早期混凝土的温度应力及裂缝控制

分类号:TUUDG:624学号德04121148单位代码:10004硕士研究生学位论文论文题目:早期混凝土的温度应力及裂缝控制研究生:张玉梅指导教师:刘保东弓俊青专业:结构工程论文提交日期:2007年4月1d日论文答辩日期:2006年12月20日学位授予单位:北京交通大学二00七年四月日摘要:关键词:早期混凝土;温度应力;徐变;钢筋;裂缝分类号:Tu;THEABSTRACTABSTRACT:This/Paper/stduied/thermal/stress/of/concrete/and/control/of/concrete/crack/at/early/ages;Using/finite/element/Program,the/htemral/stress/of/an/externally/restrained/concrete/slba/and/the/concrete/cushioncaPa/teariyages/are/simulated/firstly.And/the/nthere/sults/are/analyzed.The/heat/Production/induced/by/the/cementhy/dration/and/the/evolving/environmental/variation/are/considered/in/the/thermal/model.The/heat/ProductionChanges/with/time/and/it/15/the/key/afctor/of/concrete/temperuatres;the/bounday/conditions,which/15/htekey/Parameter/whiche/effcts/temPerautre/gradient,15/exPressed/by/convection/radiation/coefficient/according/to/conditions/such/as/curing/and/weather.Finiteelementmodel15asimPlifiedmodelofconsturctionPhasebecuasehtesiutcase15veyrcomPlex.ThevaribaleYoung'5moduluswhichchangeswithtimeandreProducedobjectivestressofconcreteareconsideredinthemechanicalmode.ThisPaPerconsideredinfluenceofconcreteearly一agecreePandreinofrcementtoconcretestress:GeneralcreePmodelswhichareofrlong一termconcretecreeP,arenotfitofrconcreteateariyages,Relaxationafctor15getfromlong一termconcretecreeP,which15notfitofrearlyconcretetoo,ThisPaPerusedthemostwidelyusedufnciton,theDoublePowerLwaD(PL),ofrdescribingtheearly一agecreeP,ProvidinggoodPredictions.Theresultindicatesthateariy一agecreePreducesstressofearly一ageconcreteveyrmuch.Accordingtestresultofsomedocumentation,theeeffctofreinofrcementonthethermalstressandtheriskofcrackingarecalculatedinthisPaPer.Afterconsideringtheactiveactionofreinofrcement,theultimatestrainofconcretecouldbeincreasedandthecrackofconcretecouldbePrevented.Inoneword,iftheeeffctofcreePandreinofrcementofeariyconcrete15consideredProPerly,thecrackofconcreteatearlyageswillbecontrolledeeffctively.KEYWORDS:concrete/ateariyages;htermal/stress;cree/P;reinofrcement;crackCLASSNO:TU;T目录中文摘要.................................................................................................……111ABSTRACT............................................................................................……IV绪论.....................................................................................................……11混凝土温度应力及裂缝理论...............................................................……21.1课题背景.................................................................................21.2国内外有关研究的现状..................................................................……212.1国外混凝土结构早期温度应力和裂缝研究现状..................……21.2.2国内混凝土结构早期温度应力和裂缝研究现状..................……31.3本文主要研究内容..............................................................................……41.4裂缝的概念..........................................................................................……51.4.1裂缝的基本概念..............................................................................……51.4.2混凝土的微观裂缝与宏观裂缝..................................................……61.4.3裂缝产生的主要原因......................................................................……71.5裂缝产生的机理...................................................................................……81.6影响混凝土结构早期裂缝的囚素................................................……81.6.1配筋对混凝土裂缝的影响.........................................................……101.6.2徐变对混凝土裂缝的影响.........................................................……112混凝土早期温场..................................................................................……122.1混凝土早期温度场理论..................................................................……122.1.1傅立叶法则.....................................................................................……122.1.2内部生热率.....................................................................................……132.1.3边值条件..........................................................................................……142.2有限元方法模拟.................................................................................……162.2.1有限元的发展及其概念..............................................................……162.2.2温度场有元计算原理..............................................................……172.3温度场计算实例分析.......................................................................……182.3.1工程概况..........................................................................................……182.3.2对温度场的模拟............................................................................……213混凝土早期应力场..................................................................................……253.1混凝土早期应力场理论..................................................................……253.1.1热膨胀系数.....................................................................................……263.1.2力学性能的成长............................................................................……263.1.3对徐变的考虑................................................................................……273.1.4对钢筋的考虑................................................................................……273.2热一结构效应