ASRAnetStructural Reliability&Risk Assessment4-8 July 2016Wuhan, ChinaLecture 19: Reliability Based Code Developmentand TutorialProfessor Purnendu K. DasB.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST
Structural Reliability & Risk Assessment 4 – 8 July 2016 Wuhan, China Lecture 19: Reliability Based Code Development and Tutorial Professor Purnendu K. Das B.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST 1
OverviewPrinciplesofcodecalibrationStructuralCodesandRequirementsReliabilitydifferentiationPrinciplesof limitstatedesignCodecalibrationprocedure2
Overview Principles of code calibration Structural Codes and Requirements Reliability differentiation Principles of limit state design Code calibration procedure 2
IntroductionTime-varyingquantitiesRepresentation in normal engineering designConsidering extreme values of quantities?Designforcombinationsoftime-varyingquantitiesLoadsactinginoppositedirections..3
Introduction Time-varying quantities Representation in normal engineering design Considering extreme values of quantities? Design for combinations of time-varying quantities Loads acting in opposite directions . . . 3
Principlesof codecalibrationAcodeformatisaformalsystemofvariablestogetherwithasetof rulesTherulesdefinetherelationsbetweenthesevariablesandtheir relationstothe mechanical modelingofthe structureandtheactionsonthestructureForacodeformatofthepartialsafetyfactortype,thevariablesarecharacteristicvalues,partialcoefficients,andloadreductionfactorsCalibrationlevelsJudgementalvalueassignmentcalibrationtoexistingdesignpractice,orcodeoptimization4Ref: 8
Principles of code calibration A code format is a formal system of variables together with a set of rules The rules define the relations between these variables and their relations to the mechanical modeling of the structure and the actions on the structure For a code format of the partial safety factor type, the variables are characteristic values, partial coefficients, and load reduction factors Calibration levels Judgemental value assignment calibration to existing design practice, or code optimization 4 Ref: 8
Principlesof codecalibration..Calibrationbyjudgmentwasthepredominantwayofvalueassignment until about 1960Acodethatgivessatisfactoryexperiencesof safedesignthrough several years of practical usewas consideredtohavereasonablycorrectvaluesoftheparametersDrawbacksofjudgementalcalibrationuseofnewmaterials,newstructuralprinciples,anddevelopmentsinnewfieldslackof rationalanalysisleadtounnecessarilysafeandexpensivestructures5Ref:8
Principles of code calibration . . . Calibration by judgment was the predominant way of value assignment until about 1960 A code that gives satisfactory experiences of safe design through several years of practical use was considered to have reasonably correct values of the parameters Drawbacks of judgemental calibration use of new materials, new structural principles, and developments in new fields lack of rational analysis lead to unnecessarily safe and expensive structures 5 Ref: 8