简介:在结构损伤识别中,损伤发生的时间、损伤定位及损伤程度是三个核心问题。本文利用HHT方法结合经验遗传-单纯形算法分析刚度突变MDOF体系在地震波输入下结构的动力损伤识别问题,并以刚度突变4DOF结构体系在ELCentro地震波输入下结构动力特性识别为例进行了讨论。通过Fourier变换得到了结构损伤后的自振频率,利用HHT方法识别出结构损伤发生的时间,在此基础上运用经验遗传-单纯形算法识别出结构损伤后的刚度,从而确定了损伤的程度。
简介:Thispaperproceedsfromthegeneralcaseoftheunsymmetriclinearizedmulti-degreesoffree-dom(MDOF)systems.Byadoptingthegeneralcomplexmodaltheoryofthestatespace,theresponseanalysisforasys-temsubjectedtorandomexcitationofthesamesourceiscarriedoutusingasakindofdirectspectrumanalysismethodinfrequencydomain.Withtheinputofpowerspectraldensityfunctiongiven,theexplicitexpressionofthepowerspectraldensityfunctionmatrixoftheoutputresponsecanbeobtained.BytakingFourierinversetransform,theintegratedexpres-sionsofthecorrelationfunctionmatrixandofthespectrummomentmatrixareobtained.Comparingwiththetimedomainmethod,thismethodenjoysthemeritofvisualizationandavoidstheprocedureoftransformationfromtheobtainedre-sponsecorrelationfunctiontobesolvedfortheoutputspectrumutilizingFouriertransform.Thispaperhasextendedtheapplicationrangeofthetraditionalfrequencydomainanalysismethod.Themeansquarevaluesandvarietyofstatisticalval-uescanbeobtainedconveniently.Thismethodandthetimedomainmethodaredifferentinapproachbutequallysatisfac-toryintheirresults.
简介:Inthisstudytheseismicpoundingresponseofadjacentmulti-degree-of-freedom(MDOF)buildingswithbilinearinter-storyresistancecharacteristicsisinvestigatedthroughdimensionalanalysis.Theapplicationofdimensionalanalysisleadstoacondensedpresentationoftheresponse,andtheremarkableself-similaritypropertyforbilinearMDOFbuildingswithinelasticcollisionisuncovered.Itisshownthatwhentheresponseisexpressedintheappropriatedimensionlessform,responsespectraforanyintensityoftheexcitationcollapsetoasinglemastercurve.ThereducedΠsetexplicitlydescribestheinteractionbetweenthecollidingstructures.TheeffectofpoundingontheMDOFbuilding’sresponseisillustratedusingthreewell-dividedspectralregions(amplified,de-amplifiedandunaffectedregions).Parametricstudiesareconductedtoinvestigatetheeffectsofthestorystiffnessofstructures,thestorystiffnessratioandmassratioofadjacentbuildings,thestructuralinelasticcharacteristicsandthegapsizevalues.Resultsshowthat(i)theinfluenceofsystemstiffnessratiotothelighterandmoreflexiblebuildingismoresignificantinthefirstspectralregion,wherethemaximumresponseofthebuildingisamplifiedbecauseofpounding;and(ii)thevelocityandpoundingforceoftheheavierandstifferbuildingisunexpectedlysensitivetothemassratioofadjacentbuildings.
简介:TILLING(TargetingInducedLocalLesionsInGenomes)即定向诱导基因组局部突变技术,是近年发展起来的一种高通量检测点突变的反向遗传学方法。本研究从PCR模板量及酶切体系中CELI的酶量两个方面对家蚕TILLING技术的检测体系进行了优化。结果表明:本实验在应用TILLING技术筛选家蚕突变体过程中,用于PCR扩增的家蚕基因组DNA模板最佳用量为20ng;CELI酶切的20μL反应体系中,加入的最适酶量为0.5μL(本实验室从芹菜中自提的CELI酶10倍稀释液)。本研究初步对TILLING技术应用于家蚕化学诱导突变检测体系进行了优化,为TILLING技术在家蚕功能基因组研究中的应用奠定了基础。
简介:Itisknownthatstructuralstiffnessandstrengthdistributionshaveanimportantroleintheseismicresponseofbuildings.Theeffectofusingdifferentcode-specifiedlateralloadpatternsontheseismicperformanceoffixed-basebuildingshasbeeninvestigatedbyresearchersduringthepasttwodecades.However,noinvestigationhasyetbeencarriedoutforthecaseofsoil-structuresystems.Inthepresentstudy,throughintensiveparametricanalysesof21,600linearandnonlinearMDOFsystemsandconsideringfivedifferentshearstrengthandstiffnessdistributionpatterns,includingthreecode-specifiedpatternsaswellasuniformandconcentricpatternssubjectedtoagroupofearthquakesrecordedonalluviumandsoftsoils,theeffectofstructuralcharacteristicsdistributiononthestrengthdemandandductilityreductionfactorofMDOFfixed-baseandsoil-structuresystemsareparametricallyinvestigated.Theresultsofthisstudyshowthatdependingonthelevelofinelasticity,soilflexibilityandnumberofdegrees-of-freedoms(DOFs),structuralcharacteristicsdistributioncansignificantlyaffectthestrengthdemandandductilityreductionfactorofMDOFsystems.Itisalsofoundthatathighlevelsofinelasticity,theductilityreductionfactoroflow-riseMDOFsoil-structuresystemscouldbesignificantlylessthanthatoffixed-basestructuresandthereductionislesspronouncedasthenumberofstoriesincreases.
简介:提出了基于经典层压板理论的层压板刚度矩阵的两种识别方法,精确识别法和参数减少识别法。在精确识别法中全部层压板刚度参数作为未知数并可利用足够的试验数据由层压板本构方程——虎克定律直接求出。在参数减少识别法中全部层压板刚度参数被展开成一些重要参数诸如纤维与基体的杨氏模量、纤维体积含量及纤维体积含量沿厚度方向的分布参数的线性函数。这些参数在以前的研究中被证明对层压板刚度参数及屈曲栽荷有很大的影响。通过线性化,待识别的参数由18个刚度参数减少为6个材料性能及纤维体积含量分布参数。这些参数可利用层压板设计参数(铺层顺序、铺层角及各层厚度)和少量试验的测量数据确定。在两种方法中采用常规方法求解带约束最小二乘统计问题。给出了验证两种刚度矩阵识别方法的算例,其中参数减少识别法采用真实试验测量结果;精确识别法采用虚拟理想试验测量结果。
简介:摘要:在钻井作业实践中,套管经常由于各种原因不能完全下到位,需要重新拔出套管,进行通井作业,或者就地固井,重新侧钻,启动备用井眼尺寸,更甚者,导致钻井失败。失败的主要原因是套管下入刚度不适用钻具刚度,导致套管弯矩增大,井眼曲率半径过大而无法通过井眼。因此本文利用惯性矩计算方法,对比通井钻具组合和套管刚度,得到钻具与套管刚度匹配性方法,成功解决中东某碳酸盐井表层套管多次下套管不到位的难题,为后期类似的碳酸盐井通井钻具组合提供了理论依据。