新型協(xié)同轉(zhuǎn)動四邊形曲殼單元研究

1、浙江大學(xué)建筑工程學(xué)院碩士學(xué)位論文新型協(xié)同轉(zhuǎn)動四邊形曲殼單元研究姓名：劉永方申請學(xué)位級別：碩士專業(yè)：結(jié)構(gòu)工程指導(dǎo)教師：李忠學(xué)20080601AbstractAmadvaflced9一nodecurvedquadrilateralshellelementforlargedisplacementandlargerotationanalysisisdeveloped，wherethelocalcoordinatesystemisaco。rota

2、tionalfra】[I】ework，ittranslatesandrotatesrigidlywiththeelement，butdoesnotdeformwiththeeleInentThus，thecontributionofrigidbodymotiontonodaldisplacementsandrotationscanbeexcludedinadvance，makingitsimplertoobtaintheelementt

3、angentstiffnessmatrix。T11e∞are3translationaldegreesoffreedomand2rotationaldegreesoffreedomateachnode，鋤dmelattersarethetwosmallestcomponentsofthemid—surfacenormalvectorateachnode，andadditiveinanincrementalsolutionprocedur

4、e，takingadvantageinupdatingthetangentstiffnessmatrixFurthermore，theGreen—LagrangestrainsspecializedfortheshallowcurvedsheHareemployed，andtheinternalforcevectorand￡i)ee蛔鍘ftangentstiffnessmatrixarecalculatedrespectivelyast

5、hefirstderivativeandthesecondderivativeofthestrainenergywithrespecttOlocalnodalvariablesCc，nsideringthecommutativityofallnodalvariables，theachievedelementtangentstiffnessmatrixissymmetricTheuniformlyreducedintegrationmet

6、hodCaneliminate／alleviatelockingproblems，butsometimesitmayleadtotheoccurrenceofelementrankdeficiencyandspurioussingularmodesToovercometheseproblems，theHellingerReissnerfunctionalisadoptedinwhichpartofconformingstrainsare

7、replacedbyassumedstrainsTheassuInedstrainsconsistofthelowerorderstrainandthehigherorderstrain，andtheformerisinterpolatedlinearlybyusingthecorrespondingdisplacement—basedstrain，whilethelatterplayingtheroleofstabilizingstr

8、ainisformulatedbasedonanassumedstrainprocedureTheelementtangentstiffnessmatrixderivedfromHellingerReissnervariationalprincipleisstillsymmetricFinallv8elasticflatplateandcurvedshellproblemsaresolvedtoevaluatetheperformanc

9、eoftheproposedelementThegeneralizeddisplacementcontrolmethodlSemployedinsolvingtheseproblemsItisshownthatlockingphenomenahasbeeneliminate洲alleviatedinthepresentelement，andthereliability，computationalefficiencyandconverge