Presentasi1 Bagian Fatigue-nominal Stress Approach

8/2/2019 Presentasi1 Bagian Fatigue-nominal Stress Approach

1/43

December, 2011


2/43

HullStruc

turalAssessment

1. Introduction

2. Objectives and Scope of Works

3. Code and Standard

4. Methodology

5. Data

6. Calculation of Static Load

7. Finite Element Model

8. Stress Analysis Result

9. Remaining life

10. Conclusion and Recommendation


3/43

HullStruc

turalAssessment


4/43

HullStruc

turalAssessment

The Pertamina Hulu Energi (PHE) ONWJ production sharing contracts in

the Java Sea cover 8,300 square kilometers, from north of Cirebon in the

east to Pulau Seribu in the west.

PHE ONWJ will assess the structural of Arco Ardjuna Hull based on actual

condition.

The condition influenced by problems of aging hull structural such as

general corrosion and local pitting, thinner material leads to higher stress

and lower buckling capacity and fatigue damage accumulation, cracks

and crack growth.


5/43

HullStruc

turalAssessment

Arco Ardjuna Hull structural assessment for evaluation of FSO hull

strength is needs to be done to provide the necessary structural integrity

throughout its service life.

For this purpose, the environmental condition is defined with a specific

combination of wind, waves and current.

This environmental load combined to the operational and deformation

load used as load input to the analysis.


6/43

HullStruc

turalAssessment The objective of this assessment is to obtain safety factor from stress

analysis result and life time for the hull structure based on actual

condition.

Data collection and preliminary study

Site visit

Calculation of environmental, operational and deformation load

Perform stress analysis for hull structural using finite element method with

static, dynamic and impact loading

Strength/structural integrity evaluation

Calculation of hull structural life time with consideration of: Corrosion

Fatigue

Stability due to cargo transfer operation

Stability due to buckling or collapse

Mechanical damage Generate conclusion and recommendation


7/43

HullStruc

turalAssessm

ent

Preliminary Study

Site Visit

Data Collection

Stress Analysis

Structural Integrity

Evaluation

Remaining Life

Presentation


8/43

HullStruc

turalAssessm

ent


9/43

HullStruc

turalAssessm

ent

Floating Storage and Offloading Barge (FSO)ARCO Ardjuna

Name ARCO Ardjuna

Description Floating Storage and Offloading Barge (FSO)

Classification society American Bureau of Shipping (ABS)

Class notation A1, Oil Tank Barge, Storage Service

LOA (Length Overall) 142.6 m

LBP (Length Between

Perpendicular)142.6 m

Molded Breadth 48.2 m

Molded Depth 26.5 m

Max. Draft (design) 24.0 m

Min. Draft (Light Load) 6 m

Dead weight 137,673 tonnes

Gross tonnage 54,236 tonnes

Net tonnage 53,653 tonnes

Light ship weight 15,529 tonnes

Light draft 2.52 m

Summer draft 19.68 m

Free board 6.87 m


10/43

HullStruc

turalAssessm

ent


11/43

HullStruc

turalAssessm

ent


12/43

HullStruc

turalAssessm

ent

1. Static Hull Girder Loadsa. Hull girder still water bending moment

b. Hull girder still water shear force

2. Local Static Loads

a. Static sea pressureb. Static tank pressure

c. Static deck loadSagging

Hogging


13/43

HullStruc

turalAssessm

ent

Data Symbol Value UnitWave coefficient Cwv 8.775

Block coefficient Cb 0.6

SAGGINGat amidship Msw -579747.4 kNmat any longitudinal position

Still-water Bending Moment at 0.4L

amidship Msw -579747.4 kNmStill-water Bending Moment at 0.1L from

A.P. or F.P. Msw -86962.1 kNmStill-water Bending Moment at A.P. or F.P. Msw 0.0 kNm

HOGGINGat amidship Msw 931483.5 kNmat any longitudinal position

Still-water Bending Moment at 0.4L

amidship Msw 931483.5 kNmStill-water Bending Moment at 0.1L from

A.P. or F.P. Msw 139722.5 kNmStill-water Bending Moment at A.P. or F.P. Msw 0.0 kNm


14/43

HullStruc

turalAssessm

ent


15/43

HullStructuralAssessm

ent

Still-water Shear Force Symbol Value Unit

Considering the Side Shell

Plating

SWSFp (at 0L) #DIV/0!

kN

SWSFp (at 0.2L-0.3L) #DIV/0!SWSFp (at 0.4L-0.6L) #DIV/0!SWSF (at 0.7L-0.85L) #DIV/0!

SWSFp (at L) #DIV/0!SWSFn (at 0L) #DIV/0!

SWSFn (at 0.2L-0.3L)

#DIV/0!

SWSFn (at 0.4L-0.6L) #DIV/0!SWSn (at 0.7L-0.85L) #DIV/0!

SWSFn (at L) #DIV/0!

Considering Various

Longitudinal Bulkhead Plating

SWSFp (at 0L) #DIV/0!

kN

SWSFp (at 0.2L-0.3L) #DIV/0!SWSFp (at 0.4L-0.6L) #DIV/0!SWSF (at 0.7L-0.85L)

#DIV/0!

SWSFp (at L) #DIV/0!SWSFn (at 0L) #DIV/0!

SWSFn (at 0.2L-0.3L) #DIV/0!SWSFn (at 0.4L-0.6L) #DIV/0!SWSn (at 0.7L-0.85L) #DIV/0!

SWSFn (at L) #DIV/0!


16/43


ent

Local Static Loads Symbol Value Unit

Static sea pressure Phys kN/m2

Static tank pressure Pin-tk kN/m2

Static deck Pdeck 16 kN/m2


17/43


ent


18/43


ent

Modeling:Geometry, Material, Property

Input Parameter:Constrain and Loads

Finite Element Analysis

Convergent Result

Output:

Stress Contour andDeformation

No

Yes

The FEM software that used forcalculate and analyze the

maximum stress is performed by

MSC Nastran.


19/43


ent


20/43


ent


21/43


ent

Bottom Stiffener

Bottom Stiffener


22/43


ent

Amidship and Bracket

Amidship Stiffener


23/43


ent

OT Stiffener


24/43


ent


25/43


ent

Swash Stiffener


26/43


ent


27/43


ent


28/43


ent


29/43


ent


30/43


ent


31/43


ent


32/43


ent

RemainingLife

Corrosion

Fatigue

Stability dueto cargotransfer

operation Stability due

to bucklingor collapse

Mechanicaldamage


33/43


ent

Remaining Life

ratecorrosion

ttLifemaining actual minRe

Where:

tactual = the thickness, in mm, recorded at the time of inspection for a

given location or componenttmin = minimum allowable thickness, in mm, for a given location or

component

Corrosion Rate

actualprevious

actualprevious

tandtbetweenyears

ttRateCorrosion

Where:

tprevious = the thickness, in inches (millimeters), recorded at the same

location as t actual measured during a previous inspection.


34/43


ent

Main Deck 25 30 17.5 14.7 0.278 -10

Bottom Plating - CT1 21 20 16.8 21.9 0.278 18

Bottom Plating - WT1 21 20 16.8 21.5 0.278 17

Bottom Plating - CT2 21 20 16.8 21.6 0.278 17

Bottom Plating - WT2 21 20 16.8 21.8 0.278 18Bottom Plating - CT3 21 20 16.8 21.7 0.278 18

Bottom Plating - WT3 21 20 16.8 21.5 0.278 17

17 25 12.75 22.4 0.278 35

18 25 13.5 22 0.278 31

Remaining

Life (Years)

Side Shell

Original

Thickness

[mm]

Max. Alwb

Dim

[%]

Min allowable

thickness

(mm)

Min actual

thickness

(mm)

Max corrosion

rate

(mm/year)


35/43


ent

Based on Palmgren-Miner cumulative damagerule. The fatigue capability is not acceptable

if DM > 1

The fatigue assessment is to be applied towelded connections where the steel has a

minimum yield strength of less than

400N/mm2.

=

=

=1

ni: Number of cycles of stress range Si

Ni: Number of cycles to failure at stress range Si

ntot: Total number of stress range blocks


36/43


ent

Materials

Data

Stress Range

Load

Selection ofthe Design S-

N Curve

Calculation ofCummulative

Damage =

2

=1

=

1

+

2

+

3

+

4

/

2

= 2


37/43


ent

Static loadWave induced loads

Impact loads

Cyclic loads

Transient loads

Residual stress

Hull girder loads

Dynamic wave pressuresDynamic tank pressure loads resulting from

ship motion


38/43


ent

fSN 1,06; factor to account for joint in combined

protected & unprotected environment

f1, f2, f3, and f4 stress combination factor

Sv Stress range due to vertical bending moment,N/mm2

Sh Stress range due to horizontal bending moment,

N/mm2

Se Stress range due to external wave or internaltank pressure, N/mm2

Si Stress range due to external wave or internal

tank pressure, N/mm2

=

1

+

2

+

3

+

4

/

2


39/43


ent

S Stress range cumulative

N predicted number of cycles to failure

under stress range

m constant depending on material andweld type, type of loading, geometrical

configuration and environmental conditions

(air or sea water)

K2 constant depending on material and

weld type, type of loading, geometrical

configuration and environmental conditions

(air or sea water)

= 2


40/43

HullStru

cturalAssessm

ent

DMi Cumulative fatigue damage ratio for

the applicable loading condition

i = 1 for full load condition

= 2 for normal ballast condition

=2

=1


41/43

HullStru

cturalAssessm

ent


42/43

HullStru

cturalAssessm

ent


43/43

HullStru

cturalAssessm

ent

Documents

Presentasi1 Bagian Fatigue-nominal Stress Approach