tween elements.

All checks performed shall be documented. For in-stance all thickness plots of all webframes, longitudi-nal girder sections, decks and the bottom and side shell have to be printed out as shown in Fig. 2.11.

F. Evaluation

1. Permissible stresses

The following limits are applicable for the nominal stresses:

normal stress 175/k [N/mm2]

shear stress 110/k [N/mm2]

equivalent stress 190/k [N/mm2]

Where k is the material factor:

k ReH [N/mm2] 1,0 235

0,78 315 0,72 355 0,66 390 0,62 460

2. Buckling strength

The buckling strength is checked for compliance with the GL Structural Rules for Container Ships (I-1-5), Section 3, F. with a safety factor of S = 1,1.

Two-axial element stresses of the FE-model contain the Poisson-effect and stress values will be modified ac-cording to the specifications in the GL Structural Rules for Container Ships (I-1-5), Section 3, Note in F.1.

3. Fatigue of hatch corners

The global analysis already allows for the considera-tion of fatigue aspects. In such a simplified fatigue analysis, the shape of the stress spectrum, the number of load cycles and other fatigue parameters are as-sumed on the basis of the GL Structural Rules for Container Ships (I-1-5), Section 20.

3.1 Local model

It is required to carry out a fine mesh analysis for every hatch corner by means of a local model. This model shall extend two web spaces aft and forward of the considered hatch corner in the longitudinal direc-tion, and one container height above and below.

The results are sensitive to the mesh arrangement in way of the hatch corner area. Therefore, it is required that an arc equal to a quarter of a circle be divided at least into 10 elements.

To evaluate the edge stresses of the hatch corner it is useful to arrange truss elements along the free edge with a zero cross sectional area.

Secondary stiffeners may be represented by truss elements as in the global model.

3.2 Load application

A maximum stress range is to be derived within each loading condition.

The deflections obtained from the global analysis will be applied to the relevant nodes of the local model as forced deformations.

If the size of the local model is greater than in the description above, local loads like container loads and sea pressures shall be applied on the local model if they are relevant.

4. Fatigue of longitudinal stiffeners

The global uniaxial stress and the corresponding local lateral pressure for the longitudinal stiffeners in the side shell can be evaluated by the global strength analysis. With these data, the fatigue strength for the connection between the longitundinal stiffeners and the web frames shall be assessed. For each loading condition the maximum and minimum stress has to be determined. Port side and starboard side are to be combined to determine the maximum stress range, because wave directions were considered from only one side in the load case selection. The total stress is the

V - Part 1 GL 2011


F

sum of the global stress (equivalent to the FE-stress) and the local stress due to stiffener bending. The local stress shall be calculated on the basis of the GL Struc-tural Rules for Container Ships (I-1-5), Section 9, B. In addition to the outside pressure based on the wave load analysis, the static pressure due to a full wing tank shall also be considered. Finally, the minimum required detail categories should be calculated on the basis of the GL Structural Rules for Container Ships (I-1-5), Section 20.

Note

Other significant fluctuating stresses in the longitudi-nals due to deflections of supporting transverses as well as additional stresses due to the application of non-symmetrical sections have to be considered.

G. Documentation

1. Structure of report

The global strength analysis has to be documented by a report. In general the report shall be structured as follows:

– Scope of investigation

– General

– Description of the strength investigations

– Ship specifications

– Main ship data

– Container arrangement

– Finite element model

– Considered drawings

– Characteristics of the FE-model

– Loading conditions

– Load cases

– Global loads resulting from the seaway

– Slamming loads on bow and stern

– Results

– Global deformation

– Hatch cover deflections

– Permissible stresses

– Proof of buckling strength

– Proof of hatch corner stresses

– Stress plots

– Fatigue results of longitudinal stiffeners

– Summary

2. Content of report

In addition to the textual component, the report shall also provide the following information in the form of figures and tables:

2.1 Drawings and basic information

A general arrangement plan together with a list of relevant drawings including dates and versions shall be provided as well as frame table and a list of ele-ment groups.

2.2 3-D views of the FE-model

It is recommended that overview 3-D plots of the FE model be included. Colour plots of plate thickness and/or material yield strength provide added clarity.

2.3 2-D views of the FE-model

2.3.1 All relevant structural members have to be documented by plots (Fig. 2.11).

The plots shall contain the following information:

– plate thickness [mm] (plane stress or shell ele-ments)

– cross sectional area [cm2] (trusses)

– cross section number (beams)

The cross sectional properties of beams have to be summarised in a separate table.

2.3.2 Using an element "shrink" option, truss and plane stress elements can be separated. Depending on the mesh fineness it might be necessary to present 2 figures, showing plate thicknesses and truss sectional areas respectively.

2.3.3 Standard scales used in drawings shall be chosen.

2.3.4 The dimensions proposed for documentation may differ from those recommended for the preferred units. This could be caused by an internal data conver-sion. The units have to be indicated on plots that have common geometric dimensions.

2.4 Mass distribution

The mass distribution of the lightship weight and the analysed loading conditions have to be documented. The weight and centre of gravity of each weight group shall be listed in tables. In addition for each bay the number of containers is to be listed. Additionally, the in-hold and on-deck containers shall be separated (Fig. 2.12).

2.5 Summary of load cases

The selected load cases for the FE-analysis have to be documented. The wave parameters considered and the maximum sectional forces and moments will be listed in a table (Fig. 2.13).



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2.6 Envelope curves of all load cases

The bending and torsional moments shall meet the design values to be documented by envelope curves. Fig. 2.14 shows the envelope curve for the torsional moment of all selected load cases.

2.7 Documentation of the load cases For each selected load case, the distribution of the sectional forces and moments over the ship length shall be documented as in Fig. 2.15.

2.8 Global deformation In order to obtain an impression of the global defor-mation behaviour, overall deformation for every se-lected load case is to be documented in 3-D- and 2-D-views (Fig. 2.16).

2.9 Hatch cover deflection One important result of the global strength analysis is the determination of the deformed hatch diagonal dimension and the determination of the hatch cover movements relative to the hatch coaming and relative to the adjacent hatch covers. In Fig. 2.17 the different positions are shown.

2.10 Fatigue of hatch corners

The fatigue results regarding hatch corners have to be summarised in tables. Fig. 2.18 shows the results in detail for one hatch corner and the summary for one deck.

2.11 Fatigue of longitudinal stiffeners

The fatigue results regarding longitudinal stiffeners have to be summarised in tables. Fig. 2.19 shows an example for the presentation of the results.

2.12 Stress plots

Fig. 2.20 shows an example for a stress plot. The maximum stress of all load cases for each element shall be documented.

2.13 Buckling results

Buckling analysis for plate fields shall be documented.

2.14 Changes of the ship design

Proposed structural modifications, if necessary, shall be included in the report.

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Fig. 2.11 2-D views of the FE-model, two plots of the same bulkhead section showing plate thick-ness of plane stress elements in [mm] and separately the cross sectional area for truss elements in [cm2] attached to this bulkhead



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Mass distribution ofMax SWBM condition at scantling draft, Depature

L.C.G V.C.GTEU Weight/ WEIGHT FROM FROM

ITEMS TEU A.P. BL[t] [m] [m]

NO.01 BAY HOLD 26 10 260 108.08 16.86NO.03 BAY HOLD 32 10 320 101.76 15.67NO.05 BAY HOLD 40 10 400 93.49 14.34NO.07 BAY HOLD 46 10 460 87.17 13.46NO.09 BAY HOLD 56 10 560 78.90 12.39NO.11 BAY HOLD 60 10 600 72.58 11.73NO.13 BAY HOLD 70 10 700 64.31 11.19NO.15 BAY HOLD 80 10 800 57.99 11.00NO.17 BAY HOLD 80 10 800 49.72 10.65NO.19 BAY HOLD 80 10 800 43.40 10.59NO.21 BAY HOLD 80 10 800 35.13 10.59NO.23 BAY HOLD 80 10 800 28.81 10.59NO.25 BAY HOLD 60 10 600 20.54 10.59NO.27 BAY HOLD 40 10 400 14.22 10.59NO.29 BAY HOLD 30 10 300 5.95 10.59

NO.01 BAY DK 44 10 440 108.08 25.06NO.03 BAY DK 50 10 500 101.76 25.06NO.05 BAY DK 56 10 560 93.49 25.06NO.07 BAY DK 58 10 580 87.17 25.06NO.09 BAY DK 58 10 580 78.90 25.06NO.11 BAY DK 58 10 580 72.58 25.06NO.13 BAY DK 84 10 840 64.31 26.37NO.15 BAY DK 84 10 840 57.99 26.37NO.17 BAY DK 84 10 840 49.72 26.37NO.19 BAY DK 84 10 840 43.40 26.37NO.21 BAY DK 84 10 840 35.13 26.37NO.23 BAY DK 74 10 740 28.81 26.37NO.25 BAY DK 74 10 740 20.54 27.66NO.27 BAY DK 60 10 600 14.22 27.66NO.29 BAY DK 60 10 600 5.95 27.66

CARGO TOTAL 1872 18720 54.01 19.49

DEP. BUNKER 1045 45.77 5.60

NO.2 S.W.B.T.(S) 305 90.00 5.60NO.2 S.W.B.T.(P) 305 90.00 5.60NO.6 S.W.B.T.(S) 367.5 49.05 6.83NO.6 S.W.B.T.(P) 367.5 49.05 6.88NO.7 S.W.B.T.(S) 367.5 69.87 6.83NO.7 S.W.B.T.(P) 367.5 69.87 6.83NO.6 L.S.W.B.T.(S) 339.6 49.04 4.02NO.6 L.S.W.B.T.(P) 339.6 49.04 4.02NO.5 S.W.B.T.(S) 205.5 84.01 11.25NO.5 S.W.B.T.(P) 205.5 84.01 11.25

WATER BALLAST 3170 66.29 6.57

DEADWEIGHT 22935 55.33 17.07

LIGHT SHIP WEIGHT 7100 55.60 9.75

DISPLACEMENT 30035 55.39 15.34

DRAFT FORWARD [m] 9.88DRAFT AFT [m] 10.15

TRANSV. METACENTRE KMT [m] 16.07VERT CENTRE OF GRAV KG [m] 15.34METAC. HEIGHT GM [m] 0.73

Fig. 2.12 Mass distribution for a loading condition

V - Part 1 GL 2011


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Loading condition A Max SWBM Torsion Rule 184982Hor.Bend. Rule 448990

Taft [m] Tfore [m] v [kn] Vert.Bend. Rule 654001 hogg8.52 8.49 20.0 768630 sagg

No. Wampl Wadyn Wl/L AoE X-wave heel H-Shear V-Shear Torsion %Ru Hor.Bend. %Ru Vert.Bend. %Ru[m] [m] [-] [°] [m] [°] [kN] [kN] [kN/m] [kN/m] [kN/m]

1 0.000 0.000 0.00 0 0.00 0 5 16479 -191 0 101 0 564628 02 4.584 4.584 1.00 180 91.55 0 6 26482 -136 0 120 0 1059009 763 4.584 3.666 1.00 180 8.98 0 6 -9132 -275 0 105 0 -13884 -754 4.255 4.230 0.80 150 101.50 0 -1863 24507 36846 20 70811 16 990552 655 3.638 3.472 0.50 120 120.27 0 4145 19721 84925 46 192761 43 735538 266 3.230 2.963 0.35 120 51.34 0 -4621 12295 -88913 48 -208923 47 369854 -257 4.255 3.760 0.80 30 141.30 0 -1885 7971 -45472 25 -78358 17 212441 -468 3.688 3.649 0.80 150 104.82 10.4 5668 22132 -89564 48 240880 54 884004 499 3.512 3.348 0.45 120 120.63 10.4 7376 19025 117298 63 344648 77 712609 23

10 3.527 3.511 0.70 30 82.84 10.4 -5919 17565 -136926 74 274503 61 693411 2011 3.378 3.064 0.40 120 48.47 -10.4 -5992 12529 -98712 53 -286489 64 376767 -2412 3.527 3.376 0.70 120 119.19 -10.4 -1144 20165 52096 28 -43235 10 756979 2913 1.819 1.817 0.50 150 87.40 18.1 5552 15777 -100950 55 215425 48 538338 -314 1.688 1.625 0.40 120 117.40 18.1 6895 15858 -130200 70 306974 68 561922 015 2.128 2.106 0.80 150 104.82 18.1 6663 17656 -124342 67 276217 62 660211 1516 1.757 1.600 0.45 120 49.54 -18.1 -5708 13365 115211 62 -241177 54 420699 -1917 1.688 1.681 0.40 60 82.93 -18.1 -4572 13958 92597 50 -166359 37 495283 -918 2.213 2.207 0.90 0 85.09 -18.1 -5502 16659 121488 66 -235292 52 622941 9

Fig. 2.13 Summary of load cases

-1500000

-1000000

-500000

0

500000

1000000

1500000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

x / L

Env.

Cur

ve T

orsi

onal

Mom

ent [

kNm

]

Design Values MSW + MWTDesign Values MWT

Enveloping Curve LC 1-36

Fig. 2.14 Envelope curve for the torsional moment



G

Fig. 2.15 Load case documentation with longitudinal strength distribution

V - Part 1 GL 2011


G

Fig. 2.16 2-D-views of the global deformation



G

container sustaintion point

y stopper

xy stopper

P0A

P11A

P12F

P11F

P0F

P13F

C2F

C2A

P13A

P12A

C1A

S13A

S12A

S13F

S12F

C1F

S11F

S0A S0F

S11A

Δ = S14A

= P14AΔ = P14F

= S14FΔ

Δ

SB

S1

C

P1

PS

C5F

P15F

S15F

Fig. 2.17 Hatch cover deflections

V - Part 1 GL 2011


G

No. 5 Stringer

Location R th Reh DSR FE-Calc. Allow. FE-Calc. Allow. Usage [mm] [mm] N/mm2 N/mm2 N/mm2 N/mm2 N/mm2 N/mm2

FR. 27 200 12 235 125 289 318 498 320 1.56FR. 31 200 12 235 125 197 331 184 306 0.60FR. 32 200 12 235 125 202 310 458 304 1.51FR. 36 200 12 235 125 274 313 498 316 1.58FR. 71 100 10 235 125 201 350 147 326 0.57FR. 72 100 10 235 125 174 355 170 342 0.50FR. 77 100 10 235 125 243 352 169 357 0.70FR. 78 100 10 235 125 172 368 136 355 0.47FR. 83 100 10 235 125 250 346 150 360 0.72FR. 84 100 10 235 125 159 371 143 358 0.43FR. 107 200 16 235 125 332 309 211 321 1.07FR. 108 200 14.5 235 125 116 306 85 299 0.38FR. 109 200 13 235 125 114 348 110 297 0.37FR. 110 200 14.5 235 125 321 308 206 332 1.04FR. 111 200 14 235 125 290 334 160 336 0.87FR. 112 200 14 235 125 128 350 131 292 0.45FR. 114 200 14 235 125 214 301 192 329 0.71FR. 116 200 14 235 125 129 303 187 321 0.58FR. 117 200 14 235 125 234 310 111 310 0.75FR. 121 200 14 235 125 394 315 195 331 1.25FR. 122 200 14 235 125 326 312 183 320 1.04FR. 124 200 14 235 125 145 340 156 297 0.53FR. 126 200 14 235 125 189 318 132 313 0.59FR. 127 200 14 235 125 150 334 84 300 0.45FR. 129 200 14 235 125 131 320 110 317 0.41FR. 131 200 11 235 125 279 315 213 353 0.89FR. 132 200 11 235 125 394 311 208 346 1.27FR. 136 200 11 235 125 290 326 175 356 0.89

DimensionsFatigue Input Data (DSR=Detail Cat.)

Max. Stress Ampl. Cond. Max SWBM

Max. Stress Ampl. Cond. Min SWBM

Fig. 2.18 Fatigue results for hatch corners



G

Fig. 2.19 Fatigue results for the longitudinal stiffeners of the side shell

V - Part 1 GL 2011


G

Fatig

ue L

ong.

Pro

file

Res

ult f

or fa

tigue

at z

=3.2

13 o

ver r

efer

ence

Spa

ce a

nd L

oadc

ases

1-1

6

Life

Cyc

le =

20

year

sM

axC

ase

Min

Cas

eR

ange

Fatig

uex-

Coo

rdy-

Coo

rdz-

Coo

rdpr

ofTy

pth

ick

Pre

ssLo

cStr

Glo

bStr

TotS

trLC

Pres

sLo

cStr

Glo

bStr

TotS

trLC

Pre

ssLo

cStr

Glo

bStr

TotS

trM

eanS

trfr

Det

Cat

mm

mm

mkN

/m^2

N/m

m^2

N/m

m^2

N/m

m^2

kN/m

^2N

/mm

^2N

/mm

^2N

/mm

^2kN

/m^2

N/m

m^2

N/m

m^2

N/m

m^2

N/m

m^2

N/m

m^2

102.

518

.64

3.21

L 3

00*1

3.0*

90*

17.0

16-3

528

1038

1472

-58

-157

-215

1610

785

167

253

-88

1.26

5710

4.98

18.9

33.

21L

300

*13.

0* 9

0*17

.016

-36

2811

4014

77-6

1-1

54-2

1513

112

8916

625

5-8

81.

2558

108.

1419

.26

3.21

L 3

00*1

3.0*

90*

17.0

16-3

629

1039

1478

-62

-151

-213

1311

491

161

252

-87

1.25

5710

9.76

19.4

23.

21L

300

*13.

0* 9

0*17

.016

-36

296

3514

76-6

1-1

59-2

1916

113

9016

425

4-9

21.

2657

111.

3419

.53

3.21

L 3

00*1

3.0*

90*

17.0

16-5

342

648

1469

-55

-158

-213

1612

297

164

261

-82

1.24

6011

4.46

19.7

53.

21L

300

*13.

0* 9

0*17

.016

-53

422

4414

69-5

5-1

62-2

1716

122

9716

426

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61.

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116.

9419

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21L

300

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0* 9

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.016

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422

4414

70-5

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64-2

1916

123

9816

626

3-8

71.

2560

119.

4220

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3.21

L 3

00*1

3.0*

90*

17.0

16-5

339

544

1470

-51

-164

-215

1612

391

169

259

-86

1.25

5912

2.58

20.1

53.

21L

300

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0* 9

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398

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1816

124

9117

426

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125.

7420

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L 3

00*1

3.0*

90*

17.0

16-5

339

948

1471

-52

-171

-223

1412

491

180

271

-88

1.25

6112

8.9

20.3

13.

21L

300

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0* 9

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-53

399

4714

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2714

125

9218

327

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131.

3820

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L 3

00*1

3.0*

90*

17.0

16-5

339

947

1473

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-175

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1412

592

183

275

-90

1.25

6213

3.86

20.4

13.

21L

300

*13.

0* 9

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.016

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388

4614

73-5

4-1

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3014

125

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137.

0220

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3.21

L 3

00*1

3.0*

90*

17.0

16-5

238

644

1474

-54

-176

-230

1412

592

182

274

-93

1.25

6213

9.77

20.4

73.

21L

300

*13.

0* 9

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.016

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1130

416

74-5

5-1

76-2

3114

8966

206

272

-95

1.25

6214

1.35

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93.

21L

300

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3030

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6220

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041.

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143.

3420

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21L

300

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3334

684

-62

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6320

927

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021.

2661

145.

8220

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21L

300

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0* 9

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3436

670

-52

-187

-238

873

5422

127

5-1

011.

2662

148.

320

.53.

21L

300

*13.

0* 9

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3840

671

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-240

874

5522

628

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001.

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151.

4620

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21L

300

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21L

300

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877

5723

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7820

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21L

300

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5823

329

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160.

2620

.53.

21L

300

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7420

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21L

300

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165.

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.53.

21L

300

*13.

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5155

673

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-235

879

5823

229

0-9

01.

2466

169.

0620

.43

3.21

L 3

00*1

3.0*

90*

17.0

16-6

452

576

72-5

3-1

80-2

348

7858

233

290

-88

1.24

6617

1.75

20.3

33.

21L

300

*13.

0* 9

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.016

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5256

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877

5723

329

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91.

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173.

3320

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L 3

00*1

3.0*

90*

17.0

16-2

116

5268

662

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883

6123

329

4-7

91.

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174.

720

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3.21

L 3

00*1

3.0*

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17.0

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115

5267

661

-45

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882

6123

229

2-7

91.

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177.

1820

.14

3.21

L 3

00*1

3.0*

90*

17.0

16-2

015

5368

661

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881

5922

928

9-7

71.

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180.

3419

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3.21

L 3

00*1

3.0*

90*

17.0

16-1

914

5468

663

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1082

6022

128

1-7

31.

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182.

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00*1

3.0*

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17.0

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5366

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5921

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01.

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184.

2919

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L 3

00*1

3.0*

90*

17.0

16-2

253

556

71-5

2-1

61-2

1310

7454

214

268

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1.24

6118

6.66

19.6

23.

21L

300

*13.

0* 9

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L 3

00*1

3.0*

90*

17.0

161

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486

71-5

7-1

53-2

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202

259

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1.24

5919

1.62

19.2

63.

21L

300

*13.

0* 9

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1067

5419

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4-7

91.

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194.

7818

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L 3

00*1

3.0*

90*

17.0

162

-250

496

66-5

3-1

48-2

0110

6451

198

250

-76

1.24

5719

7.94

18.7

3.21

L 3

00*1

3.0*

90*

17.0

164

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476

63-5

1-1

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9811

5847

198

245

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1.24

5620

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83.

21L

300

*13.

0* 9

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7-6

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1155

4519

323

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203.

5818

.11

3.21

L 3

00*1

3.0*

90*

17.0

168

-744

376

61-5

3-1

42-1

9511

5345

186

232

-79

1.25

5320

6.06

17.8

23.

21L

300

*13.

0* 9

0*17

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9-8

4435

659

-51

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-188

1150

4318

122

3-7

61.

2551

209.

2217

.43

3.21

L 3

00*1

3.0*

90*

17.0

1612

-10

4131

657

-49

-126

-175

1146

3916

720

6-7

21.

2547

212.

3817

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3.21

L 3

00*1

3.0*

90*

17.0

1614

-12

3827

655

-48

-120

-168

1142

3615

819

4-7

01.

2644

215.

5416

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3.21

L 3

00*1

3.0*

90*

17.0

1616

-14

3622

653

-46

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-160

1138

3215

018

2-6

91.

2641

218.

0216

.23.

21L

300

*13.

0* 9

0*17

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18-1

632

166

53-4

7-1

13-1

6011

3430

146

176

-72

1.27

39

Fig. 2.20 Stress plot for a support bulkhead



G

container ship guidelines - gl

Documents

additional

hot spot stress

gl structural

ertical horizontal

germanischer

global strength

primary structural

primary structural