简介:Theextendingofacantileverandtransversemovingofadrillingfloorenablethejack-uptooperateinseveralwellpositionsaftertheJack-uphaspitched.Thecantileverallowableloadnephogramisthecriticalreferencewhichcanevaluatethejack-up’sdrillingability,designthecantileverstructureandinstructajack-upmanagertomaketheoperationssafe.Theintentofthispaperistoexploretheinterrelationshipsbetweenthecantileverposition,drillingfloorandtheloadsincludingwindforce,thestandset-backweightetc.,throughanalyzingthestructureandloadcharacteristicsofthex-typecantileverandthesimplifiedmechanicsmodelwiththerestrictionofthemaximummomentcapacityofthecantileversinglesidebeam.Referringtoseveraltypicalpositiondesignsloadvalues,thecantileverallowableloadnephogramisobtainedbyusingthesuitableinterpolationmethod.Thepapergivesamethodforcantileverallowableloaddesign,whichisprovedreliableandeffectivebythecalculationexample.
简介:Acomplianttowerismodeledasapartiallydry,partiallytapered,dampedTimoshenkobeamwiththesuperstructuremodeledasaneccentrictipmass,andanon-classicaldampedboundaryatthebase.Thefoundationismodeledasacombinationofalinearspringandatorsionalspring,alongwithparallellinearandtorsionaldampers(Kelvin-Voigtmodel).Thesuperstructureaddstothekineticenergyofthesystemwithoutaffectingthepotentialenergy,therebyreducingthenaturalfrequencies.Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam,reducingitsnaturalfrequenciesfurther.Theemptyspacefactorduetothetruss-typestructureofthetowerisincluded.Theeffectofsheardeformationandrotaryinertiaareincludedinthevibrationanalysis;withthenon-uniformbeammode-shapesbeingaweightedsumoftheuniformbeammode-shapessatisfyingtheendcondition.TheweightsareevaluatedbytheRayleigh-Ritz(RR)method,andverifiedusingfiniteelementmethod(FEM).Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam.Kelvin-Voigtmodelofstructuraldampingisincluded.Apartofthestructurebeingunderwater,thevirtualaddedinertiaisincludedtocalculatethewetnaturalfrequencies.Aparametricstudyisdoneforvariousmagnitudesoftipmassandvariouslevelsofsubmergence.ThecomputationalefficiencyandaccuracyoftheRayleigh-Ritzmethod,ascomparedtotheFEA,hasbeendemonstrated.Theadvantageofusingclosed-formtrialfunctionsisclearlyseenintheefficacyofcalculatingthevariousenergycomponentsintheRRmethod.
简介:自2015年4月份进入汛期以来,桂林遭遇了自2008年以来最严重的洪涝灾害。暴雨、大风、冰雹等强对流天气一轮又一轮,考验着这个城市和这个城市的管理人员……在防汛抗洪的大军中,有一支队伍始终冲在最前线,风里来、雨里去,每天乘坐摩托艇巡航在因为暴雨而显得面目狰狞的漓江中,守护着中外游客和当地群众的生命财产安全;作为市里应急队伍不可或缺的成员单位,在水上交通安全和秩序受到挑战的关键时刻、在人民群众需要他们的危急关头,他们总是挺身而出,所到之处危机立刻化解;作为桂林国际旅游胜地防汛队伍的重要成员,他们高擎那面象征荣誉和使命的深蓝色旗帜,无论是“住家船”、排筏、客渡船还是水上水下施工作业区域,哪里需要他们,哪里就有海事人的身影。