ASRAnetStructural Reliability & Risk Assessment4-8 July 2016Wuhan, ChinaLecture 18: Response surface methodsProfessor Purnendu K. DasB.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST
Structural Reliability & Risk Assessment 4 – 8 July 2016 Wuhan, China Lecture 18: Response surface methods Professor Purnendu K. Das B.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST 1
ContentsBackgroundandbasicconceptsAnalysis of some simple examples. AccuracyApplication to buckling of a stiffened panel based on FEManalysis(iterativeresponsesurfacemethod)Application to analysis of riserfatigue due to Vortex-lnduced-Vibrations (VIV)Summaryandconclusions2
Contents • Background and basic concepts • Analysis of some simple examples. Accuracy • Application to buckling of a stiffened panel based on FEM analysis (iterative response surface method) • Application to analysis of riser fatigue due to Vortex-InducedVibrations (VIV) • Summary and conclusions 2
Backgroundand basic concepts3
Background and basic concepts 3
BackgroundFreguently,limit statefunction is onlyknown implicitlythroughaprocedure such as a Finite Element Analysis.Safe domain can then be defined only through point-by-pointdiscovery (i.e. by repeated numerical analysis with different inputvalues)Twobasicschemesarerelevant:1.Thecomputerprogramtobeappliedforreliabilityanalysisisconnecteddirectlytothecomputerprogramfornumericalanalysisofthe limitstatefunction-ll(iThelimitstatefunctionisfirstevaluatedforanumberofvaluesoftheinputparameters(i.e.atanumberofpoints).(i)Asmoothfunction issubsequentlyfitted based onthesepoints.(ii)Thesmoothfunction is subsequently appliedbythe reliability analysisprogram
Background • Frequently, limit state function is only known implicitly through a procedure such as a Finite Element Analysis. • Safe domain can then be defined only through point-by-point discovery (i.e. by repeated numerical analysis with different input values) • Two basic schemes are relevant: – I. The computer program to be applied for reliability analysis is connected directly to the computer program for numerical analysis of the limit state function – II (i)The limit state function is first evaluated for a number of values of the input parameters (i.e. at a number of points). (ii)A smooth function is subsequently fitted based on these points. (iii) The smooth function is subsequently applied by the reliability analysis program
Background. Option l: Direct coupling of reliability analysisprogram and computer program fornumerical evaluation of limit state functionReliability analysis computer programEvaluation of limit state function forgiven parameter combinationFinite Element computer program
Background • Option I: Direct coupling of reliability analysis program and computer program for numerical evaluation of limit state function Reliability analysis computer program Evaluation of limit state function for given parameter combination Finite Element computer program