This document summarizes a 3-day PhD course on reliability and risk analysis of wind turbines and wave energy devices held from December 3-5, 2012 at Aalborg University. The course will cover topics such as uncertainty modeling, reliability analysis methods, probabilistic design, inspection planning, and reliability assessment of wind turbines and wave energy devices. Participants are expected to have a basic knowledge of wind turbines and probability/statistics. Upon submitting completed coursework, participants can receive a diploma for the 3 ECTS credits course.

1. PhD course:
Reliability and risk analysis of wind turbines and wave energy devices
Dates: December 3-5, 2012
Place: Aalborg University, Department of Civil Engineering
Sohngaardsholmsvej 57, Room B222
Description:
Reliability is a very important issue for both wind turbines and wind energy devices. Reliability is
important both for estimating failure rates and probabilities for different components and members
in structures, and for planning optimal operation and maintenance. In traditional deterministic code-
based design the structural costs are influenced by the value of the safety factors. These reflect the
uncertainty related to the design parameters. Improved design with a consistent reliability level for
all components can be obtained by use of probabilistic reliability-based design methods, where
explicit account of uncertainties related to loads, material strength, and calculation methods is
made.
The course will include the following topics:
 Introduction to risk and reliability analysis
 Stochastic modeling of uncertainties and failure rates, incl. Bayesian techniques
 Reliability analysis of electrical and mechanical components
 Reliability analysis of structural members by FORM/SORM and simulation methods
 Reliability assessment using theoretical models in combination with information from tests
 Methods for reliability analysis of wind turbines
 Methods for reliability analysis of wave energy devices
ECTS: 3.0

2. DRAFT - Schedule:
Monday, December 3
 9:00-12:00
o Introduction
o Uncertainty modelling (strength, loads, lifetimes, models, ...)
o Characteristic values
o Example – STATREL+Matlab
 Exercise 1 – statistical analysis for strength data
 Exercise 2 – statistical analysis for wind and wave data
 12:00-12.45 lunch
 12.45-16.30
o Risk analysis
o Estimation of failure probability by FORM (reliability index
method)
o Example – STRUREL
o Exercise 3 – reliability index
Tuesday, December 4
 9:00 – 12:00
o Estimation of failure probability by SORM and Simulation
o Classical reliability of mechanical and electrical components
(failure rates)
o System modelling: Reliability of series and parallel systems
o Example – SYSREL
o Exercise 4 – classical system reliability
o Exercise 5 – structural system reliability
 12-12.45 lunch
 12:45-16:30
o Probabilistic design
 Inspection planning - example
o Partial safety factor calibration
o Bayesian statistical methods
o Design by testing
 EN 1990, Annex D + coupon/subcomp/full-scale test + test
planning
o Probabilistic modeling of defects + Fatigue test data + statistical
analysis + partial safety factors
o Exercise 6 - model uncertainty
o Exercise 7 – system + partial safety factor calibration
Wednesday, December 5
 9:00 – 12:00
o Stochastic processes - Load combinations - Inverse FORM
o Design Load cases in IEC 61400 – probabilistic modelling
o Statistical load extrapolation
o Exercise 8 – reliability analysis dlc 2.2
 12-12.45 lunch
 12:45-16:30
o Design Load cases in IEC wave – probabilistic modelling
o Reliability- and risk-based planning of Operation & Maintenance
o Exercise 9 - OM

3. Lecturers:
Professor John Dalsgaard Sørensen
Ass. professor Henrik Stensgaard Toft
PostDoc Jannie Sønderkær Nielsen
Information
The course is organized by Professor John Dalsgaard Sørensen, Department of Civil Engineering,
Aalborg University, from whom further information may be obtained.
Phone +45 99 40 85 81 or
e-mail: jds@civil.aau.dk
Participants
The participants are assumed to have a basic knowledge on wind turbines and probability theory &
statistics.
Evaluation and diplomas
Participants are encouraged to submit completed portfolio / exercise reports no later than one month
after conclusion of the course, as this will form the basis of the issue of diplomas.
Study Material
The following notes and papers form the basis for the lectures. Ref [1] is e-mailed to the
participants. Refs [2] – [16], copy of slides and additional notes will be provided at the first day of
the course.
1. Sørensen, J.D.: Notes in ‘Structural Reliability Theory - and Risk Analysis’. Aalborg
University, 2004
2. Ditlevsen, O. & H.O. Madsen: Structural Reliability Methods. Wiley, 1996.
(supplementary)
3. Sørensen, J.D.: Framework for risk-based planning of operation and maintenance for
offshore wind turbines. Wind Energy, Vol. 12, 2009, pp. 493-506.
4. Sørensen, J.D. and Henrik S. Toft: Probabilistic design of wind turbines. Energies, Vol. 3,
2010, pp. 241-257.
5. Toft, H.S., J.D. Sørensen & D. Veldkamp: Assessment of Load Extrapolation Methods for
Wind Turbines. Journal of Solar Energy Engineering, Vol. 133, No. 2, 2011, pp. 1-8.
6. Toft, H.S., K. Branner, P. Berring & J.D. Sørensen: Defect Distribution and Reliability
Assessment of Wind Turbine Blades. Engineering Structures, Vol. 33, 2011, pp. 171-180.
7. Nielsen, J.J. & J.D. Sørensen: On Risk-Based Operation and Maintenance of Offshore Wind
Turbine Components. Journal for Reliability Engineering & System Safety, Vol.96, No. 1,
2011, pp. 218-229.
8. Ragan,P. & L. Manuel: Statistical extrapolation methods for estimating wind turbine
extreme loads. Journal of Solar Engineering, Vol. 130, No. 1, 2008.
9. Toft, H.S., A. Naess, N. Saha & J.D. Sørensen: Response load extrapolation for wind
turbines during operation based on average conditional exceedance rates. Wind Energy, Vol.
14, No. 6, 2011, pp. 749-766.
10. Sørensen, J.D.: Reliability-based calibration of fatigue safety factors for offshore wind
turbines. International Journal of Offshore and Polar Engineering. Vol. 22, No. 3, 2012, pp.
234–241.
11. Winterstein, S.R., Ude, T.C., Cornell, C.A., Bjerager, P., and Haver, S. 1993. Environmental
parameters for extreme response: inverse FORM with omission factors. Proceedings,
ICOSSAR93, Innsbruck, Austria.
12. Christensen, C.F. and Arnbjerg-Nielsen, T.: Return Period for Environmental Loads –
Combination of Wind and Wave Loads for Offshore Wind Turbines. Rambøll, 2000.

4. 13. Sørensen, J.D., I.B. Kroon and M.H. Faber: Optimal Reliability-Based Code Calibration.
"Structural Safety", Vol. 15, 1994, pp. 197-208.
14. Sørensen, J.D. & N.J. Tarp-Johansen: Reliability-based optimization and optimal reliability
level of offshore wind turbines. International Journal of Offshore and Polar Engineering
(IJOPE), Vol. 15, No. 2, June 2005, pp. 1-6.
15. Sørensen, J.D., S. Frandsen and N.J. Tarp-Johansen: Effective Turbulence Models and
Fatigue Reliability in Wind Farms. Probabilistic Engineering Mechanics, Vol. 23, 2008, pp.
531-538.
16. Tarp-Johansen, N.J., P.H. Madsen and Sten Frandsen: Partial safety factors for extreme load
effects. Risø report R-1319, 2002.
Notes:
1. Characteristic values
2. Model uncertainty
3. Maximum Likelihood
Additional material:
 Madsen, H.O. & S. Krenk & N.C. Lind: Methods of Structural Safety. Prentice-Hall, 1986.

5. Location
Aalborg University, Department of Civil Engineering
Sohngaardsholmsvej 57
Building D, Roon D-222, see map below
B-222