Study Of Continuously Reinforced Concrete Pavement Transverse Crack In Early Times In Cold Area

This contents in the paper is relied on the project of "Study of ContinuouslyReinforced Concrete Pavement(CRCP) in Cold Area" funded by Traffic Office JilinProvince.In the paper,the mechanism and distributing orderliness of transverse crackof CRCP in early times are studied.The transverse crack of CRCP considered dryingshrinkage of concrete and thermal shrinkage is calculated by numerical iterativemethod,and relevant calculate program is compiled by Visual Fortran 6.Thedevelopment disciplinarian of CRCP transverse crack and the influence of eachcalculation parameter on CRCP transverse crack are gained by calculate program.Itincludes five chapters.Chapter three and chapter four are emphases of the paper.Chapter 1 is mainly talk about the study background,study content and itemsource.CRCP is one kind of high performance structure with enough continuouslysteel bars in the longitudinal direction.With the exclusion of transverse expansion orcontraction joints of Portland Concrete Pavement,CRCP has more advantagesincluding better riding quality,higher bearing capacity,longer service life and lessmaintenance work.CRCP accords with the trend of highway transportation ofcontainerization,heavy load and large traffic volume,and it has a vast application inhigh-grade highways in the future.It has widely used for arterial of highway andairport pavement in advanced countries such as the United States and West Europeancountries.The application and correlative study about CRCP is relatively late in ourcountry.Some preliminary work has also been done in our country in recent years,butthe theories and construction techniques is not perfect.Three greatest designs index ofCRCP are: space between transverse cracks,breadth of transverse crack and maximalsteel stress.Chapter 2 introduces the distributing orderliness of transverse crack of CRCP inearly times,analyzes some factors including concrete,steel,environment,the bondstress between concrete and steel,and friction stress between concrete and base ofCRCP.Among the factors,Drying shrinkage and thermal shrinkage of concrete are themain infection factors on transverse crack of CRCP in early times.Whatsmore,tensilestrength,creep,elastic module of concrete and the relation between concrete and steel,concrete and base affect transverse crack of CRCP in early times.In order to studyingtransverse crack,relation formula of concrete age transformation to coefficient ofdrying shrinkage,coefficient of thermal shrinkage,tensile strength,elastic module,intensity of bond stress between concrete and steel is introduced.Numerical formulabasing on the temperature variety of Changchun per year is given.Chapter 3 is theoretical analysis part of calculating transverse crack of CRCP inearly times.Calculating model of transverse crack is put forward in this chapter.Thereare three basic suppositions,(a) Bending stress of pavement arose by thermal gradientis ignored.(b) Subsection linear relation of friction stress between concrete and base isused,and uniform distributing of friction stress between concrete and base issupposed.(c) Stress and displacement of steel and concrete distribute symmetrically inpavement between cracks is considered.Longitudinal direction or latitudinal directiondisplacement of whole pavement is not occurred is supposed.This calculating modelis calculated by numerical iterative method in this chapter,and flow chart of thismethod is put forward,and calculate program is compiled by Visual Fortran 6.Chapter 4 is calculation result and parameter effect analysis part of CRCPtransverse crack.Transverse crack of CRCP and effect of parameters to three greatestdesigns index of CRCP are calculated.The conclusion of calculation result oftransverse crack is that stress and displacement between cracks in pavement can bedevided into the area of cracks appearance,the area of cracks transition and the area ofcracks security.The conclusion of calculation result of parameters is that reinforcementratio,cooling,drying shrinkage of concrete and relation of bond stress betweenconcrete and steel are important factors affecting to three greatest designs index ofCRCP.Chapter 5 is the conclusion and awaiting researching questions of the paper.Fourconclusions are mainly got from the paper.(a) The main cause of transverse crack ofCRCP in early times is that bigger stress in pavement occurs because the displacementof pavement formed by drying shrinkage of concrete and thermal shrinkage isrestricted by bond stress and friction stress.When the stress is over tensile strength ofconcrete,transverse cracks are occurred.The cracks will stabilize after threemonths.(b)Under the condition of same reinforcement ratio,reinforcement mode of"minor diameter,more number" is more reasonable than the mode of "major diameterless number" because the first mode can offer more wrapping area for steel.Fallingtemperature is also important effect factor.So it must be considered completely whenCRCP is built in cold area.Although drying shrinkage of concrete is disadvantageousto transverse cracks of CRCP,it is advantageous to the steel in pavement becausemaximal steel stress minishes along with increasing coefficient of dryingshrinkage.Friction stress of base is less effect to three greatest designs index of CRCP,but it is advantageous to whole going of CRCP.From the analysis of calculatingresult,the height of pavement is disadvantageous to CRCP,but less. (c)Bond relationbetween steel and concrete affects prominently to transverse crack of CRCP accordingto the result of using different relation.It is necessary that bond experiment betweensteel and concrete is done in the calculation of practice CRCP project.(d)Constructiontime affects less to the development of crack in July and October according to theresult of considering timeliness parameters.