UPDATING FAILURE PROBABILITY OF A WELDED JOINT IN OWT SUBSTRUCTURES - - PowerPoint PPT Presentation

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UPDATING FAILURE PROBABILITY OF A WELDED JOINT IN OWT SUBSTRUCTURES - - PowerPoint PPT Presentation

Jul 21, 2023 107 likes •379 views

UPDATING FAILURE PROBABILITY OF A WELDED JOINT IN OWT SUBSTRUCTURES Q. Mai 1 J.D. Srensen 2 P. Rigo 1 1 Department of ArGEnCo University of Liege 2 Department of Civil Engineering Aalborg University OMAE Conference - Busan, 2016 Motivation 2

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UPDATING FAILURE PROBABILITY

OF A WELDED JOINT IN OWT SUBSTRUCTURES

  • Q. Mai1

J.D. Sørensen2

  • P. Rigo1

1Department of ArGEnCo

University of Liege

2Department of Civil Engineering

Aalborg University OMAE Conference - Busan, 2016

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Motivation

Reduce O&M Costs RBI Update Pf (insp.) Limit State Function

  • Q. Mai | FAD in Updating Failure Probability
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Message Objective

Fatigue Assessment Diagram can be used to update the failure probability of an existing OWT substructure when new informa- tion about either loading, structural responses or inspections is available.

  • Q. Mai | FAD in Updating Failure Probability
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4

Outline

Fatigue Assessment Diagram Updating Probability of Failure Results

  • Q. Mai | FAD in Updating Failure Probability
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Outline

Fatigue Assessment Diagram Updating Probability of Failure Results

  • Q. Mai | FAD in Updating Failure Probability
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Fatigue Assessment Diagram

Lr

0.2 0.4 0.6 0.8 1 1.2 1.4

Kr

0.2 0.4 0.6 0.8 1

Figure: Level 2A Fatigue Assessment Diagram

BS-7910, 2005. Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures. British Standard Institution (BSi).

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Fatigue Assessment Diagram

Lr

0.2 0.4 0.6 0.8 1 1.2 1.4

Kr

0.2 0.4 0.6 0.8 1

Lr,max = σY +σU 2σY

Figure: Level 2A Fatigue Assessment Diagram

BS-7910, 2005. Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures. British Standard Institution (BSi).

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Fatigue Assessment Diagram

Lr

0.2 0.4 0.6 0.8 1 1.2 1.4

Kr

0.2 0.4 0.6 0.8 1

✓ Lr = σref σY ; Kr = KI Kmat ◆

Figure: Level 2A Fatigue Assessment Diagram

BS-7910, 2005. Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures. British Standard Institution (BSi).

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Fatigue Assessment Diagram

Lr

0.2 0.4 0.6 0.8 1 1.2 1.4

Kr

0.2 0.4 0.6 0.8 1

✓ Lr = σref σY ; Kr = KI Kmat ◆ Safe

Figure: Level 2A Fatigue Assessment Diagram

BS-7910, 2005. Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures. British Standard Institution (BSi).

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Fatigue Assessment Diagram

Lr

0.2 0.4 0.6 0.8 1 1.2 1.4

Kr

0.2 0.4 0.6 0.8 1

✓ Lr = σref σY ; Kr = KI Kmat ◆ Unsafe

Figure: Level 2A Fatigue Assessment Diagram

BS-7910, 2005. Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures. British Standard Institution (BSi).

  • Q. Mai | FAD in Updating Failure Probability
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Outline

Fatigue Assessment Diagram Updating Probability of Failure Results

  • Q. Mai | FAD in Updating Failure Probability
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Uncertainties

Variable Value ν

  • No. of cycle/year

1×107 t Steel thickness [mm] 65 R Outer radius [mm] 79.5 L Joint length [mm] 100 ησ

  • Bend. to memb. ratio

0.81 ∆Ktr Transition SIF range 196 m1 Paris law, 1st line 5.10 m2 Paris law, 2nd line 2.88 Ca/Cc C ratio for a and c 0.9 Variable Distr. Mean CoV S Stress range [MPa] W k=0.8 N(µ,σ) σY Yield strength [MPa] LN 368.75 0.07 σU Ultimate strength [MPa] LN 750 0.04 ∆Kth SIF range threshold LN 160 0.4 Kmat Fracture toughness 3p W

  • C1

Paris law, 1st line LN 4.8×10−18 1.7 C2 Paris law, 2nd line LN 5.86×10−13 0.6 a0 Initial crack depth LN 0.15 0.66 a0/c0 Initial aspect ratio LN 0.6 0.40 Bscf Uncertainty in SCF LN 1 0.05 Bsif Uncertainty in SIF LN 1 0.05

  • Q. Mai | FAD in Updating Failure Probability
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Updating method

Uncertainties

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Updating method

Kmat ∆Kth FM σY σU ∆σ a0,c0 SIF SCF

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Updating method

Kmat ∆Kth FM σY σU ∆σ a0,c0 SIF SCF Limit State Function Pf Updating Pf POD Decisions

Yeter, B., Garbatov, Y., and Soares, C. G.,

  • 2015. “Fatigue Reliability of an Offshore Wind

Turbine Supporting Structure Accounting for Inspection and Repair”.

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Updating method

Kmat ∆Kth FM σY σU ∆σ a0,c0 SIF SCF Limit State Function POD Decisions Crack Growth Simulation

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Updating method

Kmat ∆Kth FM σY σU ∆σ a0,c0 SIF SCF Limit State Function POD Decisions Crack Growth Simulation Updated Pf

  • Q. Mai | FAD in Updating Failure Probability
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Crack Growth Simulation

Crack depth a and crack length 2c are coupled during the simulation. 8 > < > : da dN = Ca (∆Ka)m ∆Ka ≥ ∆Kth dc dN = Cc (∆Kc)m ∆Kc ≥ ∆Kth (1) ∆Ka = SYa √πa (2) ∆Kc = SYc √πa (3)

  • Q. Mai | FAD in Updating Failure Probability
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Crack Growth Simulation

Life time Semi crack length C

Figure: Crack growth in combination with inspections

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Crack Growth Simulation

Life time Semi crack length C Cd i Inspection i

Figure: Crack growth in combination with inspections

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Crack Growth Simulation

Life time Semi crack length C Cd i Inspection i

Figure: Crack growth in combination with inspections

  • Q. Mai | FAD in Updating Failure Probability
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Outline

Fatigue Assessment Diagram Updating Probability of Failure Results

  • Q. Mai | FAD in Updating Failure Probability
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Results

Crack Propagation

Year

2 4 6 8 10 12 14 16 18 20

Crack depth [mm]

1 2 3 4 5 6 7 8 9

Figure: Crack propagation

  • Q. Mai | FAD in Updating Failure Probability
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Results

No Crack Detected

Year

2 4 6 8 10 12 14 16 18 20

Probability

#10-3 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Annual Failure Probability

No crack detected No inspection

Figure: Annual POF

  • Q. Mai | FAD in Updating Failure Probability
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Results

Crack Detected & Repaired

Year

2 4 6 8 10 12 14 16 18 20

Probability

#10-3 0.5 1 1.5 2 2.5 3 3.5

Annual Failure Probability

Normal Repair Perfect Repair

Figure: Annual POF

  • Q. Mai | FAD in Updating Failure Probability
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Summary

Fatigue Assessment Diagram can be used to update the failure probability of an existing OWT substructure when new informa- tion about either loading, structural responses or inspections is available.

I Outlook

I Reduction of uncertainty related to stress-ranges given new

information about loading and structural response

I Improved modelling of crack growth after reaching the wall

thickness.

  • Q. Mai | FAD in Updating Failure Probability
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Acknowledgement

This research is funded by the National Fund for Scientific Research in Belgium — F.R.I.A - F.N.R.S. About me: Quang MAI University of Liège, Belgium aq.mai@ulg.ac.be

  • Q. Mai | FAD in Updating Failure Probability