Design of Outfit Elements in Ships for Fatigue Technical ... - EWF

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Design of Outfit Elements in Ships for Fatigue Technical ... - EWF

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DVS – DEUTSCHER VERBAND

FÜR SCHWEISSEN UND

VERWANDTE VERFAHREN E.V.

Preface

At the suggestion of Working Group AG A 6.2 “Damages in welded

Ship Structures” in the DVS – Deutscher Verband für Schweißen

und verwandte Verfahren e.V. the Technical BulletinDesign

of Outfit Elements in Ships for Fatigue” has been worked

out.

The Technical Bulletin is based on the results of the research

project “Beanspruchungsgerechte Gestaltung von Ausrüstungselementen

an der tragenden Schiffskonstruktion (Design for

Strength of Outfit Elements at the Load-carrying Ship Structure)”

(Author: Dr.-Ing. J. Roerup, Head of Dept.: Prof. Dr.-Ing. H.

Petershagen). The project was conducted at the Technical University

Hamburg-Harburg and was financially supported by the

Arbeitsgemeinschaft industrieller Forschungsvereinigungen “Otto

von Guericke” e.V. (AIF). For details reference is made to the

Research Report No. 295/2001 of the Center of Maritime Technologies

(CMT), Hamburg.

The Working Group wishes to make this Technical Bulletin available

to the shipyards as an aid in the design and arrangement of

outfit elements in load-carrying ship structures. The Working

Group is interested in receiving feedback from its application together

with suggestions for its improvement, which may be considered

and incorporated in subsequent versions.

Germanischer Lloyd (GL) has contributed to this work by advising

and will, as far as applicable, use this Technical Bulletin in the

assessment of structures presented for approval. GL, however,

reserves the right of decisions deviating from its contents in individual

cases.

This publication has been prepared by a group of experts in honorary

co-operation and is recommended for consideration as an

important source for information. The user must always check to

what extent its contents are applicable to his particular case and

whether the version in hand is still valid. Responsibility cannot be

accepted, neither by DVS nor by those having participated in the

preparation of the Technical Bulletin.

Catalogue of Details in Outfit Design

With this catalogue data for the fatigue assessment of outfit design

elements made of steel are provided for practical application.

In the preparation of the catalogue the results of the project

“Beanspruchungsgerechte Gestaltung von Ausrüstungselementen

an der tragenden Schiffskonstruktion (Design for Strength of

Outfit Elements at the load-carrying Ship Structure)” as well as

data from other sources are used. The catalogue is arranged with

a view to an extension by additional elements in the future.

Design of Outfit Elements

in Ships for Fatigue

The catalogue has been worked out in close co-operation with

Germanischer Lloyd (GL) and is based on the Rules of GL. For

further interest it will be decided at a later date whether Rules of

other Classification Societies will be considered.

The fatigue assessment corresponds in actual individual cases to

that according to GL-Rules Issue 2003 (Rules for Classification

and Construction, I-Ship Technology, Part 1 - Seagoing Ships,

Chapter1 - Hull Structures, Section 20 - Fatigue Strength). Accordingly

it must be proven that ∆σmax ≤ ∆σp. In this ∆σmax is the

largest stress range expected during the service life and ∆σp the

permissible stress range. ∆σp is obtained by multiplying the detail

category with a number of coefficients taking stress spectrum,

mean stress, material, weld shape (postweld treatment) and

significance of the structural part into consideration. Details are

given in the GL-Rules mentioned above.

It is further assumed that the welds between outfit elements and

structural members meet the quality requirements for load-carrying

ship structures (see e. g. the GL-Rules mentioned above).

The calculation of maximum permissible stresses in ship hulls is

not explained in detail in this document. It is assumed that

respective data are available to the user. As these data will be

determined by means of structural design software in most

cases, this document is based on the widely spread program system

POSEIDON as an example.

With the application of the programme system POSEIDON the

assessment is simplified to ∆σRperm ≤ ∆σR in way of longitudinal

structures. The lowest permissible detail category ∆σRperm with

regard to the expected service load is then determined within the

program. The user then can find by means of the detail category

the permissible outfit details for the area of the load-carrying ship

structure in question from the catalogue without any further

calculation. Fig. 1 shows a record with lowest permissible detail

categories for the plate panels in way of a midship section. Because

of the higher-tensile steel applied and corresponding higher

permissible stresses in the strength deck outfit details with

detail categories below ∆σR = 50 are not allowed in this area. In

certain areas such as hatch coamings even higher detail categories

are necessary with regard to the existing stress level. In addition

to the ∆σRperm for plate panels POSEIDON also determines

the respective value for longitudinal stiffeners. It must be noted

that at present only stresses due to vertical and horizontal hull

bending and local bending of plates and stiffeners are considered

in POSEIDON. Other possible stress components, e.g. by bending

of grillage structures are not taken into account. If such additional

components are not considered in a separate calculation, it

is recommended for the time being to increase the lowest permissible

detail category ∆σRperm by one category. The format of the

detail catalogue corresponds largely to the catalogue of notch

cases in the GL-Rules, issue 2003. The arrangement follows a

selection of frequently used elements of outfit.

This publication has been drawn up by a group of experienced experts in cooperative work on an honorary basis and it is recommended to pay attention to it as an

important source of knowledge. The user must always check to what extent the contents can be applied to his/her special case and whether the version in his/her

possession is still valid. Any liability on the part of the DVS and those people who have been involved in the elaboration work is excluded.

DVS, Technical Committee, Working Group ″Welding in Shipbuilding and Marine Engineering″

Orders to: DVS-Verlag GmbH, P. O. Box 10 19 65, 40010 Düsseldorf, Germany, Tel.: + 49(0)211/1591- 0, Fax: + 49(0)211/1591-150

November 2004

Technical Bulletin

DVS 3501


Page 2 of DVS 3501

Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

Stress concentrations caused by the

opening to be considered as follows

140

(m0 = 4)

Plate edges punched or machine-cut by means of a thermal

cutting process. The cutting surface is free of cracks and

notches. Cutting edges are chamfered or rounded

1.1 Openings uniaxially loaded

∆σmax = K1 ⋅ ∆σN bzw. ∆σRperm ≤ ∆σR /K t

K t: Notch factor according to GL Section 3

∆σN: Nominal stress range related to net

section

alternatively direct determination of ∆σmax from FE-calculation, especially in case of

multiple arrangement of openings

Plate edges which are not meeting the above mentioned

requirements, but are free from cracks and sharp notches

125

(m0 = 3.5)

Machine cut or punched:

or σ x >> σ y

100

(m0 = 3.5)

Manually cut:

Stress concentrations caused by the

opening to be considered as follows

140

(m0 = 4)

Plate edges punched or machine-cut by means of a thermal

cutting process. The cutting surface is free of cracks and

notches. Cutting edges are chamferred or rounded

1.2 Openings biaxially loaded

∆σmax = K1 ⋅ ∆σN K t: Notch factor according to Fig. 2

∆σN : Nominal stress range related to net

section

alternatively direct determination of ∆σmax from FE-calculation, especially in case of

multiple arrangement of openings

Plate edges which are not meeting the above mentioned

requirements, but are free from cracks and sharp notches

125

(m0 = 3.5)

Machine cut or punched:

100

(m0 = 3.5)

Manually cut:

σ x ≈ σ y

Stress concentrations caused by the

opening to be considered as follows

140

(m0 = 4)

1.3 Openings shear-loaded Plate edges punched or machine-cut by means of a thermal

cutting process. The cutting surface is free of cracks and

notches. Cutting edges are chamferred or rounded

∆σmax = K1 ⋅ ∆σN K t: Notch factor according to Fig. 3

∆σN : Nominal stress range related to net

section

alternatively direct determination of ∆σmax from FE-calculation, especially in case of

multiple arrangement of openings

Plate edges which are not meeting the above mentioned

requirements, but are free from cracks and sharp notches

125

(m0 = 3.5)

Machine cut or punched:

100

(m0 = 3.5)

Manually cut:


Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

71

63

1.4 Pipe penetration Pipe penetrating a plate with circumferential fillet weld

d ≤ 50 mm

d > 50 mm

Note:

In case of large diameters an assessment based on local

stresses is recommended

Assessment corresponding to doubling

plate

63

56

50

1.5 Drain plugs Drain plugs according to DIN 87721-1

(Diameter about 190 mm)

tD ≤ 0.8 t

0.8 t < tD ≤ 1.5 t

tD > 1.5 t

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category, however not beyond 80

80

71

63

56

Stiffener welded to a plate in loading direction

R ≤ 50 mm

50 mm < R ≤ 150 mm

150 mm < R ≤ 300 mm

R > 300 mm

2.1 Holder in unsupported plate

panel

arranged parallel to main load

80

Stiffener welded to a plate transversely to load direction

(valid for short and long stiffeners)

2.2 Holder in unsupported plate

panel

arranged transverse to main load

Page 3 of DVS 3501


Page 4 of DVS 3501

Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

Fillet weld to plate panel loaded in bending Assessment in individual cases by means

of hot spot stress concept with

∆σSR = 90

2.3 Holder in unsupported plate

panel with or without doubling

plate

Application of a doubling plate can be necessary depending on the local stiffness resulting from the dimensions of plate panel, holder and doubling

plate and from the position of the holder within the plate panel.

Example: Holder 60 mm × 15 mm, position of the holder in the center of the plate panel

Permissible acceleration forces F 2 in [N] for 1 m lever arm, (F 1 = 0)

Location of crack initiation

Plate panel 1800 mm × 600 mm with t

=

10 mm 15 mm 20 mm

Variant

without doubler 1090 N 2680 N 5340 N plate to holder

1940 N 4400 N 8000 N plate to doubler (1)

2000 N 2120 N 2150 N doubler to holder (2)

with doubler

∅ = 100 mm

t = 10 mm

While the permissible force for a 10 mm thick plate panel is increased by a factor of about 2 if a doubling is fitted, the permissible force for a 20 mm

thick plate panel is by a factor of about 2,5 higher for the holder without doubling plate.

incomplete circumferential weld may be

applied in dry spaces only.

Unloaded overlapped plate fillet welded to longitudinally

loaded structural member

2.4 Holder at stiffener

Alternative 1

For R > 150 mm ∆σR to be downgraded

by one category, for R 50 mm ≤ ∆σR can

be upgraded by one category

56

50

– at bulb flat profile or flat bar

– at angle bar

For structural members loaded by

bending ∆σR to be downgraded by one

category

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category, however not beyond 56.

Plate welded to an edge of a plate or girder flange

R ≤ 50 mm

50 mm < R ≤ 150 mm

150 mm < R ≤ 300 mm

R > 300 mm

2.5 Holder at stiffener

Alternative 2

For plates or girder flanges loaded in inplane

bending ∆σR to be downgraded by

one category

56

50

45

40


Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

Holder to be arranged in neutral axis of

stiffener if possible

Stiffener welded to a plate in load direction

R ≤ 50 mm

50 mm < R ≤ 150 mm

150 mm < R ≤ 300 mm

R > 300 mm

2.6 Holder at stiffener

Alternative 3

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category, however not beyond 80

80

71

63

56

80 The detail category is also valid for not

fully circumferential welded holders (see

2.4).

Fillet-welded stiffener transverse to loading direction (valid

for short and long stiffeners)

2.7 Holder at stiffener

Alternative 4

For stiffeners loaded in bending ∆σR to be

downgraded by one category.

In way of the rounded corner of an opening

with the radius r a minimum distance x

from the edge to be kept (hatched area):

2.8 Holder at cut-out or opening Holder welded in way of an opening and arranged parallel

to the edge of the opening.

x [mm] = 15 + 0.175 ⋅ r [mm]

100 mm ≤ r ≤ 400 mm

In case of an elliptical rounding the mean

value of both semi-axes to be applied

R ≤ 150 mm

not valid for hatch corners

Circular doubler plate with max. 150 mm diameter.

tD ≤ 0.8 t

2.9 Doubler plate for holder in

unsupported plate panel

Page 5 of DVS 3501

71

63

56

0.8 t < tD ≤ 1.5 t

tD > 1.5 t


Page 6 of DVS 3501

Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category, however not beyond 80

80

71

Stiffener welded to a plate in loading direction

R ≤ 50 mm

50 mm < R ≤ 150 mm

3.1 Rail stanchions

arranged parallel to the main

loading direction

80

Stiffener welded to a plate transverse to the loading

direction

3.2 Rail stanchions

arranged transverse to the main

loading direction

80 The sketch shows the connection of a

bollard to a deck. The main stress is

approximately directed perpendicular

towards the bollard wall for all angles

3.3 Bollard Fillet-welded stiffener transverse to the loading direction

(valid for short and long stiffeners)

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category.

56

50

Stiffener welded to a plate in loading direction

150 mm < R ≤ 300 mm

R > 300 mm

4.1 Foundations

Ends of girders parallel to main

loading direction

80

Fillet-welded stiffener transverse to the loading direction

(valid for short and long stiffeners)

4.2 Foundations

For girders tranverse to main

loading direction


Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category.

Stiffener welded to a plate in loading direction

R > 300 mm 56

Assessment of the opening edges by

means of a direct determination of the

notch factor only

4.3 Small hatches

Assessment of weld at transition

from deck to coaming in a hatch

corner

For t2 ≤ 0.7 ⋅ t1 ∆σR can be upgraded by

one category.

71

63

56

Stiffener welded to a plate in loading direction

R ≤ 150 mm

150 mm < R ≤ 300 mm

R > 300 mm

4.4 Container foundations

Assessment of girder end parallel to

main loading direction

∆σR may be upgraded by one category:

– reinforced end weld

– weld angle ≤ 30°

– connection length ≤ 150 mm

End of a long doubler at the flange of a girder

tD ≤ 0.8 t

56

50

45

0.8 t < tD ≤ 1.5 t

tD > 1.5 t

5.1 Hatch cover bearings (pads)

Assessment with regard to loading

of ship structure

Load-carrying fillet weld Assessment in individual cases by means

of hot-spot concept with ∆σSR = 90

5.2 Hatch cover bearings (pads)

Assessment with regard to

container loads

Page 7 of DVS 3501


Page 8 of DVS 3501

Comments

Description of Type of connection Detail

category

∆σR Equipment Detail Sketch of connection with

fatigue crack and stress

considered σ

Required throat thickness "a" of fillet

welds related to weld penetration depth

"e"

80

Stiffener arranged transverse to main loading direction

σ2 ≤ 0.4 σ1 Assessment to be based on σ 1 only

5.3 Hatch cover locking device

Arranged transverse to main

loading direction

αmin 0.82 t 1 2.8 e ⎛ –


-- ⎞

t ⎠

0.74

=

⋅ ⋅

t: Thickness of locking device. Otherwise

assessment as cruciform joint

Assessment with regard to biaxial load

Assessment to be based on σ2 only

Biaxially loaded fillet welded cruciform joint, failure from the

weld root.

(reference stress to be determined for the weld section) 30

Assessment of unsupported hatch cover

guide corner see 4.4.

71

63

5.4 Hatch cover guide Detail welded to girder flange, bulb or plate with soft

transition (tapered end or radius); c ≤ 2 t2, max. 25 mm

r ≥ 0.5 h

r < 0.5 h or ϕ ≤ 20°

ϕ > 20° as stiffener in load direction

For t2 ≤ 0.5 t1 ∆σR may be increased by one category.


Figure 1. Lowest permissible detail categories in the midship section of a container vessel.

Kt

12

10

8

6

4

2

0

l/a=2

l/a=4

l/a=1

0 0.1 0.2 0.3 0.4 0.5

r/a

Figure 2. Notch factors K t for rounded rectangular openings under biaxial load.

a

σy

l

r

σx = σy

σx

Page 9 of DVS 3501


Page 10 of DVS 3501

Kt

18

16

14

12

10

8

6

4

2

0

l/a=2

l/a=4

l/a=1

0 0.1 0.2 0.3 0.4 0.5

r/a

Figure 3. Notch factors K t for rounded rectangular openings under shear load.

Publications, Normative References

Research Report No. 295/2001 Center of Maritime Technologies (CMT), Hamburg

GL-Rules Issue 2003 Germanischer Lloyd, Hamburg

DIN 87721-1 Ablassverschraubungen – Teil 1: Zusammenstellung, Einbau

a

l

r

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