已阅读5页,还剩63页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
在线教务辅导网HTTP/WWWSHANGFUWANGCOM更多课程配套课件资源请访问在线教务辅导网41FLEXURALBEHAVIOROFREINFORCECONCRETEBEAMRC受弯构件正截面性能2018/1/102NPLAINCONCRETEBEAMAREINEFFECTIVEASFLEXURALMEMBERSBECAUSETHETENSILESTRENGTHINBENDINGISASMALLFRACTIONOFTHECOMPRESSIVESTRENGTHNASACONSEQUENCE,SUCHBEAMSFAILONTHETENSIONSIDEATLOWLOADSLONGBEFORETHESTRENGTHOFTHECONCRETEONTHECOMPRESSIONHASBEENFULLYUTILIZEDNREINFORCEDCONCRETEBEAMSTEELREINFORCINGBARSAREPLACEDONTHETENSIONSIDEASCLOSETOTHEEXTREMETENSIONFIBERNINSUCHAREINFORCEDCONCRETEBEAM,THETENSIONCAUSEDBYTHEBENDINGMOMENTISCHIEFLYRESISTEDBYSTEELREINFORCEMENT,WHILECONCRETEALONEISUSUALLYCAPABLEOFRESISTINGTHECORRESPONDINGCOMPRESSIONREINFORCEDCONCRETEBEAMUNDERLOADREINFORCEMENTPLACEMENTINCONTINUOUSBEAMSORSLABSNSUCHJOINTACTIONOFTHETWOMATERIALSISASSURED,IFRELATIVESLIPISPREVENTEDNTHISISACHIEVEDBYUSINGDEFORMEDBARSWITHTHEIRHIGHBONDSTRENGTHATTHESTEELCONCRETEINTERFACE,AND,IFNECESSARY,BYSPECIALANCHORAGEOFTHEENDSOFTHEBARSDEFORMEDBARSANCHORAGEDEFORMEDBARRIBRELATIVESLIPBETWEENCONCRETEANDSTEELISPREVENTEDBYUSINGDEFORMEDBARSWITHTHEIRHIGHBONDSTRENGTHATTHESTEELCONCRETEINTERFACENTHREETYPESOFREINFORCEDCONCRETEBEAMSASINGLYREINFORCEDRECTANGULARBEAMS单筋梁BDOUBLYREINFORCEDRECTANGULARBEAMS双筋梁CSINGLYORDOUBLYREINFORCEDTBEAMST形梁NTHEREINFORCEMENTRATIOARATIOOFAREASOFSTEELANDCONCRETEREPRESENTTHERELATIVEAMOUNTOFTENSIONREINFORCEMENTINABEAMH0BASREINFORCEDCONCRETEBEHAVIORMODERATEREINFORCEDBEHAVIOR适筋适筋OVERREINFORCEDBEHAVIOR超筋超筋LIGHTLYREINFORCEDBEHAVIOR少筋少筋MODERATEREINFORCEDBEHAVIOR适筋NWHENTHERELATIVELYMODERATEAMOUNTOFREINFORCEMENTAREEMPLOYED,ATSOMEVALUEOFTHELOADTHESTEELWILLREACHITSYIELDPOINTFUFYOYIELDPOINTCRUSHINGOFTHECONCRETEENSUESATALOADONLYSLIGHTLYLARGERTHANTHATWHICHCAUSEDTHESTEELTOYIELDTHETHREESTAGESOFTHEBEAMSTEELYIELDCONCRETECRUSHTHEEXTERNALLOADPCAUSETHEBOTTOMFIBERSTOEQUALTOTENSILESTRENGTHOFTHECONCRETETHETENSILESTRENGTHOFTHECONCRETEEXCEEDSFTANDCRACKSDEVELOPCONCRETELOSESTENSILESTRENGTHANDSTEELSTARTSWORKINGEFFECTIVELYANDRESISTSTHEENTIRETENSILELOADTHEREINFORCEMENTYIELDSFAILUREOFTHEBEAMNATTHATSTRESSYIELDPOINT,THEREINFORCEMENTYIELDSSUDDENLYANDSTRETCHESALARGEAMOUNTANDTHETENSIONCRACKSINTHECONCRETEWIDENVISIBLYANDPROPAGATEUPWARD,WITHSIMULTANEOUSSIGNIFICANTDEFLECTIONOFTHEBEAMWHENTHISHAPPENS,THESTRAININTHEREMAININGCOMPRESSIONZONEOFTHECONCRETEINCREASESTOSUCHADEGREETHATCRUSHINGOFTHECONCRETEENSUESAT跟着发生ALOADONLYSLIGHTLYLARGERTHANTHATWHICHCAUSEDTHESTEELTOYIELDTASFSCCU0003CRUSHINGFUFYOSTRETCHESALARGEAMOUNTCRUSHINGOFTHECONCRETENEFFECTIVELY,THEREFORE,ATTAINMENTOFTHEYIELDPOINTINTHESTEELDETERMINATESTHECARRYINGCAPACITYOFMODERATELYREINFORCEDBEAMNSUCHYIELDFAILUREISGRADUALANDISPRECEDEDBYVISIBLESIGNOFDISTRESS恶化,损坏,SUCHASTHEWIDENINGANDLENGTHENINGOFCRACKSANDTHEMARKEDINCREASEINDEFLECTIONOVERREINFORCEDBEHAVIORNCONCRETEFAILSBEFORETHEYIELDOFSTEELDUETOTHEPRESENCEOFAHIGHPERCENTAGEOFSTEELINTHESECTIONONTHEOTHERHAND,IFLARGEAMOUNTSOFREINFORCEMENTORNORMALAMOUNTSOFSTEELOFVERYHIGHSTRENGTHAREEMPLOYED,THECOMPRESSIVESTRENGTHOFTHECONCRETEMAYBEEXHAUSTEDBEFORETHESTEELSTARTSYIELDINGOVERREINFORCEDBEHAVIORNCONCRETEFAILSBYCRUSHINGWHENSTRAINSBECOMESOLARGETHATTHEYDISRUPTTHEINTEGRITYIN5TERITI完整性OFTHECONCRETENCOMPRESSIVEFAILURETHROUGHCRUSHINGOFTHECONCRETEISSUDDEN,OFANALMOSTEXPLOSIVENATURE,ANDOCCURSWITHOUTWARNINGFUFYOSTEELDOSENOTYIELDCRUSHINGOFTHECONCRETENFORTHISREASON,ITISGOODPRACTICETODIMENSIONBEAMSINSUCHAMANNERTHATSHOULDTHEYBEOVERLOADED,FAILUREWOULDBEINITIATEDBYYIELDINGOFTHESTEELRATHERTHANBYCRUSHINGOFTHECONCRETELIGHTLYREINFORCEDBEHAVIORNFLEXURALSTRENGTHOFTHECRACKEDSECTIONISLESSTHANTHEMOMENTTHATPRODUCEDCRACKINGOFTHEPREVIOUSLYUNCRACKEDSECTIONNBEAMFAILSIMMEDIATELYANDWITHOUTWARNINGOFDISTRESSUPON紧接着FORMATIONOFTHEFIRSTFLEXURALCRACKLIGHTLYREINFORCEDBEHAVIORNTOENSUREAGAINSTTHISTYPEOFFAILURE,ALOWERLIMITCANBEESTABLISHEDFORTHEREINFORCEMENTRATIOBYEQUATINGTHECRACKINGMOMENT,COMPUTEDFROMTHECORRESPONDINGPLAINCONCRETEBEAM,TOTHESTRENGTHOFTHECRACKEDSECTION钢筋混凝土梁的MY素混凝土梁的受弯承载力MCRDESIGNOFREINFORCEDCONCRETEBEAMSTRENGTHDESIGNOFRECTANGULARBEAMWITHTENSIONREINFORCEMENTONLYSINGLYREINFORCEDBEAMNBASICASSUMPTIONS1SECTIONSPERPENDICULARTOTHEAXISOFBENDINGTHATAREPLANEBEFOREBENDINGREMAINPLANEAFTERBENDING平截面假定THISASSUMPTIONENSURESTHATTHECROSSSECTIONOFTHEMEMBERDOESNOTWARPWCP使翘曲DUETOTHELOADSAPPLIEDITFURTHERMEANSTHATTHESTRAINATANYPOINTONTHECROSSSECTIONISDIRECTLYPROPORTIONALTOITSDISTANCEFROMTHENEUTRALAXISNSTRAINATANYPOINTONTHECROSSSECTIONISDIRECTLYPROPORTIONALTOITSDISTANCEFROMTHENEUTRALAXISBASICASSUMPTIONSN2APERFECT5PEFIKTBONDEXISTSBETWEENTHEREINFORCEMENTANDTHECONCRETESUCHTHATTHESTRAININTHEREINFORCEMENTISEQUALTOTHESTRAININTHECONCRETEATTHESAMELEVEL钢筋的应变和相同位置处混凝土的应变相同假定混凝土与钢筋之间粘结可靠N3CONCRETEISASSUMEDTOFAILWHENTHECOMPRESSIVESTRAINREACHES00033THISISACLEARLYDEFINEDLIMITINGSTRAINOFCONCRETEINBENDINGCOMPRESSIONBEYONDWHICHTHECONCRETEWILLBETAKENASREACHINGTHESTATEOFCOLLAPSEITISVERYCLEARTHATTHESPECIFIEDLIMITINGSTRAINOF00033DOESNOTDEPENDONTHESTRENGTHOFCONCRETECOLLAPSEOFCONCRETELIMITINGSTRAINOFCONCRETEN4THEACCEPTABLESTRESSSTRAINCURVEOFCONCRETEISASSUMEDTOBEPARABOLIC抛物线的,像抛物线的混凝土受压时的应力应变关系U0OCFCCN5THETENSILESTRENGTHOFCONCRETEISIGNOREDCONCRETEHASSOMETENSILESTRENGTHVERYSMALLBUTNOTZEROYET,THISTENSILESTRENGTHISIGNOREDANDTHESTEELREINFORCEMENTISASSUMEDTORESISTTHETENSILESTRESS认为拉区混凝土开裂并退出工作HOWEVER,THETENSILESTRENGTHOFCONCRETEISTAKENINTOACCOUNTTOCHECKTHEDEFLECTIONANDCRACKWIDTHSINTHELIMITSTATEOFSERVICEABILITYN6THEDESIGNSTRESSESOFTHEREINFORCEMENTAREDERIVEDFROMTHEREPRESENTATIVESTRESSSTRAINCURVES钢筋的应力应变关系NTHEMAXIMUMSTRAININTHETENSIONREINFORCEMENTINTHESECTIONATFAILUREIS001THISASSUMPTIONENSURESDUCTILEFAILUREINWHICHTHETENSILEREINFORCEMENTUNDERGOESACERTAINDEGREEOFINELASTICDEFORMATIONBEFORECONCRETEFAILSINCOMPRESSIONMAXIMUMSTRAININELASTICDEFORMATIONREPRESENTATIVESTRESSSTRAINCURVESNDURINGTHELOADINGTOFAILUREOFAREINFORCEDCONCRETEBEAM,STRAINDISTRIBUTIONOVERTHEDEPTHOFTHEBEAMISASSUMEDTOBELINEARSTRESSDISTRIBUTIONINTHECONCRETEABOVENEUTRALAXISISESSENTIALLYPARABOLICINSHAPEIDEALIZEDSTRESSDISTRIBUTIONEQUIVALENTRECTANGULARSTRESSDISTRIBUTION压区混凝土等效矩形应力图形NTHECOMPRESSIVEZONEISMODELEDWITHAEQUIVALENTSTRESSBLOCKNITISASSUMEDTHATATFAILURETHETENSIONREINFORCEMENTHASYIELDEDANDTHATTHEMAXIMUMCOMPRESSIVESTRAINIS00033NTHEINTENSITYOFTHEEQUIVALENTUNIFORMCOMPRESSIVESTRESSANDITSDEPTHAREEASILYCALCULATEDFROMTHETWOCONDITIONSTHAT1THETOTALCOMPRESSIONFORCEC,AND2ITSLOCATION,IE,DISTANCEFROMTHETOPFIBER,MUSTBETHESAMEINTHEEQUIVALENTRECTANGULARASINTHEIDEALIZEDSTRESSDISTRIBUTIONIDEALIZEDSTRESSDISTRIBUTIONEQUIVALENTRECTANGULARXNXNSAMEAMOUNTANDLOCATIONOFTOTALCOMPRESSIONFORCEC原则C的大小和作用点位置不变IDEALIZEDSTRESSDISTRIBUTIONEQUIVALENTRECTANGULARSTRESSDISTRIBUTIONEQUIVALENTRECTANGULARSTRESSDISTRIBUTION压区混凝土等效矩形应力图形极限受弯承载力MOMENT/ULTIMATESTRENGTHNTHEEQUIVALENTRECTANGULARSTRESSDISTRIBUTIONCANBEUSEDFORDERIVINGTHEULTIMATESTRENGTHDESIGNEQUATIONSOFBEAMSNTHEBASICDESIGNEQUATIONSFORTHEMOMENTCAPACITYOFASINGLYREINFORCEDRECTANGULARBEAMCANBEESTABLISHEDBYCONSIDERINGTHEEQUILIBRIUMOFFORCESANDMOMENTSBH0H0X/2H0ULTIMATESTRENGTHDESIGNEQUATIONSOFBEAMSFORBEAMSREINFORCEDWITHMODERATEAMOUNTOFSTEELSFYXBH0BH0H0X/2H0EQUILIBRIUMOFFORCESANDMOMENTSMOMENTCAPACITYBALANCEDSTRAINCONDITIONNATBALANCEDFAILURE,THESTEELSTRAINISEXACTLYEQUALTOTHEYIELDSTRAINWHENTHESTRAININTHECONCRETESIMULTANEOUSLYREACHESTHECRUSHINGSTRAINOFRELATIVECONCRETECOMPRESSIONZONEDEPTH相对受压区高度REINFORCEMENTRATIOXREVEALSTHEAREARATIOANDSTRENGTHRATIOBETWEENREINFORCEMENTANDCONCRETESTRENGTHRATIOAREARATIOBALANCEDRELATIVECONCRETECOMPRESSIONZONEDEPTH界限受压区高度50120MAX,BBCUBHFMXXAMOMENTCAPACITYATBALANCEDFAILURETHERELATIVECONCRETECOMPRESSIONZONEDEPTHISONLYRELATEDTOTHEMATERIALPROPERTIESBALANCEDREINFORCEMENTRATIO适筋梁的最大配筋率(平衡配筋梁的配筋率)RMAXUNIQUERVALUETOGETSIMULTANEOUSEC0003截面的弯矩较大,高度不能无限制地增加BEAMCROSSSECTIONISALTERNATELYSUBJECTEDTOPOSITIVEANDNEGATIVEMOMENT截面承受正、负变化的弯矩COMPRESSIONREINFORCEMENTTENSIONREINFORCEMENTREASONSFOR
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 新余市重点中学2026届初三下学期检测试题卷(一)语文试题含解析
- 周口市重点中学2026届初三第二学期期末质量检查英语试题含解析
- 昭通市重点中学2026年高级初三(卫星班)化学试题含解析
- 辽宁省大连市甘井子区达标名校2026年初三3月联考英语试题理试题含解析
- 2026年广州省惠阳市惠城区初三下学期第一次大检测试题英语试题含解析
- 跨部门协作流程规范化工具包
- 企业知识管理库建设及维护标准
- 供应商资质审核未通过回复函(3篇)
- 海外学习安全承诺书范文4篇
- 化学品泄漏现场隔离与疏散预案
- 银屑病诊疗指南2024
- 刺杀操课件教学课件
- 国企应聘报名登记表
- 2024年黑龙江省哈尔滨市中考英语试题卷(含答案及解析)
- 医院培训课件:《静脉中等长度导管临床应用专家共识》
- 光伏组件回收再利用建设项目可行性研究报告写作模板-拿地申报
- 《管理学-原理与方法》历年考试真题试题库(含答案)
- 吉他变调夹团体标准
- 《城镇智慧水务术语》
- 高空蜘蛛人施工专项施工方案
- 第六单元课时练习 部编版语文七年级下册
评论
0/150
提交评论