住宅裂缝分析

住宅工程现浇楼板裂缝的原因分析及防治近年来，我们发现，现浇钢筋混凝土楼板出现裂缝的情况较多，这已经成为影响住宅工程质量的一大通病，现对裂缝成因及防治措施简析如下：●现浇钢筋混凝土出现裂缝的主要情况1、多层砖混结构2、小高层现浇钢筋混凝土短肢剪力墙结构3、高层现浇钢筋混凝土剪力墙结构4、多层现浇钢筋混凝土框架结构出现现浇钢筋混凝土楼板裂缝的工程，以住宅楼较为多见，商业楼、公建用房相对少些。若按层次分布情况，大部分裂缝与层次无关，只有极个别工程去，其裂缝在从上到下有递减趋势。●结构楼板裂缝开始出现的时间一般多在结构封顶半年后陆续出现，如不及时采取补强措施，在1年至2年时间内，裂缝继续发展。三、裂缝所在部位及其特征1、现浇钢筋混凝土楼板裂缝，多分布在房屋转角所在的房间楼板上。裂缝一般呈45度斜向，有时一只角出现两条裂缝，裂缝基本上为上下贯通。2、部分裂缝产生在板内电线管道埋设位置。3、个别工程的楼板裂缝产垂直于板跨方向，或呈不规则状分布。●裂缝原因分析经过各种分析因素的对比，认为1、现浇钢筋混凝土楼板裂缝，主要有混凝土的温度变形和收缩变形引起的。钢筋混凝土梁、板、墙、柱等构件处在一个共同的大气环境中，当环境的温度和湿度变化时，这些混凝土的构件多会产生相应的温度变形和湿度变形。由于体形上的差异，板的体积与表面积的比积较小，在水平方向上楼板的收缩变形一般均超过（或大于）梁、柱、墙使板内出现拉应力，梁内呈压应力。另一方面外纵墙和山墙在外界气温的影响下，经历热胀和冷缩的反复作用，它们的温差合力对房间对外墙角部楼板，将产生较大的主拉应力。以上两个力的叠加，对板Residentialconstructionofcast-in-situfloorcrackscauseanalysisandcontrolInrecentyears,wefoundthatcast-in-placereinforcedconcretefloorcracksismore,ithasbecomeasituationahousingprojectqualityeffectofcrackendemic,nowcausesandpreventionmeasuresareasfollows:introductionA,cast-in-situreinforcedconcretecracksmainconditions1,multi-layerbrickandconcretestructure2,smallhigh-risecast-in-situreinforcedconcreteshortshearwallstructureThree,high-risecast-in-placereinforcedconcreteshearwallstructure4,multilayercast-in-placereinforcedconcreteframestructureAppearcast-in-placereinforcedconcretefloorcracksintheengineering,residentialbuildingmoreseemore,businesses,publichousingisrelativelyless.Ifpressleveldistribution,mostfracturesandhierarchyisirrelevant,onlytheextremelyindividualprojectsinthecracks,fromtoptobottomhasdegressivetendency.Second,thefloorcracksbegantoappearstructureoftimeMorecommonlyinsuccessioninstructurecappedafterhalfayear,suchasnottaketimelyappearreinforcingmeasures,inoneyeartotwoyearstime,crackcontinuedevelopment.Three,cracktheirpositionsandtheircharacteristics1,cast-in-situreinforcedconcretefloorcracksinhousing,distributionintheroomfloorspaceAngle.Crackis45degreesofinclinedtocommonly,sometimesahorn,cracksappearedtwocracksupbasicallyisthrough.2,partofthecracksintheboardinsidewireembeddedpipeposition.3,individualprojectinthefloorcracksacrossdirectionperpendiculartotheboard,oranirregularshapedistribution.Four,crackcausesanalysisAftervariousanalysesfactorsthatthecontrast1,cast-in-situreinforcedconcretefloorcracks,basicallyhaveconcretetemperaturedeformationandcontractiondeformationcause.Reinforcedconcretebeam,plate,walls,column,etccomponentinacommonatmosphericenvironment,whentheenvironmentaltemperatureandhumiditychanges,theseconcretecomponentwillproducethecorrespondingtemperaturedeformationandhumiditydeformation.Duetothedifferencesandplateshapethanthevolumeandsurfaceareaofdepositioninahorizontaldirectiononsmaller,floorsystolegenerallyexceeded(ormore)beamsandcolumns,thewallplateoccurswithinatensilestressandbeamstress.InOntheotherhandoutsideinverticalwallandoutsidetemperaturegableundertheinfluenceofheatandcold,andexperience,theyrepeatedlyroleofroomtemperatureofforceforeigncorner,willproducelargerfloorLordtensilestress.Abovethesuperpositionoftwoforcesonboard,themostunfavorablecondition,formedthetensilestresswhenboardoverconcretetensilestrength,andfloordeformationisgreaterthanthelimitsofreinforcementconcretetensile,floorcrackswithin.Crackpositiondependontwofactors:thefirstistherestraint,2itistensileability.Onthefloorfor,constraintsinfourcornerposition,becausethecornerofthewallbeamorbiggest,ittofloorstiffnessoftheconstraintsfromthelargestalso,andoutsidetemperaturebyexteriorwallcornerofinfluence,floorsystole'slargestarea.Generallyspeaking,boardinsidereinforcementparalleltotheboardbymorethantwoadjacentedgeSettings,i.e.,cornerofficescorelinedirectiontheweakesttensileability.Somostboardcracksappearalongthewallupinacornerplace,only45degreesofinclinedtoradial.2,thecurrentengineeringconstructionofcast-in-situreinforcedconcretefloor,widelyusedtheconcretepumpingconcrete,thedosageofcement,watercementratio,suchascollapsbillityislarger,gravel,radiussmallerthaninthepast,concreteshrinkagemixingofthephenomenon,inordertoresisttheplateuneventemperaturedifferenceandcontractionbytheinfluenceofthelocalstressconcentrationandappearonly,ifwallcornerfloorslabreinforcementritual,cannotadapttochangingthenewsituation.3,floorburiedwirecasing,especiallywithinthepopularizationinrecentyearsastheuseofPVCpipereplacemetaltubesafter,makeboardinsideeffectivebydifferentdegreesofsectionweakened.Andbecausethetubeinconsistentwithconcreteexpansioncoefficientandbondingeffectispoorer,thenalongthewirecasingwouldlikelybecauseembeddingdirectionstressconcentrationandcrack.4,duetoimproper,floorconstructionarrangementsinthenegativemomentnearlybearingsteelareoftenoperatorstramplesinking,anddidn'tgettimelycorrecting,makeitscannoteffectivelyplayinthenegativemomentrole.Five,thecontrolcountermeasuresofreinforcedconcretefloorcracks;\One,intheready-mixedconcretepumpingconstructionbytheconditions,theroomisoutsidecornerofcast-in-situreinforcedconcretefloor,shouldbeappropriatelyenlargingthelimitsofreinforcementconcretetensileability,thetechnicalmeasuresconditionsasfollows.1,appropriatelyincreasethickness.2,improvethereinforcementplate.3,steelfiberconcrete,inordertoimprovethetensilestrengthofconcrete.4,USESthe"secret"reinforcedsteelreinforcementsecretmethod.Theaboveseveralmethodsduetodifferentconditionsoftherestrictions,reasonshouldimprovefloorofsquaresteelratio,stillcaneffectivelyLordpointedlyZengPeiinexteriorwallcornerradioactivereinforcement.Second,improvingexteriorwallinsulationstandardpart,especiallytheoutwardwallcornerinmetope,usetheheatinsulatingmaterialstobestucktofloorslabtemperaturecrack,impact,reducedtotheminimum.Three,researchanddevelopmentoflowpumpingconcreteshrinkageofconcrete,thedryexclusivelyinincast-in-situreinforcedconcretefloorproject.Four,floorofPVCwireinsidecasing,withparalleltotheflooronlyallowedforcedirection,buriedinPVCwireembeddedcasing,shouldaddwidthtopandbottomnotlessthan400mmofsteelwire,asreinforcingmeasures.Five,theconditionalmightaswelluse"put"specialtectonicmeasures.Forexample:willendcrossdesignedtosimply-supportedplateforms,namelyinfloorandbeamconstructionjointsbetweensettingquarantine.6:strictconstructionmanagement,andpoureddaoconcretefloor