《船舶与海洋工程结构风险评估》课程教学课件（讲稿）Lecture 10 & 11 Stiffened Shells I &II

ASRAnetStructural Reliability & Risk Assessment4-8 July 2016Wuhan, ChinaLecture 14 & 15: Stiffened Shells & IlProfessor Purnendu K. DasB.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST

Structural Reliability & Risk Assessment 4 – 8 July 2016 Wuhan, China Lecture 14 & 15: Stiffened Shells I & II Professor Purnendu K. Das B.E., M.E., PhD, CEng, CMarEng, FRINA, FIStructE, FIMarEST 1

asRanetIntroductionAn important structural component in buoyant semi-submersible andTension legtypeoffshoreplatforms.Inherent ability to resist high axial loads and bending moments withlateralpressureloadsNumerical techniques to account model complexitiesImportance of Structural reliabilityNeedforarobustclosedformrelationforstrengthevaluationA revised formulation for the strength assessment of ring stiffened andring-stringer stiffened cylindersStatistical comparison of proposed formulation with DNV-RP-C202(2013) andAPIBul2U (2002) codes2

Introduction An important structural component in buoyant semi-submersible and Tension leg type offshore platforms. Inherent ability to resist high axial loads and bending moments with lateral pressure loads. Numerical techniques to account model complexities Importance of Structural reliability Need for a robust closed form relation for strength evaluation A revised formulation for the strength assessment of ring stiffened and ring-stringer stiffened cylinders Statistical comparison of proposed formulation with DNV-RP-C202 (2013) and API Bul 2U (2002) codes 2

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asranetBuckling of stiffened cylindersRingStringerstiffenedandstiffened,Ring-StringerR1(orthogonally) stiffened cylinders.Cylinder fabrication-Butt weldingStiffeners -Flat bar,Angle bar,T-bar etcThe strengthof thestructureBasicgeometrical&materialstructuraldesignparameters6

Buckling of stiffened cylinders Ring stiffened, Stringer stiffened and Ring-Stringer (orthogonally) stiffened cylinders. Cylinder fabrication-Butt welding. Stiffeners - Flat bar, Angle bar, T-bar etc. The strength of the structure Basic geometrical & material structural design parameters. 6

aSRanCE41.OrthogonallyStiffened cylinder(lnternallystiffened)2. Panels3. Stringer or longitudinal stiffener4. Ring stiffener7

1. Orthogonally Stiffened cylinder (Internally stiffened) 2. Panels 3. Stringer or longitudinal stiffener 4. Ring stiffener 7

SRAnGtBuckling of stiffened cylindersGeometrical imperfectionsResidualstressesLoading conditionsSupport conditionsType and direction of stiffenersBuckling failure of Stiffened cylindersSnap-through bucklingClassical type of bifurcation buckling8

Buckling of stiffened cylinders Geometrical imperfections Residual stresses Loading conditions Support conditions Type and direction of stiffeners. Buckling failure of Stiffened cylinders Snap-through buckling. Classical type of bifurcation buckling 8

asranet_Local shellbucklingGeneralRinginstabilitystiffenedLocal stiffenerbucklingLocal shellbuckling0BayStringerstiffenedinstabilityLocal stiffenerbucklingLocal shellbucklingRing andLocalstiffenerstringerbucklingstiffenedBayinstabilityGeneralinstability9

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asranetLocalPanelBucklingbetweenstiffenersLocal BucklingencompassingseveralstiffenersBuckling ofindividualstiffeners10

Local Panel Buckling between stiffeners 10 Local Buckling encompassing several stiffeners Buckling of individual stiffeners